Report to the Chairman, Subcommittee

on Military Research and Development,

Committee on Armed Services,

House of Representatives

United States General Accounting Office

GAO

April 2001 LAND MINE

DETECTION

DOD's Research

Program Needs a

Comprehensive

Evaluation Strategy

GAO-01-239
Page i GAO-01-239 Land Mine Detection

Letter 1

Appendix I Scope And Methodology 21

Appendix II Land Mine Detection Mission Requirements 23

Appendix III Land Mine Detection Technologies 26

Bibliography 35

Tables

Table 1: Ten Candidate Technologies with Known Operational

Limitations 14

Table 2: Potentially Promising Technologies Funded by DOD 16

Table 3: Examples of Environmental Limitations and Uncertainties

Associated with Potentially Promising Technologies 17

Table 4: Criteria for Target and Operational Parameters 24

Table 5: Criteria for Environmental Parameters 25

Figures

Figure 1: Candidate Technologies for Land Mine Detection 13

Figure 2: Technologies for Land Mine Detection that Send

Electromagnetic Energy 27

Abbreviations

DARPA Defense Advanced Research Projects Agency

DOD Department of Defense

EM electromagnetic

FCS Future Combat Systems

GSTAMIDS Ground Stand-off Mine Detection System

HSTAMIDS Handheld Stand-off Mine Detection System

IR infrared

LIDAR Light Detection and Ranging

MURI Multidisciplinary University Research Initiative

NVESD Night Vision and Electronics Sensors Directorate

Contents
Page ii GAO-01-239 Land Mine Detection

SASO Stability and Support Operations

SPIE The International Society for Optical Engineering

TNA thermal neutron analysis
Page 1 GAO-01-239 Land Mine Detection

April 17, 2001

The Honorable Duncan Hunter

Chairman, Subcommittee on Military Research

 and Development

Committee on Armed Services

House of Representatives

Dear Mr. Chairman:

Recent U.S. military operations, such as those in the Balkans, have shown

that land mines continue to pose a significant threat to U.S. forces. U.S.

land mine detection capabilities are limited and largely unchanged since

the Second World War. A U.S. military that now uses million dollar cruise

missiles, tens of million dollar aircraft, and billions of dollar ships still

generally detects land mines with a metal detector and a probe. The

Department of Defense (DOD) has an extensive research program aimed

at developing new detectors to improve its capabilities.

Improving DOD’s land mine detection capability is a challenging

technological issue. Because of the threat that land mines pose to U.S.

armed forces, you requested that we assess the abilities of competing

technological options to address DOD’s mission needs for land mine

detection. Specifically, our objectives were to determine whether DOD

(1) employs an effective strategy for identifying and evaluating the most

promising land mine detection technologies and (2) is investing in the

most promising technologies to fully address mission needs.

To evaluate DOD’s strategy for identifying the most promising land mine

detection technologies, we reviewed regulations, policies, and procedures,

and interviewed DOD officials. To determine if DOD is investing in the

most promising technologies to fully address mission needs, we identified

prospective technological options by reviewing the literature connected

with land mine detection technologies, interviewing researchers from

universities and corporations and other federal agencies, and reviewing

proposals that had been submitted in response to DOD solicitations to

fund land mine detection research. We then developed and applied a

systematic framework to evaluate the prospects of these technological

options for meeting countermine mission needs to determine which were

the most promising. (See app. I for a detailed discussion of our scope and

methodology.)

United States General Accounting Office

Washington, DC 20548
Page 2 GAO-01-239 Land Mine Detection

DOD’s ability to make progress in substantially improving its land mine

detection capabilities may be limited because DOD lacks an effective

strategy for identifying and evaluating the most promising technologies.

While DOD maintains an extensive program of outreach to external

researchers and other nations’ military research organizations, it does not

use an effective methodology to evaluate all technological options to guide

its investment decisions. More specifically, DOD has not identified all

relevant mission needs to guide its research programs and does not

systematically evaluate the broad range of potential technologies that

could address those mission needs. In addition, its productive program of

basic research for addressing fundamental science-based questions is

threatened by a proposed curtailment of funding. Lastly, because DOD’s

testing plans do not require adequate testing of land mine detectors

currently in development, the extent of performance limitations in the

various operating conditions under which they are expected to be used

will not be fully understood.

Although DOD is investing in several technologies aimed toward

developing a better solution to the mine detection problem, it is not clear

that DOD has selected the most promising technologies. Because DOD has

not systematically assessed potential land mine detection technologies

against mission needs, we conducted our own assessment. Our evaluation

reveals that the technologies DOD is exploring are limited in their ability

to meet mission needs or are greatly uncertain in their potential

capabilities. We identified other technologies that might address DOD’s

needs, but because they are in immature states of development, there is

uncertainty about whether they are more promising than the approaches

that DOD is exploring. Further, because of all these uncertainties, it is also

not clear whether combining two or more technologies will allow DOD to

fully meet its mine detection needs.

To improve the Department’s ability to identify and pursue the most

promising technologies for land mine detection, we are recommending

that the Secretary of Defense direct the establishment of a comprehensive

research program to periodically evaluate all applicable land mine

detection technologies against a complete set of mission-based criteria,

such as target signatures, operational requirements and expected

environmental conditions, and provide a sustained level of basic research

to sufficiently address scientific uncertainties. We are also recommending

that the Secretary of Defense require the services to provide adequate test

conditions for systems in development that better reflect the operating

environment in which they will likely have to operate. DOD concurred and

elaborated on its current programs.

Results in Brief
Page 3 GAO-01-239 Land Mine Detection

Since the advent of modern warfare, the presence of mines and minefields

has hampered the freedom of movement of military forces. The origins of

mine warfare may be traced back to crude explosive devices used during

the Civil War. Since that time, the use of land mines has increased to a

point where there are now over 750 types of land mines, ranging in

sophistication from simple pressure-triggered explosives to more

sophisticated devices that use advanced sensors. It is estimated that there

are about 127 million land mines buried in 55 countries.

Land mines are considered to be a valuable military asset since, by

slowing, channeling, and possibly killing opponents, they multiply the

combat impact of defending forces. Their attractiveness to smaller military

and paramilitary organizations, such as those in the Third World, is further

enhanced because they do not require complex logistics support and are

readily available and inexpensive. Virtually every combatant can make

effective mines, and they will continue to be a viable weapon for the

future.

U.S. forces must be prepared to operate in a mined environment across the

spectrum of military operations, from peacetime activities to large-scale

combat operations. Detection is a key component of countermine efforts.

In combat operations, the countermine mission revolves around speed and

mobility. Mines hinder maneuver commanders’ ability to accomplish their

missions because unit commanders need to know where mines are located

so they can avoid or neutralize them. In peacekeeping operations, mines

are used against U.S. forces to slow or stop daily operations. This gives

insurgents a way to control traffic flow of defense forces and affect the

morale of both the military and civilian population.

Since World War II, the U.S. military’s primary land mine detection tool

has been the hand-held metal detector used in conjunction with a manual

probe. This method is slow, labor intensive, and dangerous because the

operator is in close proximity to the explosive. The Army has also recently

acquired a small number of vehicle-based metal detectors from South

Africa to be used in route clearing operations and to be issued to units, as

needed, on a contingency basis.

Metal detectors are also sensitive to trace metal elements and debris,

which are found in most soils. This limitation leads to a high level of false

alarms since operators often cannot distinguish between a metal fragment

and a mine. False alarms translate into increased workload and time

because each detection must be treated as if it were an explosive. The

wide use of mines with little to no metal content also presents a significant

Background
Page 4 GAO-01-239 Land Mine Detection

problem for metal detectors. For example, according to DOD intelligence

reports, about 75 percent of the land mines in Bosnia are low-metallic and

some former Yugoslav mines containing no metal were known to have

been manufactured. In fact, the Army has stated that the inability to

effectively detect low metal and non-metallic mines remains a major

operational deficiency for U.S. forces.

