Earth Radius In Fs

[dragonflightdesign 98]

Can someone tell me what this is? I have the figure of 6378137.000 metres from somewhere but everything I calculate (great circle, bearing, cross track, etc.) is slightly off. Actually, sometimes miles off. For example: KORD - 3CK should be a bearing of 308 degrees and 27nm (43km) but I'm getting 318 and 43nm (71km). Could be that my formulae are up the creek but let's start small...

 

-Dai

[James Bennett 52]

Interesting, i'd like to know this too.

[ddawson 35]

Try using the GPS functions to calculate the distance from 0°N 0°W to 0°N 90°W and multiply by 2/pi?

[dragonflightdesign 98]

Good thought Doug. I'll have a go at that when I get home and post my results.

 

-Dai

[mgh 89]

The FSX SDK gives the two radii - the polar and equatorial.

 

They are in Terrain and Scenery - Appendix II: The World Coordinate System

[mgh 89]

Following up, the P3D SDK is the same as FSX and doesn't use WGS84.

 

P3D SDK simObject API References calls GetWorldConstants() to return the polar and equatorial radii, so those values can be checked.

[dragonflightdesign 98]

The FSX SDK gives the two radii - the polar and equatorial.

 

They are in Terrain and Scenery - Appendix II: The World Coordinate System

Right in the obvious place :blush: Thanks for that.

 

-Dai

[JRBarrett 3,050]

Which formulae are you using for your calculations? I have found the techniques in the Aviation Formulary web site work very well for creating apps or subroutines for solving navigation problems.

 

http://williams.best.vwh.net/

[COBS 25]

Dai ,

 

I'm using :

Earth radius = 3440.065 nmiles

1852.0 meters = 1 nm

 

3440.065 x 1852.0 = 6371000.4 meters

 

Cheers

Karol

 

PS ; from page 182 of

FS9GPS MODULE

an empirical xml guide v.1.1

By Bob McELRATH

June 2011

 

Earth radius,

R = 3437.74677 nautical miles

R= 6378.7 kilometers

R = 3963.0 statue miles

[dragonflightdesign 98]

Which formulae are you using for your calculations? I have found the techniques in the Aviation Formulary web site work very well for creating apps or subroutines for solving navigation problems.

 

http://williams.best.vwh.net/

Not as accurate as he could be e.g. in the example the locations for LAX and JFK are rounded to the nearest arc-minute of longitude and latitude, or 1/60th of a degree. That gives a distance of 2144 when it's actually 2151. If that's out, what else is not quite right?

 

 

Dai ,

 

I'm using :

Earth radius = 3440.065 nmiles

1852.0 meters = 1 nm

 

3440.065 x 1852.0 = 6371000.4 meters

 

Cheers

Karol

Bob McElrath! I half contemplated buying that book recently but decided it was overkill.

 

COBS... hmmm. That's what the French girl at work called me last Tuesday, then she admitted she'd only learned the word 'cantankerous' on the previous day!

 

-Dai

[Propwash 2]

 

Bob McElrath! I half contemplated buying that book recently but decided it was overkill.

 

 

Sheesh Dai, it's free.

 

 

 

 

[dragonflightdesign 98]

:blush: Eejit here was thinking of something else - of course I've already got that downloaded and safely tucked away!