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SRTM_3ArcSec_To_BGL (BGL File Sizes)

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Hi, I am using Matthew Styles program and I converted 5 HGT files totaling abou 125MB and when it was done I had one file of about 2.5MB and this does not look right. I checked and double checked the setup and it all looks oK, but the file when I view it in TMF viewer does not look right lots of yellow with very little blue in it? Can someone tell me please what I may have done wrong? Thanks for you help in advance.Danny

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Are you saying there should be lots of ocean coverage in that mesh? ie "very little blue in it"SRTM data does not alway contain ocean data at sea level (ie 0 metres), but FS2002 corrects this by setting ocean elevation to 0, since FS2002 has knowledge of where the coast line is.How does it look in FS2002?BTW, the my interpolator (to fill in missing data) is not as good as it could be. Maybe thats the problem. Was there lots of missing data in the original SRTM file? You can use Microdem to view the SRTM tile and check for missing data.Im working on a new verion of the utilities so maybe that will help.Can you post an screen shot of the TMFviewer.Matthew

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Matt,I downloaded Microdem last night and being very new at this I am just getting a look at the hgt files. They look OK, but again when I look at the bgl file, it is mostly all yellow with little red blotches in it? I will try to study more today to learn what to look at. If you have broadband I could send you the bgl file itself, about 2.5mb, please le me know.ThanksDannyPS Included screenshot

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Hi Danny,A couple of thoughts that may help:>I converted 5 HGT files totaling abou 125MBMy typical hgt files are less than 3MB, so your estimate seems very unlikely. Should be < 15MB, maybe much less!>when it was done I had one file of about 2.5MBThis could be correct, assuming LOD9. Open your bgl file in Tmfviewer and shrink the image with the "-" key until you can see all four borders. (Use the arrow keys to center the image.) You may be looking at just a small part of total area covered by the bgl file.Stevewww.fs-traveler.com

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Hi Steve,>A couple of thoughts that may help:>>>I converted 5 HGT files totaling abou 125MB>>My typical hgt files are less than 3MB, so your estimate seems>very unlikely. Should be < 15MB, maybe much less!I went back and checked and each of the files are about 25MB...Here is the link where I downloaded them. ftp://edcsgs9.cr.usgs.gov/pub/data/srtm/U...1arcsec/1arcsecAm I using the wrong data?Did what you said with the - key and was able to see the whole block...yellow on left total blue in middle and yellow on the right, one of the things I am struggling with is learning to see where my scenery is in FS2002. I know approximately but hard to tell.Could I send you the BGL file? It is about 2.5 MB?Thanks for the help...Danny>This could be correct, assuming LOD9. Open your bgl file in>Tmfviewer and shrink the image with the "-" key until you can>see all four borders. (Use the arrow keys to center the>image.) You may be looking at just a small part of total area>covered by the bgl file.>>Steve>www.fs-traveler.com

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My file sizes are for 3arcsec data, which explains that difference. I don't believe Matthew's software supports 1arcsec data yet.Suggestions:Start with something simple. Try using 3arcsec data (not as accurate, but should work, and covers larger area per hgt file), from:ftp://edcsgs9.cr.usgs.gov/pub/data/srtm/N...arcsec/3arcsec/Pick an inland area with rugged terrain, somewhere in the Appalachian Mountains, for example. The default mesh is low resolution here, so the effects will be more obvious. Be sure you have no addon mesh active for the same area.Construct your mesh files in squares. The SDK Resample program trims off the edges of most perimeter hgt files, the interior quadrants will be complete. (So use a minimum of 3x3 hgt files).You can use Microdem to merge the 1arcsec hgt files and save as a Microdem DEM file, then use BIGBSQ, available at:http://www.terrainmap.com/to convert to a form that can be used by the SDK. You will have to write your own inf and bat files, however. Instead of sending the bgl, just give me the hgt filenames you are using. I'll download the data and see what I can build with it.You can use the cursor in Tmfviewer to determine locations, reported in the status bar ar the bottom. (You can also check elevations here.) Record a pair of coordinates, then use the Map View in FS to GOTO those coordinates. You can also move the pointer from the interior out across the edges to determine the boundaries, or use BGLAnalyze to get the boundaries. Then fly within these boundaries.You should install all your test bgl files in a testscenery folder, preferably under the ADDON SCENERY folder. Then Add the area in the Scenery Library menu. This way you can compare your mesh with the default by checking and unchecking the area. (Screenshots help.)Steve

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Steve,Thanks for taking the time..You have given me a lot to look at today and I appreciate the help. I will be busy checking this out but will get back. Also I went to your web site and should have started there first. Lots of stuff. What do you charge for the 6 cd set? If you cannot post here just drop me an email, I could not find prices.The files that I used from the site I sent you were :n29w081.hgt thru n29w085.hgtHave a good day... Danny

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You're welcome.You can check prices and place an order online. Select the "Place Order" menu item on the left side of the screen, then the "High resolution mesh ..." link to go to the price list. (The 6 cd 30m set for the US is $39.95)I'll take a look at the files you used, but I am sure the problem is due to the 1arcsec data. Good luck.Steve

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I've taken a look at both the 1arcsec and 3arcsec SRTM data for your area. The bad news is, both data sets have so much missing data that they are of almost no value.You can get much better data from http://seamless.usgs.gov/, but there is a lot more work involved in preparing the mesh.The good news is, I downloaded the NED-tiff data for the same area to see how good it is, and constructed sample mesh for you. I normally use LOD10 for 1arcsec data but this is LOD9 to keep the file size down, to 750kb. It ahould still provide a substantial improvement in such flat terrain. I've included the text file my software generates to show you the coordinates of both the source data and the mesh produced from it. You can download them at:www.fs-traveler.com/cgi-bin/ned-1arcsec-fl.zipI haven't tested the data in the sim, but the bgl does look more like Florida than yours does in Tmfviewer! ;)Reminder: Increase your TERRAIN_MAX_VERTEX_LEVEL to 21 in fs2002.cfg to see even more detail.Enjoy!Steve

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Steve is right, you need to use the 3arc second filesI'll upload the 1 arc second version of the utility today.Sorry about the confusion :(Matthew.

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Thanks Matthew, I went back and re-did some with the 3 arc and it works much better, I will be looking for the 1 arc version also. I can see right now you guys put a lot of blood , sweat, and tears in this stuff. Need to nickname FS2002 "Widow-Maker" LOLThanks,Danny

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Hi Steve,Sorry I did not get back with you yesterday but I got involved in some other products. A friend of mine wanted some help putting a new graphics card in and I was busy with that.Anyway it looks as if this Mesh design is more than I can handle and I am thinking that I may hold off till FS2004 and see how that looks and I may add some mesh after that, this is just taking up too much time. Anyway want to think you and Matthew for all the help.In the meantime I am going to still piddle with the 3 arc stuff and I did some yesterday, came out a little better, I was trying the New River Gorge in WVA and it did ok but I got one long strip and I need to double check that.I will be watching the boards here, but thanks a lot for the help, and also I will be re-reading your web site and getting some hints there.Best Regards,Danny

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