Given the limitations of the metal detector, DOD has been conducting

research and development since World War II to improve its land mine

detection capability. For example, during the 1940s the United States

began research to develop a detector capable of finding nonmetallic

mines. Since then, DOD has embarked on a number of unsuccessful efforts

to develop a nonmetallic detector and to field a vehicle-based land mine

detector. DOD now has new programs to develop a vehicle-based detector

and an improved hand-held detector. DOD expects to field these new

systems, both with nonmetallic capability, within the next 3 years.

Airborne detectors are also being developed by both the Army and the

Marine Corps for reconnaissance missions to locate minefields.

Countermine research and development, which includes land mine

detection, is funded by a number of DOD organizations and coordinated

through a newly established Unexploded Ordnance Center of Excellence.

The Army is designated as the lead agency for DOD’s countermine

research, with most of its detection research funding being managed by

the Night Vision and Electronic Sensors Directorate (NVESD) and the

Project Manager for Mines, Countermine and Demolitions. The Marine

Corps and the Navy are also supporting a limited number of land mine

detection research efforts. Additionally, the Defense Advanced Research

Projects Agency (DARPA) has been involved with a number of land mine

detection programs throughout the years.

In fiscal years 1998 through 2000, DOD funded over $360 million in

countermine-related research and development projects, of which

approximately $160 million was aimed specifically toward land mine

detection. DOD sponsored an additional $47 million in research during this

period for unexploded ordnance detection (which includes land mines) in

support of other DOD missions such as humanitarian demining and

environmental cleanup. Because of the basic nature of detection, these

other efforts indirectly supported the countermine mission. Overall, DOD

funding levels for countermine research have been sporadic over the

years. Major countermine research initiatives and fieldings of new

detectors have coincided with U.S. military actions, such as the Korean

War, the Vietnam War, Operation Desert Storm, and the recent
Page 5 GAO-01-239 Land Mine Detection

peacekeeping operations in the Balkans. Following each influx of

countermine research funding has been a corresponding lull in activity.

A countermine program assessment conducted for the Army in 1993

concluded that whereas mine developments have benefited from the

infusion of leap ahead technologies, countermine tools have been

essentially product improved counterparts of World War II ideas.

However, according to DOD, countermine development is a slow process

because of the technological challenges inherent to land mine detection.

Not only must a detector be able to find mines quickly and safely through

large variety of soils and at varying depths in battlefield conditions with

clutter and even countermeasures, but it must also be able to discriminate

between mines (which vary considerably in size, shape, and component

materials) and other buried objects.

DOD’s ability to develop meaningful land mine detection solutions is

limited by the absence of an effective strategy to guide its research and

development program. DOD maintains frequent contact with the external

research community to constantly learn about new detection approaches

and technologies. However, it has not developed a comprehensive set of

mission needs to guide its research programs and does not systematically

evaluate the broad range of potential technologies that could address

those mission needs. In addition, its resources for conducting critical basic

research for addressing fundamental science-based questions are

threatened. Lastly, because DOD’s testing plans do not require adequate

testing of land mine detectors in development, the extent of performance

limitations in the variety of operating conditions under which they are

expected to be used will not be fully understood.

DOD has not developed a comprehensive and specific set of mission-based

criteria that reflect the needs of U.S. forces, upon which to base its

investments in new technologies in land mine detection. Although DOD’s

overall acquisition process sets out a needs-based framework to conduct

research and development, DOD has not developed a complete statement

of needs at the early stages of research when technologies are first

investigated and selected. The process calls for an evolutionary definition

of needs, meaning that statements of needs start in very general terms and

become increasingly specific as programs mature. Early stages of research

are generated from and guided by general statements of needs

supplemented through collaboration between the combat users and the

research communities.

DOD Does Not

Employ An Effective

Strategy For

Identifying Promising

Land Mine Detection

Technologies

DOD Has Not Adequately

Specified Mission Needs to

Guide Its Research
Page 6 GAO-01-239 Land Mine Detection

In the case of land mine detection, the Army stated a general need of

having its forces be able to operate freely in a mined environment. This

need has received a broad definition, as “capabilities for rapid, remote or

standoff surveillance, reconnaissance, detection, and neutralization of

mines.” Further specification of the need is left to representatives of the

user community and researchers to determine. It is only with respect to

specific systems at later stages of the acquisition cycle that more

formalized and specific requirements were established to guide decisions

about further funding.

Although we found that a comprehesive set of specific measurable criteria

representing mission needs had not been developed, we did find some

specific criteria in use to guide research efforts, such as rates of advance

and standoff distances. However, a number of these criteria were

established by DOD to reflect incremental improvements over the current

capabilities of technologies rather than to reflect the optimal needs of

combat engineers. For example, the Army was using performance goals to

guide its forward looking mine detection sensors program. The objective

of this program was to investigate and develop mine detection

technologies to increase standoff and speed for route clearance missions

beyond current capabilities. Performance goals included developing a

system with a standoff of greater than 20 meters with a rate of advance of

20 kilometers per hour. However, these goals were primarily driven by the

capabilities and limitations of the systems being considered. According to

an Army researcher, they were based on what existing technologies could

achieve in a limited time period (3 years) and not on what the combat

engineers would ultimately need. During our assessment of technologies,

which is described in the next section of this report, we found that the

standoff desired by combat engineers was almost 50 meters for route

clearance missions with a rate of advance of 40 kilometers per hour.

One barrier to DOD’s developing a comprehensive set of mission needs is

large gaps in information about target signature characteristics and

environmental conditions. For example, significant information gaps exist

about the rate at which land mines leak explosive vapors and the

environmental pathways that the vapors take once they are released. Also,

knowledge gaps about soil characteristics in future battlefields limit

DOD’s ability to fully specify mission needs and knowledgeably select

among competing technologies. They also reduce the pace of

technological innovation by hampering researchers from predicting how

their devices will function. DOD is currently funding research to answer

several important questions in these areas. But, as discussed below,

continued DOD funding is threatened.
Page 7 GAO-01-239 Land Mine Detection

Just as DOD has failed to adequately specify countermine mission needs

for assessing promising technologies, we found that it had not

systematically assessed the strengths and the limitations of underlying

technologies to meet mission needs. DOD employs a number of

mechanisms to obtain ideas for promising land mine detection solutions.

These include attending and sponsoring technical conferences, arranging

informal system demonstrations, convening workshops, and publishing

formal solicitations for research proposals. However, DOD does not

systematically evaluate the merits of the wide variety of underlying

technologies against a comprehensive set of mission needs to identify the

most promising candidates for a focused and sustained research program.

Instead, it generally evaluates the merits of specific systems proposed by

developers against time-driven requirements of its research programs.

One way DOD identifies land mine detection ideas is through sponsoring

and attending international technical conferences on land mine detection

technologies. For example, it sponsors an annual conference on

unexploded ordnance detection and clearance, at which countermine

related detection is a major focus. Additionally, DOD research officials

have chaired mine detection conferences within annual sensing

technology symposia of the International Society for Optical Engineering

(SPIE) since 1995. The most recent SPIE conference on mine detection,

held in April 2000, included over 130 technical presentations by

researchers from DOD and other organizations worldwide. SPIE provides

DOD land mine research officials an opportunity to network with

researchers working in different areas of sensing technologies. DOD also

identifies new technologies through reviewing researchers’ ideas outside

of the formal solicitation process by occasionally allowing researchers to

demonstrate their ideas at DOD facilities. Technical workshops are

another mechanism used by DOD to identify new ideas. For example,

DOD’s Unexploded Ordnance Center of Excellence held a workshop, in

part, to identify new land mine detection technologies in 1998. This

workshop, largely attended by DOD staff and contractors, explored

technological approaches that were not receiving a lot of attention. The

report of the workshop pointed out several potential paths for future

investment for land mine detection.

Of all the mechanisms DOD uses to identify new technologies, issuing

announcements in the Commerce Business Daily is its principal means for

communicating its research needs to the outside research community and

receiving ideas and approaches to improve land mine detection

capabilities. In our interviews with non-government researchers, we found

that they use DOD’s announcements as their principal means for

DOD Does Not

Systematically Evaluate

Technological Options for

Land Mine Detection

Solutions
Page 8 GAO-01-239 Land Mine Detection

familiarizing themselves about DOD’s needs. In connection with our

efforts to identify candidate technologies for land mine detection, we

searched databases, such as the Commerce Business Daily, containing

DOD announcements. We found that the Army placed 20 of the 25

announcements we identified from 1997 through 2000. NVESD accounted

for 17 of the solicitations.

