encompass all levels of impact and have been used 
for studies of training impact in the past. They 
occupy an area of approximately 220 km^. 
3. DATA SOURCES 
3.1. Imagery 
The following satellite images were 
acquired: 
1) Landsat TM (Path 33, Row 38) - 28 
October 1984, 29 October 1990, 4 June 
1992, 19 September 1993. 30m 
resolution. 
2) SPOT XS (J 567, K 286) - 6 October 
1990. 20 m resolution. 
Two sets of vertical aerial photos covering 
portions of the northern MAs at Ft. Bliss were 
acquired: 
1) 54 B&W prints, March 1978, 1:18,000. 
Complete coverage over the northern 
MAs. 
2) 13 color IR transparencies, October 
1994, 1:16,000. Sporadic coverage. 
3.2. Databases 
Several databases were considered 
potentially useful for this research. These included 
the Army's Form 88 data and Archaeological and 
Impact Assessment data. 
The Form 88 database, maintained by the 
military, records all proposed training activity in 
the MAs. The database was largely unusable for 
this study. Specifically, training activities for the 
week were logged beforehand, that is, as they were 
expected to occur in each MA. In addition, 
maneuvers were not tracked at specific locations. 
Instead, vehicle counts were recorded over large 
areas, often over long periods of time. Thus, 
precise location information did not exist on where 
maneuvers actually occurred and to what extent. 
Data for an Archaeological and Impact 
Assessment project collected by Ft. Bliss staff in 
the summer of 1994 were also considered. The 
purpose of that study was to determine if 
occurrence of archaeological sites was related to 
vehicle traffic. Because vehicle impact was noted, 
it was thought that the data would be useful as 
ground truth for this study. These data were 
collected in transects spaced 15 meters apart, 
located on a UTM grid which was overlaid on 
enlarged aerial photographs. A field in the 
database titled “Age of Impact” was used in the 
classification of impact study. Age was reported 
in the database as either “Recent”, “Older” or 
126 
“Trace”. Recent was defined as “treads are still 
distinct and vegetation is dying”. Older was 
defined as “treads nearly or all gone, ruts visible, 
and vegetation in ruts is dead.” Trace was defined 
as “tracks are visible, but vegetation is growing 
back in” (pers. comm., Joe Brandon, Ft. Bliss). In 
all, 826 points of the database were coincident with 
this project’s study area. Of these, 76 were 
reported as Recent, 195 were Older, and 555 were 
Trace. Three Arc/Info coverages were generated 
from the UTM coordinates of these points. 
3.3. Field Investigations 
Field work undertaken during the week of 
January 9-14, 1995 was based on two objectives: 
1) to become familiar with the maneuver areas and 
learn to recognize different levels of use, and 2) to 
identify significant features evident in the satellite 
imagery. Both of these objectives were met with 
considerable assistance from Ft. Bliss staff. 
Field work proceeded along the following steps: 
1) Select a site of interest. 
Sites were chosen based on one of two criteria; 
level (i.e., intensity) of impact or presence of a 
significant feature. Level of impact was roughly 
determined in the field by Ft. Bliss staff. Sites 
were chosen based on an arbitrary five-level scale 
which were as follows: high impact, moderate 
impact, low to none and two intermediate classes. 
Significant land cover features were 
determined from false color infrared (CIR) and 
principal components imagery derived from 
Landsat TM data acquired 4 June 1992. The 
principal component image was especially useful 
for directing investigations to terrain which was 
distinctly different from other features in the 
imagery as well as areas whose broad extent in the 
imagery could be described as typical land cover. 
2) Navigate to and locate the site using GPS. 
A  Trimble Pathfinder Professional Global 
Positioning System (GPS) unit provided by the 
y was used to navigate to the field sites. 
These receivers can track up to 8 satellites, 
yielding 2-5 meter accuracy after differential 
corrections are applied. At each site a GPS file 
was collected for differential post-processing. The 
logging interval was set at one second; a minimum 
of 180 positions were collected for each point. 
Each location was also marked on the 1:50,000 
scale Defense Mapping Agency (DMA) maps of 
the base and on color prints of the June 1992 TM 
scene. 
  
  
  
  
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