NADIR heading reads low for distant waypoint

[Ramsay]

EDIT: The Gazelle compass readings are consistent with readings in the A-10C and L-39C in 1.5.4, if there is an error, it is likely beyond the scope of Polychop.

 

Description: The NADIR waypoint direction/needle reads less (8°) than it should for long distances i.e. Batumi to Tbilisi-Lochini

 

I created a mission to test my understanding of the NADIR polar copy function and after making some dead reckoning estimates of the magnetic heading from Batumi to Tbilisi-Lochini decided to see what the reading really was using the NADIR, unfortunately the NADIR reading seems inaccurate and I haven't been able to fault my methodology.

 

DCS Version: 1.5.4.54596

Steam: yes

Map: Caucus

SP/MP: SP

Airframe SA-342M/SA-342L: both

Reproducible: Yes

Step to Reproduce:

 

 

 

• 
  
• Create a mission with a Gazelle (parking hot/runway start) at Batumi and a waypoint at Tbilisi-Lochini
  
• Select the Tbilisi-Lochini waypoint on the NADIR
  

• the NADIR waypoint needle reads approx. 75°

  
  

• Set the NADIR mode to 'TPS CAP' (ETA Heading)
  
• the digital heading reads 75°
  
• Check the F10 Map with the Geographic grid enabled
  
• the Geographic lines of latitude run at approx. 83° as measured by the ruler.
  
• measure the distance and direction from Batumi to Tabilisi-Lochini using the F10 ruler
  
• it reads approx. 280km @ 82°
  
• this is 1° less than the lines of latitude
  
• so Tabilisi-Lochini should have a bearing of approx. 90°-1° = 89° TRUE
  
• as the Gazelle instruments use magnetic bearings, the bearing should read approx. 89°-6° = 83° Magnetic (assuming a +6° E declination).
  
• this is 8° more than the NADIR digital display
  
• as a idiot check, measuring the same in Google Earth = 278km @ 88° True
  

Screenshot/Video available: Screenshot

 

 

 

Track Available: N/A

Controllers: X52 Pro (Throttle), MS Sidewinder FFB2 (cyclic), TrackIR

OS: Win 10 Pro

RAM: 12GB

GPU: GTX 670 2Gb

Mods: JSGME all disabled

 

Edit:

Any Additional Information: ADF has the same error.

 

I checked the ADF bearings to a couple of NDB's and found the same error (if I place a NADIR waypoint over a NDB, the 2 needles align).

 

NDB's

Ali, 353.0 kHz AL, F10 ruler: 179km @ 65°, ADF reading: 60°

Mukhrani, 520.0 kHz DF, F10 ruler: 250km @ 75°, ADF reading: 70°

 

F10 Lines of latitude = 83°

F10 correction = 90°-83° = +7°

Magentic delination = +6° E

 

i.e. Ali = F10 ruler + correction = 65°+7° = 72° True / 66° Magnetic

Edited July 14, 2016 by Ramsay
ADF has same error, effects other modules as well.

[ESAc_matador]

inacurate 1º degree? for 250 km???

 

mmmmmm

[Ramsay]

inacurate 1º degree? for 250 km???

 

mmmmmm

Not sure where you get the 1° ?

 

Tbilisi-Lochini should be at 82° Magnetic, the Gazelle reads 75° Magnetic, a 7° error.

 

The 7° error effects closer waypoints as well (25km), as it is related to the local geographic grid. The reason I choose the 250km baseline for the report, was to minimise any measuring error.

 

EDIT (correct the description of the in game effect, it was wrong as all instruments share the error):

 

The in game effect isn't major as instruments share the same error. However the absolute values have changed, so if you have a old visual flight plan with distance x @ y° legs, it'll need revising i.e. Maykop to Smolenskaya NDB was 276° T and is now 271° T in 1.5.4.

 

For 1.5.3 and previous versions, the F10 ruler bearings are a little 'strange' and the F10 map isn't a perfect representation of how 3D assets are placed in the 3D world.

 

For DCS modules A10, L-39, Gazelle, etc.

 

The 'relative' position of assets associated with an airport - runway, inner/outer markers, etc.

 

 

• 
  
• F10 ruler=True North
  

For more distant assets the F10 ruler =

 

• 
  
• the game grid on which latitude and longitude coordinates are projected
  
• is not related to true north or magnetic north
  

you read bearings using the geographic grid as it displays how True North, etc. has been projected onto the game grid.

 

EDIT: Modules like the A-10, L-39, etc. DO NOT take the ISO grid into account.

 

 

For FC3 modules

 

• 
  
• F10 ruler = game grid, cockpit compass, etc.
  

 

Hopefully this will change for the better once Caucus and Nevada maps are merged.

 

Old thread on F10 map measurement/projection

Edited July 22, 2016 by Ramsay
Corrected description of in game effect

[Ramsay]

This report can be closed.

Apologies to Polychop as it looks as if something has changed in 1.5.4 that effects all modules.

 

I tested the SA-342L, L-39C and A-10C in a Maykop navigation exercise I've used before and the waypoint bearings (to Smolenskaya NDB) look to have changed by 5° (can't be 100% sure due to usually using the RSBN radial). However the Gazelle's readings were consistent with the other modules.

 

Edit: Deleted bad speculation about it being a symptom of 2.5 changes, it's the same in 1.2.16

 

For reference, the A-10C reads Batumi to Tbilisi-Lochini as 256°-180° = 76° Magnetic in 1.5.4.

 

 

and the same in DCS 1.2.16

 

 

I always thought the compass in full DCS modules took the geographic grid into account, it seems it's only used for lat. and long. coordinates ?

Edited July 14, 2016 by Ramsay
included the ammount the NDB bearing changed