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"How to insert 10m & 30m DEMS into your route"

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landnrailroader (68 posts)
Dec-12-01, 10:58 AM (EST) "How to insert 10m & 30m DEMS into your route" Gentleman,This is a repost of a reply I made to someone else, and so get your rocks, slings, rotten veggies, etc. out & get read to throw.At the risk of having all kinds of slings & arrows, and rocks thrown my way, I am going to plunge ahead and describe how I got DEM insertion to work. So far, XYZmerge does not work for me. Night before last, it ran over 10 hours and completed but did not ever produce an output file. The instructions from Lawrence' SD40 site indicated that I should go ahead and mix 10 & 30m DEMS and I think that was the problem. If one attempts to merge 10m DEMs, one soon runs out of available column & row space in MicroDem, as the help file indicates. About a month ago, I discovered a method that works for me, after which I use a suggestion of Lawrence's that also works, but not too well in one situation of mine.Download the desired DEMS from whereever you can get them, preferably for free. Each DEM has a range value, i.e. from one corner to the other, which is listed in the text file that goes with each DEM. If there are both 10m & 30m DEMS available, download only the 30m DEMS (smaller file size is the giveaway here), otherwise download whatever is available. It helps me to layout a grid, free-hand, and list the coordinate lat/long values on the edges, so I can list the DEMS in their proper relationship in the grid. That way, if I miss one, I know what to look for to complete my merge. If I get an undesirable ditch, I also know, approximately, where it is on the DEM layout. They most often occur in the boundaries, E-W, between 10m and 30m DEMs.Decompress the GZ files for the 30m DEMS, thus creating <name>.DEM files, where I choose the name of the Quad for the <name> of the file. Do not use PkZip for this, instead use the decompression routines in MicroDem. Then resample the 10m DEMS, and when the screen appears giving the rows & columns, change these values to 1/3 of the value given rounded up. The process is explained in the help file and works very well if you follow those instructions. It might also be possible to use the "thin" command, but I have not tried this method. As the files are resampled, to reduce the density, give the resulting DEM files the naming convention as above.Now, using the instructions Lawrence has provided on several occasions, merge the DEM files into one DEM. I have found that if you try to add another DEM file on the edge of existing scenery, it will probably mess up existing scenery, so I found it was better to just use DEMEX on the whole route again (and again and again if necessary until it looks right). Convert the merged DEM into an XYZ file, and run DEMEX with it. Yes, you will mess up that nice work you already have done, but then it is a good idea to be sure you have all you need first, and in my case, I found that the second time through, using the "y" key went very fast, and I also knew where NOT TO USE IT, like at bridges and tunnels. I have put in track on 137 miles of mainline, and am completing the associated coal branches.Now, about SeamFill. This works great on relatively flat, or flat scenery, where "ditches" are smoothed out to the general contours of surrounding areas, but it doesn't cut it at all in mountainous terrain. I found that I had a ditch at a critical point on Blue Ridge, where the Clinchfield loops are (the loops are right on the juncture of 4 quads) and it was about 400 ft. deep. When I ran SeamFill, the result was a "spine" about 400 ft. above the surrounding terrain, so in this instance, I will manually correct the problem, which will be easy when I lay the track at the correct elevation.I did find that further down in SC, where a ditch occurred in relatively flat terrain, SeamFil handled it very well.Therefore, when the little map pops up and shows you the result of creating your massive merged DEM (or if you load it as a DEM file into MicroDem) note any streaks, usually running E-W that are in it. These will be on DEM boundaries. By referring to the GRID I mentioned making above, you can determine the precise lat/long of the centerlines of these ditches. Go into Geometry Extractor, and load the route and the Quad tree associated with it. Zoom into the route and put the cursor on the lat/long of one of the ditches. Note the tile names that appear in the header and jot these down. You will need the tiles along the C/L and one tile either side of the C/L. Create a directory tree on your hard-drive somewhere. I used D:\routes\blueridge\tiles and copy or move, the tile files (I copied all files with the same name, but evidently the ".t" file is the critical one) into the directory you created. Then run SeamFill on this directory, or group of tile files. The advantage to this, is that it runs faster, and it allows you to select the areas where SeamFill will probably do fine. In any questionable areas, you could keep a copy of the tile files in some other directory until you are satisfied with the result. If you cannot get a satisfactory result, just restore the offending files.J. H. Sullivan, P.E.
retired from CSX(Old railroaders never quit, they just get recycled - hence I'll be returning to work 1/2002 working through a Temp service.)
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Subject Author Message Date ID RE: How to insert 10m & 30m DEMS in... wbgx Dec-12-01 1

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wbgx (26 posts)
Dec-12-01, 03:19 PM (EST) 1. "RE: How to insert 10m & 30m DEMS into your route" I found your method of using SeamFill a great time saver. I can only add that someone wanting to use the method should place the copied or cut tile files in the 'tile' directory. Initailly I choose to call my temp. folder 'temp'. The SeamFill program will only recongize a folder as 'TILES' as the place to perform its task.This was clear in your post, but I used too much artistic freedom Boomer Remove | Alert Edit | Reply | Reply With Quote | Top

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