3D Surface Model Data
X,Y,Z Surface File from USGS 10 and 30 Meter Digital Elevation Models
The USGS 10 and 30 Meter DEM (Digital Elevation Model) data consists of a grid of
elevation values posted every 10 or 30 meters. You can export an X,Y,Z surface file
for use in many Surface Analysis Programs. The X,Y,Z file is an ASCII file consisting
of all the DEM elevation points. Each point consists of an X, and Y position in
the desired map projection, and a Z value (elevation) in either feet or meters.
If you tile several quads together, then the X,Y, Z file is also tiled together.
Click here for a page contrasting the 10 and 30 meter
data.
TopoDepotOnDVD also provides the capability to extract just a smaller portion of
an XYZ file. This can be very useful since the number of points within a single
quad is quite large.
A number of different XYZ output formats are supported.
Currently, TopoDepot exports in the following formats:
AUF AutoDesk Uploadable File
PENZ (space delimited)
X,Y,Z Comma Delimited
X,Y,Z Space Delimited
X,Y,Z Tab Delimited
Eagle Point
N,E,Z Comma Delimited
AutoDesk Civil 3D, as well as many other 3D analysis programs can use 3D surfaces
exported from the USGS DEM data within TopoDepot.
These 3D surfaces can be used for 3D rendering, surface analysis, contour generation,
drainage analysis, and fill analysis.
Often, these 3D programs can consume text files containing the X coordinate (Easting),
Y coordinate (Northing), and the elevation. These are often called XYZ, ENZ, NEZ,
or other names. For example, AutoDesk Civil 3D uses a particular format called AUF,
or AutoDesk Uploadable File format. This is a variant of an XYZ text file.
These XYZ files are exported in the Projection, Units, Horizontal Datum, and Vertical
Datum selected.
Note that the 10 Meter data has 9 times more points than the 30 meter data. While
this provides greater accuracy, it also increases file sizes by approximately 9
times.
It is also now possible to select the vertical datum when you output the data.
