GISDigitalElevation

Synopsis

provides a convenient user interface (UI) to the GISDEM module.

Input Ports

• None.

Parameters

NewFile	UIbutton	Select new USGS DEM file.
Subsample	UIslider	Select subsampling factor.
Radius	UIslider	Select global radius.
Ingest	UIbutton	Read in the selected USGS DEM file.

 

Output Ports

QuadName	UItext	Textual info from the DEM name field
Information	UItest	Textual info from the DEM info field
demGrid	Mesh	Output mesh from the DEM file.

 

Description

This macro is a user interface wrapper around the GISDEM module which provides a convenient user interface for reading in US Geologic Survey (USGS) Digital elevation Model (DEM) file sets.

GISDigitalElevation provides the means for the user to set a single subsample parameter to assist in reading in the large (approximately 10 Megabytes) DEM files. For a complete description on information contained in a USGS DEM file, see GISDEM .

Parameters

NewFile

Depressing this button produces a file selector box that allows you to quickly change to a new USGS DEM dataset.

Subsample

This slider allows you to decimate the DEM data set as its being read in. The USGS DEM data sets are quite large, as a result many systems with tight memory requirements may not be able to quickly manipulate the resulting volumetric data. For a complete description of the subsampling feature, please consult the documentation for GISDEM.

Radius

If you want to project this information via GISMapTransform, the resulting mesh may produce strange results. The DEM files represent elevation as meters above the datum, however many of the map transformation use global radii as the reference units. The results can lead to very distorted volumes if the projection is three dimensional, such as the Globe projection. Setting a global radius places everything into the same elevation space.

Ingest

Reads in the DEM file according to the setting provided in the other parameters.

Output Ports

QuadName

All USGS DEM files contain a 40 character quadrangle name embedded in the file. This field displays the contents of that field.

Information

All USGS DEM files contain a 40 character additional information name (normally the USGS quadrangle designation code). This field displays the contents of that field.

demGrid

This is the output Mesh that results from reading in the elevation data. For a full description of this field, see GISDEM .

Example

None

File

v/gis2.v

See also

• GISMeshProject
• GISMeshInvProject
• GISDEM
• GISMapTransform

 




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