reported Present position difference between TSD and map

[vctpil]

Hi,

There is a difference in position between the MGRS coordinates displayed in the TSD and the map mode. See screenshots.

Thanks,

Vincent

[FalcoGer]

the top left corner of the map displays your mouse coordinates. the coordinates of the selected element pop up in the bottom left corner.

If you're talking about the MGRS being only groups of 4 digits, that is normal. The AH64 uses 10m accurate grid coordinates, not 1m accurate coordinates like displayed on the map. you can just truncate the last digit off each of the group of 5 to get the 4 digit number used in the AH64.

There could also be some drift in the INU. But the easting is perfectly correct, the northing 49336 on the map is off by 200m from what the aircraft displays (4913[0]). My bet is that the mouse position is not exact. Use the window in the bottom left of the map screen to get accurate coordinates for selected objects on the F10 map.

[NeedzWD40]

I believe this might be a small coordinate conversion error, because LL is usually about right, while MGRS is typically a hair off:

The external view info bar, if available, gives a more accurate reading of your position, so be sure to compare it where possible.

[FalcoGer]

@NeedzWD40 Just checked. 38 T KM 93141 72729 = N 42° 10.7623' E 042° 29.7161', using a non DCS system. The coordinates are correct and not "off".

Powered by the coordinatesharp library, using the ellipsoid earth model for added precision.

Edited January 18 by FalcoGer

[NeedzWD40]

1 minute ago, FalcoGer said:

@NeedzWD40 Just checked. 38 T KM 93141 72729 = N 42° 10.7623' E 042° 29.7161', using a non DCS system. The coordinates are correct and not "off".

 

Compare with the Present Position indication on the TSD. The cutouts are from the external infobar and are accurate; the TSD PP however is off on the MGRS, while the truncated LL is about right.

[FalcoGer]

17 minutes ago, NeedzWD40 said:

Compare with the Present Position indication on the TSD. The cutouts are from the external infobar and are accurate; the TSD PP however is off on the MGRS, while the truncated LL is about right.

I see. Yes, it seems the MGRS coordinates are off by around 220m.

It seems there is a bug with converting coordinates from L/L to MGRS in the AH64. The correct coordinates for N 42° 10.7600' E 042° 29.7200' are 38T KM 9315 7272 (38T KM 93146 72725)

With L/L decimal minutes and 2 digit precision there should be a maximum of ~16m difference, and MGRS with 4 digits groups is 10m accurate. There shouldn't be a discrepancy of ~200m. And if it were INU drift, both numbers should be off, not just MGRS. And again 200m is way too much for a modern laser ring gyro system and military 1m accurate GPS updates.

Edited January 18 by FalcoGer

[Lord Vader]

Hi @vctpiland repliers. 

There does indeed seem to be a discrepancy in the TSD coordinate data. 

I have raised this internally for analysis.