DEM


GIS Data

Updated 3D Global Topo Data from NASA

Updated 3D Global Topo Data from NASA

Based on measurements from NASA’s Terra spacecraft, a new 3D topographic map has been released as a joint effort by NASA and Japan.  The digital elevation model (DEM) was developed from imagery obtained from the Japanese Advanced Spaceborne Thermal Emission and Reflection Radiometer, or ASTER, instrument aboard Terra.  ASTER is one of five […]

GIS Data

Overview of Elevation Data

Overview of Elevation Data

Hypsography, topography, elevation, TINS, and contours. There are many different terms for data relating to elevation. This article reviews some of terminology and types of elevation based datasets available to GIS. Digital elevation data are sets of elevation measurements for locations distributed over the land surface. Elevation data have many […]

GIS Software

How to Select Ridgelines From a DEM Using Spatial Analyst

How to Select Ridgelines From a DEM Using Spatial Analyst

Selecting out ridgelines from a DEM using ArcView 3x’s Spatial Analyst extension is pretty straightforward. These steps assume the initial DEM is called “elev”. Time Required: 10 minutes Here’s How: Compute a flow direction grid – a grid with codes indicating for each cell which of the eight possible directions […]