Suggested citation:

Matthews, N. A. 2008. Aerial and Close-Range Photogrammetric Technology: 

Providing Resource Documentation, Interpretation, and Preservation. 

Technical Note 428. U.S. Department of the Interior, Bureau of Land 

Management, National Operations Center, Denver, Colorado. 42 pp.

BLM/OC/ST-08/001+9162
Aerial and Close-Range Photogrammetric Technology: Providing 

Resource Documentation, Interpretation, and Preservation

By Neffra A. Matthews Technical Note 428

Bureau of Land Management September 2008

National Operations Center

Denver, Colorado 80225
ACKNOWLEDGMENTS

I thank my colleagues within the National Operations Center–Division 

of Resource Services and other offices within BLM who have supported the 

use of photogrammetry in the Bureau. In addition, I especially thank my 

coworker, Tom Noble. Several years ago Tom began applying his knowledge 

of mathematics, surveying, and software programming to photogrammetry. 

The BLM and the use of close-range photogrammetry in general have greatly 

benefited from his efforts. I thank the following persons for their reviews of 

this manuscript:

Alan Bell, USDI, Bureau of Reclamation

Mike Bies, USDI, Bureau of Land Management

Brent Breithaupt, University of Wyoming

Matthew Bobo, USDI, Bureau of Land Management

Debra Dinville, USDI, Bureau of Land Management

Rebecca Doolittle, USDI, Bureau of Land Management

Jason Kenworthy, Oregon State University

Dave Kett, USDI, Bureau of Land Management 

Lisa Krosley, USDI, Bureau of Reclamation

Lucia Kuizon, USDI, Bureau of Land Management

Carolyn McClellan, Smithsonian Institution, 

National Museum of the American Indian

Tom Noble, USDI, Bureau of Land Management

Vanessa Stepanak, USDI, Bureau of Land Management

Bill Ypsilantis, USDI, Bureau of Land Management
CONTENTS

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

What Is Photogrammetry? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Aerial Photogrammetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Aerial Photogrammetry Workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Project Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

 Photo Layout and Flight Line Index Map . . . . . . . . . . . . . . . . . . . . . . . . 7

 Survey Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

 Image Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Interpreting the Imagery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Photogrammetrically Derived Products . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

 Digital Terrain Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

 Digital Orthophoto . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

 Vector Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Close-Range Photogrammetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Close-Range Photogrammetry Workflow . . . . . . . . . . . . . . . . . . . . . . . . 12

Project Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

 Photo Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

 Survey Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

 Image Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Interpreting the Imagery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Close-Range Photogrammetry Products . . . . . . . . . . . . . . . . . . . . . . . . . 15

Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Cyclic Documentation for Change Detection . . . . . . . . . . . . . . . . . . . . . 17

Integrating Multiscale Imagery for Riparian Habitat . . . . . . . . . . . . . . . 20

Documenting Cultural Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Appendix A. Concepts of Stereoscopic Photography . . . . . . . . . . . . . . . . 29

Appendix B. Choosing a Camera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Appendix C. Taking Good Pictures and Suggested Camera Settings . . . . 37

Appendix D. Conducting a Close-Range Photogrammetric Project . . . . . 41
Oblique low-level aerial view of Highway 89, Kanab Creek, north of Kanab, Utah.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 1

The United States Department of the Interior, 

Bureau of Land Management (BLM) is 

charged with managing almost 104 million 

ha (256 million acres) of surface land. This 

vast landscape includes some of the most 

ecologically and culturally diverse, scientifically important lands in Federal ownership. 

Documenting and evaluating the present 

condition—and in some instances, past 

condition—of its land is a critical part of the 

Bureau’s mission. Not only do these condition 

data provide information on the health 

of the land and serve as a basis for future 

decision making, but they also provide a 

tool for determining the effectiveness of 

present management practices. To most 

efficiently support the BLM’s management 

effort, documentation methods that are 

quantifiable and repeatable are needed.

A tool for capturing present condition is 

photography. While visually enlightening, a 

single photograph is in many ways anecdotal 

and can be biased by the perceptions of 

the photographer (Mudge et al. 2006). 

However, photographs can be taken in 

such a way as to provide detailed and 

measurable three-dimensional (3D) data, 

thus providing a more robust dataset from 

which an analyst can derive quantifiable 

ABSTRACT

Photogrammetry is the art and science of obtaining precise mathematical measurements 

and three-dimensional (3D) data from two or more photographs. The Bureau of Land 

Management has benefited from its in-house photogrammetric capabilities, support, and 

expertise for more than 20 years. This support includes creating unique and value-added 

digital datasets and serving as subject matter experts and contracting officer’s representatives to obtain aerial photography and other types of 3D data. Traditionally, most 

people think of photogrammetry in the context of aerial photography. Photogrammetric 

techniques can be applied to virtually any source of imagery, whether it comes from 

35-mm digital cameras or an earth-orbiting satellite. As long as the images are captured 

with stereoscopic overlap, one can derive accurate 3D data at a very wide range of scales.

The rapid evolution of digital cameras and increasing capabilities of computers and 

analytical software has dramatically expanded the variety of situations to which photogrammetry may be applied, while simultaneously decreasing the costs of acquisition, 

processing, and analysis. A variety of resource specialists (such as hydrologists, soil scientists, 

archaeologists, paleontologists, biologists, range conservationists, and engineers) can 

greatly benefit from 3D products derived from modern photogrammetric techniques. 

This is especially true in the field of ground-based or close-range photogrammetry. This 

document provides a general overview of photogrammetry, with separate sections focusing 

on traditional aerial photogrammetry and close-range photogrammetry. The appendices 

contain technical information on the equipment and suggested methods for capturing 

stereoscopic imagery. Their purpose is to assist field resource specialists in the successful 

completion of the imagery collection portion of a basic, close-range photogrammetry project.

INTRODUCTION
2 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

information. The science and technology 

of this process is called photogrammetry 

(Appendix A). The basic requirement for 

photogrammetry is an overlapping pair of 

photographs taken to mimic the perspective 

centers of human stereoscopic vision. 

Photography, at virtually any scale (from a 

pair of images taken from an earth-orbiting 

satellite to extremely close-up images of a 

delicate biological soil crust), can be processed by using photogrammetric techniques. 

The resulting datasets integrate both 

corrected imagery and 3D surface data that 

can be viewed, manipulated, and measured 

by using GIS and other similar software.

Since the 1930s, most of the topographic 

and thematic maps produced in the United 

States have been made according to aerial 

photography and photogrammetric methods. 

Aerial photography, digital imagery, 

ground control survey data, and photogrammetry are the basic components for 

many of the maps and geographic information systems (GIS) data used by the BLM. 

For more than 20 years, the BLM has 

maintained some in-house photogrammetric capability with specialized expertise 

and equipment. This capability assists the 

Bureau in meeting its unique data needs 

(e.g., riparian boundary litigation) and by 

providing large-scale mapping products not 

available from other government agencies.

Within the last decade, advances in digital 

imagery and photogrammetric software, 

combined with lower equipment costs 

(Matthews et al. 2004), have enabled the 

use of photogrammetric methods over a 

wider range of applications, while at the 

same time reducing equipment costs and 

decreasing computing times, making the 

entire process more cost-effective. These 

advances have revolutionized close-range 

photogrammetry by removing many of the 

rigors of traditional aerial photogrammetry, 

thus moving stereoscopic image collection 

from the hands of the photogrammetric 

expert to those of field personnel.

A significant advantage of close-range 

photogrammetry is that images for a small 

project can be acquired with minimal field 

equipment and a small amount of training. 

Once taken, these images can be processed 

to a detailed, 3D grid of thousands of precise data points or archived and processed 

when needed to provide quantifiable 

measurements of condition. This can 

support long-term comparisons and provide 

a visual and metric dataset that cannot 

be achieved through any other method. 

Because accurate measurements can be 

made from the dataset, the resulting 

determinations are more defensible than 

simple anecdotal evidence (e.g., a single 

photo). In addition, these datasets can 

be more persuasive to both the internal 

and external audience, thus supporting 

better-informed conclusions.

In the past year, the 3D measuring and 

modeling software used to process closerange photographs has increased in its 

capability and ease of use and decreased 

in cost. Both traditional aerial and closerange photogrammetric processing are 

presently limited to BLM staff at the BLM 

National Operations Center (NOC) and the 

Alaska State Office. However, software 

and hardware innovations will continue 

to increase the accessibility of both 

stereoscopic processing and viewing, making 

photogrammetry more accessible within 

the BLM and providing a cost-effective, 

responsive, and quantifiable documentation 

and monitoring technique.

This report is intended to provide resource 

specialists with an overview of photogrammetry—both traditional aerial and 

close-range—and to provide examples of 

projects to which these technologies have 

been applied. In addition, the appendices 

contain the requirements of stereoscopic 

image capture, describe proper camera 

settings, and outline the basic procedure 

for field capture of images for a small, 

close-range project.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 3

Photogrammetry is the science behind the 

creation of almost every topographic map 

made since the 1930s. The human ability to 

perceive depth is the basis for the science 

(and technology) of photogrammetry. This 

ability to see in three dimensions is due to 

the offset in perspective centers between 

the left and the right eyes. Photographs 

taken to mimic this perspective shift 

are referred to as stereoscopic or stereo 

(meaning two). A stereo pair (or series) of 

images is taken from consecutive positions 

and overlap each other by at least 60%. 

Through the use of photogrammetry, 

highly detailed three-dimensional data 

can be derived from the two-dimensional 

photographs of a stereo pair.

The formal definition of photogrammetry 

is the art, science, and technology of obtaining reliable information about physical 

objects and the environment through the 

process of recording, measuring, and 

interpreting photographic images and 

patterns of electromagnetic radiant 

energy and other phenomena. In many 

instances, the use of photogrammetry can 

be more efficient, less labor-intensive, and 

more cost-effective than other types of 

field 3D data collection, resulting in products that have a level of detail, accuracy, 

range, and price that is difficult to match 

with other technologies (Birch 2006). As 

described previously, the main component 

necessary for a photogrammetric project 

is a series of overlapping stereoscopic 

images. The stereo images may be captured 

by a large variety of cameras at almost 

any height or platform (from tripod to 

earth-orbiting satellite).

Photogrammetry is informally divided into 

two basic categories according to the height 

of the platform—traditional (or aerial) and 

nontraditional (or close-range). Advances 

in commercially available and cost-effective 

photogrammetric software, high-resolution 

digital cameras, high-performance laptop 

computers, and unmanned aerial systems 

(UAS) have caused those categories to 

overlap in recent years. This document 

refers to the traditional process of acquiring 

and using large-format (e.g., 9 × 9 inch; 

Figure 1), vertical (film or digital) aerial 

images as aerial photogrammetry. Close 

range is used to refer to photographs with an 

object-to-camera distance of less than 300 m.

Figure 1. Example 

of a large-format 

(9 × 9-inch) vertical, 

natural-color, aerial 

photograph taken at 

a scale of 1:12,000. 

The area covered by 

the image is in northcentral Wyoming. The 

Red Gulch Dinosaur 

Tracksite lies near the 

center of the image.

WHAT IS PHOTOGRAMMETRY?
Onboard a Department of the Interior helicopter at Kanab, Utah, Airport preparing 

to conduct low-level aerial photography of Moccasin Mountain Tracksite. 
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 5

Aerial photogrammetry utilizes large-format 

imagery and ground coordinate information 

to effectively recreate the geometry of a 

portion of the earth in a virtual environment. In this virtual environment, reliable 

horizontal and vertical measurements can be 

made and recorded (or compiled) directly 

into a geospatial data file. Accurate 

measurements can be recorded from aerial 

photographic images, by using traditional 

methods, only when the following conditions are met: a) stereoscopic image pairs 

(two or more overlapping photographs) 

cover the object to be analyzed; b) accurate 

x, y, and z coordinates are known for at 

least three defined object points in the 

overlapping photographs; and c) a calibrated 

mapping or metric camera is used to take 

the photographs.

