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latlon2pix

Convert latitude-longitude coordinates to pixel coordinates

Syntax

[row, col ] = latlon2pix(R,lat,lon)

Description

[row, col ] = latlon2pix(R,lat,lon) calculates pixel coordinates row, col from latitude-longitude coordinates lat, lon. R is either a 3-by-2 referencing matrix that transforms intrinsic pixel coordinates to geographic coordinates, or a geographic raster reference object. lat and lon are vectors or arrays of matching size. The outputs row and col have the same size as lat and lon. lat and lon must be in degrees.

Longitude wrapping is handled in the following way: Results are invariant under the substitution lon = lon +/- n * 360 where n is an integer. Any point on the Earth that is included in the image or gridded data set corresponding to r will yield row/column values between 0.5 and 0.5 + the image height/width, regardless of what longitude convention is used.

Examples

Find the pixel coordinates of the upper left and lower right outer corners of a 2-by-2 degree gridded data set.

R = makerefmat(1, 89, 2, 2);
[UL_row, UL_col] = latlon2pix(R,  90, 0)     % Upper left
[LR_row, LR_col] = latlon2pix(R, -90, 360)   % Lower right
[LL_row, LL_col] = latlon2pix(R, -90, 0)     % Lower left

Note that the in both the 2nd case and 3rd case we get a column value of 0.5, because the left and right edges are on the same meridian and (-90, 360) is the same point as (-90, 0).

See Also

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