I was following http://www.qgistutorials.com/en/docs/working_with_terrain.html This tutorial.

I added hgt file from SRTM3 as a raster layer, and tried to clip a small area in 1:150000 scale. But this clipping takes eons of time, and the result file seems more than 100gb. I tried the same process with tif file from GMTED data, but the same symptom occurred.

How can I escape from this situation?

Is there anyway to shorten the clipping time, and create result file in small size?

edit 1) I'm not sure how the files looks like, but their size were very small. Looks like they were compressed.

edit 2) Following is the command in command line gdal_translate -projwin 13984505.7052 4710091.33247 14010189.9721 4674886.87201 -of GTiff -co "COMPRESS=LZW" C:/Users/myname/Documents/QGIS_test/NxxExxx.hgt/NxxExxx.hgt C:/Users/myname/Documents/QGIS_test/NxxExxx.hgt/cliptest.tif

-co "COMPRESS=LZW" line helped to reduce the size of the file, but still it takes really really long time to clip

  • Can you provide a few more details? For example, how big is your DEM raster (rows by columns)? Are you clipping the DEM using a vector? If so, how complex is the vector? – WhiteboxDev Aug 25 '16 at 18:02
  • @WhiteboxDev Sorry I'm not using DEM. I'm just trying to clip a area from HGT (or TIF) data. – exsonic01 Aug 25 '16 at 18:11
  • The SRTM data, contained in a TIFF or .HGT file, is a digital elevation model (DEM). – WhiteboxDev Aug 25 '16 at 18:15
  • @WhiteboxDev Aha, Welp, I'm new to QGIS so I'm not familiar with all those initials. – exsonic01 Aug 25 '16 at 18:17
  • @WhiteboxDev Their size looks small. I'm not sure how the raw data looks like, but their size are small. HGT is only 2.75MB, and TIF is 16.5MB. Looks like they are... compressed?... I'm clipping them by "Raster ‣ Extraction ‣ Clipper", and using "extent" mode. – exsonic01 Aug 25 '16 at 18:20

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