7.5 Min DEM's. Anyone used them?

[Guest Richard Hill]

I have tried the STRM Data but at even LOD=7 it is not realistic. I wanted to ask if anyone has used 7.5 Min DEM's and what is the best program to use them. In my state of West Virginia there are constant elevation changes but FS2K either looks like Steep clifts or at a lower LOD the true elevations are much reduced. Any thought/Richard;

[Holger 0]

Hi Richard:I can't answer the question about the 7.5 Min DEM but I wonder about your statement "even LOD=7 it is not realistic": you do know that higher LOD numbers represent higher resolution, not vice versa? Since SRTM data resolution lies somewhere between 90 and 120 meters, LOD8 (152 meters) or LOD9 (76 meters) compilation will give the best representation of SRTM quality without over- or undersampling. Have you tried those two?Cheers, Holger

[Guest Richard Hill]

I tried the STRM2BGL at 9 the default and all my area had near vertical sides while in most cases areas are slopping hills, I set it to 7 that helped some. The STRM data was at 30 Meter.Richard;

[rhumbaflappy 113]

Hi Richard.Did your area have rivers or lakes? The reason I ask, is that misplaced default lakes or rivers will cause higher LOD levels to display cliffs where there should be none. ( The flattening properties of the default water causes the cliffs. )This is a nasty problem, in that we can't easily undo the flattening effects of the default water, even though we can eliminate or move the water... the flattens remain. :(I'm hoping FS2004 will resolve that problem.Dick

[Guest Richard Hill]

Dick;As you know I have made over 4.8 GB of TerraScene produced scenery. While the Default mesh fits great in most cases with my scenery, the elevation extreems are quite a bit off, either the low is not low enough, or the high is not high enough. I do not have any FSRegen texture, and from what I have read it is a long drawn process. I was going to try Ground2K but there is a 10,000 pixel limit. However Christin has said he would remove the limit soon.I have been praying as have many we would get a program like TerraScene and as User Friendly. I am also waiting to see if any great iomprovments are made in FS2004 before I consider 128MB video card for opne thing.Thanks for the reply...Richard;

[rhumbaflappy 113]

Hi Richard.The SRTM data is raw... not processed or corrected or verified. It may well have errors in elevation.The 7.5 minute dems? Are they the NED set (?):http://seamless.usgs.gov/viewer.htmThis set is probably the best for the US. It has been corrected and is ready to go for processing. After selecting the download area. you can use the "Modify Data Request" button to change the download format to BIL.Here's an example of an INF file for the BIL format:{Source}Type = ElevS16LSBSourceDir = "."SourceFile = "N38W120NED.BIL"NullCellValue = -32767Lat = 37.99986111207111Lon = -119.99986111271100 NumOfCellsPerLine = 3600NumOfLines = 3600CellXDimensionDeg = 0.00027777777780CellYDimensionDeg = 0.00027777777780{Destination}LOD = 9DestDir = "."DestBaseFileName = "N38W120NED"UseSourceDimensions = 1The position and cell dimension numbers are from the BLW file that accompanies the data. It worked for me. The format of the BIL is geographic, and the datum is NAD83 ( I don't think converting the datum to WGS84 is of much value ).The NED set has been extensively reworked to provide accuracy. The SRTM set may not have this level of accuracy for some years... but for areas outside the US, it may be the best available, even in it's raw state.Dick

[Guest Richard Hill]

Dick;Thjanks for the help. I will have to ask someone who has DSL or other fast modem to DL them for me. At my best 14,400 this would be some endever.Again thanks for the help.Richard;

[Guest]

Ok I am using Matthew Styles neat utility to convert into bgl's. It uses the hgt files downloaded from the US website.What utilty are you guys talking about to convert the BIL's into the correct format??? I am new at this and using Matthews sofware I was able to make my local mesh ( Edmonton Canada) look much better.Paul

[rhumbaflappy 113]

Hi Paul.We were discussing the seamless NED data for the US... not SRTM data.The NED data in BIL format needs no conversion. The above INF file example, is an example of how to make the BGL from resample.Dick

