Object's Precise Alignment

[SQ347]

Hi
As you may know I am designing Singapore Changi Airport .
The Terminals are Divided in Gmax into relatively small sections, as the distance from one side to the other is more than 1.7km .


Anyway some of these sections need to be very accurately placed . I'd say with a tolerance of some centimeters so thereafter slewing the Aircraft would not be precise enough , at least for my joystick

So I was looking for a way to find the Geographical Coordinates of a point [ P ] knowing the Coordinates of the starting point [ O ] the Distance and Real Course [ not magnetical ] .

I don't need necessarily a program but just formulas , as I can implement it into Excel or Matlab . My math are good enough to do it . But I am not really expert in that part of physics and I am not sure of how the FS is modeled ( I'd hardly expect it to be too realistic ) .

hope there is someone can help on this

Best Regards

 

[arno]

Hi Andrew,

In the terrain SDK you can find the parameters with which the FS world is modelded (I think they are very close to the WGS84 parameters). You could use a simple assumption that the earth is a sphere, but I am not sure you get the accuracy you are looking for in that case .

I have placed my objects in a similar way (as I have the exact position from a CAD drawing) and they indeed line up perfectly. But I had my data in the Dutch RD projection system, so my formula's won't help you much.

 

[SQ347]

Hi Arno,

from SDK

In Flight Simulator, the earth is defined as an “oblate spheroid,” an ellipse rotated about its minor axis. In terms of shape, it's much like a sphere that is a little bit fat around the equator. In Flight Simulator, the earth has the following dimensions:

• Equatorial diameter=12756.27 km
• Equatorial circumference=40075.0 km
• Polar diameter=12734.62 km
• Polar circumference=40007.0 km

I am not sure how to use them . I can assume it's a sphere. As Singapore is at N1 , it's really close at the Equator , I could omit the Spheroid effect and stay within an error of few centimeters .

BTW the Ground Stuff [Taxi Lines/ Ground Textures ] will be made in Gmax .
Is it possible / Convenient [ Frame-wise ] to make only one MDL of all the Taxiway lines or it's better to slice it into more MDL's [with different Reference Point's ] ?
Cause If I will divide the Taxilines into more MDL's I am afraid I will need a even greater accuracy

 

[arno]

Hi Andrew,

I am not sure how to use them . I can assume it's a sphere. As Singapore is at N1 , it's really close at the Equator , I could omit the Spheroid effect and stay within an error of few centimeters .

Ah, didn't think of that. As it is that close to the equator I think that should indeed work. Then you could just use that the 360 degrees is equal to 2*pi*radius of the earth.

BTW the Ground Stuff [Taxi Lines/ Ground Textures ] will be made in Gmax .
Is it possible / Convenient [ Frame-wise ] to make only one MDL of all the Taxiway lines or it's better to slice it into more MDL's [with different Reference Point's ] ?
Cause If I will divide the Taxilines into more MDL's I am afraid I will need a even greater accuracy

I would only advice the ground textures, lines, etc NOT to be placed in MDL files. They are crap for making ground elements, use the old Fs2002 gamepack for them instead.

 

[SQ347]

I would only advice the ground textures, lines, etc NOT to be placed in MDL files. They are crap for making ground elements, use the old Fs2002 gamepack for them instead.

Yeah I will use the FS2002 Gamepack. I forgot Fs8 don't use MDL files

Thanks for your Help

 

[arno]

OK , in case you are working on a big airport (and I guess you are), it might be better for the framerate to split it into different BGL files. If you just export as one big scene all elements in it will display at the same time. For the performance it is a lot better to give certain markings a lower visibility range for example.

 

[lmoelleb]

I have previously posted the formulas here:

http://www.scenerydesign.org/forum/showthread.php?t=1607&highlight=offset

I have never had any precission problems with these. You will need to calculate the x and y offset from headnig and direction yourself.

 

[SQ347]

I have previously posted the formulas here:

http://www.scenerydesign.org/forum/showthread.php?t=1607&highlight=offset

I have never had any precission problems with these. You will need to calculate the x and y offset from headnig and direction yourself.

I used these formulas :
Longitude=Long[O in deg]+distanceX*360/[ 40075000]
Latitide=Lat [O in deg ]+ DistanceY*360/[40007000]

where DistanceX and distanceY are calculated with simple cos/sin calculations.
distance is in Meters.

public PointG GetOffsetPointByMeters(PointF distance)
{
double lat = Latitude.Radian + distance.Y / (40007000.0 / (2.0 * Math.PI));
double lon = Longitude.Radian + distance.X / ((40075000.0 / (2.0 * Math.PI)) * Math.Cos(Latitude.Radian));
return new PointG(new Latitude(lat), new Longitude(lon));
}

I don't know what's the Cos(Latitude.Radian) have to do there.

 

[arno]

I don't know what's the Cos(Latitude.Radian) have to do there.

That is to correct for the fact that the radius in longitudinal direction does depend on your latitude (this radius goes to 0 as you approach the poles of the earth). As you are close to the equator it does not matter too much for you, but here in the Netherlands for example it makes a huge difference.