The compilation of planimetric features 

(such as roads and streams) and topographic 

information (such as digital terrain models 

[DTM] and topographic contours) from 

the photographic sources is accomplished 

through the use of digital stereoscopic 

instruments. Digital, or softcopy, photogrammetric workstations require specialized 

software and hardware for viewing a pair 

of stereo images. In this virtual environment, 

an experienced operator can link the 

images with the ground control to collect 

precise horizontal and vertical coordinates 

for a point, line, polygon, or surface. The 

photogrammetric workstation recreates 

the geometry of the field subject through 

a series of mathematical operations 

(Figure 2). These procedures require a 

high level of expertise and repetition to 

maintain the operator’s skill. The softcopy 

instrument has analytical capabilities to a 

submillimeter level. Thus, high-accuracy 

ground control coordinate positions are 

needed to fully exploit the analytical 

capabilities of these instruments 

(Matthews et al. 2006).

Aerial Photogrammetry 

Workflow

Most large-format aerial photography is 

acquired through commercial contractors 

and is available in hard copy (film) or digital 

formats. With the exception of the BLM 

Alaska State Office, the Bureau does not 

have the capability to acquire large-format 

aerial imagery without the assistance of a 

commercial contractor. In most instances, it 

is best to work through photogrammetric 

specialists, such as the staff of the Division 

of Resource Services (DRS) at the NOC to 

ensure that the technical and user requirements are met. It is important to begin 

planning for the acquisition of imagery 

early in the project. Many elements need 

to be considered to ensure that project 

requirements are met (e.g., size of the 

area, terrain, vegetation cover, sun angle, 

type of sensor, and product accuracy).

Generally, aerial acquisition is designed 

and planned according to the specifications 

needed to generate a particular product 

Figure 2. Digital, or softcopy, photogrammetric

workstations support stereoscopic viewing 

and measuring in a 3D environment, where 

an overlapping pair of images is viewed with 

special polarized glasses.

AERIAL PHOTOGRAMMETRY
6 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

with a specific scale and accuracy. The 

desired resolution dictates the height at 

which the contractor must fly to acquire 

the imagery. The following equation states 

the relation between scale and flying height 

of the aircraft (Hussain and Bethel 2004).

scale = focal length

flying height above terrain

For example; when film-based aerial 

photography is flown at a height of 305 m 

(1,000 feet) above mean terrain with a 

153-mm (6-inch) focal length lens, the 

resulting photography has a scale of 1:2,000. 

With the resolving power of modern 

natural color film, the smallest object that 

can be detected is 5 cm. The distance of 

the sensor from the subject in commercial 

aerial photography is restricted by the 

altitude at which the plane can operate 

safely. In addition, the Federal Aviation 

Administration (FAA) imposes a minimum 

altitude limit of 1,000 feet above 

populated areas.

Many land management agencies, including 

the BLM, maintain collections of historical 

aerial photography of the lands they 

manage. The National Agriculture Imagery 

Program (NAIP) is managed by the U.S. 

Department of Agriculture Farm Services 

Agency (FSA) and acquires imagery of 

agricultural lands in the United States. 

Other governmental agencies work with 

the FSA to produce statewide coverage of 

natural-color, 1-, 2-, and 10-m resolution 

imagery that has been corrected for terrain 

and image distortions and is geospatially 

correct (orthorectified) on a cyclical basis. 

Information on these archives is available 

through individual agency websites. 

The BLM’s aerial photography archive is 

maintained at the NOC. 

Traditional, large-format (9-inch × 9-inch) 

aerial photography is film-based and is 

available in black and white, natural color, 

or color infrared formats depending on 

the project requirements. Each aerial 

camera has its own camera calibration 

report. This is a report generated with the 

results of a series of tests developed to 

reveal the geometric characteristics of the 

camera and lens. The photogrammetrist 

uses this information in subsequent calculations to remove distortions, which helps 

to ensure a high-quality product. However, 

the imaging and mapping industry has 

started to migrate to a fully digital process 

in recent years. Often, traditional film is 

not used, as the imagery is captured in a 

digital format.

Presently, several sensor systems are able 

to capture aerial images digitally. The 

frame digital sensor is similar to a film 

camera in that it captures single frames. 

A push broom sensor (an array of several 

thousand charge coupled device [CCD] 

sensors) continuously collects data and 

then divides the data into frames. Digital 

images can also be captured in panchromatic, multispectral, and infrared modes 

simultaneously. This is advantageous 

because the images may be captured 

concurrently and do not require additional 

flights. Digital sensors also offer capabilities 

that allow the photogrammetrist to 

enhance portions of the image through 

image processing techniques to compensate 

for adverse conditions such as shadows 

or high-contrast areas. This allows data 

collection in areas that might be obscured 

on film.

Project Implementation

Many elements need to be considered to 

ensure that proper project design is met. 

These elements include the size of the 

area, scale of the photography, terrain 

(mountains or rolling hills), vegetation 

cover (desert or forest), accessibility (rivers, 

cliffs, or ownership restrictions), sun angle 

(latitude, longitude, or time of year), and 

type of sensor. Perhaps the most important 
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 7

consideration is determining the level of 

accuracy necessary for the final product. 

Accuracy, photographic scale, and project 

size are directly related. Typically, the 

higher the level of accuracy required, the 

larger the scale of photography necessary, 

which in turn affects the magnitude and 

complexity of the job. 

Photo Layout and 

Flight Line Index Map

One of the most important goals of 

project design is to ensure that there will 

be complete stereoscopic coverage of the 

area of interest, at the proper scale. Photo 

layout is a depiction of the extent of 

each photo in relation to the desired area 

of coverage. The graphic representation 

of the photo layout is often referred to 

as a flight line index map. Depending on 

the final photo scale, the flight line index 

map for traditional aerial photography 

flights are designed on 1:100,000- or 

1:24,000-scale topographic or digital 

orthophoto maps (Figure 3). When designing 

the flight line, care must be taken to 

ensure that there is complete overlap 

between photographs. If more than one 

line of photographs is needed, there must 

be adequate side lap between the photos.

Survey Control 

Another vitally important part of this 

process is the ground control survey. The 

survey is the link between the ground and 

the aerial photography. Surveys give the 

geospatial products their identity with 

regard to projection, coordinates, and 

final accuracy. A high level of accuracy 

(geodetic quality) is of the utmost 

importance when gathering the survey 

(horizontal and vertical) data. Locations 

for ground survey control points are 

indicated in the flight line map. Correct 

spacing and location of ground control 

survey points determine the area that can 

be mapped. Before the aerial photography 

acquisition, ground control panels or 

targets must be placed on the ground 

as indicated by the flight line index map 

(Figure 4). A center point for each panel 

will be indicated by a monument (often 

with a survey nail or rebar driven into the 

ground). To make this point meaningful 

on the final aerial photographs, large 

“legs” of white material will be nailed 

down in a cross centered on the nail or Figure 3. Examples of 

flight line maps and 

photo layouts. 
8 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

rebar. Ideally, high accuracy horizontal 

and vertical coordinates for each paneled 

point will be surveyed before the aerial 

photography acquisition.

Image Acquisition

After the project requirements have been 

developed and the flight line and control 

layouts have been designed, a specification 

package goes out to bid. At this time standard contracting procedures and schedules 

come into play. After the contract is 

awarded, coordination must take place 

between the contractor, NOC DRS staff, 

and the field office to ensure the ground 

control targets are in place before imagery 

is acquired. After the imagery is acquired, 

a review copy is provided to the Contracting 

Officer’s Technical Representative for 

inspection. Once it has been determined 

that the aerial photography meets the 

contract specifications, the imagery is 

accepted. The aerial film and paper prints (if 

requested) or digital files are then provided 

to the NOC for processing and inclusion in 

the BLM’s aerial photography collection.

Interpreting the Imagery

The process of extracting data from the 

aerial imagery begins with combining the 

digital imagery with the ground control 

coordinate data. These imagery files can 

be supplied directly from a digital sensor 

or by scanning aerial film. Film scanning 

is performed with an extremely accurate 

(micrometer accuracy level) scanner. The 

result is a digital representation of the 

film. The photogrammetric workstation 

re-creates the geometry of the field 

subject through a series of mathematical 

calculations. Aerotriangulation is a mathematical process (least squares bundle 

adjustment) by which the survey data 

are used to tie the photos together and 

adjusted coordinate values are distributed 

throughout the entire project. The oriented 

image files are displayed on a computer 

monitor in a way that enables the operator, 

equipped with a pair of specially designed 

glasses, to view the digital image files in 

a 3D environment. In this virtual environment the photogrammetrist can record 

(or compile) the horizontal and vertical 

data necessary for producing a reliable 

map directly into a geospatial data file.

Photogrammetrically 

Derived Products

A large variety of 3D digital data in 

support of land use planning and decision 

making can be developed from both 

aerial and close-range photography. 

The photogrammetric process enables 

the interpretation of imagery and 

the collection of data necessary to 

produce reliable maps that support land 

managers’ decisions and are defensible 

in court. These data customarily take 

the form of topography (terrain or land 

surface) or planimetric (such as streams, 

transportation routes, vegetation 

boundaries, and cultural) information.

Digital Terrain Model

A digital terrain model (DTM) provides a 

digital representation of the terrain surface. 

A DTM can be produced in a manual or 

automated mode. Manual mode is a process 

in which a specialist, using a photogrammetric workstation, observes each point in 

accordance with a specified spacing and 

records its location, both horizontally and 

Figure 4. Example of a simple, flight line 

layout indicating ideal locations for survey 

control points.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 9

vertically. Automated digital terrain 

extraction is commonly referred to as 

autocorrelation or digital image matching. 

It is a process in which sophisticated software matches pixels (picture elements) with 

unique spectral and geospatial values in 

one digital image to similarly valued pixels 

in the adjacent image of the stereo pair. The 

addition of more information, such as breaklines (polylines in which each vertex has its 

own x, y, z, location) may be required to aid 

the software in determining pixel matches 

in difficult-to-interpret areas. Topographic 

contour lines can be generated by using 

DTM, breakline, and planimetric data.

Digital Orthophoto

A digital orthophoto is a photograph that 

has been corrected to eliminate distortions 

and differences in scale (Figure 5a.). The 

effects of camera tilt and relief displacement (features at higher elevations are 

displaced away from the center of the 

photo) are the main causes of these distortions. To eliminate these, the ground 

geometry is re-created as it would appear 

from directly above each point in the 

photo. This is accomplished by applying a 

process called differential rectification to 

each pixel in the image. The resulting 

corrected image can be used as a map.

The orthophoto can be printed as a standalone product or displayed as a backdrop 

with other spatial information. Perspective 

views can be produced by draping the 

orthophoto image over the terrain surface. 

This process allows one to make a “virtual” 

visit to the area. The parameters of this 

virtual surface can be further manipulated 

to enhance, exaggerate, or isolate a certain 

feature or part of the image. Topographic 

contours and planimetric data can be 

draped onto the orthophoto in threedimensional space. This virtual visit 

can be extremely useful for land use 

planning decisions and communicating 

with the public.

Vector Map

Vector data customarily take the form 

of topography (terrain or land surface) 

or planimetric (streams, transportation 

routes, vegetation, and cultural) 

information. Planimetric features are 

compiled in a manual mode, in which 

the photogrammetric operator digitizes 

(in real-world coordinates) points, lines, or 

polygons representing features of interest 

(Figure 5b and 5c). The resulting data 

files can be imported directly into 

ArcMap for GIS use or into AutoCAD 

for engineering design.

Figure 5. a. Digital 

orthophoto map.

b. Vector map depicting 

roads and topography. 

c. A combination of the 

vector map overlain on 

the digital orthophoto 

map. These digital 

products were created 

photogrammetrically 

at the BLM National 

Operations Center 

(Denver, Colorado) in 

support of remediation 

at the Rip Van Winkle 

Mine site in Elko County, 

Nevada.

a.

b.

c.
Imagery captured from a variety of perspectives such as this image 

of a mesa west of Kanab, Utah, can be acquired from aerial platforms.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 11

The same basic principles of traditional 

aerial photogrammetry can be applied to 

stereoscopic pictures taken from lower 

altitudes or from the ground. Terrestrial, 

ground-based, and close-range are all 

descriptive terms that refer to photos 

taken with an object-to-camera distance of 

less than 300 m (1,000 feet). This distance 

equates to the minimum safe flying height 

above populated areas, as required by the 

FAA. Since the same basic principles apply 

to photographs taken from a camera 

mounted on a tripod (terrestrial) or 

suspended from a light sport aircraft (lowlevel aerial), both types of nontraditional 

photogrammetry are referred to in this 

report as close-range photogrammetry (CRP).

