# Documentation

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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).