General Accounting Office Reports

Global Positioning Technology: Opportunities for Greater Federal Agency Joint Development and Use

Global Positioning Technology: Opportunities for Greater Federal Agency

Joint Development and Use (Letter Report, 09/28/94, GAO/RCED-94-280).

Recent technology has made it possible to greatly improve the accuracy

of global positioning information available from satellites. This

technology, called Differential Global Positioning Systems, allows

pilots, surveyors, and other using satellite positioning information for

civil uses to determine their position on earth to within a few

meters--or even a few centimeters. Many civilian federal agencies, such

as the Federal Aviation Administration, are actively pursuing the use of

this technology. GAO looked into whether federal agencies are taking

full advantage of opportunities to share or jointly develop their

systems so as to minimize the cost to taxpayers. This report discusses

(1) the extent to which agencies have been developing joint systems or

sharing equipment and (2) additional steps that may be needed to enhance

joint development or sharing of Differential Global Positioning Systems

equipment, facilities, and information.

--------------------------- Indexing Terms -----------------------------


     TITLE:  Global Positioning Technology: Opportunities for Greater 

             Federal Agency Joint Development and Use

      DATE:  09/28/94

   SUBJECT:  Interagency relations

             Research and development


             Transportation operations

             Geographic information systems

             Technology transfer

             Federal procurement

             Information gathering operations

             Systems compatibility

             Systems design

IDENTIFIER:  DOT Intelligent Vehicles and Highway System

             FAA Wide Area Augmentation System



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================================================================ COVER

Report to Congressional Requesters

September 1994





Global Positioning Technology


=============================================================== ABBREV

  BLM - Bureau of Land Management

  DGPS - Differential Global Positioning System

  DOD - Department of Defense

  DOT - Department of Transportation

  EPA - Environmental Protection Agency

  FAA - Federal Aviation Administration

  NGS - National Geodetic Survey

  NOAA - National Oceanic and Atmospheric Administration

  OMB - Office of Management and Budget

  RINEX - Receiver Independent Exchange


=============================================================== LETTER


September 28, 1994

The Honorable Norman Y.  Mineta


The Honorable Bud Shuster

Ranking Minority Member

Committee on Public Works and Transportation

House of Representatives

Recent technology has made it possible to greatly improve the

accuracy of global positioning information available from satellites. 

This technology, called Differential Global Positioning Systems, or

DGPS, allows pilots, surveyors, and others using satellite

positioning information for civil uses\1 to determine their position

on earth to within a few meters--or even a few centimeters.  Many

civilian federal agencies are actively pursuing the use of this

technology.  For example, to improve aircraft navigation and

landings, the Federal Aviation Administration (FAA) is planning a

national DGPS network costing about $500 million. 

In response to your request of July 21, 1993, we performed a review

to determine whether federal agencies are taking full advantage of

opportunities to share or jointly develop their systems so as to

minimize the cost to taxpayers.  Specifically, we focused on (1) the

extent to which agencies have been developing joint systems or

sharing equipment and (2) additional steps that may be needed to

enhance joint development or sharing of DGPS equipment, facilities,

and information. 


\1 Our review focused on civil use of global positioning system

technology.  The Department of Defense operates the global

positioning system and does not use DGPS technology for military



------------------------------------------------------------ Letter :1

Between 1988, when federal agencies began to use differential global

positioning system technology, and 1993, few federal agencies were

developing joint systems or sharing equipment.  To a large extent,

this early lack of coordination is not surprising.  Agencies differed

in the applications they were trying to develop, and the federal

government had no clear mechanism to coordinate interagency efforts. 

Beginning in 1993, agencies changed this approach in two ways. 

First, two agencies developing large-scale systems--the Coast Guard

and Federal Aviation Administration--changed their systems to make

them easier for other agencies to use.  Second, the Departments of

Defense and Transportation formed a task force to study global

positioning issues, including options for greater joint development

or use of differential global positioning system technology by

civilian agencies--at least on a voluntary basis.  However, the

interagency coordinating mechanisms proposed by the task force and

now being put in place have no authority over civilian agencies

outside the Department of Transportation.  This limited authority

leaves other civilian agencies free to develop systems on their own. 

The rapid growth in government-sponsored differential global

positioning system applications is expected to continue.  Such growth

and the potentially significant budget implications it carries

heighten the need for effective governmentwide coordination. 

Continuing efforts are under way to address the technical aspects of

such coordination--for example, development of standards to ensure

that various differential global positioning system applications can

use the same equipment.  However, these efforts address technical

issues only--not issues related to ensuring that agencies will agree

to coordinate their development and use of differential global

positioning systems. 


------------------------------------------------------------ Letter :2

Global positioning information comes from a network of 24 Department

of Defense (DOD) satellites.  Planes, boats, vehicles, and mapping

and survey teams can determine their position on earth by using

equipment that receives and interprets signals from these satellites. 

For civil applications, the satellites provide a signal that is

accurate to about 100 meters without the use of DGPS. 

DGPS is a technology for improving the accuracy of this positioning

information.  This greater accuracy is potentially useful in such

ways as improving the accuracy of maps, enhancing search and rescue

efforts, improving navigation in crowded waterways, and helping

planes land in bad weather.  DGPS increases the accuracy of the

satellite signal through the use of earth-located "base" or

"reference" stations (see fig.  1).  The cost of these base stations

varies from about $10,000 to $200,000 depending on the type of

application and communication link needed to get the information to

the user.  Other costs are for acquiring field receivers that can

capture the signals from satellites and base stations and for

monitoring and maintaining the equipment and the data it generates. 

