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# ltln2val

Extract data grid values for specified locations

## Syntax

val = ltln2val(Z, R, lat, lon)
val = ltln2val(Z, R, lat, lon, method)

## Description

val = ltln2val(Z, R, lat, lon) interpolates a regular data grid Z with referencing vector R at the points specified by vectors of latitude and longitude, lat and lon. R can be a geographic raster reference object, a referencing vector, or a referencing matrix.

If R is a geographic raster reference object, its RasterSize property must be consistent with size(Z).

If R is a referencing vector, it must be a 1-by-3 with elements:

`[cells/degree northern_latitude_limit western_longitude_limit]`

If R is a referencing matrix, it must be 3-by-2 and transform raster row and column indices to or from geographic coordinates according to:

`[lon lat] = [row col 1] * R`

If R is a referencing matrix, it must define a (non-rotational, non-skewed) relationship in which each column of the data grid falls along a meridian and each row falls along a parallel. Nearest-neighbor interpolation is used by default. NaN is returned for points outside the grid limits or for which lat or lon contain NaN. All angles are in units of degrees.

val = ltln2val(Z, R, lat, lon, method) accepts a method string to specify the type of interpolation: 'bilinear' for linear interpolation, 'bicubic' for cubic interpolation, or 'nearest' for nearest neighbor interpolation.

## Examples

Find the elevations in topo associated with three European cities—Milan, Bern, and Prague (topo elevations are in meters):

```load topo
% The city locations, [Milan Bern Prague]
lats = [45.45; 46.95; 50.1];
longs = [9.2; 7.4; 14.45];
elevations = ltln2val(topo,topolegend,lats,longs)

elevations =
313
1660
297```