mergetiles

Import adjacent raster tiles, merge the tiles into a single raster, and display the merged raster on a map.

Read four DTED tiles into the workspace. The tiles form a quadrangle with latitudes from 39 to 41 degrees and longitudes from –107 to –105 degrees. For each use of the readgeoraster function, the first output is an array that contains elevation values, and the second output is a reference object that contains spatial referencing information.

[A1,R1] = readgeoraster("w106/n39.dt0",OutputType="double");
[A2,R2] = readgeoraster("w106/n40.dt0",OutputType="double");
[A3,R3] = readgeoraster("w107/n39.dt0",OutputType="double");
[A4,R4] = readgeoraster("w107/n40.dt0",OutputType="double");

Merge the tiles into one raster.

[B,RB] = mergetiles(A1,R1,A2,R2,A3,R3,A4,R4);

Create a map and display the merged raster as a surface. Apply a colormap that is appropriate for elevation data. Then, add a labeled color bar.

usamap(B,RB)
geoshow(B,RB,DisplayType="surface")

demcmap(B)

c = colorbar;
c.Label.String = "Elevation (m)";

This example uses modified data from the US Geological Survey.

The mergetiles function requires the input raster tiles to form a filled quadrangle or rectangle. If your data has missing tiles, then you can fill the gaps with values that represent missing data.

Read three DTED tiles into the workspace:

[A1,R1] = readgeoraster("w106/n39.dt0",OutputType="double");
[A2,R2] = readgeoraster("w106/n40.dt0",OutputType="double");
[A3,R3] = readgeoraster("w107/n39.dt0",OutputType="double");

The tiles are bound by a quadrangle with latitudes from 39 to 41 degrees and longitudes from –107 to –105 degrees. However, the quadrangle is missing the tile with latitudes from 40 to 41 degrees and longitudes from –107 to –106.

To merge the three DTED tiles by using the mergetiles function, you can create a fourth tile of NaN values that accounts for the missing data. If the NaN function does not support the data type of your tiles, such as uint8 values in tiles of RGB data, then you can use numeric values such as 0s or 1s.

missingR = R3;
missingR.LatitudeLimits = [40 41];
missingR.LongitudeLimits = [-107 -106];

missingA = NaN(missingR.RasterSize);

Merge the DTED tiles and the tile of NaN values into one raster.

[B,RB] = mergetiles(A1,R1,A2,R2,A3,R3,missingA,missingR);

Create a map and display the merged raster as a surface. Note that the northwest corner of the map is blank. Apply a colormap that is appropriate for elevation data. Then, add a labeled color bar.

figure
usamap(B,RB)
geoshow(B,RB,DisplayType="surface")

demcmap(B)

c = colorbar;
c.Label.String = "Elevation (m)";

This example uses modified data from the US Geological Survey.