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Guest Dianne_S

Question about image projection in photo scenery

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Hi,I'm experiementing with USGS 3.75 minute color infared digital orthophotoquads (what a mouthful!) as a source for aerial images in designing photoreal scenery for FS2004.The USGS site details that this particular imagery is projected in UTM format, based on the NAM83 reference datum. It is my understanding that NAM83 conforms to the WGS84 standard specified in Microsoft's Terrain Tools SDK. Am I good to go then with UTM/WGS84 imagery of this kinds in terms of correct projection and alignment in FS2004?Thank you!

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Hi,You will need to convert the data slightly before you can use it. The UTM-projected data will need to be reprojected to geographic for use with flightsim. I think the datum is suitable (corrections, anyone?) but the projection - the way the flat, 2D image corresponds to the curved, 3D surface of the datum - is different for UTM and Geographic.Have a look at this [a href=http://forums.avsim.net/dcboard.php?az=show_topic&forum=123&topic_id=20484&mesg_id=20484&listing_type=search]thread[/a] which describes a free tool for reprojecting. I've not used it myself, but I hear it works well.HTH,Jim Keir

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The guys have pointed you to threads that will explain how to reproject your image to the geographic projection. I found that in doing this I lost some quality in my image.I did a test, using the freeware from digital grove, I did a reprojection of a color utm usgs image. I then produced fs terrain textures using resample.exe on that image.For the comparison, I took the fresh utm image, and layered that in photoshop above the reprojected image from the above step. Then I used the transform tools in photoshop, to imitate the reprojection. Once it matched up well, I made new terrain textures. The second set of images were clearly of higher quality. Far less resolution loss in just transforming the image, than in the reprojection process.Bob Bernstein

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Thanks very much for all of the great information guys! My next step now is going to be to polish up my reprojecting skills. :) One of the forum threads referenced to me here has a great tutorial, can't wait to try it and see how it goes with the freeware tools mentioned. I'm currently experimenting with USGS 3.75 minute CIR photography, utilizing the preview images available through Earth Explorer on the USGS site. I can fairly easily create a faux true-color image by using the color replacer function in either Photoshop or Paint Shop - with a little effort the effect works pretty darn good. The only problem with the preview imagery I'm using is that the USGS makes overlapping images; I must therefore find a way to reference absolute geographic edges of the images before I can accurately place my photo-scenery. The USGS provides very accurate coordinate information, however, the image edge overlap throws that off - I've got to come up with a way to get around that problem.Here is an example of the USGS 3.75 minute CIR aerial preview imagery I'm experimenting with: http://members.cox.net/diannesk/Pictures/abilene west se org.jpeg I've already re-colorized it from the original color-infared infared. There is complete geographic coverage of the continental United States. Using Elrond's Resample Tools and the integrated image resizing filter, these CIR's are great for Flight Simulator (at least before reprojection, which I haven't tried yet :) ). Thanks so much again for all of the helpful advice! This is so facinating to learn about!

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Thanks Jim! I didn't realize this could be done - the FS9 palette makes a world of difference! I've downloaded and saved your FS9 .pal file and will use it from now on; I use Paint Shop Pro so it will be very easy to utilize. Here is the original color infared image, what a difference a little color replacing and the right palette make huh? http://members.cox.net/diannesk/Pictures/abiwest1.jpgI'll post some shots of some of the imagery from Flight Simulator, it's really not bad at all and the preview imagery is available for free at USGS.gov :)Thanks again.

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