Having fun with projections

Using GIS data to create your scenery has become a lot more common in FsX. Vector data can for example converted from shapefiles and for new version of resample can process GeoTIFF images as well. If you have access to this kind of GIS data or can create it yourself, this makes creating the scenery a lot easier (and more fun as well).

But there are also aspects of working with GIS data that are hard to get for people not used to this. One of these is the use of projections. All FsX scenery design tools expect the data in the WGS84 projection. This means that you can usually not use any scanned map.

Today at work we came across a similar problem with the use of projections and I want to talk about it here as well, because it illustrates very nicely what a big influence a wrong projection can have.

For the flight simulator we have a visual database that contains the airport of Paris CDG and Sion, plus some terrain between these two airports. So the projection used for this database has been optimized for the area it covers, we are using a Lambert Conformal Conic (LCC) projection for this database. A few days ago they asked us if we can add an airport in Africa (Mali to be more specific) as well, because they wanted to fly from there to Paris for an experiment.

So our first thought was let’s try to add the additional airport to the same database (which also means using the same projection). So we downloaded some Landsat images of Mali and started adding them to the database. But to our suprise (or maybe not really), the results were not very good. Below you can see a screenshot of the airport in the LCC projection of our Paris database (left) and a screenshot of the same airport when we use a UTM projection chosen for Mali (right). 

As you can see, the heading of the runway differs something like 60 degrees. Which is of course much to much (how to explain the pilot that runway 06-24 is actually facing North). To be honest we already expect some trouble with the projection system, but we just want to try and see how worse it was. And it was much worse than we ever expected.

But I think this nicely shows that you can not ignore the projection you are using when working with GIS data. To prevent problems like the one we had, MS has chosen to use WGS84 for all scenery elements. So to get the correct placement, all you have to do as a scenery design is to make sure your data is in WGS84 or else convert it.

One thought on “Having fun with projections

  1. Chris Huolt says:

    Hi Arno,
    I am currently try to learn how to load my own data into FS2004 and was wondering if you could point me in any kind of direction that would help me a little more. I work for a forestry consulting company and basically we want to insert our data so our clients can fly virtually through their forests. I am looking to add vector and polygonal data files as well as input aerial photos.

    I realize that I might sound like I dont know what I am talking about but any kind of guidance that you could give me would be greatly appreciated. You can email me at chris.huolt@silvacom.com


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