   Figure 1:  Basic Components of


   (See figure in printed


   Note:  Positioning data is

   needed from at least four

   satellites to determine the

   three-dimensional position on


   (See figure in printed


DGPS takes two main forms, each with its own equipment requirements. 

One form, called real-time, transmits positioning information

instantaneously to the user, while the second form, called

post-processing, stores the information for later use.  Real-time has

been used largely for navigation, and post-processing has been used

mainly for mapping and surveying.  Costs are higher for equipment and

operations related to real-time than for post-processing. 

DGPS development is still considered to be in its infancy.  One of

the first federal applications was a system installed by the U.S. 

Forest Service in 1988 for managing forest resources.  While usage in

both the government and the private sector has mushroomed since that

time, global positioning system industry officials estimate that

about 95 percent of the market remains to be tapped.  They expect

DGPS to be commonplace for such additional activities as responding

to medical and police emergencies, locating and tracking vehicles,

and installing utility services.  This continued growth means that

the federal investment in DGPS technology--already more than $518

million through fiscal year 1998--can be expected for some time to





------------------------------------------------------------ Letter :3

Most DGPS applications within the federal government before 1993

focused on single-agency systems.  We reviewed the activities of nine

federal agencies that had been active in designing or implementing

DGPS applications during this period.\2 (Table 1 shows the nine

agencies and the kinds of applications they were developing.  For

additional details on each agency's plans, see app.  I.) Eight of the

nine began their efforts by designing or implementing a single-agency

approach.  In other words, each agency planned to acquire its own

equipment, including base stations, and to set up the system to meet

specific agency needs. 

                           Table 1

                   Agency DGPS Applications



Agency            Aviation   Marine     mapping    Other

----------------  ---------  ---------  ---------  ---------

Federal Aviation  X


Coast Guard                  X                     X\a

Environmental                           X



Bureau of Land                          X


Forest Service                          X

U.S. Geological                         X


St. Lawrence                                       X\a




National Oceanic                        X

and Atmospheric


Army Corps of                X                     X\a



\a Includes buoy setting and/or dredging. 

The one exception to this single-agency approach was the National

Oceanic and Atmospheric Administration's (NOAA).  NOAA lacked the

funds to build its own system but was able to use the Coast Guard's

equipment to supply its information requirements.  (We will discuss

the NOAA-Coast Guard effort in more detail later in this report.)

In many respects, it is not surprising that joint development of DGPS

applications was initially limited.  One main reason was that the

type of application and geographic coverage varied considerably.  For

example, the Coast Guard and FAA had navigation applications, but the

Coast Guard's was for marine navigation largely along the coast and

in the Great Lakes, while FAA's was for aircraft navigation

throughout the country.  Many other agencies had nonnavigational

applications, such as surveying and mapping, which required a

different kind of system (post-processing rather than real-time) and

which often focused on those areas of the country they were

responsible for managing. 

Even when agencies had similar DGPS needs and applications, other

factors often limited the amount of joint development that could

occur.  These factors related both to the operation of the system and

to a limited opportunity or need to coordinate with other agencies. 


\2 We contacted 13 federal agencies that were involved in

transportation, surveying, or mapping--the activities supported by

DGPS.  Nine of them indicated they had been actively designing,

implementing, or operating DGPS applications. 




---------------------------------------------------------- Letter :3.1

Single-agency applications developed for mapping, surveying, and

related uses sometimes could not share information with other

applications because equipment was incompatible.  Equipment developed

by one manufacturer can have software programs or data-storing

formats that cannot be used by another manufacturer's equipment.  For

example, a Bureau of Land Management (BLM) official said several

other agencies stopped trying to access information from a BLM base

station because of the time needed to resolve equipment

incompatibility problems.  Similarly, several agencies were

unsuccessful in accessing Forest Service data relating to the

locations of streams, bridges, and other features because of computer

hardware and DGPS data format limitations.  Although a common data

format (called Receiver Independent Exchange, or RINEX) had been

developed that would allow field receivers made by one manufacturer

to share data with post-processing base stations from another

manufacturer, several studies conducted during 1991-94 indicated that

some manufacturers do not always adhere to this format. 

Another information-sharing problem stemmed from differences in

agency operating procedures.  For functions like mapping and

surveying, during which positioning data are collected and stored for

later use, agencies establish specific time intervals at which the

base station will collect signals from the global positioning

satellites.  However, these intervals may vary within and between

agencies, meaning that positioning data collected and stored to

support one application may not support another agency's application. 

Also, the hours when equipment was available and operating varied. 

For example, some BLM offices operated their base stations 12 hours a

day, 3 days a week, while others operated 12 to 24 hours a day, 5 or

7 days a week.  The St.  Lawrence Seaway Development Corporation

operated its equipment only for short periods of time when the agency

was positioning buoys.  Finally, the length of time an agency will

archive the positioning data ranged from about 2 weeks to

permanently.  Officials with three agencies said they were reluctant

to use DGPS data from other agencies unless they had assurance that

the data would be archived long enough to resolve questions that

might arise after a project was finished. 



---------------------------------------------------------- Letter :3.2

Many agency officials said they were unaware of what other agencies

were doing and did not know where to go to find out.  For some

agencies, this situation may not have changed.  For example, during

our review we spoke with an Environmental Protection Agency (EPA)

official in Chicago who wanted to implement DGPS for his region.  The

official was unaware that the Coast Guard had a base station in

Milwaukee, about 90 miles away, and was planning to put in additional

base stations on the Mississippi River that could serve his region. 

After we informed him about the Coast Guard's equipment, he said he

planned to investigate its possible use. 

