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gaugi1

Microdem Bug

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Dear All:When i merge two adjacent SRTM dems without holes, i get the merged files with "holes" in the border between the two sources like a line of holes, why?I have to correct manually the holes to avoid this trouble.There is any solution?Thanks Alfredo Mendiola LoyolaLima Peru

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Hi Alfredo:that's odd! According to the SRTM website the raw data actually are cut to have one data column/row of overlap (in the East and North, I believe). One thing I noticed when playing with the data is that MircroDEM doesn't seem to "see" these extra lines, at least not according to the Analyze > Header readings. Perhaps others know where this discrepancy comes from? In any case, you can instruct MicroDEM to auto-fill holes on merge: it's in the Options > Import/Export sub-window. I use "10" as the max gap width but you can experiment with different settings.Hope this helps. Cheers, Holger

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Dear Holger:Even using 50 as max gap, the no data lines are in the DEM, i will have to interpolate manually to delete the lines with no data.Do you have other solution?Thanks.Alfredo Mendiola LoyolaLima Peru

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I have the same problem and I have resolved it with the Data manipulation->Edit->Fill DEM holes function. Attention ! These holes can also be in border. I have resolve this other problem in merging the adjacent DEMs, filling DEM holes and extracting (subset function) data set covering the wanted region.

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Folks: Are you using a current version of Microdem? I've merged over 3500 SRTM hgt files with no such problem! (I'm using the April 2003 version)Hi Holger:I think the overlap means that the data includes the boundary row/column on the right and top sides. These are not necessary when one is merging the data, but it does provide a full degree of data when used as a single file. A nice touch, actually.For example: N40W073 extends from W073 to W072 N40W072 extends from W072 to W071 these files have duplicate (overlaping) data for the W072 columnA little math using the header info:the sw corner (x coord) of N40W073 is -262800 arcsec1201 cols = 1200 cells x 3arcsec/cell = 3600 arcsec width-262800 + 3600 = -259200 arcsec for the se corner-259200/3600 arcsec/degree = 72 degrees; a full degree of coverage!Steve

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Dear All:The problem isn't no data holes, i ge lines with 0 meters of elevation between the merged dems.I'm interpolating the data do delete the 0 meters dem

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If there is no sea level data, you can correct the lines with 0 meters like thatData manipulation-> Edit -> Missing data to specified z -> 0followed by Edit -> Fill dem holes

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