[Guest Richard Hill]

Dick;I selected the area of NED I wanted I didn't find 7.5 DEM's option. Could you send me a text file or screen shot of the options I need prior to downloading. I have a friend in Florida who will D/L the files I need and send them to me. He realy likes my TerraScene generated scenery. Only wish it wouldn't take 4 minutes to load the files. But then again 4.8 GB of 1/4 degree scenery files, thousands of compreesed .BMP files, I guess one has to put up with this.Although I have no regen and havent seen an update to Ground2K to remove the immage size limit. I just keep hopeiung someone will make a FS2K version of a program like TerraScene, that would automatically create nedded data to produce regen based on USGS data files.Richard;

[Guest sgreenwood]

Hi Richard,Perhaps I can help a bit.7.5 min Dems refers to the standard USGS quadrant sizes. SDDS merges these for you so you can specify any area, not just specific quadrants.The NED data set is 1 arcsec (30m) and probably what you are looking for. Check this option on the top-right corner of your screen.http://forums.avsim.com/user_files/19296.jpgWhile you can select your areas graphically, I prefer to use the "Define Area by Coordinates" option (at the bottom of this image). This is much more precise and you can use LOD quadrant boundaries to refine your requests. Be careful when specifying the areas or you may leave gaps in your mesh due to trimming of data by Resample.http://forums.avsim.com/user_files/19297.jpgThis option brings you to the screen where you enter your boundary coordinates. You can toggle between degree.fraction and degree/min/sec formats here. Once the coordinates are entered, click "Add Area" to continue.http://forums.avsim.com/user_files/19298.jpgThe next screen is the Request Summary Page. Yours won't look like this yet. Click on the "Modify Data Request" button to proceed.http://forums.avsim.com/user_files/19299.jpgThe Enhanced Request Option Page allows you to specify exactly what data you want for the area you specified. Select the BIL Data Format and change other entries if desired. Then click the "Save Changes & Return to Summary" button. This should return you to the previous screen with the correct options selected.Now click the "Download" link to start preparing your data. Maximum file size is 100MB, if you request more, the data will be subdivided into smaller files. (sizes are estimated and not the final zip file size)http://forums.avsim.com/user_files/19300.jpgGood luck,Stevewww.fs-traveler.com

[rhumbaflappy 113]

Hi Steve.Thanks for answering Richard's question. That's exactly the process.This NED data is probablythe best reworked elevation data for the US... until the raw srtm data is reworked. It should be pretty much free of errors.Default lakes and rivers of FS2002 will still weak havok with the areas they flow through... and even if they are remasked as land, the old elevations persist.There are 2 cures:remesh with Area16n ( SCASM code ) or LWM invisible masks ( perhaps from Ground2K ).or...decompile the default HYP file(s) with the latest BGLAnalyze. Theycan then either be altered to remove the offending elevations, or processed with cfs2conv, to remove all elevational code ( letting the mesh determine elevations of lakes and rivers ).http://library.avsim.net/esearch.php?DLID=...mann&CatID=Roothttp://library.avsim.net/esearch.php?DLID=...hor=&CatID=RootDick

[Guest Richard Hill]

Steve;Thanks for the GREAT help and taking the time to reply! I wonder how long it will be before we have a single program that will D/L data for a set area, both elevation and LandClass and LandUse or Shape files to automaticaly create ReGen near photo quality scenery. I have over 4.8 GB of my home state of near Photo Quality *.TGA scenery created with TerraScene. I wonder if anyone will develope a program simular to TerraScene that I think is a fantastic Freeware program, but would be more than willing to pay for one simular that would generate ReGen scenery.Again. Thank you.Richard;

[Guest]

>Steve;>>Thanks for the GREAT help and taking the time to reply! >>I have over 4.8 GB of my>home state of near Photo Quality *.TGA scenery created with>TerraScene.Anyone interested in flying over the mountains of West Virginia and seeing it in all it's splendor should check out Richard's work..Lots of data to load but well worth the 4-5mins to load..Thanks Richards, Danny in Florida