Some attempts at providing information had been made, but they were

split between several sources, and the information available was

largely incomplete: 

  In 1992, the Federal Geographic Data Committee, an interagency body

     responsible for coordinating all mapping and surveying activity,

     established a subcommittee that maintained a list of federal,

     state, and private-sector DGPS base stations, but the list was


  In 1989, the Coast Guard established a committee to provide a forum

     for public- and private-sector users to exchange technical

     information about the global positioning system, but the

     committee did not maintain data on the location and

     characteristics of federal DGPS facilities or capabilities. 

     Since 1990, the Coast Guard has also operated a center that

     provides information on the status and operational condition of

     the global positioning system satellites and other related

     navigation systems, but this center does not provide information

     about federal DGPS facilities. 



---------------------------------------------------------- Letter :3.3

Agencies with systems already under way had little incentive to share

information about their systems with other agencies.  Several agency

officials said coordinating DGPS activities with other agencies

requires additional work and expense and can delay the development

and implementation of an individual agency's DGPS applications. 

Agencies also indicated that, besides the initial development's being

affected, the ongoing operation of the system could also be adversely

affected because of the additional drain on resources.  For example,

a Forest Service official said his office lacked the staff to provide

technical assistance and support to agencies unfamiliar with DGPS

applications.  As a result, his office stopped sharing DGPS data

unless the other agency agreed to share data in return.  A BLM

headquarters official said that because equipment is often not

designed for multiagency use, agency personnel in the field are

reluctant to spend the additional time and resources needed to make

DGPS equipment or data available to other agencies. 

Lacking any governmentwide requirements or policies on how they

should develop their DGPS applications, agencies established their

own polices and procedures for operating the equipment and sharing

the data with other agencies.  The differences in procedures

sometimes extended to individual offices within an agency.  For

example, a Forest Service office in one region of the country has an

interagency agreement with a nearby BLM office to share DGPS data,

while Forest Service offices in other regions restricted access to

DGPS data in order to safeguard the integrity of other sensitive

information stored on the same computer system.  Several EPA regions

established an ad hoc committee to coordinate the development and

implementation of DGPS because they had not received any guidance

from their headquarters office. 




------------------------------------------------------------ Letter :4

Several agency officials and DGPS experts we contacted\3

noted that the development of additional DGPSs or purchase of

additional DGPS equipment by federal agencies was increasing the

potential for overlap and duplication and that some had already

occurred.  For example, the Forest Service and BLM installed 11 base

stations in Arizona and New Mexico--6 for the Forest Service, 5 for

BLM, and according to agency officials, both agencies basically use

the same positioning data for mapping and natural resource inventory

applications and have the same type of DGPS equipment.  DGPS experts

said that to meet positioning requirements for resource management

applications, only one or two DGPS base stations are needed within

most states.  Forest Service and BLM officials agreed that some of

their base stations overlap and duplicate one another, yet BLM is

planning to install four more in these two states because of

difficulties in obtaining ready access to the Forest Service's DGPS


In 1993, anticipating the expected future growth in DGPS, some

federal agencies took steps to facilitate greater joint development

of DGPS capabilities.  These steps fell into two categories: 

modifying DGPSs to accommodate the needs of other agencies, and

examining issues related to greater interagency coordination of DGPS



\3 We discussed DGPS developments with industry and federal agency

officials with technical knowledge of DGPS and/or responsibilities

for designing and implementing DGPS programs.  See app.  II for a

list of the officials contacted. 



---------------------------------------------------------- Letter :4.1

We identified three instances in which agencies had modified or were

modifying their DGPS equipment or systems to accommodate joint use. 

  To accommodate NOAA's mapping and surveying requirements, the Coast

     Guard acquired dual-frequency base stations instead of

     single-frequency ones.  NOAA contacted the Coast Guard because

     it did not have the resources to set up its own system. 

     However, NOAA's surveying and mapping needs required

     dual-frequency equipment in order to provide greater accuracy

     than the Coast Guard's planned single-frequency equipment would

     provide.  Such equipment was more expensive than what the Coast

     Guard initially planned to buy and had funds to pay for.  When

     the equipment dropped in price, however, the Coast Guard was

     able to obtain the more sophisticated equipment within the

     amount originally budgeted for the system.  In return for the

     Coast Guard upgrading its DGPS base station equipment, NOAA has

     agreed to perform the geodetic surveying needed to install the

     base station equipment. 

  The Office of Management and Budget (OMB) asked the Army Corps of

     Engineers, in lieu of developing a separate DGPS in the lower

     Mississippi River Valley, to determine whether the Coast Guard's

     system would meet its needs for surveying and mapping

     information for dredging, levee construction, and other related

     activities on the river.  Corps officials said they were

     reluctant at first to pursue a joint venture because of concerns

     that the Coast Guard's system, which was designed to meet

     navigational needs, would not provide data sufficiently accurate

     for dredging and hydrographic surveying purposes.  However,

     after testing an enhanced version of the Coast Guard's system,

     Corps officials found it could meet their needs.  In 1994, the

     Corps adapted its plans so that it could use the Coast Guard's

     system and expand it to cover inland waterways rather than build

     a separate system. 

  To accommodate a request by NOAA's National Geodetic Survey (NGS)

     for additional DGPS base stations for precise mapping and

     surveying, FAA modified its Wide Area Augmentation System for

aviation navigation.  Each FAA base station will be equipped

     with computer and telecommunications equipment to meet NGS'

     mapping and surveying needs as well as to provide the navigation

     information for which the system was initially designed.  FAA's

     modifications will also allow other agencies to use its system. 

Substantial dollar savings will result from these examples of joint

use.  A NOAA official anticipates that NOAA's use of the Coast Guard

and FAA systems will save about $10 million in equipment costs alone,

and perhaps millions in operating costs over the life of the project. 

