[GRASS-user] CHELSA climate data set

[Helmut Kudrnovsky]

> According to gdalinfo, the pixel sizes are
> Pixel Size = (0.008333333300000,-0.008333333300000)
> should be
> Pixel Size = (0.008333333333333,-0.008333333333333)
> i.e. fp precision is too low which explains why west is not exactly on
> -180 but -180.0001389, just as south is not exactly -90 but
> -90.0001389.
> 
> There are 43207 columns, but with 30 seconds there should be 43200
> columns meaning that there are 7 excess columns to the east.
> Considering that the 7 westernmost columns and the 7 easternmost
> columns overlap, their values should be identical.
> 
> There are 21599 rows, but with 30 seconds covering -90, 90 there
> should be 21600 rows. The northernmost row is missing and north should
> be 89:59:30. The data would need to be prepared with gdal_translate,
> cutting off the 7 excess columns to the east and fixing the extents,
> before they can be imported into GRASS.

I had a conversation with the data provider.

according to them, the climate rasters are based upon GMTED2010 [1]

in the description of the GMTED2010 data [2]

30 arc-seconds GMTED2010  data:
Resolution (decimal degrees) 0.0083333333
West extent: minimum X-coordinate (longitude) -180.0001388888
South extent: minimum (for mean): -90.0001388888 (for others:
-56.0001388888)
East extent: maximum X-coordinate (longitude) 179.9998611111
North extent: maximum Y-coordinate (latitude) 83.9998611111
Rows (for mean): 20,880 (for others: 16,800)
Columns: 43,200

it seems the original GMTED2010 data has an intentional half-pixel-shift.

any idea?
[1]
http://erouault.blogspot.co.at/2011/12/seamless-access-to-remote-global-multi.html
[2]https://pubs.usgs.gov/of/2011/1073/pdf/of2011-1073.pdf



-----
best regards
Helmut
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