A variety of cameras and platforms may be 

used to obtain the photographic images 

to be used in CRP processing, including 

cameras housed in unoccupied airborne 

vehicles, suspended below helium-filled 

blimps, and mounted on tripods (Figure 6; 

Breithaupt et al. 2004). Through the use of 

these nontraditional methods, a resolution 

or ground sample distance of 0.25 mm and 

a spatial accuracy equivalent to 0.025 mm 

can be achieved. Theoretically, there is 

no limit to the resolution that can be 

achieved from CRP images (Matthews 

et al. 2006).

The BLM’s national center in Denver has 

used close-range photogrammetric techniques to document resources since the 

late 1980s. At that time, although producing 

high-quality results, the close-range 

photogrammetric process could be tedious 

and time-consuming mainly because of 

the need to apply traditional techniques, 

workflow, and equipment to close-range 

image capture and processing. However, 

recent advances in commercially available 

and cost-effective three-dimensional 

measuring and modeling (3DMM) software, 

high-resolution digital cameras, and highperformance laptop computers have 

revolutionized the CRP process. With these 

advances, the photogrammetric process can 

be moved from the laboratory environment 

into the field, and taken strictly from the 

hands of the photogrammetry expert and 

moved to the hands of the resource specialist.

Figure 6. A variety of 

cameras and platforms 

may be used to obtain 

the photographic 

images used in closerange photogrammetric 

processing, including 

cameras housed in 

unoccupied airborne 

vehicles, suspended 

below helium-filled 

blimps, and mounted 

on tripods. All images 

were taken at the BLM’s 

Red Gulch Dinosaur 

Tracksite in Wyoming.

CLOSE-RANGE PHOTOGRAMMETRY
12 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

Close-Range Photogrammetry 

Workflow

As with traditional photogrammetry, the 

first step in the close-range project workflow is establishing project requirements. 

These requirements include the area to be 

covered, type of ground cover, access to 

areas surrounding the subject, weather, 

accuracy of the final product, format of the 

final product, public visitation at the site, 

and others. However, with the relatively 

recent availability of reasonably priced, 

high-quality digital cameras and 3DMM 

software, many of the traditional requirements in the photogrammetric process can 

be accomplished in nontraditional ways, 

providing a high level of flexibility.

An example of the increased flexibility 

can be seen in image acquisition. In most 

situations, a person who is experienced 

with CRP (such as the staff at the NOC), 

using a high-resolution commercial digital 

single-lens reflex (SLR) camera, can successfully capture ground-based photographs 

for a variety of projects. Most persons, 

following a few simple rules and taking 

good-quality photographs, can capture 

the images necessary for completing a 

successful CRP project. See Appendix C for 

more details on taking proper photographs 

and camera requirements and settings.

Project Design

Once project requirements have been 

determined, the process of project planning 

can begin. Accuracy, photographic scale, and 

project size are directly related. Typically, the 

higher the level of accuracy required, the 

larger the scale of photography necessary, 

which in turn increases the magnitude of 

the job. CRP projects can be placed into 

one of two categories. These categories 

are small (simple) and large (complex).

Small projects are those for which the area 

of interest is equivalent to about 5 m2 or 

smaller. This type of project may also be 

referred to as extreme close range, as a 

high precision of data points is expected. 

Although proper planning strengthens 

any project, the small terrestrial project 

may afford greater flexibility in the planning process. Project design and image 

acquisition for projects of this scope may 

be successfully carried out by the resource 

specialists in the field. By following a set of 

standard operating procedures (Appendix 

C), successful completion of the capture 

of imagery for an extreme close-range 

project may be accomplished.

Large projects are those for which the area 

of interest is greater than 5 m2 or where 

complexities of terrain or access add to the 

level of expertise needed for planning and 

execution of the project. Projects that fall 

into this category may require a preliminary 

site visit or the inspection of overview 

photographs taken of the area. A preliminary reconnaissance of the area will 

determine if close-range photogrammetry 

is the best method for data capture, and if 

so, estimate resources necessary to accomplish the project. Also at this time, the 

data requirements and expectations of the 

end user can be discussed. Projects of this 

scope are best accomplished by those who 

have experience with close-range image 

capture and processing. 

Sometimes the needed vantage points 

to capture imagery may not be present, 

necessitating alternatives to ground-based 

capture. In these situations, a large ladder, 

aerial blimp, UAS, or other type of elevated 

platform may be needed. For these reasons, 

it is advantageous to contact the photogrammetric specialist for consultation 

early in project development to help with 

such items as budget, scheduling, site visit 

input, and others.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 13

Photo Layout

Close-range photogrammetric projects 

have more latitude in their design and 

execution than do traditional aerial projects 

because the 3DMM software is more 

capable of handling photographs taken 

at oblique angles to the subject and in 

connecting lines of stereophotos that have 

less consistent overlap than conventional 

aerial photogrammetry software. Nonetheless, knowing the lay of the land in 

advance can be critical to project success. 

This type of evaluation can be gained 

either through an onsite visit (which is 

preferable for complex projects) or from 

inspection of existing imagery. This imagery 

may take the form of snapshots of the 

area taken from the ground or existing, 

small-scale aerial imagery. It is a good 

investment in time and resources to 

investigate the existence of digital 

orthoimagery, which may be available over 

the Internet, or historical, large-format 

aerial photography available from agency 

collections. Site reconnaissance not only 

aids in identifying strategies for capturing 

complete stereoscopic coverage of the 

subject, but can also be used to identify 

obstacles to imagery acquisition. These 

obstacles most often take the form of 

vegetation, which can obscure points of 

view and terrain issues. Terrain obstacles 

can range from a lack of an elevated 

perspective to perilous drop-offs adjacent 

to the subject of interest.

While the formal flight line index map 

described previously in the aerial photogrammetry section may be bypassed for 

simple close-range projects, preplanning 

can certainly maximize field time, as it 

would calculate the object-to-camera 

distances, proper base-to-height ratio, 

and size and number of reference targets. 

However, flight line planning is advised for 

complex projects, especially those using 

photographs taken from a light sport

aircraft or UAS. In these instances, a formal 

flight line index map may be required to 

convey expectations to the pilot.

Survey Control

“Surveyed” ground control is not needed 

for a CRP. During the 3DMM processing, 

the camera lens system is calibrated. This 

technique elevates the camera from simply 

a device for capturing images to a virtual 

surveying and data collection instrument. 

By placing an object of known length in 

the overlap area of stereo models, a very 

accurate coordinate system can be created. 

However, GPS survey does give the products 

an identity as far as projection, coordinates, 

and final accuracy are concerned and can 

be easily integrated into a CRP project.

Image Acquisition

The increased flexibility provided by CRP 

is most completely realized in the image 

acquisition. Because many of the rigors 

imposed by traditional photogrammetric 

processing are removed from CRP, almost 

any person who can take good quality 

photographs can take the photos necessary 

for 3D data processing (see Appendix 

A). This can be most successfully realized 

when field personnel have undergone 

training or thoroughly read this technical 

note and have completed their own small 

project. For a large CRP project, a person 

who is experienced with CRP, such as the 

staff at the NOC, can successfully capture 

ground-based photographs for a variety 

of projects. 

When the needed vantage points to 

capture stereoscopic imagery cannot be 

attained from a ground-based setup, it 

will be necessary to investigate more “airborne” options. This may include simply 

using a ladder or elevated platform to 

obtain the needed perspective. However, 

when the area to be documented is large 

and there is no opportunity for oblique 

image collection, it may be necessary to 

employ the use of some type of low-level 
14 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

aerial system. In such instances, it will 

probably be necessary to go through a 

commercial provider as is done with 

traditional aerial imagery acquisition.

Interpreting the Imagery

The process of extracting data from the 

CRP imagery is another area where 

increased flexibility is realized compared 

to traditional aerial photogrammetry. The 

3DMM software can run very efficiently on 

most laptop computers. Thus, processing 

of digital images may begin in the field 

as soon as the imagery is acquired and 

downloaded. This can provide a real time 

look at the success of the photography 

coverage and provide for near real time 

measuring and recording of features. In 

addition, the photographs may be taken 

by trained field personnel and archived for 

later processing in a workstation environment. The resulting 3D image files can be, 

in turn, sent back out to field personnel 

for viewing in free viewer software. If 

more in-depth analysis is required, ArcGIS 

Stereo Analyst and LIECA Photogrammetric 

Suite (LPS) (both 

available within the 

Bureau) can be used 

for data compilation.

Figure 7. a. Digital 

orthophoto map. 

b. Vector map depicting 

topography. c. Digital 

terrain surface colorized 

by elevation. These 

maps were produced by 

photogrammetry at the 

BLM National Operations 

Center (Denver, 

Colorado) with a tripodbased camera and closerange photogrammetric 

techniques; they depict 

a dinosaur trackway 

from the BLM’s 

Red Gulch Dinosaur 

Tracksite in Wyoming.

a. b. c.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 15

Figure 8. Three-dimensional surface and image datasets can be packaged as industry standard 

files that can be viewed and rotated in 3D by a number of software programs. Shown is a 

right angle cliff face from the Bighorn Basin, Wyoming.

Close-Range 

Photogrammetry Products

The same cadre of products (digital terrain 

model, digital orthoimagery, vector maps, 

and others) that can be created from 

traditional aerial photogrammetry can 

also be generated from CRP (Figure 7). In 

addition, new and unique visuals can be 

easily produced from within the 3DMM 

software (Figure 8). Therefore, it is much 

more efficient to produce animations and 

digital-rotatable 3D objects that can be 

integrated into 3D raster streaming Web 

technology. A 3D Adobe Portable Document Format (PDF) file can be produced 

and embedded in PowerPoint presentations and documents. In addition, the 

dense and accurate 3D surface files can be 

used to produce solid model printouts 

using a variety of techniques at very large 

scales, even 1:1.
Getting a better vantage point to photograph a test plot in the Falcon Road Open OHV area within the 

Gunnison Gorge National Conservation Area near Montrose, Colorado.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 17

preparation, and photographing for all 

five plots were accomplished in 2 days.

In September 2006, the five plots were 

reestablished and site preparation, GPS 

coordinate collection, and photography 

were conducted in 1 day. Real-time 

kinematics (RTK) GPS positions (accurate 

to <1 cm) were taken for the control 

monuments and selected points within 

each plot locality. The resulting coordinate 

data were used to tie the digital terrain 

models to a real-world coordinate system 

(NAD83 Colorado Central State Plane Zone). 

In addition, this control was used to process 

both the 2005 and 2006 photography to 

aid in ensuring positional integrity between 

the 2 years (Ypsilantis et al. 2007).

Ten unique, highly detailed 3D surface 

datasets were produced photogrammetrically. The estimated vertical accuracy 

Figure 9. Five permanent 

study plots were 

established in 2005 in 

the vicinity of Montrose, 

Colorado: A. Scratch 

and Dent; B. Calamity; 

C. Falcon; D. Falcon II; 

and E. Beyond Falcon 

(Ypsilantis et al. 2007).

EXAMPLES

Cyclic Documentation 

for Change Detection

The ability to detect small changes in soil 

movement can provide valuable insight for 

assessing the effects of surface disturbing 

activities across the landscape (Matthews 

et al. 2007). Close-range photogrammetry 

is an excellent method for capturing 

detailed information about changes, such 

as erosion, on scales ranging from 1 square 

meter plots up to an entire hillslope. CRP is 

especially effective for monitoring erosion 

on areas that are devoid of vegetation, 

such as roads, OHV trails, and construction 

sites (Ypsilantis, personal communication). 

Close-range photogrammetry was used 

to create 3D surface information to help 

quantify effects from rapidly increasing 

off-highway vehicle (OHV) use in the BLM’s 

Uncompahgre Field Office. In August 2005, 

five permanent, variable-sized plots were 

established north of Montrose, Colorado. 

