Prior to Operation Desert Storm, ground combat vehicles used MGRS maps and simple compasses.
During Operation Desert Shield, officers used the Loran system. Those produced Latitude/Longitude then had to be converted to MGRS and back.
On 24 February 1991, advanced units such as the Cavalry in VII and XVIII Airborne Corps including the 24th INF DIV (MECH) and Task Force 2-4 CAV were issued 4000 AN/PSN-10 Small Lightweight GPS Receivers.
The GPS was absolutely critical given there were no terrain features and area maps looked like one solid brown square.
"G-day came on February 24, beginning at 0400. U.S. Army units in both the VII Corps and XVIII Airborne Corps quickly realized the value of the GPS units. With the unexpectedly rapid advance of coalition forces, heavy reliance was placed on these small devices while navigating in a featureless desert landscape. The 24th Infantry Division used the receivers to link phase lines for the assault, helping to maintain command and control. Although seven different types of GPS devices were used during the war two models comprised the clear majority. The AN/PSN-10 Small Lightweight GPS Receiver (SLGR, pronounced "Slugger") was favored with approximately 4,000 devices deployed. The SLGR is a small rectangular, box-like hand-held unit developed by Trimble Navigation. It weighs about four pounds and can be mounted to a vehicle or aircraft. The second most prevalent device was the NAV 1000M Receiver, made by Magellan, still a leading company in GPS technology. It was smaller than the SLGR and is powered by AA sized batteries. Approximately 1,000 of these devices were utilized during the war."
- By Kaleb Dissinger. Army Heritage Museum www.army.mil