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This question was recently

answered at BLM’s Red Gulch

dinosaur tracksite in Wyoming

through the use of close-range

photogrammetry and computer

modeling techniques.

In the past, paleontologists

had to spend a great deal of

time at the site where dinosaur

tracks were found to answer this

question. Their main resources

for determining what species of

dinosaur made the tracks were

the tracks themselves. But what

if the site was not always accessible or further analysis was

required in a laboratory setting? 

Traditional methods, such as

casting, have sometimes been

used for studying dinosaur

tracks when it is not feasible to

use the original tracks. But

casting can be harmful—at best,

casting can leave material in the

tracks that can collect water and

hasten erosion, and at worst, it

can remove bits of rock from

the tracks. 

In order to minimize damage

and preserve the original tracks,

the Bureau of Land

Management’s National Applied

Resource Sciences Center

(NARSC) has been exploring

other options for analyzing

these precious resources. Closerange photogrammetry is one

option that has been tested at

Red Gulch in Wyoming. By

combining the science of photogrammetry with the modeling

capabilities of today’s computer

software, BLM is stepping from

the past into the future.

Why photogrammetry?

Photogrammetry is the science of making measurements

from photographs. Close-range

photogrammetry allows for precise measuring without degrading an object or causing it harm. 

Traditionally BLM has used

photogrammetry to compile features from standard aerial photographs, including topographic

contours, drainage features, vegetation, roads, and other manmade features. Now, specialists

at NARSC are applying these

methods to assist BLM and university paleontologists with scientific investigations in the field

by producing topographic contour maps and controlled stereoNO. 3 DATE 02/16/99

What Dinosaur Left These Tracks?
graphic images of individual

dinosaur tracks.

The contour maps provide

details such as the depth of the

track, in millimeters, and equal

elevation contours that highlight

the morphology of the track, as

well as other features that

appear on the rock strata. By

using the photogrammetrically

generated contours, a paleontologist can study the impression

made by the dinosaur’s foot to

help determine species,

height/weight, and stride.

Controlled stereographic color

images, when viewed with

red/blue glasses, bring out the

depth of the track. Along with

the contour maps of individual

tracks, they can be used for further analysis in a laboratory setting, even by scientists who have

never been to the original sites.

They can also be used as a baseline for future comparison to

determine the effects of visitation and erosion. 

How precise are the

measurements? 

By using a calibrated camera,

measurements can be taken to

within + 1 millimeter. A calibrated camera has a detailed

report that gives the precise

measurements of the reseau grid

(the + marks on the photo), as

well as the optical distortions of

the lens. This camera, in combination with a few precisely

located control points, allows

for detailed measurements of

the track.

What does this mean

for future resource

management? 

Paleontology is just one application for photogrammetry —

the potential for many other

applications is great. Projects

using close-range photogrammetry provide opportunities for

BLM to apply its traditional

method of accomplishing work

in new and innovative ways.

Submitted by Neffra Matthews, 

Cartographer

BLM National Applied Resource

Sciences Center,

Denver, Colorado

(303) 236-0176,

email: nlmatthe@sc.blm.gov

Resource Notes are intended to be

early announcements of technical and

informational topics for

Bureau of Land Management personnel

and some of their customers.

Information in this Resource Note

is based on the opinion and experience of

the author and has not been peer-reviewed.

Conclusions and opinions expressed herein

do not necessarily represent those of BLM.

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Denver, CO. 80225-0047

or pdittber@nc1155wp.sc.blm.gov

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If you would like to prepare a

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