Two sites are located in dry wash channels, 

which cut through sandstone, shale, and 

coal, in the Dry Creek Extreme OHV Area. 

An additional three sites were located in 

the Falcon Road open OHV area within the 

Gunnison Gorge National Conservation 

Area (Figure 9) on adobe badlands composed 

of Mancos shale (Ypsilantis et al. 2007).

Natural features, such as bedrock (when 

present outside the traveled area) or 

rebar plot control stakes, served as x, y, z 

coordinate reference points. The rebar 

plot stakes were buried beneath the soil 

surface to ensure that the permanent 

reference points were not disturbed and to 

eliminate safety hazards for recreational 

users. A series of stereoscopic photographs 

were taken of the plots, concurrently with 

the camera calibration photographs, to 

facilitate stereoscopic viewing and analysis 

of the subject area. Establishing plots, site 
18 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

of these data is between 0.1 and 1.0 cm. 

The ten (2 years for each of five plots) 3D 

digital terrain datasets were analyzed in 

ArcGIS by using ArcMap and ArcScene. 

This process included creating a tin surface 

from the 3D datasets, converting the tin 

to a grid, and generating a hillshade from 

the grid (Figure 10). The grids were created 

with a resolution of 3 cm. Cut-and-fill and 

surface subtractions were made using the 

surface grids (Figures 10 and 11). According 

to the results of the analysis of the surfaces, 

all five sample plots exhibit loss and gain 

(or movement) of soil.

Figure 10. Falcon II 

plot. a. Photograph 

taken in August 2005. 

b. 3D surface model 

generated from the 

2005 photography 

rendered as a hillshade. 

c. Photograph taken 

in September 2006. 

d. 3D surface model 

generated from the 2006 

photography rendered as 

a hillshade (Ypsilantis et 

al. 2007).

a. c.

b. d.

Figure 11. Falcon II 

plot. The 3D surfaces 

generated from the 2005 

and 2006 photography 

were compared in 

ArcGIS. a. Graphic 

generated by using 

surface subtraction of 

the 2005 surface from 

the 2006 surface. The 

dark blue and dark red 

colors represent areas 

The soil gains and losses on the Mancos 

Shale hillslopes in the Gunnison Gorge 

NCA are high, with average soil loss rate 

of 163, 219, and 121 tons/acre calculated 

for the three sites. Figure 11b illustrates 

an area of high impact at the top of the 

slope at one site and an area of minimum 

impact at a similar slope position. The 

soil loss for the area of high impact was 

585 tons/acre and 367 tons/acre for the 

area of minimum impact. This indicates 

that soil loss is greater in the dirt bike trail 

entrenched into the hillslope than in the 

area that showed little visual evidence of 

recent OHV use (Ypsilantis et al. 2007).

a. b.

of greatest separation between the two surfaces. b. Falcon II 

plot. Volumetric loss between 2005 and 2006 for two areas of 

17.77 m2 (Ypsilantis et al. 2007).
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 19

The Dry Creek Basin sites were along a 

trail in an ephemeral drainage area. The 

modified OHVs on the trail can climb 

boulders and dig the sides of their tires 

into the hillslopes (Figure 12). This results 

in deposition of soil material below that 

hillslope, which is available for transport 

by the stream during high precipitation. 

One interesting anomaly shown in Figure 13 

is the two large boulders that have been 

moved approximately 2 m downslope, 

apparently by OHV activity. The amount 

and direction of movement could be 

reliably determined through the use of

stereoscopic images taken during the study.

The results of the study were compiled 

into a report (Ypsilantis et al. 2007) and 

provided to the Uncompahgre Field Office 

for use in the travel management plan. In 

addition, graphics generated from the 

report are being used in public presentations 

in support of management decisions.

c. Photograph taken in 

September 2006. d. 3D surface 

model generated from the 

2006 photography rendered 

as a hillshade (Ypsilantis 

et al. 2007).

a. b.

c. d.

Figure 12. Scratch and Dent plot. 

a. Photograph taken in August 

2005. b. 3D surface model generated from the 2005 photography 

rendered as a hillshade.

Figure 13. Scratch and Dent plot. 

Two boulders (A and B), each 

approx 1 × 0.6 × 0.5 m, moved 

about 2 m down the channel 

(A’ and B’) between August 2005 

and September 2006 (Ypsilantis et 

al. 2007).
20 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

Integrating Multiscale Imagery 

for Riparian Habitat

Coalbed methane discharge water has the 

potential to influence aquatic and riparian 

habitats in and along the Powder River of 

northeastern Wyoming (Figure 14). The 

Powder River Aquatic Task Group is investigating the use of remote sensing data 

and techniques to develop economical and 

effective means of monitoring change in 

affected aquatic and riparian habitat 

(Figure 15). This study is evaluating the 

utility of very large scale aerial (VLSA) 

imagery for classifying riparian and aquatic 

habitat types, as well as testing close-range 

photogrammetric, stereo-based image 

modeling techniques for change detection, 

documentation of vegetation composition 

and structure, and quantifying bank 

erosion and stability (Bobo et al., 2008).

A transect-based aerial-sampling protocol 

was proposed for the first phase of this 

project to facilitate the capture of ground 

control to support the CRP work. In related 

work, the integration of GPS/IMU systems 

with CRP techniques to accurately and 

rapidly geocorrect VLSA photography is 

being explored. The georeferenced VLSA 

imagery can in turn be used as training 

data for wider area mapping by using 

Figure 14. Location map for the Powder River, 

Wyoming, coalbed methane aquatic monitoring 

study (Bobo et al. 2008).

Figure 15. 3D image model developed from close-range photogrammetry along the Powder River, Wyoming. Images from 

two different times of year are merged to highlight the change in vegetation. With the 3D information available from 

multi-temporal 3D dataset, changes in vegetation heights, bank erosion, slope, water depth, vegetative cover, and bare 

ground can be measured (Noble et al. 2008).

satellite platforms such as Quickbird. 

Georeferencing of the VLSA imagery is 

presently conducted with both 0.60-m 

resolution Quickbird imagery and 0.25-m 

resolution AeroCam imagery (Noble et al. 

2008; Figure 16). Once the spatial links 

between the three sets of imagery were set, 

the VLSA was used as a classification tool 

for the more coarse resolution imagery.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 21

Figure 16. Photo targets 

were placed along 

selected transects 

across the Powder 

River, Wyoming, 

to assist with 

geocorrection of largescale aerial imagery 

(Noble et al. 2008).

The integration of GPS/IMU systems, VLSA 

imagery, and CRP techniques hold the 

potential to greatly expand field sampling 

intensities, thus enabling more representative coverage of the environmental gradients 

in the landscape. This will lead to better 

monitoring information and increased 

classification accuracies of coarse-scale 

remote sensing data. Additionally, the 

integration of these technologies would 

facilitate the development of proactive 

monitoring protocols for invasive species.

At all three study sites for which VLSA 

imagery was obtained, tamarisk (Tamarix 

spp.)—a salt-accumulating, desiccationtolerant invasive alien species—was shown 

to have cover values comparable to the 

native cottonwood (Populus fremontii). 

Given the high percentage of emergent 

features of the Powder River channel and 

the documented tamarisk succession 

scenarios of other western streams, 

tamarisk poses an immediate threat to 

the aquatic habitat and native riparian 

vegetation. By automatically geocorrecting 

VLSA imagery using the integration of 

GPS/IMU systems, great potential for 

cost-effective monitoring exists. This will 

allow for the development of protocols 

for riparian corridors that would enable 

invasive species to be identified before 

becoming so infested in an area that 

management actions become too 

expensive to implement (Bobo et al. 2008). 
22 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

Documenting 

Cultural Resources

The Legend Rock State Archaeological Site 

enables visitors to view more than 300 

petroglyphs spanning a period of thousands 

of years and representing multiple cultures. 

Legend Rock, located 28 miles from the 

town of Thermopolis in north-central 

Wyoming (Figure 17), was listed on the 

National Register of Historic Places in 

1973 and is world-renowned. A series of 

sandstone cliffs contain the petroglyphs. 

Ownership of the cliffs is split among a 

private land owner, Wyoming State Parks, 

and the BLM. In 2006, the Legend Rock 

Interagency Steering Committee was 

formed. This Committee includes land 

management agencies, as well as State and

local preservation groups and museums. 

The mission of the Committee is to provide 

guidance and recommendations to the 

Wyoming Division of State Parks and 

Historic Sites on the restoration, maintenance, management, interpretation, 

promotion, and public accommodation at 

the Legend Rock State Archaeological Site 

(Loendorf et al. 2008).

Photogrammetry staff from the NOC was 

included in the committee from its inception. In fall 2006, NOC staff, accompanied 

by imaging specialists for Cultural Heritage 

Imaging, a nonprofit organization that is 

developing an imaging technique (Mudge 

et al. 2006) complementary to CRP, joined 

archaeologists for a visit to the site. This 

reconnaissance visit provided an opportunity to see and access the site and to 

determine the approach and resources 

needed to fully photograph the rock art 

panels. As a result of the scoping trip, 

several proof-of-concept 3D image datasets 

were produced. These virtual 3D models 

and the CRP techniques were presented 

at committee meetings, professional 

archaeological meetings, and for the 2007 

Wyoming Joint Senate House Subcommittee 

on Recreation, Travel, Wildlife, and Cultural 

Resources. The 3D models provided stunning 

visualizations of the intricacies and 

uniqueness of the rock art, offering an 

early success and a catalyst to energize the 

committee (Figure 18).

A multiphased approach for documenting 

the site was developed. During the first 

phase, a spatially accurate photographic 

mosaic base map of the sandstone cliff 

was created. The corrected mosaic, tied to 

a digital real-world system with RTK GPS, 

served as base maps for field location, 

Figure 17. The 

Legend Rock State 

Archaeological Site 

is 28 miles from 

Thermopolis in 

north-central Wyoming.

Figure 18. The close-range photogrammetric 

digital 3D image models can be created and 

viewed on a laptop computer in the field, 

providing an on-site demonstration.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 23

inventory, and documentation of rock art 

panels. The cliff face was photographed 

from a distance of about 200 m with a 

150-mm lens (Figure 19). A resulting 

resolution and positional accuracy of 

about 1 cm was achieved (Figure 20). In 

addition, the digital photo mosaic can be 

used to provide visual context to more 

detailed, three-dimensional digital models 

of individual panels.

The second phase provides detailed threedimensional modeling and imaging of 

individual petroglyph panels. The virtual 

models can be used to record the petroglyphs 

and to detect even minute changes to the 

rock art that may occur over time. These 

highly detailed digital re-creations of the 

individual panels provide a resolution and 

accuracy in the tenths of millimeters and 

provide a baseline for monitoring the site 

for natural degradation and vandalism. 

Because of the enormity of the workload 

for DRS staff, the NOC photogrammetrists 

provided training in stereoscopic 

image capture to a State of Wyoming 

archaeologist involved in the project 

(Figure 21). In summer 2007, all the 

panels on the State-managed land were 

successfully photographed. In summer 

2008, the remaining rock art panels were 

photographed during a Passport in Time 

(PIT) project. The PIT program, originated 

by the Forest Service, allows qualified 

volunteers to assist in the restoration, 

recording, and preservation of cultural 

resource sites. During the 2-week program, 

photogrammetrists from the NOC provided 

training in stereoscopic image collection 

and software processing to the PIT 

volunteers (Loendorf et al. 2008).

Since the formation of the Legend Rock 

Interagency Steering Committee, funding 

for the site has increased, resulting in 

improvements to infrastructure. An 

archaeological survey was conducted 

(Walker et al. 2007) before improvements 

were made to roads, trails, and parking. 

The construction of a visitor’s center and 

accommodations for a site host are under 

way. The photogrammetric documentation 

will be used as a baseline for inspection 

and monitoring and for interpretive 

materials, to include a guide book for the 

site and interactive digital displays that 

Figure 19. The cliff 

face at Legend Rock 

State Archaeological 

Site, Wyoming, was 

photographed from 

about 200 m with a 

150-mm lens. Inset 

shows camera 

orientation and setup.
24 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

incorporate the virtual 3D image models. 

