# Documentation

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# tbase

Read 5-minute global terrain elevations from TerrainBase

## Syntax

```[Z,refvec] = tbase(scalefactor) [Z,refvec] = tbase(scalefactor,latlim,lonlim) ```

## Description

`[Z,refvec] = tbase(scalefactor)` reads the data for the entire world, reducing the resolution of the data by the specified scale factor. The result is returned as a regular data grid and an associated three-element referencing vector.

`[Z,refvec] = tbase(scalefactor,latlim,lonlim)` reads the data for the part of the world within the latitude and longitude limits. The limits must be two-element vectors in units of degrees.

## Background

TerrainBase is a global model of terrain and bathymetry on a regular 5-minute grid (approximately 10 km resolution). It is a compilation of the public domain data from almost 20 different sources, including the DCW-DEM and ETOPO5. The data set was created by the National Geophysical Data Center and World Data Center-A for Solid Earth Geophysics in Boulder, Colorado.

### Note

For details on locating map data for download over the Internet, see the following documentation at the MathWorks Web site: Finding Geospatial Data.

## Examples

collapse all

Set the scale factor to read every 10th point.

`scalefactor = 10;`

Read the data and view the size of the returned variables.

```[Z,refvec] = tbase(scalefactor); whos Z refvec ```
```Name Size Bytes Class Z 216x432 746496 double array refvec 1x3 24 double array ```

Determine the latitude and longitude limits of the geographic quadrangle bounding the data grid.

```limitm(Z,refvec) ```
```ans = -90 90 -180 180```

Set the scale factor to `1` and set the longitude and latitude limits. This example reads the data for Korea and Japan.

```scalefactor = 1; latlim = [30 45]; lonlim = [115 145]; ```

Read the data and view the size of the returned variables.

```[Z,refvec] = tbase(scalefactor,latlim,lonlim); whos ```
```Name Size Bytes Class Z 180x360 518400 double array refvec 1x3 24 double array```