Hanlie Pretorius wrote: > I have an existing CSV file that has the headers lat, long and precip. > The precipitation is a floating point number to two decimal places. > The coordinates in the CSV file define the centre of a quarter degree > square. The first set of coordinates in the file is -19.625,15.875. > > Becuase the TRMM data defines the centre of the square, I subtracted > 0.125 from the first set of coordinates to get the north-west corner > of the raster. And I added 0.125 to the last coordinate in the CSV > file, which is -34.875,34.125, to get the south-east corner of the > raster.
This seems wrong; positive-X is east, positive-Y is north, so you should be adding to north and east, subtracting from south and west. > In the CSV file, the latitude stays constant for 74 rows while the > longitude increments in quarter degree steps. The whole file contains > 4588 rows, so a grid of the data should have 74 rows and 62 columns, > right? > > So I reformatted the data to 74 rows and 62 columns and added the header: > > north: -19.5 > south: -35.0 > east: 15.75 > west: 34.25 Positive-X is east, so either east and west are the wrong way around, or they should both be negative, or this represents a span of 341.5 degrees. > rows: 74 > cols: 62 > null: -319.99 > > > The output of g.region -p is: > > projection: 3 (Latitude-Longitude) > zone: 0 > datum: wgs84 > ellipsoid: wgs84 > north: 18S > south: 36S > west: 15E > east: 35E Here, east and west have been swapped relative to what you say above. > nsres: 0:15 > ewres: 0:15 > rows: 72 > cols: 80 > cells: 5760 > > > I then imported the reformatted file using the command: > > r.in.ascii -f input="3B42RT.2010032409.6.bin.sa.grass"\ > output="2010032409.6.precip" \ > title="Precipitation 2010032409.6"\ > mult=1.0 or read from header nv="* or read from header" > > > When imported, I get two thin strips of data on the sides of the > image. The raster shouldn't contain any nulls (the text file doesn't > contain the value -319.99), so something is wrong. > > r.info gives a very strange resolutions: > > > | Type of Map: raster Number of Categories: 255 > | Data Type: FCELL > | Rows: 74 > | Columns: 62 > | Total Cells: 4588 > | Projection: Latitude-Longitude > | N: 19:30S S: 35S Res: 0:12:34.054054 > | E: 15:45E W: 34:15E Res: 5:30:29.032258 The west edge is east of the east edge, resulting in a span of 341.5 degrees. 341.5 / 62 = 5.508064516129032 = 5:30:29.032258. > | Range of data: min = 0.000000 max = 7.470000 > > > Can someone perhaps help me to see what's happening here? East and west are swapped. -- Glynn Clements <gl...@gclements.plus.com> _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user