In addition, the Wyoming Joint Senate 

House Subcommittee on Recreation, 

Travel, Wildlife, and Cultural Resources 

made the preservation and interpretation 

of Wyoming’s cultural resources its first 

priority for interim study in 2008.

Figure 20. a. A corrected 

mosaic of the cliff 

face at Legend Rock 

State Archaeological 

Site, Wyoming, was 

created by using closerange photogrammetric 

techniques. b. Closeup view of the mosaic 

indicated by the black 

rectangle in a. The 

pixel resolution of the 

mosaic is about 1 cm.

a.

b.

Figure 21. 3D image model of a rock art panel from Legend Rock State Archaeological Site, 

Wyoming. The stereoscopic images were taken by a State of Wyoming archaeologist during 

on-site training conducted by photogrammetric staff from the BLM National Operations Center.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 25

to increase efficiencies. However, the 

basic geometry will remain the same 

and allow for measurements to be made 

from stereoscopic photographs taken 

100 years ago, yesterday, or 100 years in 

the future. Because of this, the concepts 

of capturing the data and not processing 

via specific software have been stressed in 

this document.

The following appendices contain technical 

information to assist field resource specialists in the successful completion of the 

imagery collection portion of a basic 

close-range photogrammetry project. 

Appendix A outlines the basics of stereoscopic photography. Appendix B discusses 

the features that should be considered 

when choosing a camera for CRP documentation. Appendix C discusses factors 

that can affect picture quality and offers 

suggestions on taking photographs that 

will provide successful results. Finally, 

Appendix D outlines the general steps 

for conducting the field collection of the 

photographs for a small CPR project. Also 

included in Appendix D is an equipment 

list. When reviewing this list, note that the 

majority of items (with, perhaps, a few 

exceptions) are the standard equipment 

most often taken to the field. That is the 

benefit of CRP: for the initial field trial 

of this technology, there is no substantial 

investment in equipment, only of time—

time to read and be familiar with the 

contents of this document and time to 

practice taking the needed photographs in 

the field.

CONCLUSION

Documenting and evaluating the condition 

of its land is a critical part of the Bureau’s 

mission. Condition data obtained by 

applying photogrammetric techniques 

provide information on the health of the 

land and serve as a basis for future decision 

making; they also provide a tool for 

determining the effectiveness of present 

management practices. The availability 

of digital cameras and the increasing 

capabilities of computers and analytical 

software have dramatically expanded the 

variety of resource applications to which 

photogrammetry may be applied, while 

simultaneously decreasing the costs of 

acquisition, processing, and analysis. The 

software used to process stereoscopic 

images to the viewing stage (corrected 

imagery and 3D surface data) and for use 

in GIS is presently available within only a 

few BLM offices. However, the capability 

to take the needed photographs for 

close-range photogrammetric projects is 

not. Field personnel with a vision toward 

the future will see the value in capturing 

stereoscopic photographs now. As the 

types, capability, efficiencies, and availability of 3DMM software increase, these 

photographs can be used in the future to 

document changes in condition critical to 

the Bureau’s mission.

The fundamentals of perceiving 

depth, stereoscopic viewing, and 

photogrammetry have remained constant 

through changing technologies. Various 

3DMM softwares available on the market 

today may suggest additional photographs 
A fixed grid of varying height was used as an early method of providing 

x,y, and z control at the Red Gulch Dinosaur Tracksite in Wyoming.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 27

Birch, J. S. 2006. Using 3DM Analyst Mine 

Mapping Suite for rock face characterisation. In F. Tonon and J. Kottenstette, 

editors. Laser and Photogrammetric 

Methods for Rock Face Characterization.

Bobo, M., T. Booth, S. Cox, N. Matthews, 

R. McDougal, G. Meyer, and T. Noble. 

2008. Application of high resolution 

remote sensing for monitoring aquatic 

and riparian habitats within the Powder 

River Basin in Wyoming. In 12th Biennial 

USDA Forest Service Remote Sensing 

Applications Conference RS-2008. 

[abstracts and program]

Breithaupt, B. H., and N. A. Matthews. 

2004. An integrated approach to threedimensional data collection at dinosaur 

tracksites in the Rocky Mountain West. 

Ichnos 11(1–2):11.

Forbes, K., A..Voigt, and N. Bodika. 2002. 

An inexpensive, automatic, and accurate 

camera calibration method. In Proceedings 

of the Thirteenth Annual Symposium of 

the Pattern Recognition Association of 

South Africa.

Hussain, M., and J. Bethel. 2004. Project 

and mission planning. In J. C. McGlone, 

editor, Manual of Photogrammetry, 5th 

edition. American Society for Photogrammetry and Remote Sensing. 1151 pp.

Loendorf, L., and C. McClellan. 2008. 

Management of Legend Rock 

Archaeological Site. Paper presented 

at the Binational Petroglyph Conference, 

Albuquerque, New Mexico, 

September 2007.

Matthews, N. A., T. A. Noble, and B. H. 

Breithaupt. 2004. Page 348 in Dinosaur 

tracks to dam faces: A new method 

for collecting three-dimensional data. 

Geological Society of America Abstracts 

36(5).

Matthews, N. A., T. A. Noble, and B. H. 

Breithaupt. 2006. The application of 

photogrammetry, remote sensing, and 

geographic information systems (GIS) 

to fossil resource management. Pages 

119–131 in S. G. Lucas, J. A. Spielmann, P. 

M. Hester, J. P. Kenworthy, and V. L. Santucci, editors. Fossils from Federal Lands. 

New Mexico Museum of Natural History 

and Science Bulletin 34.

Matthews, N. A., T. A. Noble, M. Bies, L. 

Loendorf, D. N. Walker, M. Mudge, and 

C. McClellan. 2007. Photographing the 

past, protecting the future: Using closerange photogrammetry to capture 3D 

images of the Legend Rock Petroglyph 

Site, WY. In 34th Annual Meeting of the 

American Rock Art Research Association, 

Abstracts and Program. La Pinta 33(4).

Matthews, N. A., T. A. Noble, W. G. Ypsilantis, 

and D. Murphy. 2007. Of time and the 

soil: Detecting microtopographic 

changes using extreme close-range 

photogrammetry.

Mudge, M., T. Malzbender, C. Schroer, and 

L. Marlin. 2006. New reflection transformation imaging methods for rock art 

and multiple-viewpoint display. In M. 

Ioannides, D. Arnold, F. Niccolucci, and 

K. Mania, editors. Proceedings of the 

Seventh International Symposium on 

Virtual Reality, Archaeology, and Cultural 

Heritage (VAST2007). Eurographics 

Association.

REFERENCES
28 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

Noble, T. A., and N. A. Matthews. 2007. A 

new look at capturing detailed 3D 

images of rock art: Advances in closerange photogrammetry. In 34th 

Annual Meeting of the American Rock 

Art Research Association. La Pinta 33(4). 

[abstracts and program]

Noble, T. A., N. A. Matthews, T. Booth, S. 

Cox, and M. Bobo. 2008. Application of 

close-range photogrammetric techniques 

to Very Large Scale Aerial (VLSA) 

Photography for monitoring aquatic 

and riparian habitats. In 12th Biennial 

USDA Forest Service Remote Sensing 

Applications Conference RS-2008. 

[abstracts and program]

Walker, D. N., M. Bovee, M. Karnopp, 

and T. Noble. 2007. Archaeological 

Investigations and Rock Art Recording at 

Legend Rock State Archaeological Site, 

Wyoming. In 65th Annual Plains 

Anthropological Conference Abstracts.

Ypsilantis, W. G., T. Noble, and 

N. Matthews. 2007. OHV Use Monitoring 

with Extreme Close-Range Photogrammetry. Project report to the BLM Field 

Office in Montrose, Colorado. Bureau of 

Land Management, National Science and 

Technology Center, Denver, Colorado. 

6 pp. [unpublished]
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 29

Figure A.1. Stereoscopic 

photograph pairs of a 

dinosaur track from the 

Red Gulch Dinosaur 

Tracksite, Wyoming.

Figure A.2. The large 

black dots represent 

photo centers and thus 

the camera position. 

A dashed rectangle is 

associated with each 

photo center dot and 

represents the field 

of view, or footprint, 

of that image. The 

best stereophoto pairs 

overlap each other by 

60%. This is achieved 

by actually moving the 

camera position of each 

photo by 40% of the 

photo’s footprint.

Stereoscopic photographs are taken to 

mimic the three-dimensional viewing 

capability resulting from the offset of a 

person’s left and right eyes (Figure A.1). 

The first consideration when designing the 

stereophoto layout is the needed precision 

(scale) that is required to adequately 

represent the subject. As in traditional film 

photogrammetry, the scale has a geometric 

relationship between the height of the 

sensor and the focal length of the lens 

(Hussain and Bethel 2004).

APPENDIX A

CONCEPTS OF STEREOSCOPIC PHOTOGRAPHY
30 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

Figure A.3. In this example, each image footprint is 1.65 m, thus the 

amount of stereoscopic overlap (at 60%) is 0.99 m (0.60 × 1.65 = 0.99). 

To achieve 60% overlap, the camera must be moved by 40% of the image 

footprint, which is 0.66 m (1.65 × 0.4 = 0.66).

Figure A.4. Graphic of parallel images with typically 60% overlap 

(Birch 2006). An imaginary ray (dashed line) drawn through the center 

of the lens should be as perpendicular to the plane of the subject 

as possible. All images are taken with one camera that is moved in 

sequence from position one to two, to three, and so forth.

scale = focal length

height above terrain

For example: 6 inches (0.5 feet) = 0.00025

2,000 feet

1/0.00025 = 4,000

Scale = 1:4,000

The pixel resolution, or Sensor Pixel Size 

(SPS), of a commercial digital camera can 

be factored into the preceding equation 

to determine the ground resolution, or 

ground sample distance (GSD), of the 

resulting image. The SPS is computed by 

taking the physical width of the sensor 

divided by the width of the sensor in pixels.

GSD = SPS * H / f

where SPS is the Sensor Pixel Size 

(in micrometers),

H is the camera height, or distance 

from the object (in meters), and

f is the focal length of the lens 

(in millimeters).

GSD will be in meters; multiply 

by 1,000 for GSD in millimeters

The best stereophoto pairs have an overlap 

of 60% (Figure A.2). Once the desired GSD 

is determined, the camera height and 

distance between camera stations can 

be calculated.

For example, when using a 10 megapixel 

SLR with a sensor size of 23.6 × 15.8 mm 

and pixel dimensions of 3,872 × 2,592, the 

SPS = 23.6 / 3,872 = 0.00610 mm. Therefore, with a 20-mm lens, and shooting at 

a height of 1.4 m above the subject, the 

GSD—is 0.43 mm. The area covered 

(or footprint) of each photo would be 

1.65 × 1.11 m. For a 60% overlap, the 

distance between camera stations is 

0.66 m, which is 40% of the image 

footprint (Figure A.3).
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 31

A simple way to determine the image 

footprint in the field is to mark points on 

the ground on either side of the frame 

of the viewfinder when the camera is at 

the appropriate distance from the subject. 

Then measure the distance between these 

points and calculate 40% of that distance.

The orientation of the camera or sensor 

to the subject is also an important 

consideration. It is most desirable to have 

imagery that is taken as close to nadir—

that is, with the camera perpendicular to 

the subject—as possible. A tripod (with an 

extension arm when shooting down) can 

greatly aid in positioning the lens directly 

over the subject (Figure A.4). This also 

positions the plane of the sensor parallel 

to the subject and helps to reduce 

perspective distortions in the image 

(Figure A.5).

In some instances, nadir photography 

is not practical because of constraints 

imposed by the terrain or project size. 

In such instances, oblique photography 

must be used.

Photographs deviating significantly from 

nadir that have a high angle to the object 

are referred to as high-angle oblique photos 

(Figure A.6a). When nadir photos are not 

a practical option, high-angle oblique 

Figure A.5. It is 

important for the 

camera to maintain a 

consistent relation to 

the subject. Keeping 

a perpendicular angle 

to the subject is 

preferable. The dashed 

line represents the ray 

described in Appendix 

Figure A.4. A tripod with 

an extension arm was 

used when photographing 

a dinosaur trackway at 

the Red Gulch Dinosaur 

Tracksite, Wyoming.

photos are preferred for several reasons: 

ability to get closer to the subject while 

still filling the frame, stronger angles for 

resolving the 3D coordinate positions, and 

less distortion of features.