DOD did not perform a systematic evaluation of all the responses to its

announcements against a common set of mission-based criteria to

determine which were the most promising. Instead, we found that typically

responses that had a reasonable chance of meeting time-constrained

program milestones were more likely to receive funding. This thrust is

indicated by the following statement from a recent report of the DOD

Center of Excellence:

Countermine research and development detection funding is concentrated on four primary

technologies...There has been increasing emphasis on radar and active electromagnetics as

the technologies showing the greatest short term promise for the reliable detection of

land mines (emphasis added).1

At NVESD, which has the largest share of countermine detection research,

programs are generally time-limited. As a result, evaluations of proposals

are largely based on the maturity of the idea. An example is the Future

Combat Systems (FCS) Mine Detection and Neutralization program, which

is funded at about $21 million over 3 years. This program is designed to

have a system ready for testing by fiscal year 2002, only 3 years after the

program started. This pace is necessary to meet the Army’s overall goals

for fielding FCS. NVESD officials told us that this time constraint means

they are more apt to fund the more mature ideas. This time constraint

could therefore result in not selecting potentially promising technologies

that might involve more risk. Although NVESD officials stated that they

are receptive to less developed ideas that show promise, the requirements

of the program may make this difficult to do.

We found that DOD did not supplement its frequent announcements with

periodic reviews of the underlying technologies that the responses were

 1

Joint Unexploded Ordnance Coordination Office, UXO Center of Excellence Annual

Report for 1999, Apr. 2000, p. 17.
Page 9 GAO-01-239 Land Mine Detection

based on.2 Such a review would evaluate their future prospects and could

suggest a long-term sustained research program in a technological area

that required several thrusts, whereas the individual project proposals

might appear to have doubtful value in themselves. Along a similar vein, in

1998 a Defense Science Board task force that evaluated DOD’s efforts in a

closely related area of research and development also recommended a

two-track approach for research and development.3

 The Board found that,

“there has been too little attention given to some techniques which may

provide capabilities important for particular sites” and recommended that

DOD institute a program parallel to the “baseline” program that “would

involve an aggressive research and development effort ... to explore some

avenues which have received too little attention in the past.”

Numerous questions about the physics-based capabilities of the various

detection technologies make it difficult, if not impossible, to evaluate them

against mission needs at the present time. Although DOD has invested

funds in basic research to address some of its questions, its efforts are

expected to end after fiscal year 2001. In addition to providing support to

technology evaluations, a sustained basic research program is needed to

support DOD’s ongoing efforts to develop better systems.

Independent evaluations, as well as our assessment of candidate land mine

detection technologies, which is presented in the next section of this

report, have revealed many uncertainties about the strengths and

limitations of each of the applicable technologies with respect to

addressing countermine mission needs. In addition, DOD has noted a

number of fundamental science-based questions regarding detection

technologies. For example, 3 years ago the Center of Excellence, through

a series of workshops, identified 81 broad research needs critical to

improving detection capabilities. Examples of research needs included an

improved understanding of the impact of environmental conditions on

many of the technologies examined and better characterization of clutter,

which contributes to the problem of false alarms currently plaguing a

 2

The Defense Threat Reduction Agency recently presented a limited assessment of

alternative landmine detection technologies in its recent review of militarily critical

technologies. This assessment reviewed the strengths and limitations of the principal

technologies in terms of broad militarily relevant needs (e.g. speed and effectiveness).

3

Office of the Under Secretary of Defense for Acquisition and Technology, Report of the

Defense Science Board Task Force on Unexploded Ordnance (UXO) Clearance, Active

Range UXO Clearance, and Explosive Ordnance Disposal Programs, April 1998.

DOD’s Productive Program

of Fundamental Research

is Threatened
Page 10 GAO-01-239 Land Mine Detection

number of technologies. Some of the needs have been addressed since the

workshops. For example, the Center sponsored follow-on workshops and

independent studies of radar and metal detectors to address research

questions specific to these technologies. However, DOD officials told us

that the broad set of needs has not been systematically addressed and that

many questions still remain. Also, over the past 3 years, DOD has invested

about $4 million annually in basic research directed at answering

fundamental science-based questions supporting land mine detection. This

work has been managed by the Army Research Office, with funding

provided by both the Army and DOD through its Multidisciplinary

University Research Initiative. However, this research program is expected

to end after fiscal year 2001.

According to DOD, this basic research has been valuable to its land mine

detection program. For example, the 1999 Center of Excellence annual

report states that the basic research program has improved physics-based

modeling so that it is now possible to examine realistic problems that

include soil interactions with buried targets.4

 The results of this modeling

have yielded insights into limitations of sensor performance in various

environments. The report concludes that this modeling work needs to be

continued and expanded to systematically study soil effects. In fact, the

report recommends continued investment in basic research to increase

understanding of phenomenology associated with detection technologies,

stating that the greatest value of basic research comes from a sustained

effort.

DOD’s policy is that systems be tested under those realistic conditions that

most stress them. According to DOD, this testing is to demonstrate that all

technical risk areas have been identified and reduced. However, because

of questions about the physics-based strengths and weaknesses of land

mine detection technologies, there is uncertainty about how well the

detectors currently in development will function in the various

environmental conditions expected in countermine operations. Some of

these questions could be answered through thorough developmental

testing. However, DOD’s testing plans do not adequately subject its

detectors to the multitude of conditions necessary to address these

performance uncertainties.

 4

UXO Center of Excellence Annual Report for 1999 (Joint Unexploded Ordnance

Coordination Office, April 5, 2000).

Land Mine Detectors Are

Not Subjected to Adequate

Testing to Reduce

Uncertainties
Page 11 GAO-01-239 Land Mine Detection

We reviewed the Army’s testing plans for two land mine detection systems

currently in development to determine whether the test protocols were

designed on a framework of identifying and minimizing technical risks

stemming from the uncertainties detailed above. These are the Handheld

Stand-off Mine Detection System (HSTAMIDS) hand-held detector and the

Ground Stand-off Mine Detection System (GSTAMIDS) vehicle-based

detector. We found that the testing plans were not designed around the

breadth of environmental conditions expected for those systems or around

anticipated limitations and uncertainties. Rather, testing is to be

conducted at only a limited number of locations and under ambient

climatic conditions. As such, knowledge about the performance of these

detectors in the variety of soil types and weather conditions expected in

worldwide military operations is likely to be limited.

For example, the performance of ground penetrating radar, a primary

sensor in both the HSTAMIDS and the GSTAMIDS, is questionable in

saturated soils, such as what might occur after a heavy rain. However,

neither the HSTAMIDS nor GSTAMIDS testing plans specifically call for

testing in wet conditions. The only way this condition would be tested is if

there is heavy rain on or just before the days that testing is to occur. As

such, knowledge about the performance of these detectors in a variety of

conditions is likely to be limited.

Incomplete knowledge of the properties of candidate land mine detection

technologies makes it difficult to assess whether DOD is investing in the

most promising technologies to address countermine detection missions.

Because DOD had not performed a systematic assessment of potentially

applicable technologies against military countermine mission needs, we

performed our own evaluation. Through a broad and systematic review of

technological candidates, we identified nine technologies with potential

applicability, five of which DOD is currently exploring. However,

insufficient information about these nine technologies prevented us from

definitively concluding that any could address any of the missions.

Additionally, because of these uncertainties, we could not conclude

whether a “sensor fusion” approach involving a combination of two or

more of the technologies would yield an adequate solution.

We conducted a broad search for potential technological candidates for

solutions to the countermine problem, and then evaluated the candidates

against a set of mission-based criteria to determine which candidates were

promising for further research. A more detailed description of our

methodology is presented in appendix I. For criteria, we identified

It is Uncertain

Whether DOD is

Investing in the Most

Promising

Technologies For

Land Mine Detection
Page 12 GAO-01-239 Land Mine Detection

operational needs for each of five different types of critical countermine

missions: (1) breaching, (2) route clearance, (3) area clearance, (4) tactical

reconnaissance, and (5) reconnaissance supporting stability and support

operations during peacetime.5

 A more detailed description of these

missions is presented in appendix II.