The Corps of Engineers expects to save $25 million to $40 million

over 5 years by avoiding the need to spend money for equipment,

installation, operation, and maintenance of conventional microwave or

other systems for dredging and surveying.  Savings of this magnitude

are even more significant considering that the initial expense for

the Coast Guard's system being used by the Corps was $17.8 million. 

Corps and Coast Guard officials also believe using a common system

will enhance operational efficiencies and marine safety. 



---------------------------------------------------------- Letter :4.2

In early 1993, with both military and civil use of the global

positioning system growing, concerns were expressed about how best to

balance these competing needs while encouraging maximum civil use of

the system.  In May 1993, DOD and the Department of Transportation

(DOT) formed a task force to review these DGPS issues.\4 In a

December 1993 report, the task force concluded that continuing the

current ad hoc approach to DGPS development would likely result in

unnecessary duplication.  To resolve some of the barriers that impede

joint development and use, the task force made several

recommendations, including the following: 

  Reorganizing the civil federal global positioning system management

     structure established in the 1987 memorandum of agreement by (1)

     elevating DGPS decision-making within DOT to the assistant

     secretary level; (2) expanding the former DOT Navigation Council

     into a new Positioning/Navigation Executive Committee made up of

     representatives of DOT agencies; and (3) creating an interagency

     advisory council that would represent to the Executive Committee

     those agencies primarily interested in DGPS for nonnavigational

     purposes, such as surveying and mapping.  DOT has since begun to

     implement this structure. 

  Conducting an additional study to determine the feasibility of

     developing a nationally integrated augmented system providing

     DGPS services for aviation, marine, and land users.  This

     augmentation study, scheduled for completion in 1994, will

     examine existing and planned federal agencies' DGPS applications

     and determine the technical feasibility of developing common

     equipment standards and communication formats suitable for use

     by multiple DGPS users.  However, (as discussed below) the

     augmentation study will not address the organizational structure

     necessary to implement this system and ensure governmentwide

     coordination concerning DGPS. 


\4 In 1987, through a memorandum of agreement with DOD, DOT agreed to

serve as the primary interface within the U.S.  government for all

civil global positioning system matters.  Within DOT, requirements

for transportation were coordinated through the DOT Navigation

Council.  Input from non-DOT agencies and other civil users of the

global positioning system was provided to the Navigation Council

through a separate committee sponsored jointly by the Coast Guard and

DOT's Research and Special Programs Administration. 





------------------------------------------------------------ Letter :5

The growth in government-sponsored DGPS applications is expected to

continue.  The budgetary implications involved in designing new

systems, acquiring equipment, and administering DGPS applications

over time will increase the need to improve coordination in the years

to come.  However, it is doubtful that the management structure being

set in place as a result of the DOD-DOT task force's recommendations

will be adequate to achieve full governmentwide coordination of all

DGPS users. 




---------------------------------------------------------- Letter :5.1

The need for improved coordination can be seen in the anticipated

growth of DGPS.  In the near term, the federal investment for DGPS is

sizeable.  For example, FAA's Wide Area Augmentation System alone is

expected to cost about $500 million during 1995-2000, and the Coast

Guard plans to spend about $18 million for its DGPS network, most of

this in 1994-95.  These expenditures center on (1) an FAA network of

up to 33 base stations throughout the entire United States\5 and (2)

a Coast Guard system of 63 base stations along the coastal United

States and Mississippi River basin.  According to several experts we

contacted, once these systems are in place, the substantial

infrastructure of base stations could potentially meet the needs of

many federal and other DGPS users.  (See app.  I for a description of

the capabilities of these systems.)

The growth in federally owned or federally sponsored DGPS

applications is not expected to stop once the systems currently being

planned or implemented are in place.  Many of the nine agencies we

reviewed are planning other applications for the future, and other

agencies are likely to follow.  At least 15 other federal agencies

have identified future DGPS applications, according to an official

conducting the DGPS augmentation study.  Officials at most federal

agencies we contacted said that, because some key applications were

still undergoing research and development or operational testing,

they had not quantified planned expenditures for some future


The following examples from the nation's highway and rail

transportation systems as well as natural resource agencies'

applications illustrate some of the potential DGPS expansion in which

the federal government will likely be involved: 

  For highways, DGPS will play an increasing role in some key

     applications of the Intelligent Vehicle Highway System.\6

     Several demonstration projects are under way to test the

     feasibility of using DGPS for automatic vehicle location, in-car

     navigation, and commercial vehicle routing and scheduling.  For

     example, such private sector companies such as Southeastern

     Freight Lines and the J.B.  Hunt trucking company expect to use

     DGPS to improve vehicle tracking, scheduling, and maintenance,

     according to an American Trucking Association official.  The

     global positioning system industry projects the market for such

     applications to be about $2 billion to $5 billion by the year


  For rail systems, the Federal Railroad Administration expects that

     rail companies will be able to use DGPS to monitor the speed and

     location of trains and thereby increase the safety and

     efficiency of rail traffic routing.  Burlington Northern and

     Union Pacific railroads plan to test DGPS as part of a Positive

     Train Separation system to monitor the speed and location of


  The National Park Service, the U.S.  Fish and Wildlife Service, and

     other federal natural resource agencies plan greater use of DGPS

     for mapping and various natural resource inventory activities. 

     Use of DGPS is more reliable and much less expensive than

     traditional surveying methods, which typically require that

     survey crews spend days or weeks, often in remote areas, in

     order to inventory wetlands, timber stands, or other resources. 

     The prospect of real-time DGPS-assisted aerial photography will

     also provide efficiencies by lessening the need for ground-based

     personnel used to set out visual markers as reference points,

     according to a Forest Service official. 