Photographs taken at a low angle to 

the subject are referred to as low-angle 

oblique photos (Figure A.6b). Low-angle 

oblique photos are not desirable, as both 

the subject and control targets can be 

highly distorted. However, if an in situ 

object is being photographed and lowangle oblique photos are the only option, 

they may be used. With experience and 

care, low-angle oblique photos may 

successfully be used for measurement.

Figure A.6. A line of 

sight not directly nadir 

(perpendicular) to the 

subject is considered 

oblique. a. Photos taken 

at a high-angle oblique 

camera angle can be 

used when needed and 

will provide successful 

results. b. Photos 

taken when the line of 

sight to the subject 

is sharp (a low-angle 

oblique camera angle), 

should be avoided unless 

absolutely necessary to 

a. b. provide stereo overlap.
Extending the reach to photograph a difficult to access rock art panel in the Bighorn Basin of Wyoming.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 33

Digital cameras and 3DMM software have 

most certainly revolutionized the CRP 

process. Previously, an expensive metric 

or surveying camera was required. These 

cameras are equipped with required fixedfocus lenses with predetermined focal 

distances and are manufactured to a high 

level of precision and stability. However, 

even with care in manufacturing, lens 

distortions could not be completely 

eliminated and a manufacturer’s calibration 

report would accompany each camera. The 

calibration report includes the size of the 

frame, location of any fiducials, the focal 

length, principal point, and distortion coefficients of the camera–lens system. The 

information from the calibration report 

is used in setting up the stereo model so 

that the resulting measurements could 

be made without the effects of distortion 

from the camera–lens system.

Now the 3DMM software allows us to 

exploit the ever-increasing number of 

digital cameras on the market today. The 

main reason for this is that the 3DMM 

provides a camera calibration function. 

This not only removes the restriction of 

using an expensive metric camera, but also 

allows for the ad hoc calibration of most 

camera–lens systems. This is exciting, as it 

provides for the capability to increase the 

ground sample distance (GSD) as cameras 

come on the market with improved 

sensors. However, it also makes it difficult to 

suggest a particular camera, as innovations 

seem to occur frequently. It is important to 

note that, whereas a digital SLR camera 

is suggested, successful projects can be accomplished with a point-and-shoot camera. 

Thus, the following recommendations 

highlight features to consider when 

choosing a camera for CRP documentation.

Resolution

The final accuracy of your measurements 

and resulting terrain surface are governed 

by the resolution, or GSD, of the stereoscopic images of your subject. The GSD is 

governed by the resolution of the camera 

sensor (higher is better), the focal length 

of the lens, and the distance from the 

subject (closer is better). The resolution of 

the images is governed by the number of 

pixels per given area and the size of the 

sensor. A 6 megapixel resolution generally 

provides good results for a variety of 

subjects. However, an 8 to 10 megapixel 

resolution provides much more flexibility 

and achieves higher accuracies. The 

sensor size does have to be considered along 

with the resolution. The conventional way 

to categorize digital camera sensor size is 

similar to the sizing of television screens; 

that is, dimensions are given across the 

diagonal. The ratio of the sensor is often 

compared to the 35-mm film that it has 

replaced (43.3 mm diagional). The sensor 

does have a bearing on image quality, 

with the 28.4 mm sensor found in most 

digital SLR cameras having the best quality. 

The sensors of midrange cameras are 

often 11.0 mm, whereas those of compact 

digital cameras are 6.72 mm. These smaller 

sensors can introduce noise in the image. 

Thus, a compact digital camera with a 

1/2.7-inch sensor, even at 12 megapixels, 

would produce a less desirable image than 

one with a 11.0 mm sensor, at 8 megapixels.

APPENDIX B

CHOOSING A CAMERA
34 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

Lens Flexibility

The length of the lens directly affects the 

field of view (the base-to-height ratio, the 

distance from an object and, finally, the 

accuracy and number of photos needed to 

cover a subject). Shorter lenses (18 to 30 mm) 

provide the widest field of view and are good

for capturing a subject from close distances 

with a minimal number of photographs. 

Longer lenses (100 to 300 mm) are excellent 

for capturing a subject from greater 

distances but provide a narrower field of 

view. However, it can be expensive to have 

a variety of fixed-length lenses on hand.

Many digital SLR cameras are sold in a 

“kit” with a compound zoom lens. A fixedfocus lens will always produce a higher 

quality image; however, the kit lenses are 

good in that they provide versatility and 

can reduce start-up costs. Successful CRP 

projects can be accomplished with zoom 

lenses when special care is taken.

Manual Focus

Ensuring that a series of stereophotos are 

captured at the same focal distance is vital 

to the successful completion of a project. 

The capability to “take control” of the 

focus from the camera is accomplished by 

the manual focus setting. Most SLR and 

midrange consumer cameras have this 

capability. The manual focus setting helps 

to ensure that each photo in the stereo 

sequence is taken with the same focal 

distance (although autofocus can be used 

as long as a constant distance between the 

camera and the subject is maintained).

Aperture Priority

The aperture setting not only determines 

the amount of light that reaches the sensor 

but also controls the depth of field (the 

point at which the image begins to blur). 

Thus, it is necessary to use a camera for 

which the aperture can take priority over 

the other settings that affect the lighting, 

such as shutter speed or ISO (International 

Organization for Standardization; http://

www.dpreview.com/learn/?/Glossary/Digital_

Imaging). Although this feature is standard 

on digital SLR cameras, it may not be 

available on compact cameras.

Image Format

There are a number of different digital 

image formats. Each format has advantages 

and disadvantages based on the use and 

type of compression. Digital image files 

that are unprocessed, or RAW, contain the 

original information from the sensor 

and capture a greater bit depth than 

other standard formats. The RAW images 

must be processed in some type of image 

manipulation software, which often comes 

with the camera, or third party software 

such as Adobe Photoshop. The ability to 

manipulate the RAW image provides for 

the opportunity to make some exposure 

corrections after the photos are taken and 

may allow for the extraction of detail in 

areas of deep shadow. Other types of image 

files, such as .jpg (Joint Photographic 

Experts Group) and .tif (Tagged Image File 

Format), are processed within the camera 

and will not provide the same amount of 

flexibility in post processing (http://www.

dpreview.com/learn/?/Glossary/Digital_

Imaging). Cameras that capture images in 

RAW file format, or a combination of .jpg 

and RAW, are preferred.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 35

Lens Distortion

All camera lens systems have distortions 

because of the curvature of the lens and 

the alignment of the lens with the 

sensor. To quantify these distortions 

and effectively remove them, 3DMM 

software provides camera calibration 

functions as part of the project workflow (Figure B.1). The additional images 

needed for the camera calibration 

can be easily integrated into the 

stereoscopic workflow and are 

discussed in Appendix C.

The following cameras have been 

successfully used within the BLM for 

CRP projects: Canon Powershot A640; 

Olympus C8080 and EV500; Nikon D70, 

D80, D200, and D3; and Canon 5D 

and 1D.

Figure B.1. a. Photograph 

of a straight-line 

rectangular grid. The 

curvature of the lines 

is due to the most 

common type of lens 

distortion, which is 

barrel distortion.

a.

b.

c.

b. Graphic representation 

of lens distortion. The 

least distorted portion 

of the lens is in the 

center (depicted in 

blue). During the camera 

calibration process, the 

focal length, format 

size, principal point, and 

distortion coefficients 

(K1, K2, K3, P1, and P2) of 

the camera–lens system 

are calculated.

c. The corrected 

photograph from a. 

after the lens distortion 

parameters were applied. 

The results can be 

seen in the straightening 

of the grid lines and a 

visible change of the 

image.
Due to the minimal equipment requirements of close-range photogrammetry, subjects in difficult 

terrain, such as this area north of Albuquerque, New Mexico, can be documented more readily.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 37

The crucial element to a successful closerange photogrammetric process is attaining 

“good” photographs. In this instance, the 

term good refers to a series of pictures 

that have uniform exposure and are highcontrast, sharp images that fill the frame 

with the subject. Close-range photographs 

may never appear on the cover of National 

Geographic magazine or thrill your friends 

and neighbors, but they must be of sufficient 

quality that the autocorrelation function of 

the 3DMM software can function properly.

Environmental factors, the camera used, 

and the experience of the photographer all 

contribute to the success of the CRP project. 

The following section offers recommendations for composing your photos and 

correctly adjusting the camera settings. It 

is important to have adequate experience 

with the camera you are using and be able 

to adjust it to meet the circumstances. If 

you can operate your camera and understand the techniques for capturing CRP, you 

will be able to document, in measurable 3D, 

almost any subject at almost any time, just 

with a camera and your brain.

Taking Good Pictures

Several requirements must be met when 

taking photos suitable for photogrammetry. 

Every photo needs to be clear, properly 

exposed, and have adequate overlap with 

adjacent photos (Appendix A).

Lighting is one of the most critical factors 

in taking good CRP photographs, and 

perhaps one of the most difficult to control. 

The 3DMM autocorrelation process works 

very well for properly illuminated, highcontrast areas. However, areas of low 

contrast and uniform color, areas with 

high relief displacement, or areas that are 

obscured (by deep shadows or other 

features) can lead to mismatching and 

poor terrain correlation. One of the biggest 

causes of poor photos is inconsistent light 

caused by shadows. Shadows can be created 

by features of the subject that you are 

documenting or cast by features outside the 

area of interest (such as your head). When 

photographing out-of-doors, choose a time 

of day when shadows are minimal. This may 

occur when the sun is directly overhead. 

The resulting photographs may not 

emphasize the subject visually; however, 

properly exposed images taken in full sun 

have outstanding results during autocorrelation. Use proper camera settings to 

ensure photographs taken during full sun 

are not overexposed. Other times of consistent lighting can occur on overcast or 

cloudy days, or when the subject is in full 

shadow. In these instances, it may be 

necessary to slow the shutter speed or use a 

tripod to ensure that photographs are not 

underexposed. Keep in mind that lighting 

and weather conditions can change quickly.

When shooting indoors, make sure the 

area is as well lighted as possible. Take a 

few test shots and examine them to make 

sure that images are not underexposed or 

blurry. Indoor illumination can be a problem 

and it may be necessary to slow the shutter 

speed or use a tripod to ensure that 

photographs are properly exposed. Using 

the flash function of the camera is not a 

good option, as it can cast odd shadows 

and flares that fall differently through 

successive stereo pairs, thus affecting 

autocorrelation. However, stationary light 

sources such as floodlights, which evenly 

illuminate the subject, may be necessary in 

APPENDIX C

TAKING GOOD PICTURES AND 

SUGGESTED CAMERA SETTINGS
38 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

very low light conditions. When setting up 

lighting, make sure to provide adequate 

room around the subject for taking a 

complete set of stereophotos.

Filling the frame with the subject is also 

crucial. For small CRP projects, it may be 

most straightforward to observe the 

subject through the viewfinder to best 

determine camera height and overlap. 

When photographing a larger project or 

when oblique orientations are necessary, 

remember to center your subject in the 

frame. There is often no need to ensure 

the horizon or other points of reference are 

in every frame, especially if they detract 

from the subject that is being documented.

Camera Settings

The 3DMM software used for close-range 

photogrammetry documentation supports 

a great variety of cameras. Therefore, it is 

beyond the scope of this document to list 

each setting on each camera that could 

possibly be used for CRP documentation. 

The following should serve as a general 

checklist and reminder of settings to check 

for and should aid in avoiding pitfalls. 

However, it is important that the operator 

be familiar with the camera to be used for 

CRP and with the results that will be 

produced as settings are manipulated.

Focal Length and Distance

The settings that most dramatically affect 

success of the CRP project are the focal 

length (lens or zoom length) and focus distance. A fixed focal length lens makes this 

process most efficient; however, the zoom 

capability of multifocal length lenses can 

be an asset in variable field conditions as 

the camera lens system may be zoomed or 

focused to any setting that is appropriate 

for capturing project detail. However, it is 

necessary to perform the camera calibration 

and conduct the project at the same focal 

length and focus distance. A streamlined 

approach for multifocal length lenses is to 

zoom to either the minimum or maximum 

extent of the lens and set the focal distance 

to infinity. Use tape with a minimal amount 

of residue, such as painters tape, to fix the 

lens in position.