We then developed a set of technical criteria to specifically define

detection requirements for each mission. The criteria we developed were

based on target parameters, operational parameters,and environmental

parameters. Target parameters describe the physical characteristics of

land mines and the methods by which they are emplaced. These include

such characteristics as land mine sizes and shapes, metallic content,

explosive content, burial depths and the length of time mines have been

buried. Operational parameters describe the operational needs of the

military as they relate to countermine operations involving mine detection.

These factors include speed of advance, detection distance from the mine

(called stand-off),and the level of precision in identifying the exact

position of hidden mines. Target and operational parameters can vary

among the five types of missions. Environmental parameters, unlike target

and operational parameters, do not vary based on the type of mission.

Rather environmental parameters are site-specific. They are natural and

man-made conditions in and around the battlefield that affect mine

detection. These parameters cover a wide array of atmospheric, surface,

and sub-surface environmental conditions, such as air temperature, dust

or fog obscuration, surface snow, varying soil types and post-blast

explosive residue. A more detailed description of the criteria used in our

evaluation is presented in appendix II.

Our search yielded 19 technological candidates, which span a wide variety

of different physical principles6

 and are shown in figure 1.

 5

Stability and Support Operations (SASO), previously known as operations other than war,

involve the use of military capabilities for any purpose other than war and include such

actions as humanitarian assistance, peacekeeping operations, and support to counterdrug

operations.

6

This list of 19 reflects our pooling of similar approaches. Given the large number of similar

projects in the landmine detection field, we found it necessary to combine similar

technologies. For example, we identified a single acoustic or seismic approach after

evaluating four different technologies and concluding that one of them most closely

addressed the evaluation criteria.
Page 13 GAO-01-239 Land Mine Detection

Figure 1: Candidate Technologies for Land Mine Detection

Note: “EM” is an abbreviation for “electromagnetic”.

Source: GAO analysis.

As shown in figure 1, the majority (15) of the technologies use energy from

the electromagnetic (EM) spectrum, either to detect emissions from the

mine or to project energy at the mine and detect a reflection. The energies

used in these technologies span the entire EM spectrum, from radio waves

(characterized by long wavelengths/low frequencies) to gamma rays (short

wavelengths/high frequencies). Of the remaining four technologies not

directly utilizing EM energy, two (biosensors and trace vapor detectors)

operate by using a chemical or biological reaction to detect explosive

vapor that is emitted from mines into the surrounding soil or the air

directly above the ground. Another one is based on sending neutrons

toward the target. The last technology works by sending acoustic or

seismic energy toward a target and receiving an acoustic or seismic

1. EM signatures

2. Infrared

3. Passive millimeter wave

4. Passive microwave

1. Conductivity/resistivity

2. Electromagnetic induction

3. Electromagnetic radiography

4. Gamma ray imaging

5. LIDAR

6. Microwave enhanced IR

7. Quadrupole resonance

8. Radar

9. Terahertz imaging

10. X-ray backscatter

11. X-ray fluorescence

1. Acoustic/seismic

2. Biosensors

3. Neutron activation analysis

4. Trace vapor

Nineteen Technologies Nineteen Technologies

Technologies that exploit 

properties of the EM spectrum

Technologies that exploit 

properties of the EM spectrum Other Technologies Other Technologies

Passive EM Passive EM Technologies that 

send EM energy

Technologies that 

send EM energy
Page 14 GAO-01-239 Land Mine Detection

reflection. A more detailed discussion of these 19 technologies is included

in appendix III.

When we evaluated the 19 technologies against the operational

parameters, we found that 10 had one or more physics-based limitations

that would prevent them from achieving any of the five countermine

missions by themselves (see table 1).7

 As can be seen from table 1,

standoff and speed are the most challenging attributes of a detection

system that would meet DOD’s countermine mission needs. Nine

technologies failed to meet the standoff criterion, and four failed to meet

the speed criterion for any of the five missions.

Table 1: Ten Candidate Technologies with Known Operational Limitations

Technology

Known Target and Operational

Limitations

Conductivity/resistivity Standoff, speed

Metal detectors Standoff

Neutron activation analysis Standoff, speed

Gamma ray imaging Standoff, speed

X-ray backscatter Standoff, depth

Quadrupole resonance Standoff

EM signatures Standoff, mine types

Passive microwave Standoff, speed

Trace vapor Standoff

Microwave enhanced infrared Mine types

Source: GAO analysis.

We judged that the remaining nine technologies were “potentially

promising” because we did not conclusively identify any definitive

operational limitations to preclude their use in one or more countermine

missions.8

 For all of these nine technologies, our ability to determine their

operational capabilities was reduced by significant uncertainty as to their

capabilities. Some, such as ground penetrating radar and acoustic

technologies, have been studied for many years. Yet continuing

improvements to the sensors and the critical mathematical equations that

interpret the raw data coming from the sensors made it difficult for us to

 7

DOD is currently contracting with researchers in 6 of these 10 technologies.

8

Moreover, seven of the nine technologies had no physics-based limitation for any of the

five countermine missions.
Page 15 GAO-01-239 Land Mine Detection

predict the absolute limits of their capabilities. Our inability to draw a

conclusion about these technologies is supported by reports from the

Institute for Defense Analyses and other organizations that have found

similar uncertainty about their prospects. The critical issue for radar is

whether it will ever be capable of doing a good enough job discriminating

between targets and natural clutter to allow an acceptable rate of advance.

The issue of clutter is the fundamental problem for many sensor

approaches.

Our uncertainty about three technologies, terahertz imaging, x-ray

fluorescence and electromagnetic radiography was different because their

capabilities were not as well-studied. As a result, there was not enough

information for us to determine whether they could meet mission-based

criteria. In addition, DOD officials told us that they believe that two of

them (terahertz imaging and x-ray fluorescence) have fundamental

limitations that rule them out for countermine missions. They claimed that

terahertz energy is unable to penetrate deep enough through the soil and

that x-ray fluorescence has inadequate standoff. However, we were not

able to resolve these issues.

We believe that the lack of consensus about the capabilities of most of the

nine technologies is due, in part, to a basic lack of knowledge about the

upper limits of their capabilities. The only way to determine whether these

technologies can be employed in a detector that meets countermine

mission needs is through a systematic research program.

DOD is currently investing in five of the nine technologies (see table 2),

and it recently stopped funding a project in one of them (passive

millimeter wave).
Page 16 GAO-01-239 Land Mine Detection

Table 2: Potentially Promising Technologies Funded by DOD

Technology DOD Funded

Acoustic/seismic Yes

Biosensors Yes

Infrared, multi/hyperspectral Yes

LIDAR Yes

Radar Yes

Electromagnetic radiography No

Passive millimeter wave No

Terahertz imaging No

X-ray fluorescence No

Source: GAO analysis.

In our review of the ability of the nine technologies to operate in different

environmental conditions, we could not, with certainty, identify absolute

limitations on the ability of four to operate in expected environmental

conditions. However, all nine have uncertainties about the range of

environmental conditions in which they can adequately perform. The most

significant uncertainties relate to performance in various surface and

subsurface conditions, such as water saturated soil and differing soil

types. In most cases, these uncertainties have not been adequately studied.

Examples of environmental limitations and uncertainties for the nine

technologies are presented in table 3.
Page 17 GAO-01-239 Land Mine Detection

Table 3: Examples of Environmental Limitations and Uncertainties Associated with

Potentially Promising Technologies

Technology Known Limitation Uncertainty

Acoustic/seismic Surface water Saturated soil

Biosensors None Soil types

Electromagnetic radiography None Vegetation

Infrared, multi/hyperspectral Snow cover Rough surfaces

LIDAR Precipitation Post-blast Residue

Passive millimeter wave None Snow Cover

Radar Saturated soil Vegetation

Terahertz imaging None Saturated Soil9

X-ray fluorescence Surface water Soil Types

Source: GAO analysis.

