Say that i have two "data sources";
- A global map of average wind speeds,
- A shape file (or similar information) of all country borders in the world.
How do i combine these two sources and extract the average wind speeds of a country?
The wind speed data is structured such that each lat-lon combination has an average wind speed:
Lat, Lon, AvgSpeed -90, -180, 4.54 -90, -179, 4.55 -90, -178, 4.57 ...
The output should be somewhat similar to the input, but with "an extra column" for country:
Lat, Lon, AvgSpeed, Country -90, -180, 4.54, Country 1 -90, -179, 4.55, Country 1 -90, -178, 4.57, Country 2 ...
I have Grass GIS, R and Python installed – but your answer need not be restricted to these software packages/programming languages.
Best Answer
You first need to import the CSV file with v.in.ascii to create a vector points map. Add a new column "Country" of varchar(25) with v.db.addcol. Then simply populate the new column with v.what.vect (see also example in that manual page).