For cameras that allow the operator to switch 

freely between autofocus and manual 

focus, the following produces effective 

results: Hold the camera at the height or 

distance at which you will be shooting or 

mount it on the tripod. Turn the control to 

autofocus and take a shot. Check that the 

distance registered on the lens is accurate 

and check the LCD (Liquid Crystal Display), 

or download the image to make sure it is 

in focus. Then switch to manual focus and 

tape the lens ring to make sure it does not 

move for the session in which you will be 

shooting at that constant distance.

Focus Weighting

Many cameras allow you to dictate how 

the appropriate focus is determined. For 

example, the camera may take readings 

from the center of the field of view, average readings from a number of locations, 

or take continuous readings. It is important 

to take several test shots and vary the 

mode of determining the autofocus to 

ensure that the appropriate focus is 

achieved for a particular situation.

Aperture

Set the camera on aperture priority. An 

aperture of f8 (or 35 mm equivalent) is 

recommended for CRP, as this provides a 

good depth of field. Proper depth of field 

ensures that the entire subject is in good 

focus, which is important for image matching. When shooting at a close distance to 

the subject, it may be necessary to increase 

the aperture to f11 or stop down the 

aperture to get the best depth of field. 

Refer to your camera manual or digital 

photography guide for a thorough 

discussion of aperture and depth of field.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 39

“Film” Speed

The sensitivity of the sensor to light is 

defined by the International Organization 

for Standardization (ISO; http://www.

dpreview.com/learn/?/Glossary/Digital_

Imaging). The ISO setting affects the 

amount of light that the sensor will absorb 

during a defined period. The ISO range of 

a camera is dependent on a number of 

factors and it is helpful to consult the 

camera manual when setting the ISO. In 

general, the brighter the lighting conditions 

the lower the ISO. When shooting outside 

on a bright, sunny day, an ISO of 100 (or 

even lower if supported by the camera) 

is appropriate. In low-light situations, it 

may be necessary to increase the ISO to 

compensate for the aperture setting of f8. 

It is possible to get graininess or artifacts 

when the ISO has been pushed too high. 

Testing for the optimum ISO is important 

in low-light conditions.

Shutter Speed

While the shutter speed will be determined 

automatically by the camera once the 

aperture and ISO have been set, it is a 

good idea to be aware of the shutter 

speed. A shutter speed of at least 1/200th 

of a second is required for handheld 

photography. For lower shutter speed, 

adjusting the ISO or mounting the camera 

on a tripod may be necessary. Should there 

be camera motion from the wind or an 

unstable platform (such as a ladder), high 

shutter speeds (more than 1/1,000th of a 

second) may be necessary.

File Format

If possible, set to a combination of 

RAW + FINE. If not, set the file format to 

RAW if available; otherwise, set to the 

highest quality .tif or .jpg possible.

Image Rotation 

Turn this setting off. The photo orientation 

must be known with respect to the camera 

and lens. Automatic image rotation will 

rotate the image 90° clockwise or counterclockwise. At first, this may not seem like 

it would cause a problem, but experience 

has shown otherwise. When taking nadir 

photos, it is sometimes impossible to tell 

which way the camera was rotated when 

the picture was taken. This can easily 

happen if photos are taken on opposite 

sides of a subject with no horizon in the 

view. The camera calibration cannot be 

applied correctly if the original orientation 

is not known.

File Naming

Most digital cameras provide the option 

to customize the file name or numbering 

template. Two basic options are the 

continuous numeric incrementing of file 

names and restarting the numbering 

sequence each time the memory card is 

reinserted. Consecutive numbering is the 

best option, as it helps to ensure that 

image files are not overwritten during 

download. In addition, duplicate file 

names may be a problem when processing 

several sequences of images together in 

the same project.

Custom Settings

As digital cameras advance, so do the 

options for settings that are tailored to a 

specific brand of camera. These settings 

include auto sharpening, white balance, 

vibrating of the sensor to dislodge dust 

particles, and others. Once again, it is 

strongly recommended that time is taken 

to experiment with how each of these 

settings, will affect image quality and 

usability in a CRP project. In most instances 

(especially image sharpening, stabilization, 

and sensor vibration for cleaning), it is 

important to turn off these options.
Objects of known length, with circles at a calibrated distance and circular barcodes, surround a 

1- meter-square area of biological soil crust in the Dry Creek Basin near Montrose, Colorado.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 41

To take useable stereophotos, some procedures must be followed. By adhering 

to these procedures, quality photos and 

efficient processing of those photos is 

ensured. In general, the steps to be followed 

are the same regardless of the camera or 

subject being photographed. However, 

certain circumstances will require flexibility 

and ingenuity, which comes with experience.

Close-Range Photogrammetry (CRP) projects 

can be placed into one of two categories—

small (simple) and large (complex). Large 

projects are those with an area of interest 

greater than 5 m2 or where complexities 

of terrain or access add to the level of 

expertise needed for planning and execution 

of the project. Projects that fall into 

this category may require a preliminary 

site visit or the inspection of overview 

photographs taken of the area. In some 

instances, the needed vantage points for 

capturing imagery may not be present, 

necessitating alternatives to ground-based 

capture, such as the use of a large ladder, 

aerial blimp, unmanned aerial system, or 

other type of elevated platform. Whereas 

the same basic procedures and equipment 

apply to both small and large projects, it 

would be difficult to address all the 

complexities that could arise with large 

projects and is beyond the scope of 

this document.

Small projects have an area of interest 

equivalent to or smaller than about 5 m2. 

This type of project may also be referred 

to as extreme close-range as high precision 

of data points is expected. Design and 

image acquisition for small projects may 

be successfully carried out by resource 

specialists in the field. An overview of the 

procedures for small or extreme CRP will 

be provided in this appendix.

Project Planning

The first step in project planning is to 

establish the need for capturing 3D data 

of a subject and the detail and accuracy at 

which the data must be captured. Because 

of the versatility of the CRP process, the 

images needed for 3DMM process can be 

easily captured. This provides great flexibility in the subjects and uses for 3D data. 

Examples of data capture and use include 

the establishment of plots for vegetation 

or erosion monitoring, baseline capture of 

a feature, taking measurements of a 

delicate subject that can (or should) not 

be touched, and dense surface capture for 

hardcopy reproduction.

Because of the flexibility of the CRP technique, it is possible to obtain high accuracy 

3D data from subjects that are at almost 

any orientation with respect to the camera 

position. Documentation can be conducted 

looking straight down at the ground, 

looking straight ahead at a rock art panel 

or historical structure, looking at a hillside 

from an oblique angle, or looking overhead. In all these instances, the same basic 

principles apply. It is important to get the 

plane of the sensor and lens parallel to the 

subject, to maintain a consistent height (or 

distance) from the subject, to ensure the 

subject has consistent illumination, and 

to make sure there is an object of known 

length in at least three images. To streamline the following discussion, it will be 

assumed that the camera is facing straight 

down at the subject. If this is not the 

situation, camera distance can be 

interchanged for camera height.

In general, the subject of 3D documentation 

falls into one of two categories based on 

the size of the feature to be captured. 

Appendix D

Conducting a CRP Project
42 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

Either it is small enough that it may be 

captured in its entirety (such as a rock art 

panel) or it is so large that only samples 

of the area can be economically captured 

(such as soil erosion monitoring plots). These 

subjects are referred to as predetermined 

and sample, respectively. Predetermined 

subjects are specific features that are to 

be documented, such as a dinosaur track, 

historical structure, specific erosional 

feature, or something specific that must 

be measured. Sample features refer to 

situations where there is a defined area to 

be studied, but the exact site of the CRP 

project can be selected within that area. 

An example would be the establishment 

of a plot for erosion, vegetation, or other 

types of monitoring. The following section 

makes recommendations for establishing a 

sample monitoring plot.

Sample Plot Establishment

For areas as large as 5 m2, stereoscopic 

images with a GSD of 0.5 mm are easily 

achievable. For most applications, this 

would provide a suitable level of 3D documentation. It is, therefore, necessary to 

determine the size of the plot. Depending 

on the study to be undertaken, the size 

can vary from 0.5 × 0.5 m2 to a rectangular 

area of 1.0 × 5.0 m. It is recommended that 

sites be selected with different geomorphic 

characteristics. Keep in mind that vegetation 

can have an effect on the density of 3D 

data collection. This can result from plant 

movement caused by wind during successive 

stereophoto acquisition or by simply 

obscuring the ground. Choosing a site with 

minimal vegetation would be optimal; 

however, information may be gained by 

selecting sites with varying vegetation types, 

heights, and percentages of ground cover.

Choose a location where the effect on the 

site can be limited. Try not to step or walk 

within the sample area, especially if the 

activity will affect the results of the study. 

If the CRP is going to be repeated over 

successive intervals, it is important to place 

monuments, such as survey nails or rebar 

(if appropriate), at the four corners of the 

site and at least one additional point in 

the middle of each side, for a total of six 

monuments. Longer plots should have 

additional monuments along the sides 

(one every 1.5 m is suggested). The 

monuments should be driven flush to the 

ground to minimize movement. File the 

top of the rebar to smooth the top surface 

and the edges. Make sure the top of the 

rebar is as smooth as possible. Monuments 

should have a small center point punched 

into them for exact positioning or marking. 

It is important that the monument be visible 

in the stereo sequence. To ensure ease 

of location it is helpful to place a circular 

object over the rebar. A compact disk (CD) 

that has been spray-painted white works 

very well. It is important to ensure that the 

rebar used is small enough to fit snugly 

inside of the hole in the CD. If a number of 

plots are to be established, it is important 

to consider both the amount of time 

required to travel between sites, as well 

as setup time.

Predetermined Sites

For projects in which the subject is 

predetermined, the size of the area to 

photograph will be dictated by the extent 

of the feature. Deviations from this may 

occur when the feature is larger than 

5 m2, and only a portion of it will be documented. In this instance, it is necessary 

to choose an area that will provide the 

most representative information for the 

entire site. Although the long-term goal 

of the documentation may be monitoring, 

it is not always permissible to mark many 

subjects (such as cultural resources) with 

a monument. In these instances, selecting 

unique, photoidentifiable natural features 

as reference points may be necessary, and 

the use of high-accuracy GPS to relocate 

established control points over time may 

be required.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 43

Photo Layout

Once the size and area of interest have 

been established, the next step is to determine the most effective photo layout. It 

is important to strike a balance between 

the level of resolution needed, completely 

covering the area with overlapping 

stereophotos, setup time, and processing 

time. Two approaches can be taken—one 

minimizes the number of photos needed 

and the other sets out to achieve a 

particular resolution.

Several examples (Figures D.1, D.2, and 

D.3) illustrate the layouts that can be used 

for CRP, including single strip and block 

layouts. When preplanning a photo layout 

or doing so on an ad hoc basis in the field, 

it is important to maintain a consistent 

height and 60% overlap for good 

stereoscopic photographs (see Appendix A).

Figure D.1. A small subject requiring a single stereo pair. When needed, 

an identification (ID) sheet can be placed in the first frame of the 

stereo sequence, to the left of the area of interest. ID sheets are 

helpful when photographing a series of subjects that have reference 

identification codes, such as monitoring plot numbers or museum 

catalogue codes. The date, weather conditions, photographer, and other 

types of information can be added to the ID sheet.
44 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

Figure D.2. Photo layout for a single strip of overlapping stereoscopic photography. A single camera is used to 

photograph each image in succession by moving from one camera position to the next. Note that control points are 

only necessary when tying photographs to an established reference, such as real-world coordinates or a monitoring 

datum. An object of known length or calibrated control stick is always necessary.

Figure D.3. In some instances, the size of the subject may dictate that two or more lines, or strips, of photography 

are needed to completely capture the subject in stereo. In these instances, a block approach is taken. For a block it 

is necessary to maintain about 20% sidelap between strips. Control points in the sidelap area are useful. This figure 

uses low-level aerial images from the Powder River Monitoring project to illustrate overlap and sidelap for block setup.

