2.1.115. SURVEY WITH PLGR+96
1. The PLGR+96 is the primary means of obtaining fixation of the group center and the RSP. The PLGR+96 shall be considered an aid to navigation, much like the compass or any other navigation aid. The procedure to implement this device has been standardized with artillery procedures and shall be followed within all mortar platoons. THE PLGR+96 IS THE ONLY AUTHORIZED GPS THAT MAY BE USED FOR SURVEY. The setup is as follows:
a. The top portion of the survey card shall be filled out;
b. Current CRYPTO is loaded and recorded;
c. Correct DATUM is used and recorded;
d. Correct COORD SYSTEM is used and recorded;
e. Correct ELEVATION UNITS and REFERENCE are used and recorded;
f. Correct DISTANCE UNITS are used and recorded;
g. WAGE is on and recorded;
h. Correct MAG VARIATION and UNITS are used and recorded; and
i. Operating mode is CONTINOUS.
2. The user will verify setup data by physically checking the PLGR+96, or by setting up a second PLGR+96 and comparing the resulting location between the two PLGRs. A gross error check shall always be done with the map. All information gathered during the setup described above (sub paras b. to i.) shall be recorded on the survey card in the section that refers to GPS.
3. Once the PLGR+96 gives an accuracy of +/- 15 m or FOM 1, it shall be changed to AVERAGE and allowed to collect data for a minimum of 300 seconds (5 minutes). The 10 figure grid reference developed by the PLGR+96 shall be entered on the survey card.
4. The group commanders can now determine layout data using the PLGR+96. Regardless of whether the platoon 2IC or group commander completes this procedure it will equate to a known point. When an independent check by either the group commander or CPO verifies the grid using the same procedure it shall be considered equal to an RSP.
5. All other methods of survey are considered backup means but may be used as the situation dictates (e.g. lack of, or poor, satellite signal).
CAUTION
The utmost caution must be used when entering or recording map datums to ensure they are correct and match the map sheet being used.
6. The PLGR+96 it is at times subject to different types of interference, and the following should be avoided:
a. Masking: GPS receivers rely on electronic line of sight (ELOS) with satellites. Dense foliage, buildings, mountains and canyons may mask the signal. PLGR+96 will initially select satellites that are 10 degrees above the true horizon. If four usable satellites are not detected the set will switch to 0 degrees. After acquisition, the set will automatically switch to 5 degrees for normal operation. If enough satellites cannot be aquired the receiver must be moved;
b. Jamming: PLGR+96 is subject to jamming. When low signal noise ratios are detected or reception is blocked, jamming may be the cause. Move to a new location and try to place a large object between the receiver and the suspected jammer. If signal noise to ratio is above 34 decibels, jamming has probably been eliminated; and
c. Spoofing: Spoofing errors are caused by false satellite signals designed to generate errors in navigation and position data. Using the crypto keys and an All-Y setup selection attains maximum protection. If the PLGR+96 is in a spoofing environment, the receiver may generate a POSSIBLE SPOOFERS warning screen.