INTRODUCTION

United States
Environmental Protection
Agency

Environmental Monitoring
Systems Laboratory
P.O. Box 93478
Las Vegas NV 89193-3478

September 1992

OFFICE OF RESEARCH AND DEVELOPMENT

TECHNOLOGY SUPPORT PROJECT

Photogrammetry
for Environmental
Measurement

The Environmental Monitor-
ing Systems Laboratory, Las
Vegas (EMSL-LV) has an
active remote sensing
department, capable of
responding to all Regional
requests for obtaining and
interpreting aerial photogra-
phy. Photogrammetry is
defined as the "art and
science of obtaining reliable
measurements from photo-
graphs" (American Society
for Photogrammetry and

Remote Sensing, 1991).

Most small and medium scale
maps are made from aerial
photographs, and photogram-
metric sciences are a funda-
mental part of modern map
making. The aerial photo-
graphic holdings in the EPA
and other agencies of the
federal government are a
wealth of spatial and tempo-
ral data about environmental
conditions and processes.
EMSL-LV currently provides

qualitative information that is
interpreted from aerial photo-
graphs to characterize hazard-
ous waste sites, analyze
wetlands, identify ecological
resources and to meet a
number of environmental
monitoring needs. EMSL-LV
has now acquired the capabil-
ity to supply highly accurate
measurement information for
similar applications.

TECHNIQUE

Photogrammetric data are
produced on very precise
photo-measurement devices
called analytical
stereoplotters. These
devices, typically calibrated
to the micron level, enable

the scientist to create com-
plex mathematical models
that correct for known
distortions in the photo-
graphs. From these three-
dimensional photo models,
highly accurate measure-

ments and positional data
can be derived for mapping
and analytical purposes.
These data can be produced
in digital format directly for
input in a Geographic Infor-
mation System (GIS).

THEMATIC MAP
PRODUCTS

Cartographic information can
be produced from aerial
photographs to meet National
Map Accuracy Standards.
The information can be
traditional map features such
as roads and hydrology or
special map layers such as

historical hazardous waste
site activity and fractures in
the bedrock. Any information
that can be derived from the
aerial photo can be accu-
rately mapped in a digital
format. Once the photo
model is established, the-

matic information repre-
sented by points, lines, and
polygons can be input directly
in digital format without
transfer to a hard-copy map
and digitizing from the map
base. This saves time and
reduces errors.

MENSURATION
PRODUCTS

Exact measurements can be
accomplished on an analyti-
cal stereoplotter to help
characterize activity of
environmental interest. For

example, in studying hazard-
ous waste sites, the volume
of waste accumulation and
changes in this volume are
needed to evaluate remedial

options. Also, precise
distance and area measure-
ments can be utilized for risk
assessment and other site
characterization activities.

1130EX92OCC

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PRECISE LOCATION
OF FEATURES

Any feature that is observ-
able on an aerial photograph
can be accurately referenced
to a coordinate system.
Photogrammetry can be
extremely useful for collecting
and recording the coordinate
data that are required by the
EPA Locational Data Policy.
Information that is not readily

visible on photographs, such
as property boundaries or
pipelines locations, can be
superimposed digitally onto
the photo model for special
mapping or interpretive
purposes.

Cartographic information that
depicts the elevation of the

land surface, such as the
contour map or the digital
elevation model, can be
produced by photogrammet-
ric techniques. The resolu-
tion of this data can be
tailored to the specific needs
of the project.

ADVANTAGES

Photogrammetric products
generated from current and
historical photos have the
same advantages and data
that are interpreted from air
photos: they form a perma-
nent record of present and

past conditions, they are
defensible in court, and they
serve as valuable aids to site-
specific field work. The
ability to provide quantitative
measurements as a supple-
ment to qualitative

photointerpretation products
will significantly enhance
the products and services
available to the EPA
community.

FUTURE PLANS	More of the basic photogram-	Also, the use of digital	incorporated into future

metry and photointerpretation	imagery in the photogram-	products as will the use of

products will become avail-	metric process is currently	digital photography in the GIS

able in digital, GIS formats.	being researched and will be	environment.

REFERENCE

American Society of Photogrammetry, 1980, Manual of Photogrammetry, 4th Edition, Chester
C. Slama, Editor-in-Chief, American Society of Photogrammetry, Falls Church, VA.

FOR FURTHER INFORMATION

For further information on photogrammetry, contact the Environmental Photographic Interpre-
tation Center at:

Regions 1-5	Regions 6-10

Mr. Gordon Howard	Mr. Phil Arberg

(703) 349-8970	(702) 798-2545

FAX 557-0243	FAX 545-2692

For information about the Technology Support Center at EMSL-LV, contact:

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Mr. Ken Brown, Manager

Technology Support Center

U.S. Environmental Protection Agency

Environmental Monitoring Systems Laboratory

P.O. Box 93478

Las Vegas, NV 89193-3478

(702) 798-2270

The Technology Support Center fact sheet series is developed and written by
Clare L. Gerlach, Lockheed Engineering & Sciences Company, Las Vegas.

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