Growth is also expected in state and local government activities that

receive federal support, such as highway construction and mass

transit applications.  For example, with funding from the Federal-Aid

Highway Trust Fund, the Tennessee and Kentucky departments of

transportation have installed base stations and other equipment to

produce highway maps for transportation planning.  Transit

authorities in Milwaukee and Denver have spent $8.3 million and $11

million, respectively, on DGPS-based vehicle location systems to

increase the safety and efficiency of transit bus fleet management. 

According to a Federal Transit Administration official, other transit

agencies around the country are considering installing similar bus

tracking systems, which are 80 percent federally funded.  Neither the

Federal Highway Administration nor the Federal Transit Administration

requires that such federally funded DGPS applications be coordinated

with other federal DGPS applications. 


\5 FAA also plans to have a network of base stations at up to 701

airports to provide greater accuracy needed for precision landings. 

The cost of this system, much of which will be borne by local

airports, is not part of the $500 million estimate for FAA's Wide

Area Augmentation System. 

\6 The Intelligent Vehicle Highway System involves the integration of

electronics, communications, computer and control systems into both

vehicles and highways and is designed to enhance transportation

mobility, energy efficiency, and environmental protection.  We

recently testified on the progress DOT has made on this system (Smart

Highways:  Challenges Facing DOT's Intelligent Vehicle Highway

Systems Program [GAO/T-RCED-94-253, June 29, 1994]). 




---------------------------------------------------------- Letter :5.2

While these developments underscore the desirability of greater

coordination, the mechanisms set in place as a result of the DOD-DOT

task force's recommendations are not sufficient to accomplish this

task.  If the augmentation study being conducted as a follow-up to

the task force's work finds that a common network of base stations

can be established for joint use, it is critical that an effective

mechanism be in place to coordinate subsequent development of DGPS

applications.  However, the current mechanism does not have authority

over many agencies that use DGPS. 

Full coordination of DGPS applications essentially requires

establishing a clear bridge between two categories of DGPS

users--those who use it for real-time navigation and those who use it

for post-processing applications such as surveying, mapping, and

related purposes.  Federal agencies in the first category are DOT

agencies such as FAA and the Coast Guard that, under the reorganized

management structure now being put in place, are coordinated through

DOT's Positioning/Navigation Executive Committee.  Federal agencies

in the second category are non-DOT agencies such as NOAA, the Forest

Service, and the U.S.  Geological Survey that are coordinated through

the Federal Geographic Data Committee, the separate group responsible

for interagency use of spatial data for surveying and mapping.  Thus

far in the development of DGPS applications, there has been progress

in establishing formal mechanisms for DGPS issues between these two

groups.  However, substantial efforts will be required to achieve

full governmentwide coordination. 

Each of these categories of user agencies has improved coordination

within its own group, but coordination between the two sets of

agencies has not significantly changed.  For example, after the

December 1993 report by the DOD-DOT task force, the Federal

Geographic Data Committee made its own proposal for a consolidated

DGPS network for mapping, surveying, and related uses.  Under the

proposal, any federal agency involved in surveying or mapping

applications of DGPS or any federally funded application related to

such applications would be required to use this network.  According

to a committee official, the committee withdrew the proposal when DOT

expressed concerns that creation of such a network would be premature

because the technical feasibility of creating a network that could be

used both for navigation and for surveying and mapping applications

was still being studied. 

In our view, the organizational structure that has been put in place

as a result of the task force's recommendations does not take both

user groups equally into account.  Under this structure, formulating

policy for all civil DGPS applications will rest with the DOT

Positioning/Navigation Executive Committee.  Linkage with the

surveying, mapping, and other applications of non-DOT agencies--such

as those coordinated through the Federal Geographic Data

Committee--is through a separate Interagency Advisory Council, which

is composed of representatives from non-DOT agencies and reports to

the Positioning/Navigation Executive Committee.  Thus, while non-DOT

agencies would have an opportunity to provide their views, decisions

would ultimately be made by a committee composed solely of DOT


It is understandable that the task force did not propose a

coordinating body that included non-DOT agencies because DOT has

never received executive or legislative branch authority to

coordinate non-DOT agencies' use of DGPS.  Although DOT has agreed

with DOD to serve as the point of contact for all civil applications

of the global positioning system, neither the administration nor the

Congress has expressly designated DOT as having authority over

potential DGPS applications of non-DOT agencies.  Thus, while the

Positioning/Navigation Executive Committee may be able to set policy

for DOT agencies on navigational uses of DGPS, its authority over

non-DOT agencies is open to question. 

The Positioning/Navigation Executive Committee has been attempting to

develop memorandums of agreement between DOT and non-DOT agencies as

a way of facilitating greater interagency development and use of

DGPS.  For example, the joint-use projects described above between

the Coast Guard and the Corps of Engineers and the National Geodetic

Survey were carried out under these memorandums.  According to DOT

officials, such memorandums have been helpful in structuring the

conditions and costs associated with interagency use of DGPS

equipment and information. 

Even if such agreements are established, however, such an

agency-by-agency approach does not ensure that federal agencies, or

others receiving federal funds for DGPS applications, would not buy

their own equipment instead of using the available equipment and

facilities.  For example, if the task force and DOT decisionmakers

conclude that a nationwide system of base stations could be used by

most or all federally owned and federally sponsored DGPS

applications, the Positioning/Navigation Executive Committee has no

authority to require non-DOT agencies to even study the possibility

of using the system for future applications. 

OMB appears to be the federal agency in the best position to resolve

this problem, since it is the executive branch agency responsible for

developing governmentwide coordinative mechanisms.  As such, OMB is

the logical choice to develop interagency policies to promote

interagency cooperation concerning joint DGPS development and use. 

