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I am working with the tri.txt (terrain ruggedness index) file from this paper: http://diegopuga.org/data/rugged/

I've uploaded the raster data from the file into ArcMAP and now have it as a .tif file. My goal is to use this data and PostGIS to get the ruggedness value for certain cities in the US (I have the lat/lon values for the cities I'm interested in). I'd like to convert the raster data to points, get the lat/lon values of each of those points, and find the closest data point to each city.

Questions:

  1. The website I got the raster file from doesn't mention an srid. How do I find out what projection it uses?
  2. I'm not familiar with scripting in ArcGIS. I've found the arcpy.RasterToPoint_conversion function in Python that I think I can use for this, but I'm not sure what the arguments should be.

Thanks!

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From the ArcGIS Help Site, Raster To Point(Conversion), it lists all the valid arguments you are looking for.

Also, for checking on the SRID of your .tif file, right click the file from Catalog and click properties. This should bring up Raster Dataset Properties, scrolling down you should see a Spatial Reference section.

  • Thank you. I'm not sure what the out_point_features argument means--"The output feature class that will contain the converted points." Can you explain? Is this the file path where I want to store the result? Also the Properties menu says "Spatial Reference: <Undefined>" – forest Oct 9 '14 at 14:57
  • Therefore you can define your own and project it as you wish. – Maksim Oct 9 '14 at 14:58
  • Yes the out_point_features is the point file you wish to be made. Perhaps in a .gdb or a shapefile – Maksim Oct 9 '14 at 15:33
  • @forest You can just run the tool inside ArcMap or ArcCatalog, you don't have to script it. – ianbroad Oct 9 '14 at 16:32
  • resources.arcgis.com/en/help/main/10.2/index.html#//… How to search for tools. It is located in System Toolboxes -> Conversion Tools -> From Raster -> Raster To Point – Maksim Oct 9 '14 at 18:17
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I'd like to convert the raster data to points, get the lat/lon values of each of those points, and find the closest data point to each city

This goal is actually easier if you keep the data in raster form and use Extract Values to Points (note: Spatial Analyst extension required). If you create a set of points for each city you are interested in, then this tool will pull the raster data at each point and add it as an attribute (RASTERVALU) to the city feature.

Or, if you want to use PostGIS, the ST_Value function may do what you need. I haven't used it myself but the description matches what Extract Values to Points does:

Returns the value of a given band in a given columnx, rowy pixel or at a particular geometric point.

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