Why does latlon2pix return non-integer values?
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latlon2pix converts latitude-longitude coordinates to pixel coordinates.
[row, col] = latlon2pix(R,lat,lon)
So, as I understand it the output should be integer row and column indices into the map defined by R so that map(row,col) returns the pixel in map that contains the point [lat,lon].
I have ...
R =
0 -0.0028
0.0028 0
23.6282 -22.0506
lat = -23.8750
lon = 27.6250
then
[row, col] = latlon2pix(R,lat,lon)
returns
row = 657.1850
col = 1.4396e+003
so I have to resort to floor(row) and floor(col) before using them as subscripts. I suspect this may not be returning the intended pixel.
Any suggestions appreciated.
Best Wishes
Neil
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Accepted Answer
the cyclist
on 24 Sep 2011
I don't have the Mapping Toolbox. But reading the documentation for the latlon2pix() function, I see no indication that the output is necessarily integer pixel values. In fact, the example here: http://www.mathworks.com/help/toolbox/map/ref/latlon2pix.html explicitly mentions getting a column value of 0.5.
4 Comments
Walter Roberson
on 24 Sep 2011
Exact pixels would make sense for people who want to be able to create sub-sampled graphics. It is easy to throw away precision that you do not need, but difficult to regain precision that was thrown away on your behalf.
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