In addition, OMB's budget review process offers another potential

opportunity to help ensure that all agencies examine the alternative

of using existing equipment and facilities before proceeding with an

agency-specific--and potentially duplicative--system.  This

coordination has already occurred to a limited extent.  At the nine

agencies we reviewed, one of the instances in which interagency

coordination has led to budgetary savings was prompted by questions

raised during budget review by OMB.  As discussed above, the Corps of

Engineers had initially intended to fund its own system, but OMB

recommended that the Corps investigate joint use of the Coast Guard's


Thus far, no specific requirement exists for agencies to take such

steps as a prerequisite to submitting budget proposals for new DGPS

applications or for funding DGPS applications by state or local

governments.  Our discussions with OMB personnel indicated that

although some budget examiners had raised issues about DGPS

applications in individual circumstances, the effort was not

uniformly enforced across the many federal agencies involved in

developing or funding DGPS applications.  Given that the existing

mechanisms for cooperation and coordination are voluntary in nature

for most federal agencies, a formal check of this kind may be an

appropriate way to ensure a cost-effective approach to DGPS.  It

would still allow agencies to develop agency-specific DGPS

applications, provided the unique requirements of such systems could

not be met by the existing federal DGPS infrastructure. 


------------------------------------------------------------ Letter :6

In the past, agencies have not coordinated their efforts to develop

DGPS, and this has led to some duplication of facilities and

equipment.  Since early 1993, coordination has improved, resulting in

significant cost savings.  However, these instances of coordination

were ad hoc efforts.  Growing evidence indicates that an

agency-by-agency approach to planning and installing DGPS

applications may continue to result in duplication and unnecessary

expense.  The work of the DOD-DOT task force represents the strongest

effort to date to develop a more coordinated, systematic approach to

managing the growing demands for DGPS.  We believe, however, that the

approach that has resulted for coordinating DGPSs and DGPS

applications across agency lines is insufficient.  It does not ensure

that all federal agencies will first look to jointly use the

substantial existing and planned infrastructure of DGPS equipment and

facilities before designing systems solely to meet their individual

needs.  Ongoing DOD-DOT efforts to address technical and equipment

compatibility issues do not address the issues of interagency

coordination.  Without governmentwide coordination and

accountability, agencies can still elect to go their own way, perhaps

spending money on facilities and equipment already available



------------------------------------------------------------ Letter :7

To help ensure the cost-effectiveness of future federal or federally

financed DGPS applications, we recommend that the Office of

Management and Budget take the lead in establishing a more

coordinated governmentwide approach to managing DGPS.  Such an

approach could take the form of establishing a coordinative mechanism

for all civil DGPS applications and giving it the authority to

establish policies, procedures, and standards needed to facilitate

joint development and use of DGPS technology.  It could also take the

form of requiring that any federal agencies proposals to (1) add DGPS

base stations in fiscal years 1998 and beyond or (2) participate in

federal financing of base stations to be acquired by state or local

government units demonstrate to the Office of Management and Budget

that acquiring the base stations and related equipment would be more

cost-effective than using base stations owned or operated by other

federal agencies.\7


\7 This requirement should not apply to DGPSs undergoing research and

development or operational testing. 


------------------------------------------------------------ Letter :8

As requested, we did not obtain official agency comments on a draft

of this report.  However, we did discuss the results of our review

with officials of DOD, DOT, the Corps of Engineers, BLM, Forest

Service, the U.S.  Geological Survey, NOAA, EPA, OMB, and the U.S. 

Industry Council for Global Positioning Systems.  Generally, DOT

officials (such as the Acting Director, Radionavigation and

Positioning Staff, Office of the Assistant Secretary for

Transportation Policy) agreed with our recommendations concerning the

need for a stronger mechanism to coordinate federal DGPS activities. 

They believed the structure proposed by the DOD-DOT task force could

bring about better coordination but acknowledged that the proposed

structure lacked authority over non-DOT agencies.  Officials at OMB

with oversight responsibility over transportation and natural

resource agencies agreed action by OMB was needed to develop a

stronger coordinative mechanism for federal DGPS activities.  They

indicated they were considering various options for how best to

coordinate these activities, including our recommendation regarding

future justification of DGPS budget requests.  Officials of all other

agencies reviewed--including the Chair, Federal Geodetic Control

Subcommittee, Federal Geographic Data Committee--agreed with our

conclusions and recommendations.  Where appropriate, we have

incorporated changes suggested by agency officials to clarify the


---------------------------------------------------------- Letter :8.1

We conducted our review between August 1993 and August 1994 and

performed the work in accordance with generally accepted government

auditing standards.  See app.  II for a discussion of our scope and


As arranged with your offices, unless you publicly announce its

contents earlier, we plan no further distribution of this report

until 30 days after the date of this letter.  At that time, we will

send copies of this report to the heads of pertinent federal

departments and agencies, industry representatives, and other

interested parties.  Copies will be available to others upon request. 

If you or your staff have any questions about our review, I can be

reached at (202) 512-2834.  Major contributors are listed in app. 


Kenneth M.  Mead

Director, Transportation and

 Telecommunication Issues


=========================================================== Appendix I

Nine of the 13 federal agencies contacted were designing,

implementing, or operating differential global positioning systems

(DGPS) for various applications.\1 These applications included

navigation, surveying/mapping, and other uses.  Table I.1 provides a

brief description of these activities. 

