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Guest Mark Hazeldine

Orientation of FS2002 Airports, Roads etc

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Well I have managed to get texture maps onto the landscape. Terrabuilder is a great program.I have noticed however, that MSFS2002 default scenery airports, roads, and rivers are incorrectly orientated. Has anybody else found this?Its good that the maps I use are covering up the M40 motorway in the default scenery but Wycombe Air Park's Runway is way off. As is the control tower which is in totally the wrong position.Is it possible to remove, or modify an airport in the default scenery?

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I've been interested in this problem for years. Back in 99, Justin Tyme published what he thought was the answer. He described the problem as stemming from trying to depict the earth using flat images, when the earth isn't flat. The art of making a flat map describe features accurately is the subject of much writing, many of us have seen that projection that divides the earth in segments like an orange, and then flattens the orange peel. As I recall one source defines the number of slices by stating the longitudes that would come together at the pole, perhaps there were 11....can't remember.Anyway, scenery at that longitude would not need rotation, however as you move east or west from that longitude, you would need rotation one way or the other. And as you increase in latitude the relative need for rotation increases.I just reached a point in one of my many current projects where I saw an interesting example...I had previously created custom phototerrain for Harvey Field, and found I needed a counterclockwise rotation of 3.1 degrees to have the runway line up. My other airport close to Harvey is Monroe's Firstair Field, so I decided to create one phototerrain that included both airports. This new terrain showed the need for the rotation at Harvey but NOT a need for rotation at Monroe! Is the distance between the two enough to alter that position with respect to the central meridian of that part of the projection? Or is the positioning of the airstrips just slightly haphazard?I decided to go ahead and rotate the runway at Harvey for this project, a 3 degree rotation wouldn't be enough to alter the Number at the end of the runway, and for all I know perhaps the runway is not exactly aligned with the numbers.Bob Bernstein

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The textures you are using have to be georeferenced to the WGS84 elipsoid. MSFS is only using the WGS84 map projection. The aerial photographs you have have to be matched 100% to the data that MSFS uses, not an easy task. So one possibility is that your textures are wrong and have to be reprojected (nothing much you can do, you need the original MSFS data and quite expensive software).On the other hand the MSFS data isn't 100% either. I found a few airports with wrong orientations, maybe caused by an incorrect magnetic variation? The road, river, etc data is quite inaccurate, the max error is 2km (M$ used the freely available DCW data), and 2km is quite large. Even 1:25,000 vector data will have some error, but in most cases that's the data wich textures are matched to...In conclusion you can have 3 errors: the textures, the vector data MSFS or add-on scenery uses, or the textures aren't matched to the vector data you are using. Map projections aren't for the faint of heart and can cause all sorts of problems :)Cheers, Christian

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Wow, and I thought flight simulation was important I didn't think I would have to re-orient the world.I've done a QUICK & DIRTY fix by altering the runway background of my texture maps to line up with the default Wycombe Air Park (Booker). That way everything else in the entire area remains in the correct position. I can fly over my house now :-kewl Still some work to do on the auto-generated scenery.

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Your texture is excellant. What source did you use for the photo?B

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Hi colinlitster.I like it, too! I think hit on the best solution... live with the runway, and alter the bitmap to make it look OK. It causes the least amount of problems. Really looks good.

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You know it occurred to me that the problems I see are on the order of 3 degrees. This is well within the tolerance that could go unnoticed in Airnav...common to see roundoff to the nearest 10 degrees.I'm beginning to think its the runways that may be wrong.B

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I found a site called www.getmapping.com which has virtually all of England and Wales, as well as parts of scotland, viewable from a simple interface. I believe, in conjunction with others, they have an FS2002 product in the pipeline which will offer better resolution.

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You are probably correct. Microsoft only had the information that was available to them and a 10 degree difference in orientation could easily happen. In fact I first tried using an older Booker airfield designed for FS98/2000 by Paul Roberts. When I overlaid this on my scenery it was at least 150 Meters to the west of the airfield. I know my airfield is in the right posistion, by the way because, I have visited known landscape locations on my terrain maps in FS2002 and confirmed their location using MSAutoroute & www.streetmap.co.uk. So my terrain is ok but some of Microsoft's are considerably wide of the mark. FS98/2000 probably used an even more inaccurate co-ordinate system then. I wonder if other older FS98/2000 generated scenery is not in the correct position?The Thames Bridge at Henley for instance is at N51* 32.15 W0* 54.00, whereas FS2002's River Thames is approximately 600 meters away at N51* 32.43 W0* 53.38. Henley Bridge is an important reference point when flying into Wycombe Airpark from that direction under VFR. I can and have made a GMAX bridge, and town, but it's on dry land unless I also put the river in the right place.Thank goodness for Terrabuilder.

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neat site, beautiful images....too bad you have to pay...oh well.B

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Try www.multimap.com. Its free and goes to a higher resolution. I've also found rotational problems doing the whole of London. Not only that, but i can never get all six airports to line up. At least 4 of them must be wrongly positioned!

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