The uncertainties about the various detection technologies also prevented

us from determining if the technologies could be combined to meet

mission needs. While most of the 19 technologies cannot meet operational

and environmental mission needs, in theory a combination of different

sensors might solve the countermine problem. This type of arrangement,

known as sensor fusion, combines different approaches to compensate for

the limitations of them individually. Canada and the Army are developing

systems that use some form of sensor fusion. Canada’s Defense Research

Establishment in Suffield, Alberta, has produced a multisensor land mine

detector that employs thermal neutron activation (TNA), a type of neutron

activation analysis, as a confirmation detector in a system that also

employs a metal detector, infrared (IR), and ground penetrating radar to

scan for mines. The TNA sensor is used to confirm or reject suspect

targets that the three scanning sensors detect. The Army is developing a

detector (HSTAMIDS) that uses sensor fusion to take advantage of the

strengths of both metal detector and radar approaches. In this

configuration, the radar is used to improve the metal detector’s

performance with mines that employ small amounts of metal. However,

neither of these systems (Canada’s and the Army’s) will meet the

countermine mission needs stated previously because their component

sensors are limited. Any detection system utilizing sensor fusion would

somehow need to overcome limitations, such as standoff and speed, in

underlying technologies. As pointed out previously, the capability of the

 9

While we could not conclude that there any environmental limitations with terahertz

imaging, Army research officials told us that they believe that saturated soil is a limitation,

rather than an uncertainty for this technology.
Page 18 GAO-01-239 Land Mine Detection

identified technologies to meet mission needs is uncertain. Another

consideration in developing a sensor fusion solution is that it would

require significant advances in signal processing.

It is unclear whether DOD’s research investments are in those

technologies that, either individually or in combination, have the greatest

chance of leading to solutions that address the U.S. military’s countermine

mission needs given the lack of knowledge about the strengths and the

limitations of the various detection technologies. DOD’s strategy of

working toward incrementally improving capabilities over current

detectors may result in improvements over current capabilities. However,

without a systematic and comprehensive evaluation of potential

technologies based on a complete set of mission-based needs, DOD does

not know if it has invested its funds wisely to address the needs of the

military.

DOD’s testing plans for its land mine detection systems in development do

not provide assurance that these systems will perform adequately under

most expected conditions. Demarcating the acceptable operating

conditions of a system is a critical part of research and development. This

is important not only for determining if developmental systems will meet

mission needs but also for defining the operational limitations so that

users can make informed decisions about their use. Therefore, systems

should be tested under those conditions that most stress them. Given the

numerous environmental and climatic conditions that can be expected to

affect the performance of any land mine detector, a robust program of

developmental testing is essential to fully understand the strengths and

limitations in performance under realistic conditions. Failing to test under

a plan specifically designed around the expected environmental and

climatic conditions of use as well as the anticipated limitations of the

technologies could increase the risk of fielding the system.

To improve the Department’s ability to identify and pursue the most

promising technologies for land mine detection, we recommend that the

Secretary of Defense (1) direct the establishment of a long-range research

program to periodically evaluate all applicable land mine detection

technologies against a complete set of mission-based criteria and (2)

provide a sustained level of basic research to sufficiently address scientific

uncertainties. Mission-based criteria could include target signatures,

operational requirements, and expected environmental conditions. We

also recommend that the Secretary of Defense require the services to

Conclusions

Recommendations

For Executive Action
Page 19 GAO-01-239 Land Mine Detection

provide adequate testing conditions for land mine detection systems in

development that better reflect the operating environment in which they

will likely have to operate.

DOD provided written comments on a draft of this report (see app. IV).

DOD concurred with each of our three recommendations and augmented

its concurrence with additional comments. DOD’s comments describe and

illustrate the lack of a focused and systematic approach underlying DOD’s

research programs for land mine detectors. It is not clear from DOD’s

response what, if any, measures it plans to take to implement our

recommendations.

In responding to our first recommendation, DOD states that the Army

pursues a systematic research, development, and acquisition program to

address land mine detection needs. However, we found that its approach

lacked elements critical to the success of this program, such as the use of

a comprehensive set of mission-based criteria and a systematic evaluation

of the capability of competing alternative technologies to address these

criteria. In fact, the Army Science Board study cited by DOD in its

comments to us also recommended that “operational needs and priorities

need to be clearly thought through and quantified.” There is nothing in

DOD’s comments that is directed toward bridging these gaps. Therefore,

we continue to believe that the changes that we have recommended are

required.

Regarding our second recommendation, DOD describes the benefits

provided by its current basic research program, but does not commit to

continuing funding for basic research for land mine detection after this

fiscal year. As we discuss in this report, we believe it is extremely

important for DOD to continue with a sustained program of basic research

to support its land mine detection program given the extent of the

uncertainties surrounding the various technologies. This point was also

made by the Army Science Board panel.

In response to our third recommendation, DOD states that the testing

plans we reviewed were not detailed enough to allow us to reach our

conclusions, and it describes certain activities that it is engaged in to

incorporate realistic environmental conditions into its testing programs

for HSTAMIDS and GSTAMIDS. However, we believe that the described

activities further illustrate the lack of a systematic strategy to guide testing

during product development. DOD acknowledged the threat to the

performance of metal detectors from soils that are rich in iron oxide and

Agency Comments

And Our Evaluation
Page 20 GAO-01-239 Land Mine Detection

pointed out that it is seeking to identify a “suitable site to test the

HSTAMIDS system in unique soil environments such as laterite.” We feel

that this is an important step in the development of this system. But we

believe that this step, along with tests in saturated soils and snowy

conditions, should have been taken much earlier, before a large

commitment had been made to this system. Testing programs should also

be driven by a systematic mission-based evaluation framework. Such an

approach should delineate at the earliest stages of development the

expected environmental operating conditions based on mission needs. An

analysis should then be made to identify for testing those conditions that

pose substantial challenges or uncertainties for detector performance.

Without such a framework, there is a risk that uncertainties about the

performance of these systems will remain after they have been fielded and

that significant testing will ostensibly be conducted by users rather than

by testers.

We are sending a copy of this report to the Honorable Mitchell E. Daniels,

Jr., Director, Office of Management and Budget; the Honorable Donald H.

Rumsfeld, Secretary of Defense; the Honorable Joseph W. Westphal,

Acting Secretary of the Army; the Honorable Robert B. Pirie, Jr., Acting

Secretary of the Navy; General James L. Jones, Commandant of the Marine

Corps; and other interested congressional committees and parties. We will

also make copies available to others upon request.

Please contact me on (202) 512-2700 if you or your staff have any

questions concerning this report. Major contributors to this report were

Kwai-Cheung Chan, Dan Engelberg, Cary Russell, and John Oppenheim.

Sincerely yours,

Nancy Kingsbury

Managing Director, Applied Research and Methods
Appendix I: Scope And Methodology

Page 21 GAO-01-239 Land Mine Detection

To determine whether the Department of Defense (DOD) employs an

effective strategy for identifying the most promising land mine detection

technologies, we reviewed literature related to research program design

and met with experts in this area. We interviewed officials from the Army,

the Navy, the Marine Corps and the Defense Advanced Research Projects

Agency (DARPA) responsible for running land mine detection research

programs. We also reviewed DOD policy and doctrine related to this area

including the Defense Technology Area Plan, the Army Science and

Technology Master Plan, and Countermine Modernization Plans.

To determine whether DOD is investing in the most promising

technologies to fully address mission needs, we evaluated the set of

potential land mine detection technologies identified through a systematic

search against a set of criteria derived from mission needs. We first

designed a framework for evaluating potential technologies. This

framework assisted in identifying the most promising technologies and

research gaps for further investigation. Through our discussions with

DOD, we found out that such a framework had not previously been

created.

Because our framework was mission directed, we identified a set of

critical countermine missions that involve detecting land mines by

systematically interviewing Army and Marine Corps combat engineers to

determine how countermine activities fit into a variety of combat

scenarios and reviewing Army and Marine Corps doctrine that discuss

mine threats to U.S. forces and corresponding countermine tactics. Next,

through a review of documents and discussions with Army and Marine

Corps combat engineers, we identified technical criteria that define

detection requirements for each mission. Officials representing the two

organizations responsible for combat engineer requirements, the Army

Engineer School and the Marine Corps Combat Development Command,

reviewed and agreed with the set of criteria we developed. The critical

missions and the set of criteria we developed are discussed in appendix II.