Camera Calibration

Camera calibration photographs must 

be captured at the same settings as the 

stereophotos. This can be achieved by simply taking at least two additional photos 

turned 90° to the previous photos and 

two additional photos turned 270° to the 

previous photos (Figure D.4). This is easily 

accomplished by adding two additional 

photographs at the beginning or end of 

the stereo shots. The main purpose of the 

camera calibration is to determine and 

map the distortions in the lens with 

respect to the sensor location. The software 

accomplishes this most effectively when 

there are a large number of autocorrelated 

points in common between the stereoscopic 

images and the additional 90° and 270° 

photos (Figures D.5 and D.6). In some 

instances (such as a strip of only a few 

models), it may be desirable to recapture 

the entire strip at 90° and 270°.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 45

Figure D.4. The camera calibration process requires at least four additional photos. By concentrating the 

previously taken stereoscopic photos (landscape) and portrait-oriented photos taken at 90 ̊ and 270 ̊ over 

the same area, maximum benefit will be achieved in the camera calibration portion of the software.
46 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

Figure D.6. Camera calibration photos for a block setup. In addition to the camera calibration, images taken in the 

above configuration can serve to tie the two strips together and improve accuracy (Figure D.3).

Figure D.5. To ensure project accuracy, it is necessary to take additional photographs to be used in the camera 

calibration process. These photos are taken at right angles, or 90° and 270°, to the sequence of stereoscopic 

photos and MUST use the same settings (particularly focus and focal distance). At least four photos are needed 

and should be stereo pairs. They may be taken at any position in the stereoscopic sequence as long as they are 

in common with it. At least one stereo pair must be taken with the camera turned at 90°, and then the camera 

should be turned 270° with another pair of photographs taken at a slightly different location.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 47

Photo Control

Another level of flexibility provided by CRP 

over traditional photogrammetry is in the 

way a subject may be controlled. Control 

for a user defined coordinate system can 

be accomplished as simply as adding an 

object of known dimension (meter stick, 

6-inch scale, or other object) that is visible 

in at least two stereo models. This allows 

the subject to be scaled to real-world 

values. It is preferable to have two or 

more such objects, to ensure that they are 

visible in at least three photographs and 

for accuracy assessment. Experience has 

shown that an object of known dimension is more accurate and reliable than 

measuring between two points in the 

field. However, measuring and recording 

the distance between two or more points 

is another excellent means for confirming 

project accuracy.

Calibrated target sticks (CTS) may be used 

in addition to the object of known dimension (Figure D.7) to provide extra control, 

and in some instances, can help tie photos 

together during processing. The CTS 

depicted in Figure D.7 are equipped with 

large, black circles that are a calibrated distance apart. In addition to the calibrated 

circles, a series of circular bar codes (Forbes 

et al. 2002) can be generated within some 

3DMM software. Each unique code can be 

recognized, correlated to the same code 

visible on other photographs, and marked 

with very little user interaction. If coded 

targets are not available, solid color circles 

of high contrast to the background (black 

on white) can be used by subpixel marking 

methods to define the center of a circle.

To tie the CRP project into a real-world 

coordinate system, GPS positions for 

known points within stereo overlap are 

necessary. For monitoring or other studies 

that require a time sequence of image 

capture, it is beneficial to get high-accuracy 

horizontal and vertical coordinates from 

an RTK GPS. The GPS coordinates should 

be taken at the monumented points; 

additional coordinates can also be captured 

for other photo recognizable features to 

strengthen the resolution and for accuracy 

checking. For projects in which location is 

not as critical, a resource grade GPS unit 

may be used and point coordinates taken 

at the CTS circles.

Figure D.7. Examples of 

calibrated target sticks 

(CTS) and an object 

of known length. The 

center CTS contains 

circular bar codes, 

which are used by 

some three-dimensional 

measuring and mapping 

software and assist 

with the initial image 

orientation process.
48 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

Other Considerations

Context Photos

While capturing the stereoscopic photos, it 

is also helpful to take an overall contextual 

photo (yes, you can include the horizon). 

It helps to remind you of how things were 

set up and can be used as an interesting 

illustration (Figure D.8). Also, make sure to 

get some photographs of the photogrammetric documentation in progress (Figure 

D.9). It is preferable to have a secondary 

camera (this can be a point-and-shoot), 

which allows photographs to be taken 

without disrupting the focus or settings of 

the primary camera.

File Management

File management is extremely important. 

The digital age has advanced us to where 

the acquisition of photographs is practically 

free. With the help of 3DMM softwares, 

photos can be used to make quantifiable 

measurements, transforming them from 

just pictures to data. Stereophotos may be 

used for data extraction the day they are 

taken, or years later. To ensure that these 

photos are still accessible, it is recommended 

that a consistent approach to file 

management be taken.

One strategy is to group files into directory 

structures that are organized by State or 

field office, site, date, and then by camera 

or lens, for example:

UTMoab/date/nik25/photos.tif

This may seem unlikely, but getting more 

than 10,000 close-range photographs 

may take a relatively short time. One of 

the values of the photogrammetric techniques is that photographs taken from the 

past (or future) can be incorporated into 

a project so that sites can be compared 

and monitored for change detection. For 

some projects photographed over multiple 

years, those digits can add up quickly.

Figure D8. The results 

of merging a contextual 

photo with the camera 

locations generated in 

the three-dimensional 

measuring and mapping 

software are very good 

for displaying image 

relations. (Camera 

stations are depicted 

above the surface as 

blue rectangles and the 

image prints are depicted 

as blue and green Xs on 

the surface.) The image 

highlights locations 

of extreme closerange photogrammetric 

documentation at the 

Twentymile Wash 

Dinosaur Tracksite, 

Utah. 
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 49

Figure D9. Work in 

progress at a camel 

trackway on BLM land 

near Santa Fe, New 

Mexico.
Preparing to take a single sequence of overlapping photographs at the Red Gulch Dinosaur Tracksite in Wyoming.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 51

General Procedures for a Small, Close-Range Photogrammetric Project

•	Evaluate subject and establish extent of the area to be photographed.

- Assess public interactions. When working at a site visited by the public, it may be 

necessary to have an additional person to act as docent. This person can serve the 

dual function of reducing the effects of visitors on the photogrammetric process and 

explaining the photogrammetric work to the public.

- Temporarily mark the area to be photographed.

- If necessary, prepare the site by removing extraneous debris or objects that may be 

obscuring the terrain to be measured.

- Sweep or clean, if hard surface. Proceed with care when documenting fragile or 

protected subjects!

•	 Determine the sun angle and best location to stand or position the tripod without 

casting shadows onto the subject.

•	Establish final extents of project area.

- If appropriate, place a monument with survey nails or rebar while disturbing as little 

of the area as possible.

- Place CDs over each of the rebar monuments. (CDs should be painted with flat white 

paint). The CDs will obscure some of the sample area; however, the ground will 

already have been locally disturbed. 

•	Lay target sticks parallel to a long side, just outside the sample area.

- Follow the photo layout (Figures D.1, D.2, D.5, and D.6)

- Do not obscure features or control.

- Position the target sticks along the side that the photographs will be taken from.

•	Set up the tripod; attach the boom arm and add counterbalance weights to the legs, if

necessary, to offset the camera if working on a slope. Set the tripod to proper height.

•	Fill out the site recording sheet

- Date

- Site ID

- Record next photo number.

- Place the recording sheet clipboard on the ground outside, but near, the site.

•	Set the camera to the appropriate settings (see Appendix C). Change the ISO,

if necessary, for light conditions.

•	Mount the camera on the tripod, adjust height, and ensure that the proper

overlap is achieved.

Project Workflow

The following section is a general workflow for a small project. It is presented 

in outline form to serve as a guide and 

checklist. As the photographer becomes 

more familiar with the process, this list can 

be tailored to his or her experience and 

specific project requirements.
52 Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation

•	Set the camera to autofocus, take a picture, and inspect it for quality—focus,

exposure, and other characteristics. Make adjustments as necessary.

•	Once the focus is set, turn the camera to manual focus and

tape the focus ring in place.

•	Proceed systematically from left to right along the length of the site and take as many

photos as necessary to ensure complete stereo coverage.

- To maintain a proper 60% overlap, the camera must be moved a distance equivalent 

to 40% of a single photo field of view (Figure A.2).

- Remember—the entire area must be covered by at least two overlapping photos, 

this will require positioning the left extant of the project in the first frame of the 

sequence.

•	In order to create a camera calibration, take additional photos turned 90° and 270° to

the previous photos:

- At the end—turn and take a picture of the end of the site. Camera will be turned 

90° and 270° to the site.

- Go back to the start of the site and take a picture. Again, camera will be turned 90° 

and 270° to the site.

- Additional 90° and 270° photos can be captured anywhere along the strip.

•	When conducting several small projects in sequence, it may not be necessary to

change focus or camera settings if the height remains constant. In this situation, it is 

helpful to have a sight recording sheet in the first image of that sequence.

If possible, download photos and inspect for proper exposure and overlap before removing target sticks or CDs positioned on GPS control.

•	Back up images (including RAW files) onto DVD or external hard drive.
Aerial and Close-Range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation 53

Equipment Check List

___ People

___ Person to take photographs

___ Assistant to prep the site and keep 

track of work progress

___ Docent to interact with public 

(may be needed at visited sites) 

and take photos of documentation 

process

___ Camera and lens for CRP 

documentation

___ Secondary camera for backup and to 

document CRP process

___ Camera Accessories

___ Battery charger or extra batteries

___ Additional lenses equipped with 

protective bypass filters 

___ Painter’s tape or other lowadhesive tape

___ Spare memory cards

___ Remote shutter release

___ Lens cleaner or brush

___ Padded camera case

___ Laptop Computer

___ Card reader or appropriate cable 

for downloading images

___ Image backup—either portable 

hard drive or blank DVDs

___ Image software (preferably the 

software that came with the 

camera)

___ Power cord

___ DC adapter (if available)

___ Objects of known dimension

___ Commercial meter (or yard) sticks

___ Calibrated target sticks of varying 

lengths (see Figure D.8) 

___ Removable adhesive putty may 

be used for temporarily securing 

target sticks, although even this 

may not be appropriate for some 

delicate surfaces.

___ Sturdy Tripod

___ Boom or extension arm

___ Quick release head

___ Extra release plates

___ Small screwdriver

___ Leg weights for camera 

counterbalance to keep the tripod 

from tipping over

___ When Establishing Location

___ GPS unit

___ Resource grade or RTK system 

(depending on desired product 

accuracy)

___ Survey nails or rebar

___ Sledge hammer, small chisel, and 

file

___ CDs spray-painted white

___ Power Accessories

___ Multiple-receptacle power strip

___ DC power inverter for car use

___ Miscellaneous Items

___ Measuring tape

___ Notebook and pencil

___ Pocket calculator

___ Small dry erase board or clipboard 

with identification sheet and 

markers

___ Circular disks (such as clay poker 

chips) to mark features or image 

extents

___ Step stool or ladder

___ Small tarp for shade or wind 

protection

___ Rope

___ Duct tape

___ Wisk and push brooms (when 

appropriate)

___ Tree loppers or prunners (when 

appropriate)

___ Pin flags or flagging tape

___ General field necessities 

(water, snacks, sun screen, insect 

repellent, hat, other items)
Setting up a GPS unit to reestablish positions for change detection at the Falcon Road Open 

OHV area within the Gunnison Gorge National Conservation Area near Montrose, Colorado.
PhotoModeler is a product of Eos Systems: http://www.photomodeler.com/

ImageStation is a product of Intergraph: http://www.intergraph.com/istationssk/

3DM Analyst is a product of ADAM Technology: http://www.adamtech.com.au/

The mention of company names, trade names, or commercial products does not constitute endorsement 

or recommendation for use by the Federal Government.

Three-dimensional surface data with false color based on changes in elevation. 

Image of the natural rock art surface near Newcastle, Wyoming, shown in the inset.
Oblique aerial view, taken with a large format (9 x 9 inch) aerial camera, of 

Escalante Canyon in the Grand Staircase-Escalante National Monument in Utah.