FSX map

[Captain Llama]

I'm trying to correlate the position (ie, lat/long) of some terrain features in FSX with their positions on an external map, and FSX seems to have the features in the wrong position. Does anyone know if this is a result of the geodetic datum that FSX uses? Would getting a higher resolution scenery pack fix this? I need the terrain features in FSX to line up with the external map, and so far this isn't happening.

 

[meshman]

withdrawn.

 

[rhumbaflappy]

Hi CL.

The positions of roads, rivers, lakes, etc... are derived from GIS databases, and may not reflect real world positions. That's why scenery designers are needed for all versions of Flight Simulator. If there was nothing to correct, we'd just fly.

Dick

 

[arno]

Also if you are looking at the default landclass textures, you should also be aware that they are generic textures, they do not represent the real world exactly.

For aerial images made with resample they are in WGS84. So if when creating the scenery the developer was not aware of the projection used that might give an offset as well.

 

[Timmo]

There are a few potential issues here

What features were you trying to align exactly? In what country are you examining? What coordinate system is your map in? What format are the coordinates (decimal degrees, Deg min sec etc etc) How does the data match temporally (i.e. could the data/real world feature have moved recently)
The accuracy of vector features (shorelines, roads etc) vary greatly from country to country as it depends on what GIS data Aces was able to obtain at the time. This data, of course, is of a set accuracy (i.e. NZ is covered with 1:50 000 topographical data in FSX...this gives an accuracy of around +/- 50m but at the same time the original data hasnt been updated recently)

The location of airfields isnt always accurate either as they are usually generated from airfield plates which may only have a few written coordinates on the plate(i.e. VORs,NDBs etc). The position of the rest of the features are a best guess based on these coordinates.

 

[Captain Llama]

Well, I decided to use the Victoria International airport as an example. I tell FSX to put my plane at the airport, and it puts me at lat N48° 38' 49" lon W123° 25' 48". According to Google maps, at the same point on the runway, I should be at lat N48° 38' 29.2776" lon W123° 25' 28.308". This is a difference of at least a couple hundred metres. Both of them are supposed to be using WGS84, so the two should line up perfectly or close to it. Of course, I could also be completely wrong here.

 

[rhumbaflappy]

Hi Captain Llama.

Microsoft used the official airport published data to locate airport features. Many times this data is estimated... sometimes it's not even close. That is not Microsoft's fault.

There are not enough man-hours available to the Aces design team to verify the exact real-world locations of even the major airports of the world.

In all these instances, there are 3 possibilities:

1. The default airport's features are mislocated in the sim.

2. The images used by Google and other sources are distorted or mislocated ( and they do admit that! )

3. Both the above.

So either you can complain about the apparent mislocation, or fix it yourself, or wait until some crafty designer does it for you.

The true location of a runway could possibly be determined within a few meters by using a military grade GPS locator... or by hiring a very good surveyor ( who will use a military grade GPS ). But there would always be contention as to the EXACT location, because all measurements in the real world are estimates of greater or lesser extent. No 2 rulers measure the EXACT same inch, no do the users of those rulers. Measurement is a great deal like justice ( or truth )... usually a concensus of "close enough" is good enough.

In some circles, the exact location of a runway start point is close enough at a few hundred meters. After all, most flight simmers are more concerned about flight characteristics and simulation, than about getting the start point to within a few meters.

I'm a little shocked that this bothers you. The very presence of a scenery design forum should clue you that things are not perfect or complete in the FS world... if they were, there would be no need to create addon scenery. And most people here are scenery designers that fully understand a desire for greater accuracy.

In your specific case, I think Google maps is probably closer to truth and justice, than is the default FSX scenery.

Dick

 

[Difar]

Capt. Llama

Holger Sandmann and company have a fabulous Victoria Island and surrounding area scenery for FSX avail. at Avsim (two files I believe). And best of all... it's Freeware.
This may be what you are looking for, scenery wise.

 

[Captain Llama]

Thanks everyone for your responses.

@Difar

I'll check out Holger Sandmann scenery and see if it meets my needs. Thanks for the suggestion.

@rhumbaflappy

Personally, it doesn't matter to me if the FSX default terrain is a couple hundred metres off. The problem is I'm currently working on a project for my employer where I need locations in FSX to line up exactly or almost exactly to where the maps say they are.

 

[arno]

Hi,

When I try the coordinates you gave (N48° 38' 29.2776" W123° 25' 28.308") I do get at the start of the runway in both FSX and Google Earth. So the two seem to be spot on. This is not so surprising, as the runway data used in FSX is quite accurate (for taxiways that does not have to be true).

Are you sure that you did not enter the coordinates wrong in FS for example? It is quite common to confuse between the DD.dddd, DD MM.mmmm and DD MM SS.ss notations for example.

 

[Captain Llama]

I never input the coordinates into FSX. Instead I went to free flight and told it to put me at the airport, then I got the coordinates from FSX and tried them in Google maps and got another location a couple hundred metres away. I also went to where Google maps showed the plane's location should be (ie, the same spot on the map), and extracted the coordinates for that spot from there. Since the two sets of coordinates were in different formats, I used the FCC conversion tool to change from one format to another.

 

[scott967]

I try to find a couple different sources of position data if possible. For example, if the country has an online AIS in ICAO format, you can usually get accurate runway threshold positions from that. Canada isn't the best in my experience for online data, but it does have an official site, GeoBase Can, that can provide topographic maps and photo imagery, both of which can be used to extract position data.

Be careful to correctly convert lat/long data from the various formats. It's easy to make a mistake.

I can confirm that GE isn't perfect. Just take a look at Singapore Changi airport, where two different images are stitched together and they don't line up.

scott s.
.