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scott967

Arial Photo scenery positioning problem

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Hello, I am new to making Terrain for FS9, but have had some pretty good luck up to a point. I need some advice from you seasoned experts out there... I used some arial imagery of the county in which I live, converted it to a 4m/pixel size in BMP format using the "mrsiddecode" utility, then did the rest with Photo Scenery Maker. No problem, all is well... size is nice, positioning is very close EXCEPT at one end of the county! I lined it up almost perfectly at the eastern edge, but at the west side, about 60 miles away it is off to the south by about an 1/8th mile. Any idea what might be going on? I would sure hate to think I need to rotate my source imagery! By the way, I bought my source imagery from Image Trader, who provided it in mrsid format at 2m/pixel.DS

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I looked at the Image Trader web site, and found this:Geographic Information System (GIS) professionals- The Digital Aerial Photography CD has all the full resolution (2 meter) MrSID image file in UTM NAD83 Meters coordinate system. Everything is there for use in you favorite GIS software - All ESRI products, (ArcView, ArcInfo, ArcMap, etc.), Erdas, MapInfo, ERMapper, any other GIS software that reads MrSID format. To use this data in FS, you must reproject the data from UTM/NAD83 to Geo/WGS84. I use a payware program Global Mapper, to do this. In the special case of going from UTM to Geo, it is possible (but a big hassle) to go from UTM to Geo with freeware. Here is a link that explains how to use ERDAS viewfinder for the reprojection:http://www.digitalgrove.net/image_reprojec..._with_erdas.htmThis method works, but it's so much grief to keep track of everything that I appreciated having Global Mapper, even at $200. No commercial interest, but the support provided for this program is amazing.Note that for our purposes NAD83 and WGS84 datum are the same, so the only problem is to reproject UTM to Geo.scott s..

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Thanks Scott! I'll give that a try.. I knew this had gone too smoothly to be true, there HAD to be a catch! Perhaps I will just live with it as-is until FSX comes out, at which time my scenery will likley have to be completely re-done anyway. Doesn't hurt to experiment though. Thanks,DS

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One thing you can look at, enter the lat/long of your position into this calculator, the UTM zone, and it will compute the UTM grid convergence, or declination. I think the worst I have seen in what I've worked on is about a degree or so. It could be that if you rotate your image you could get closer. I do that with UTM bitmaps in SceneGenX, since that program sets everything in meters relative to the airport ref point, not lat/long.http://www.wherearewe.co.nz/geodetics.htmlscott s..

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