                Table I.1 Federal Agency DGPS



                     as of 3/  Planned\  Principal DGPS

Federal agency          31/94         b  application

-------------------  --------  --------  -------------------

Forest Service             26         0  Resource management

                                          activities, such

                                          as mapping and

                                          surveying property

                                          corners, roads,

                                          trails, and water


Federal Aviation            0       734  Aviation

 Administration                           navigation,

                                          including enroute

                                          flights, terminal

                                          activity, and

                                          precision and


                                          landing approaches

Environmental               4         1  Environmental

 Protection Agency                        monitoring, such

                                          as surveying and

                                          mapping landfills,

                                          wells, outfalls,

                                          and other


U.S. Coast Guard            8        55  Marine navigation,

                                          including harbor

                                          and harbor


Bureau of Land             16        11  Land management

 Management                               activities,


                                          surveying and

                                          mapping property

                                          corners, gathering

                                          geographic data,

                                          and suppressing


National Oceanic            3         2  Surveying and

 and Atmospheric                          mapping U.S.

 Administration                           continental waters

                                          and gathering

                                          spatial data for



Army Corps of              17        19  Dredging and buoy

 Engineers                                placement


U.S. Geological             2         0  Earthquake fault

 Survey                                   movement detection

St. Lawrence Seaway         1         0  Buoy placement




\a Includes only permanent DGPS base stations--that is, equipment and

facilities that are in one place for 6 months or longer. 

\b Fiscal years 1994-96. 

Among the 13 agencies contacted, the Federal Aviation


(FAA) and the Coast Guard are undertaking the largest DGPS networks. 

Their networks will not only provide DGPS coverage for air and marine

applications but also will be used by other agencies for surveying,

mapping, and other applications.  The FAA and Coast Guard DGPS

networks are briefly described below. 


\1 The remaining four federal agencies did not own or operate DGPS

base stations.  These agencies were the Federal Transit

Administration, the Federal Highway Administration, the Federal

Railroad Administration, and the Department of Defense (DOD). 

However, the Federal Transit Administration and the Federal Highway

Administration provide funding to state and local authorities, and

this funding may support DGPS base stations at the state or local

levels.  A DOD official said that DOD does not use DGPS technology

for military operations. 


--------------------------------------------------------- Appendix I:1

FAA's planned system consists of two main parts--a wide-area network

covering the entire country and a local-area DGPS to provide more

accurate positioning information needed for landings at major

airports.  By 1998, FAA plans to establish its Wide-Area Augmentation

System.  The system will augment the integrity, availability and

accuracy of the basic global positioning system signals so the

augmented system can be used as the primary means of navigation for

all phases of flight except those requiring higher accuracies (i.e.,

Category II/III precision approaches).  FAA estimates that equipment

needed for the wide-area system will cost about $500 million. 

The wide-area system will contain up to 33 base stations.  Each base

station will be composed of a primary unit and two backups to provide

a high degree of reliability through redundancy.  Base stations will

collect positioning data from global positioning system satellites

and communicate these data to up to six master control stations.  In

turn, the master control station will transmit the DGPS correctional

information to up to nine geostationary satellites for broadcasting. 

According to FAA officials, this system will provide horizonal

accuracies of about 3 meters and vertical accuracies of about 5

meters throughout the United States.  To provide continuous

navigational integrity, the system is designed to be available 99.999

percent of the time and provide notification of a bad signal within 6

seconds.  Each base station will also be able to provide DGPS data to

other federal users for post-processing applications such as

surveying and mapping. 

For its local-area system, FAA also plans to have up to 701\2

DGPS base stations to provide greater positioning accuracies for

Category I, II and III precision landings at airports

.  An FAA

official estimated that it would cost about $1 million for each of

these local area systems, but the cost of such equipment would be

financed by the local airport authority. 


\2 According to an FAA official, the total number of base stations

for the local-area DGPS at major airports could be considerably less

if national security policy permits the Wide Area Augmentation System

to generate navigation signals accurate enough to support Category I

precision approaches. 


--------------------------------------------------------- Appendix I:2

To provide electronic aids to navigation for maritime commerce in the

United States, the Coast Guard plans to install DGPS base stations at

49 sites along the coastal United States, the Great Lakes, Puerto

Rico, Alaska, and Hawaii.  Fourteen additional DGPS sites are planned

for the Mississippi and Ohio River valleys.  These additional base

stations will be jointly operated with the Army Corps of Engineers. 

(See fig.  II.I for DGPS coverage areas in the continental United

States).  The Coast Guard will also explore the possibility of

providing additional DGPS coverage for all inland waterways. 

   Figure II.1:  Location and

   Coverage Provided by Coast

   Guard and Army Corps of

   Engineer DGPS Base Stations

   (See figure in printed


   Note:  This map is based on

   Coast Guard data as of July

   1994.  Not included is DGPS

   coverage for Alaska, Hawaii,

   and Puerto Rico.

   (See figure in printed


The Coast Guard's DGPS network was designed to provide accuracies of

8 to 20 meters for harbor approach and harbor navigation.  However,

subsequent refinements have produced accuracies to 3 meters in

real-time, which can be used for river and harbor hydrographic

surveying.  Other Coast Guard uses of DGPS include positioning buoys

and aids to navigation and monitoring and controlling port traffic as

part of the Coast Guard's Vessel Traffic Services. 

Equipment at each Coast Guard DGPS site will include a dual frequency

receiver to record positioning information from global positioning

system satellites.  In turn, the base stations will broadcast

corrected signals via radiobeacons to marine users.  DGPS data will

also be stored on computers and made available to federal agencies or

the public for such post-processing applications as mapping and

surveying.\3 A second DGPS base station will be located at each site

and will monitor system accuracy and integrity via continuous

integrity checks.  A communication link between all stations will

allow remote monitoring by one West Coast and one East Coast regional

DGPS control station, which will be monitored 24 hours a day.  The

control stations will also automatically record and archive all DGPS

data as well as assess the system's ability to meet operational

performance requirements, detect system anomalies, and provide a

record of operational conditions at all stations.  The control

stations will also allow control of the DGPS system by the national

command authority in the event of a national emergency. 

