DEMs (digital elevation models), and images that include elevation data such as a GeoTIFF, are referred to as "rasters". Using the third-party software Global Mapper, GMS supports a large number of DEM formats. After importing, DEMs are listed under "GIS Data" in the Project Explorer along with other images. The raster icon File:Tree-raster-icon.png is different from the image icon File:Tree-Image-Icon.png to indicate it includes elevation data. Rasters don't have to be DEMs. For example, the values at the pixels can represent concentrations, or flow rates ... or anything.
Importing DEMs
DEMs can be imported by simply opening the file(s) or dragging and dropping the file(s) into the GMS window. Multiple files can be imported at once. DEMs can also be obtained via the Get Online Maps feature.
Creating Rasters
Rasters can be created from within GMS by interpolating from 2D scatter points. The interpolation options, the raster cell size, and the extents of the raster can all be specified in the Scatter → Raster dialog.
Interpolating From Rasters
Rasters can be interpolated to most other objects, including the z values of feature objects and to MODFLOW layers. The interpolation is done by finding the raster cells that the object's points are in and assigning to the points the values from the raster cells.
Multiple rasters can be interpolated to another object at once by simply selecting multiple rasters in the Project Explorer, right-clicking and selecting the appropriate interpolation command. This will result in the creation of multiple datasets on the object being interpolated to. If the user desires to create only one dataset from all the rasters (because they are tiled next to each other, for example), the user can create a raster catalog and interpolate from it.
Conversion From Rasters
Rasters can be converted to the following:
Raster Display Options
The GIS tab of the Display Options dialog is used to change the way rasters are displayed. DEMs are imported and displayed as either 2D images or as a 3D point cloud.
Display as 2D image
If displaying as a 2D image, the raster is only visible in plan view (like other images). This option is fast and memory efficient and can support large rasters (or several rasters). Hill shading, which enables shadows and thus makes the image appear 3D, is available in this mode.
Display as 3D points
If displaying as 3D points, the raster is visible in any view, not just plan view. 3D points are also very memory efficient but may be a little slower than the 2D image option. Also, hill shading is not available in this mode. The point size and the maximum number of points to display can be specified. Specifying a maximum number of points can be useful if the size of the raster is such that rendering becomes slow.
Shaders
With either 2D or 3D, four different shaders, which control the color ramp, are available. A color legend can be displayed to relate colors with values.
