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rhumbaflappy

recent updates to GIS freeware

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Hi all:hope you had a good start into the New Year!Just completed a round of visits to my favorite GIS websites, so here's a list of recent updates:1. Microdem has yet another build (14.60.19, Dec.19), though the help file doesn't state what the latest changes were. Find it at http://www.usna.edu/Users/oceano/pguth/website/microdem.htm2. 3DEM has a new version (18.0), which now allows for filling in void areas in SRTM data and a few other additions. (I use 3DEM's shaded top-down view for creating bitmaps of SRTM or CDED DEM tiles; I then merge these tiles and import them as background images in Ground2K4 for delineating shorelines.) http://www.visualizationsoftware.com/3dem.html3. John Childs has updated his website and also his Blackart freeware utility. Blackart has a wide range of functions, such as DEM construction from digitized contour maps, DEM editing of ASTER, SRTM, or other data, and interpolation routines for filling holes in ASTER and SRTM tiles. http://www.terrainmap.com/index.html#top Cheers, Holger

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Holger,Thank you for this excellent information. It seems that a few of these tools may help me in my creation of Mesh using SRTM source data. In particular, I have been trying to fill voids in SRTM data.I am using the excellent tool SRTM_to_BGL, and all is well except that sometimes I have some red areas using TMFViewer. These red areas are assigned a value of -32767 which is the flag value assigned to Null data. This is using resample.exe 1.0.0.1If I use the newer resample.exe 1.0.0.2 the null areas are still there except now they are white in TMFViewer.I am assuming that I need some algorithm to interpolate or fill the voids right? What do you recommend?Thanks in advance!-- Outer Marker

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Hi Outer Marker:you're welcome!I've been using MicroDEM for my SRTM-based meshes. It allows for filling void areas with other mesh data, if available, and to define the extent of any interpolation passes so that no holes remain. However, it might be a bit of an overkill to install and get to know MicroDEM if you're only interested in making a few SRTM meshes.Joe Binka just found another SRTM tool, which he has been using successfully to patch up 1-arcsec SRTM tiles of SE Alaska. Here's the link to SRTMfill: http://www.3dnature.com/srtmfill.html Look at Joe's preview images of the Ketchikan area here: http://forums.avsim.net/dcboard.php?az=sho..._id=18741&page=If I was to pick between one of the three external SRTM fill utilities (without having tried them) I'd give John Childs' Blackart a go, simply because he is one of the Ueber-Gurus of digital elevation modeling.Let us know what worked for you. Cheers,Holger

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More interesting stuff from the Ketchikan area. I notice that the default FS coastlines have been removed, and that seemingly, the custom mesh is defining the actual coast topography (cliffs etc.) This detail alone adds some serious realism.No can somebody tell me how you remove coastlines? I seem to observe coastline data in HYP?????.bgl files but I have no idea how the naming convention works, and what coastlines I would be removing if I removed a file from FS2002.Any ideas on this technique?Thanks!-- Outer Marker

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Hi again:seems like Ketchikan is a popular place for mesh and shoreline designers these days - or are you referring to these posts? ;-)http://forums.avsim.net/dcboard.php?az=sho..._id=18556&page=http://forums.avsim.net/dcboard.php?az=sho..._id=18741&page=To find the local HYP*.bgl file I suggest using Steve Greenwood's FSTFlatten, available here http://www.fs-traveler.com/flatten.shtml It will tell you the file name and assist with partially deleting default shorelines from the hyp*.bgl file.Cheers, Holger

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Thanks loads, Holger. This is just what I needed, as I just cannot leave well enough alone and redid the mesh on VGhttp://forums.avsim.net/user_files/57939.jpgBut, of course, this is not completely satisfactory and most of the data winds up in the water. Everything has to be moved so that the data points fall on the land mass. Time for some advanced data processing.Best regards.Luis

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>I am assuming that I need some algorithm to interpolate or>fill the voids right? What do you recommend?Hi,You can get at http://www.ptsim.com/en/support.htm a programme to import DTED2 and HGT files into BSQ format. It processes BSQ files in a variety of ways. You can view, merge, crop, filter, interpolate for voids, etc ...You can set the programme to completely eliminate the voids.Regards, Luis

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Hi Luis.DEM2BSQ is a very nice program. I especially like the ability to turn the BSQ to a bit map, and back again.That allows you to paint sealevel areas as "0", and get rid of the bumps the SRTM data leaves in the oceans.:)Dick

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