We then identified conventional and alternative technologies that could

have value in terms of performing these land mine detection missions. We

distinguished between technologies and systems. “Technologies are

approaches by which principles of physics are exploited to achieve tasks.”

1

 1

Kerner, David, et al. Anti-Personnel Landmine (APL) Detection Technology Survey and

Assessment. Prepared for the Defense Threat Reduction Agency. DynMeridian. Alexandria,

VA. Mar. 1999, p. 21.

Appendix I: Scope And Methodology
Appendix I: Scope And Methodology

Page 22 GAO-01-239 Land Mine Detection

Systems are implementations of technologies. By developing a

methodology that was based on identifying and characterizing

technologies, rather than systems, we sought to go beyond the strengths

and limitations of current devices and thereby provide information on

which to base a future-oriented research program. We identified candidate

technologies in three ways: One way was to review literature on land mine

detection and interview researchers and other experts in the land mine

detection field.2

 Another way was to interview experts in related fields,

such as geophysics and civil engineering, that involve similar activities

(i.e., looking for hidden subsurface objects). In this, our goal was to find

out if those fields use any tools that have not been explored by DOD. The

final way was to review proposals that had been submitted to DOD in

response to recent solicitations for funding. The technologies we

identified are presented in appendix III.

We evaluated each of the identified technologies against the set of mission

criteria to determine which were promising for land mine detection. We

identified “potentially promising” technologies by eliminating those that

have limitations that would preclude their meeting mission goals. In

performing this evaluation, we attended conferences and workshops,

reviewed published and unpublished technical literature, interviewed

developers of land mine detection systems, and contracted with an expert

in the field of land mine detection technologies to review our conclusions.

We also obtained comments from technical experts from the Army.

Finally, we determined which of the “potentially promising” technologies

DOD was exploring by reviewing agency documents and interviewing

DOD officials.

We performed our work from November 1999 to February 2001 in

accordance with generally accepted government auditing standards.

 2

The primary sources of literature we reviewed are contained in the Bibliography.
Appendix II: Land Mine Detection Mission

Requirements

Page 23 GAO-01-239 Land Mine Detection

Using our methodology, we identified land mine detection requirements.

The five critical countermine missions that involve land mine detection are

(1) breaching, (2) route clearance, (3) area clearance, (4) tactical

reconnaissance, and (5) stability and support operations (SASO)

reconnaissance. Breaching is the rapid creation of safe paths through a

minefield to project combat forces to the other side. This mission is

usually conducted while the force is under enemy fire. Route clearance is

the detection and removal of mines along pre-existing roads and trails to

allow for the passage of logistics and support forces. Area clearance is the

detection and removal of mines in a designated area of operations to

permit use by military forces. Tactical reconnaissance is performed to

identify mine threats just prior to and throughout combat operations.

SASO reconnaissance is used to assist in making decisions about where to

locate forces and for planning area clearance operations. A principal

difference between tactical and SASO reconnaissance is the time required

for performing the mission. Because SASO reconnaissance involves

peacetime operations, the speed at which it is conducted is not as critical

as that for tactical reconnaissance.

We developed a set of technical criteria to specifically define detection

requirements for each mission and grouped the criteria into target

parameters, operational parameters, and environmental parameters.

Target parameters describe the physical characteristics of land mines and

the way they are emplaced. Given that there are over 750 types of land

mines available worldwide, the target characteristics vary considerably.

The parameters we identified are presented in table 4.

Operational parameters describe the operational needs of the military as

they relate to countermine operations involving mine detection. Our set of

operational parameters are also presented in table 4. One critical

operational criterion for a mine detector is speed of advance. For time

critical missions, like breaching and route clearance, a detector needs to

function effectively at the military forces’ operational speeds. The ability

of a detector to keep up with the required rate of advance is dependent on

two factors: its scanning speed (the time to search a given area for mines)

and its false alarm rate, which is based on the number of times a detector

indicates the presence of a mine where one does not exist. False alarms

reduce the rate of advance because combat forces must stop to confirm

whether an alarm is actually a mine.

Another key operational parameter is standoff, which is the distance a

mine detector (and its operator) can be from a mine and still be able to

detect it. The minimum standoff required is the lethal radius of a mine,

Appendix II: Land Mine Detection Mission

Requirements
Appendix II: Land Mine Detection Mission

Requirements

Page 24 GAO-01-239 Land Mine Detection

which is about 35 meters (for an antitank sized mine). This distance

requirement increases as speed increases to allow for reaction time once

an alarm is sounded. In cases of minefield reconnaissance performed by

airborne detectors, the standoff required is the minimum altitude

necessary to provide safety for the aircraft from enemy ground fire. One

final operational parameter is the ability of a detector to accurately locate

the position of a buried mine. This is important for reducing the time

necessary to remove or otherwise neutralize the mine and the safety risk

associated with manually probing the ground to find the exact mine

position.

Table 4: Criteria for Target and Operational Parameters

Parameters Criteria

Target parameters

Mine types Round/flat to long/thin in shape.

Two inches to 14 inches in diameter/length.

Metal, low-metal, and non-metal content.

Explosive content from 7 grams to 25 kilograms.

Variety of explosive types to include TNT, RDX,

Tetryl, PETN and Composition B.

Aged as well as recently buried mines Mines/minefields in place from hours to years.

Buried as well as surface mines From surface laid down to burial depths of 6

inches

Operational parameters

Rate of advance 40 kph or more for breaching and route

clearance. Speed requirement for other missions

varies considerably, but can be significantly

slower than 40 kph.

Standoff From 35 meters to almost 50 meters for groundbased detectors, 1,500 meters or more for

airborne detectors.

Precision of location of mine Identify position of buried mines to within 25

centimeters.

Other operational considerations Consideration of other limitations as such as

weight, power requirements, and use of

radioactive source.

Source: GAO analysis.

The environmental parameters we identified are presented in table 5.

These are natural and man-made conditions in and around the battlefield

that affect mine detection and are grouped into atmospheric, surface,

subsurface, and other environmental conditions. While the target and

operational parameters can vary among the five mission types, the

environmental parameters are not mission-specific. Rather environmental

parameters are site-specific.
Appendix II: Land Mine Detection Mission

Requirements

Page 25 GAO-01-239 Land Mine Detection

Table 5: Criteria for Environmental Parameters

Condition Criteria

Atmospheric Conditions Air temperatures between –25 degrees F to 120 degrees F.

Sustained wind speeds up to 46 miles per hour (gusts up to 61

miles per hour).

Obscuration from fog, dust, sand, rain, or snow.

Surface Conditions Ice or snow cover.

Surface water from puddles to rivers and rice paddies.

Vegetation from short grass to broad leafy plants.

Rocky or uneven surfaces.

Subsurface Conditions Variety of soil types to include clay, sandy/loamy, volcanic as

well as man-made conditions such as road substrate.

Soil moisture content from dry/arid to saturated.

Existence of natural underground clutter such as rocks and

roots.

Other Conditions Time of day from high sun to complete darkness.

Presence of man-made clutter such as radio frequency

interference and post-blast explosive residue.

Source: GAO analysis.
Appendix III: Land Mine Detection

Technologies

Page 26 GAO-01-239 Land Mine Detection

In this appendix, we briefly describe the land mine detection technologies

and projects that we identified through our methodology. We grouped the

individual projects and lines of effort on the basis of their underlying

technological approach. Our grouping resulted in 19 distinct approaches.

These technologies vary in their maturity. Some, such as metal detectors

and radar, have been explored by many researchers for many years. Much

less is known about others such as electromagnetic radiography and

microwave enhanced infrared. Others, such as x-ray fluoresence, have

been used in other applications but have received relatively little attention

thus far in this application.

