Going to War - GPS Declassified: From Smart Bombs to Smartphones - page 117

Fig. 7.3. Manpack gps receiver by Rockwell Collins. (Courtesy Rockwell Collins)
Fig. 7.4. an/psn- 11 plgr by Rockwell Collins. (Courtesy Rockwell Collins)
the move opened the possibility of Iraqi troops acquiring and using commer-
cial receivers for their own desert navigation, a fear that never materialized.
The Air Force reactivated Selective Availability in July 1991, but within a decade
turned it off again after a policy debate (see chapter 8).
Anyone who has failed to update the software in their automobile naviga-
tion system and turned onto a new highway not shown on the screen has expe-
rienced the disorientation that using gps with outdated maps can produce.
When soldiers easily found other units in the empty desert during the Gulf
War, they knew their destination's coordinates. Without accurate, known coor-
dinates, gps could not lead troops to enemy targets. For this need non-gps
satellites, both military and commercial, made a critical difference in the war.
Most Middle East maps the Defense Mapping Agency had available in August
1990 dated from the 1960s up to 1983. 68 They used map reference systems
predating the World Geodetic System 1984 (wgs- 84), which gps uses. (Car-
tographers periodically revise the underlying frame of reference, or datum,
they use in mapmaking as methods for precisely measuring the planet improve.)