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I've got some data from "http://srtm.csi.cgiar.org/SELECTION/inputCoord.asp" and it is in *.asc form. To process them I need to convert them to shapefile (need to merge them all into one shapefile and add attribute table, on and on ...), but I don't know how. Some web sites such as "http://converter.mygeodata.eu/ " do convert my data but I'm talking about 2.5 GB of data and it is impossible for me to upload this much data ... how can I convert them inside QGIS or ArcGIS ??? Is there another software that can convert my *.asc file into *.shp ??? A lot of thanks

  • I opened the link you posted but could not find any .asc. What exactly did you download? All I was able to get was a piece of a SRTM DEM. – Filipe Dias Oct 12 '13 at 10:24
  • You have to first select the area that you want to download its info, also you have two choice of data types on bot of dialogue box which are arcInfo ASCII (.asc) and geotiff (.grd). Then click to begin search(yellow box) and you can download data from the result page :) – K. Zamen Oct 12 '13 at 12:53
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You can try the GDAL utility gdal_polygonize.py. For example, to create a shapefile output.shp from input.asc:

gdal_polygonize.py -f "ESRI Shapefile" input.asc output.shp

Prerequisites: GDAL, Python and GDAL Python bindings.

But... Are you sure that SHP is the right format in order to work with such huge data?

  • To tell You the truth no. What I want to do is that I want to creat a single file (shapefile or else) that contains 15 of these .asc files and add some attribute table to them(infact merge those 15 shapefile together). These are the first steps of a huge earthquake inversion solution and your help can help me a lot. If you have any suggestions that can help to improve my speed and also the results I'm happy to listen. – K. Zamen Oct 12 '13 at 13:00
  • I imagine that those 15 .asc files don't overlap... So gdal_merge.py could be useful to go on: gdal_merge.py -o output.tif input1.asc input2.asc ... inputN.asc – Antonio Falciano Oct 12 '13 at 13:11
  • I think I can use this command right in ubuntu terminal right ? Anyway do I have to download this gdal_merge.py (to be honest I haven't worked with it) – K. Zamen Oct 12 '13 at 13:17
  • sudo apt-get install gdal-bin python-gdal will install the prerequisites of my answer, because Python is already present. gdal_merge.py is one of the GDAL utilies. – Antonio Falciano Oct 12 '13 at 13:52
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I think your data is in Esri ASCII Raster format and this can be converted into a raster dataset usable by ArcGIS for Desktop using the ASCII To Raster tool.

Like @afalciano, I am not sure that you would want to convert this into a shapefile but if you do then the Raster To Polygon tool does that.

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