Off the shelf, onto the beach: commercial GPS in amphibious combat vehicles

GPS World, April, 2004 by Stephanie Edwards, Marlin Gendron, Maura Lohrenz, Richard Mang

The display screen was a water-resistant 10.4-inch PC color monitor, which attached to the vehicle driver's hatch as is visible in Figure 2 to be out of the way when the vehicle was not in operation.

[FIGURE 1 OMITTED]

A DGPS antenna was placed on the outside of the vehicle, slightly aft of the crew chief hatch. The antenna was connected to a DGPS receiver using a pre-existing thru-hull cavity. A heading sensor was used to stabilize the view on the moving map display while the vehicle was stationary. Without independent heading inputs from the magnetic heading sensor, the map display will spin, cause by erratic heading information from the DGPS receiver when the vehicle is stopped or moving slower than one nautical mile per hour. NRL wrote software to integrate the heading sensor data with the DGPS data for input into Falcon View. The system components are shown in Figure 1.

Testing

NRL's moving map has been tested on the AAV platform three times during the past 18 months: on both the Navy's Landing Craft Utility (LCU) and Landing Craft Air Cushion (LCAC) in addition to the AAV. Testing on the LCAC platform was not nearly as extensive as the other platforms, due to the operational cost of the craft. Therefore, any data collected from that demonstration could not be considered statistically significant. LCU testing was as extensive as the testing on the AAV platform, with similar results.

[FIGURE 2 OMITTED]

The primary difference between platforms, as far as the moving map testing was concerned, was NRL's ability to use the available gyrocompass on the LCU in order to obtain reliable heading. A magnetic heading sensor was not feasible on the LCU platform because the craft is mostly constructed using ferrous materials, as opposed to the AAV's aluminum hull. The article focuses on the AAV testing and results.

AAV testing took place at the Amphibious Vehicle Test Branch (AVTB) at Camp Pendleton, California, and at the 3rd Platoon, Company A, 4th Assault Amphibian Battalion Reserve Unit at the CB Base in Gulfport, Mississippi. After arriving on site, the NRL team spent one day installing the moving map equipment on the test vehicles and conducting a short training session for the crew. The following days were spent testing the system and evaluating crew performance navigating with the moving map versus using their baseline means of navigation.

The baseline--and only--means of navigation available to the AAV crew at this time is a military PLGR. The PLGR displays the vehicle position in latitude and longitude on a small handheld device and provides navigation guidance by indicating whether to turn left or right--based on the preset course--to reach the next waypoint. Standard procedure calls for the crew chief to operate the PLGR while relaying directional information and instructions to the driver. All driver/crew chief communication takes place through an internal radio link, as the crew chief is located on the opposite side of the vehicle, as shown in Figure 2.