The technologies use different principles. Fifteen of the 19 technologies

are based on receiving electromagnetic (EM) energy from the target.1

Eleven of the 15 EM technologies are based on sending energy (in one

case energy in the form of neutrons) into the ground. The remaining four

EM technologies are “passive electromagnetic”; they are based on

receiving energy that is emitted by the land mine. These four technologies

are similar in principle; their relative strengths and limitations with respect

to addressing countermine missions arise from the different types of

energy that they receive. The final 4 of the 19 technologies are primarily

not electromagnetic. Two capture and analyze the explosive that the mine

releases into the ground or air, one is based on acoustic or seismic energy

reflected off of the target, and one is based on sending neutrons toward

the target.

 1

The four that do not operate by receiving electromagnetic energy are acoustic/seismic,

trace vapor, neutron activation analysis and biosensors. However, certain implementations

of acoustic/seismic can be designed to utilize electromagnetic energy.

Appendix III: Land Mine Detection

Technologies
Appendix III: Land Mine Detection

Technologies

Page 27 GAO-01-239 Land Mine Detection

Eleven technologies use electromagnetic energy and operate under three

different approaches (see fig. 2).

Figure 2: Technologies for Land Mine Detection that Send Electromagnetic Energy

Source: GAO analysis

Four operate by sending EM energy into the ground, reflecting off the

mine.

Five operate by sending EM energy into the ground, creating an effect on

the explosive substance. Whereas four of the five act on the explosive

within the mine casing, one relies on detecting released explosive

molecules.

Technologies That Are

Based on Sending

Electromagnetic

Energy

1. Conductivity/resistivity

2. Metal detectors

1. LIDAR

2. Radar

3. Terahertz imaging

4. X ray backscatter

1. Electromagnetic radiography

2. Gamma ray imaging

3. Microwave enhanced infrared

4. Quadrupole resonance

5. X-ray fluorescence

Those that reflect 

energy off the mine

Those that reflect 

energy off the mine Those that detect an 

electromagnetic field

Those that detect an 

electromagnetic field Those that react 

with the explosive

Those that react 

with the explosive

Technologies that send

electromagnetic energy

Technologies that send

electromagnetic energy
Appendix III: Land Mine Detection

Technologies

Page 28 GAO-01-239 Land Mine Detection

Two operate by detecting differences in the low frequency

electromagnetic field around the mine.

Four of the 11 active EM technologies (radar, terahertz imaging, LIDAR,

and x-ray backscatter) are based on projecting energy into the ground and

reflecting off the land mine. The presence of a mine or other buried object

is detected from differences in the electromagnetic properties of the target

and those of the surrounding ground. The relative strengths and

limitations of these technologies vary with their wavelengths. Managing

the trade-off between depth of penetration and resolution is one of the

central research concerns in this area. The choice of frequency is

important; lower frequencies allow better ground penetration but will

suffer from poor spatial resolution. Radar’s relatively long wavelength (it

operates in the microwave part of the electromagnetic spectrum) allows it

to penetrate the ground deeply enough to reach buried mines. This ability,

along with the fact that it can detect plastic mines, has made radar the

focus of much research and development in the United States and in other

nations. For example, DOD has incorporated radar into its hand-held

system, Handheld Stand-off Mine Detection System (HSTAMIDS).

However, whether a system based on radar will meet countermine mission

needs remains in dispute. The poor spatial resolution of radar, which

makes it difficult at best to distinguish between buried mines and other

objects of a similar size and shape, is the largest obstacle. Another issue is

its inability to penetrate soils that are saturated with water.

The other technologies have greater resolution but have a corresponding

loss of depth penetration. Because LIDAR has a shorter wavelength than

radar, it has a limited ability to detect buried mines. X-ray backscatter can

provide detailed images of shallowly buried mines due to the extremely

short wavelength of the x-rays. It operates by detecting the difference in

the atomic number between the ground and the mine target. However, the

applicability of this technology is limited due to the limited penetration of

the x-rays into the ground. In theory, terahertz imaging should have a

similar limitation. However, a researcher studying the feasibility of

creating images of mines in the terahertz part of the spectrum told us that

Technologies That Reflect

Energy Off the Mine
Appendix III: Land Mine Detection

Technologies

Page 29 GAO-01-239 Land Mine Detection

his system might be able to penetrate more deeply by increasing the power

of the energy.2

Another general approach involves projecting energy into the ground that

reacts with the molecules of the explosive, which send a signal that is

received by the detector. Because it reacts with the explosive, rather than

the container, the approach has the advantage of more specifically

targeting land mines and being less prone to the clutter problem that

hinders other active electromagnetic approaches. However, technologies

that adopt this approach tend to be more complex and expensive.

We identified five distinct technologies that have been advanced that

utilize this general approach. One of them, quadrupole resonance, is a

relatively mature technology in land mine applications and systems have

been built around it. Less is known about the other four technologies and

how to apply them to detect land mines and what their capabilities are for

addressing countermine missions. These four are electromagnetic

radiography, microwave enhanced infrared, x-ray fluorescence, and

gamma ray imaging. Therefore, our assessments are less complete for

these than for the other more well-studied approaches.

• Quadrupole resonance has been explored for identifying explosives for

several years. Much of the basic research was conducted at the Naval

Research Laboratory. Quadrupole resonance detectors are also being

developed to screen for explosives at airports. In quadrupole resonance, a

pulse of long wavelength energy causes the nitrogen nuclei in the

explosives to emit a pulse of energy that is characteristic of the molecule.

For example, the nitrogen atoms in TNT emit a unique pulse that can be

picked up by the detector. One limitation of quadrupole resonance with

respect to countermine missions is that the detector head must be close to

the target. The speed at which quadrupole resonance can operate is in

question. Current systems are fairly slow. In addition, research questions

currently exist in several areas, including how to overcome interference

from other sources of energy and how to configure a quadrupole

resonance detector to detect TNT. Despite these limitations and questions,

DOD is developing systems that use this technology. The Marine Corps is

 2

Terahertz, or 10-12 is at the long wavelength end of the infrared part of the spectrum. A

concern with compensating in this way, however, is that the amount of energy reflected off

of the surface of the ground also increases dramatically.

Technologies that create a

detectable reaction with

the explosive
Appendix III: Land Mine Detection

Technologies

Page 30 GAO-01-239 Land Mine Detection

developing a hand-held device that uses quadrupole resonance and the

Army is developing a land mine detection vehicle that would use an array

of quadrupole resonance detectors across the front to confirm targets

presented by sensors that use either radar or metal detector.

In conversations with individual systems developers, we identified four

other examples of this land mine detection approach. The first two

technologies are based on scanning the ground with long wavelength

microwaves. This energy excites the explosive molecules that emit a signal

that is detected. The other two technologies using this approach send

shorter wavelength energy toward the target.

• Electromagnetic radiography operates by scanning the ground with long

wavelength microwaves. According to one developer, when it is struck by

this energy; the target radiates back in a particular way; exciting molecules

at atomic levels. The molecules respond with spin effects that produce “a

spectrographic signature of the target substance.” As noted previously,

very little is known at the present time about what the limits are of this

technology in terms of the operational requirements and environmental

conditions for countermine applications.

• Microwave enhanced infrared detection operates by sending long

wavelength microwaves into the ground and then detecting a “unique

thermal signature and infrared spectra of chemical explosives.” One

limitation with this approach is it cannot be used to detect metallic mines

because the microwave energy cannot penetrate metal. In addition, the

speed at which it can operate and the standoff distance are both highly

uncertain.

• The third technology illuminates the ground with x-rays that causes a

series of changes in the electron configuration of the target atoms that

results in the release of an x-ray photon (x-ray fluorescence). Unlike the

other technologies in this category x-ray fluorescence detects molecules of

explosive that are emitted from the mine. The amount of fluorescence is

dependent on the target molecule. A critical issue in dispute at the present

time is whether x-ray fluorescence can work at the distances required to

address countermine missions The short wavelength of the x-rays used has

a corresponding high degree of scattering. Several experts we spoke to

expressed reservations about standoff for this technology, although the

system developer claims to have surmounted this limitation.

• The fourth technology is gamma ray imaging. The basis of this technique is

an electron accelerator that produces gamma rays that “interact with the

chemical elements in explosives to generate a unique signature.” Because

of the scattering of the (short wavelength), x-ray and gamma ray detectors

operating on these principles must be in close proximity to the target.
Appendix III: Land Mine Detection

Technologies

Page 31 GAO-01-239 Land Mine Detection

According to a developer, the detector must be within one foot of the

target. Another obstacle is that the detector would require an extremely

large source of energy to create the gamma rays.

