[GRASSLIST:9346] Re: ArcInfo Grid vs r.in/out.gdal

[David Finlayson]

Maybe I misunderstood. I thought that you were referring to the
coordinates of an arbitrary cell value (x, y), not the bounding box of
the whole raster.

The only two raster registration systems that I have encountered are
"raster" where the cell's value is located at the center of the cell,
and "lattice" or "fishnet" where each corner of the cell has a value
(really, the intersection of row and column lines).

In the former, there are row * col values.
In the latter there are (rows + 1) * (cols +1) values.

You suggested that GRASS uses a variation on the "raster" format where
instead of the cell center, the lower-left corner was the location of
the value.

This is a 1/2 X 1/2 cell shift in coordinates from what I expected.
I've got a lot of code that is messed up if that is the case.

David

On 12/6/05, Hamish <hamish_nospam at yahoo.com> wrote:
> > I didn't know that grass referenced the lower left corner. I assumed
> > it was the cell center. Where is this documented?
>
> "The geographic boundaries of the raster file are described by the north,
> south, east, and west fields. These values describe the lines which bound
> the map at its edges. These lines do NOT pass through the center of the
> grid cells at the edge of the map, but along the edge of the map itself."
>
> (section 5.3.1 of the old GRASS 5 programmer's manual.)
>
>
> I guess it should be added here?  grass6/raster/rasterintro.html
>
>
> In the GRASS 6 programmer's manual: ???
>  make pdfdocs
>  xpdf lib/gis/latex/grass61gis_2005_12_07_refman.pdf
>
> It is mentioned in the r.in.ascii and r.in.bin help pages,
>   http://grass.ibiblio.org/grass61/manuals/html61_user/r.in.ascii.html
>
>
> Hamish
>


--
David Finlayson
Marine Geology & Geophysics
School of Oceanography
Box 357940
University of Washington
Seattle, WA  98195-7940
USA

Office: Marine Sciences Building, Room 112
Phone: (206) 616-9407
Web: http://students.washington.edu/dfinlays