Coast Guard DGPS equipment costs are estimated at $17.8 million. 

Operations and maintenance costs are estimated at $5 million

annually.  The DGPS network will have an expected useful life of 25



\3 In a May 1994 memorandum of agreement, the Coast Guard and the

Coast and Geodetic Survey, National Oceanic and Atmospheric

Administration, Department of Commerce agreed to cooperate in making

DGPS data available to federal and other DGPS users in formats

suitable for surveying and mapping.  Under the agreement, the

National Geodetic Survey would acquire and operate whatever computer

and communication equipment is needed to provide public access to the

DGPS data. 


========================================================== Appendix II

We reviewed both existing and planned DGPS equipment, facilities, and

operating policies and procedures with 13 federal agencies.  This

included six agencies within the Department of Transportation:  the

FAA, Federal Highway Administration, Federal Railroad Administration,

Federal Transit Administration, U.S.  Coast Guard, and St.  Lawrence

Seaway Development Corporation.  Other agencies reviewed included the

Bureau of Land Management, U.S.  Forest Service, U.S.  Geological

Survey, National Oceanic and Atmospheric Administration,

Environmental Protection Agency, Army Corps of Engineers, and

Department of Defense.  We selected these 13 agencies to obtain

diversity in the size and type of existing or planned navigation or

surveying/mapping DGPS applications. 

At each agency we interviewed officials responsible for designing and

implementing DGPS applications and obtained any documents, studies,

or reports related to existing or planned DGPS equipment, facilities,

or applications.  To identify existing and planned DGPS equipment and

facilities at field office locations, we contacted agency personnel

in selected regional offices of the Bureau of Land Management,

Environmental Protection Agency, Forest Service, U.S.  Geological

Survey, and Army Corps of Engineers. 

To determine efforts to coordinate federal DGPS applications, we

interviewed federal officials responsible for directing the

activities of the U.S.  Coast Guard's Global Positioning System

Information Center and the Civil Global Positioning System Service

Interface Committee.  We discussed DGPS coordination with the

Executive Secretariat of the Federal Geographic Data Committee; the

Chair of the Federal Geodetic Control Subcommittee; and the Chair of

the Fixed Reference Station Working Group, Geodetic Control

Subcommittee, Federal Geographic Data Committee.  We also discussed

federal agency DGPS activities with the Executive Secretary and the

Executive Director for Policy of the U.S.  Global Positioning System

Industry Council, and we met with Department of Transportation

representatives to the joint Department of Defense-Department of

Transportation Task Force.  We also attended the Institute of

Navigation's Satellite Division GPS-93 Conference and the 22nd

meeting of the Coast Guard Global Positioning System Civil Interface

Committee, both held in Salt Lake City, Utah, in September 1993. 

Finally, on the basis of our work at the above locations, we

developed a list of DGPS experts with whom we discussed federal

agency DGPS activities and additional steps that may be needed to

enhance joint development or sharing of federal DGPS facilities.  We

selected these experts on the basis of their knowledge, experience,

and familiarity with existing and planned federal agency DGPS systems

and applications. 

                          Table II.1

                List of DGPS Experts Contacted


organization        Name/title          DGPS expertise

------------------  ------------------  --------------------

Environmental       Brenda Groskinsky,  Responsible for

Protection Agency   Environmental       research and

                    Scientist           development for DGPS




Headquarters, U.S.  William A.          Responsible for

Army Corps of       Bergen,             coordinating Corps'

Engineers           Civil Engineer      surveying and

                                        mapping activities

U.S. Army Corp of   Sally Frodge,       Conducting a study

Engineers,          Geodesist           on the feasibility

Topographic                             of a national DGPS

Engineering Center                      network

Trimble             Dr. Peter Loomis,   Involved in DGPS

Navigation, Ltd.    Staff Scientist     research for 9 years

National Oceanic    William Strange,    Chairman, Fixed

and Atmospheric     Chief Geodesist     Reference Station

Administration                          Working Group,

                                        Federal Geodetic

                                        Control Subcommittee

FAA Mitre           Robert Loh,         Involved with

Corporation         Wide-Area DGPS      aviation GPS and

                    Program Manager     DGPS research for

                                        more than 11 years

FAA                 Joseph Dorfler,     Many years of

                    Satellite Program   experience with

                    Manager             aviation engineering

                                        and research

U.S. Coast Guard    Joseph W.           Involved in GPS

                    Spalding,           research for 8 years

                    Project Manager,

                    Research and

                    Development Center

U.S. Coast Guard    Cmdr. Doug Alsip,   Project manager for

                    Chief,              the Coast Guard's

                    Radionavigation     DGPS network

                    and Development


U.S. Geological     Larry Hothem,       Responsible for

Survey              GPS Research and    implementing GPS

                    Applications        technology into

                    Manager             agency earth science


U.S. Global         Mike Swiek,         Since 1991, the U.S.

Positioning System  Executive           Global Positioning

Industry Council    Secretary           System Industry

                                        Council has been

                    Ann Ciganer,        active in addressing

                    Executive           the regulatory,

                    Director, Policy    political, and

                    and Government      technical issues

                    Affairs Liaison,    facing the global

                    Trimble Navigation  positioning system


U.S. Forest         Anthony             Since 1988, has been

Service             Jasumback,          responsible for all

                    Global Positioning  Forest Service DGPS

                    System Program      test and evaluation

                    Leader, Missoula    activities

                    Technology and

                    Development Center



========================================================= Appendix III




Allen Li


Brian A.  Estes

Stanley G.  Stenersen

Ronald E.  Thompson

Randall B.  Williamson

Gary E.  Ziebarth