We identified two technologies that are based on detecting an

electromagnetic field.

• The first is electromagnetic induction. As discussed in the background

section, metal detectors that utilize this approach are the principal means

for detecting land mines at the present time. Metal detectors generate a

magnetic field that reacts with electric and/or magnetic properties of the

target. This reaction causes the generation of a second magnetic field,

which is received by the detector.3

 The restriction to metallic objects is a

limitation given the increasing development of mines with extremely small

amounts of metal. Increasing the sensitivity of a metal detector to detect

extremely small amounts of metal in these mines leads to its detecting

other objects in the ground. Metal detectors are also limited by the need to

be relatively close to the mine target in order to operate effectively.

• The second technology is conductivity/resistivity that involves applying

current to the ground using a set of electrodes and measuring the voltage

developed between other electrodes. The voltage measured at the

electrodes would be affected by the objects in the ground, including land

mines. The conductivity technique was originally developed to locate

minerals, oil deposits, and groundwater supplies. The need to place the

electrodes in or on the ground is a concern for land mine detection

applications of this technology.

We identified four technologies that have been proposed which do not

actively illuminate the target, but are based on detecting energy emitted or

reflected by the mine. Three detect the energy naturally released by

objects. They are ostensibly cameras that operate in a very similar fashion

to video cameras, although they view not red, green, and blue frequencies,

but other parts of the spectrum. Land mine detectors that use passive

sensing principles spot either (1) a contrast between the energy emitted or

reflected from the mine and that of the background or (2) the contrast

 3

Magnetic devices are another type of passive metal detector that sense perturbations in

the earth’s magnetic field caused by the presence of ferrous objects, such as iron. Because

they are employed almost exclusively to detect magnetic objects, magnetometers are less

useful as mine detectors.

Technologies that detect

an electromagnetic field

Passive

Electromagnetic

Technologies
Appendix III: Land Mine Detection

Technologies

Page 32 GAO-01-239 Land Mine Detection

between the (disturbed) soil immediately surrounding a buried mine and

the top layer of soil. They can be designed to pick up this energy

difference in different wavelength bands. Passive detectors have been

designed or proposed to operate in different parts of the EM spectrum. We

identified technologies that operate using infrared, millimeter wave, and

microwave principles. Infrared, millimeter, and microwave techniques

have different strengths and limitations. The trade-offs between scattering

and resolution that exist with the active backscatter approaches (radar

and LIDAR) also exist for passive EM technologies. For example, the

longer wavelengths of microwave and millimeter waves allow them to

penetrate through clouds, smoke, dust, dry leaves, and a thin layer of dry

soil but provide more limited resolution of targets.

These four technologies are capable of greater standoff than others.

Several nations are developing systems that use IR detection to detect

minefields (tactical reconnaissance). Systems are also being developed to

gather information in several infrared wavelength bands at the same time

(“multi-spectral infrared”). This approach increases the amount of

information available to distinguish mine targets from the background.

The Marine Corps is conducting research in this area.

One of the constraints with infrared detection systems is that the mines’

signature against the background will tend to be reduced at certain times

during the day. To overcome this limitation, researchers funded by DOD’s

Multidisciplinary University Research Initiative (MURI) recently

investigated amplifying the infrared signal by heating the ground with

microwave energy. Their early findings suggest that microwave heating

enhances the infrared signature of objects buried under smooth surfaces.

However, much work remains. Given continued funding, they plan to add

increasing complexity to their experimentation by testing with rough

surfaces, random shapes, and different mine and soil characteristics. They

will need to conduct additional research to determine whether the rate of

heating is consistent with the speed required to meet most countermine

missions.

The fourth passive electromagnetic approach is based on detecting the

energy produced by the circuitry of advanced mines that contain

sophisticated fuses. DOD has recently funded work on this approach as

part of the MURI initiative. Apart from the limited applicability of this

technology, questions remain concerning how feasible it is and how easily

a detector operating on these principles might be fooled with a decoy.
Appendix III: Land Mine Detection

Technologies

Page 33 GAO-01-239 Land Mine Detection

We identified four technologies that are not based on electromagnetic

principles. They are acoustic/seismic, neutron activation, trace vapor and

biosensors. Sensors that utilize an acoustic/seismic approach operate by

creating an acoustic or seismic wave in the ground that reflects off the

mine. The energy can be delivered in a number of different ways such as a

loudspeaker, a seismic source coupled with the ground, and a laser

striking the ground over the mine. In addition, there are different ways of

receiving the signal from the target (electromagnetically through a doppler

radar or doppler laser device or acoustically through a microphone).

Numerous questions remain about whether an acoustic/seismic approach

can meet the operational needs for countermine missions and the

environmental factors that would influence its employment.

Although we identified no certain, absolute limitations to an

acoustic/seismic approach meeting countermine missions, we did identify

significant concerns. Acoustic waves are capable of imaging buried land

mines. However, clutter is a major concern with acoustic approaches.

Interference from rocks, vegetation, and other naturally objects in the

environment alter the waves as they travel in the ground. Additional work

needs to be conducted to assess the limits of an acoustic/seismic approach

for detecting land mines. An acoustic system is one of the technologies

that the Army is currently exploring for the Ground Stand-off Mine

Detection System (GSTAMIDS).

Neutron activation analysis techniques operate on the principle that mine

explosives have a much higher concentration of certain elements like

nitrogen and hydrogen than naturally occurring objects. There are several

neutron-based techniques for detecting these explosive properties in bulk

form. All systems are composed of at least a neutron source – continuous

or pulsed, emitting in bursts – to produce the neutrons that have to be

directed into the ground, and a detector to characterize the outgoing

radiation, usually gamma rays, resulting from the interaction of the

neutrons with the soil and the substances it contains (e.g. the explosive).

Neutron activation analysis cannot be used as a standoff detector. Our

review indicated that neutron activation analysis must operate directly

over the mine target. The limited speed of this technology is another

restriction for most missions. In addition, unanswered questions about this

technology concern the depth of penetration and whether it can be used to

detect smaller anti-personnel mines. Because of these limitations and

questions, neutron activation analysis is currently envisioned as having a

role as a confirmation detector alongside faster sensors on systems that

are remotely piloted. For example, as described above, Canada’s military

has developed a vehicle that incorporates thermal neutron activation as a

Other Technologies
Appendix III: Land Mine Detection

Technologies

Page 34 GAO-01-239 Land Mine Detection

confirmation sensor. The vehicle would need to stop only when one of the

scanning sensors indicated a possible mine target.

The other two technologies are trace vapor and biosensors. Trace vapor

detectors involve sensing molecules of the explosive that emanate from

the buried mine and then analyzing them. There are several different

approaches for capturing and analyzing these molecules. In 1997, DARPA

initiated a research program aimed at detecting land mines via their

chemical signatures, referred to as the “electronic dog’s nose” program.

The program was established because DARPA believed that the

technologies DOD was developing (metal detectors, radar and infrared)

were limited in that they were not seeking features unique to land mines

and were susceptible to high false alarm rates from natural and man made

clutter. Through this program, DARPA hoped to change the overall

philosophy of mine detection in DOD by detecting the explosive, a unique

feature of land mines. This work has been transitioned over to the Army.

However, the role of trace vapor detectors in most countermine missions

is likely to remain limited due to the limited standoff that can be achieved.

The central feature of the biosensor technology approach is a living

animal. Current examples of biosensors are dogs, bees, and microbes that

detect explosives. Many research questions remain with these approaches.
Appendix IV: Comments From the Department

of Defense

Page 35 GAO-01-239 Land Mine Detection

Appendix IV: Comments From the

Department of Defense
Appendix IV: Comments From the Department

of Defense

Page 36 GAO-01-239 Land Mine Detection

Now on p. 18.
Appendix IV: Comments From the Department

of Defense

Page 37 GAO-01-239 Land Mine Detection

Now on pp. 18-19.

Now on p. 18.
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