usgs24kdem
(Removed) Read USGS 7.5 minute (30 meter or 10 meter) Digital Elevation Models
usgs24kdem
has been removed. Use readgeoraster
instead. For more information, see Compatibility Considerations.
Syntax
Description
[
reads a USGS 1:24,000 digital elevation map (DEM)
file in standard format. You select the file interactively.
lat
,lon
,Z
]
= usgs24kdemusgs24kdem
reads the entire file,
subsampled by a factor of 5, returning a geolocated data grid with a
latitude array, lat
, longitude array,
lon
, and an elevation array,
Z
. Horizontal units are in degrees,
vertical units might vary. The 1:24,000 series of DEMs store data as
a grid of elevations spaced either at 10 or 30 meters apart. The
number of points in a file varies with the geographic
location.
[
reads a subset of the DEM data from lat
,lon
,Z
]
= usgs24kdem(filename
,samplefactor
)filename
,
where samplefactor
is a scalar integer that
specifies the sample frequency.
[
reads the subset of the elevation data from
lat
,lon
,Z
]
= usgs24kdem(filename
,samplefactor
,latlim
,lonlim
)filename
specified by the two-element
vectors latlim
and lonlim
. You
specify the latitude and longitude limits in degrees. Elements in
the vectors must be in ascending order. The data might extend
outside the requested area.
Examples
Input Arguments
Output Arguments
Tips
The U.S. Geological Survey has created a series of digital elevation models based on their paper 1:24,000 scale maps. The grid spacing for these elevations models is either 10 meters or 30 meters on a Universal Transverse Mercator grid. Each file covers a 7.5-minute quadrangle. The map and data series are available for much of the conterminous United States, Hawaii, and Puerto Rico. The data has been released in several formats. This function reads the data in the “standard” file format.
This function reads USGS DEM files stored in the UTM projection. The function unprojects the grid back to latitude and longitude.
The number of points in a file varies with the geographic location. Unlike the USGS DEM products, which use an equal-angle grid, the UTM projection grid DEMs cannot simply be concatenated to cover larger areas. There can be data gaps between DEMs.
You can obtain the data files from the U.S. Geological Survey and from commercial vendors. Other agencies have made some local area data available online. The DEM files are ASCII files, and can be transferred as text. Line-ending conversion is not necessarily required.