# Documentation

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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)` where `method` specifies 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```