Digital Elevation Models (DEMs)
LIME loads digital elevation or other surface grid data in some standard formats:
- Georeferenced image files (*.tif, *.png)
- Erdas Imagine (*.img)
- ESRI ASCII/binary grids (*.asc, *.adf)
- USGS DEM (*.dem)
- ZMap+ grid (*.asc, *.dat, *.zgf)
Colorado/Green River confluence, Canyonlands, UT, USA, coloured by elevation, 1 km grid and a transparent contour layer.
DEMs represent real-world surface topography as raster grids of height values. They are commonly found in GIS projects and are made available by national mapping agencies around the world. With today’s satellite sensors, there is complete coverage of the earth’s surface, though available resolution may depend on country, data source and access restrictions.
In LIME, DEMs are a good way to visualise the surroundings of your virtual 3D models – as well as being a source of important information in their own right!
Loading a DEM (or multiple DEM files) is straightforward. We immediately get a low-resolution preview of the terrain file to allow us to crop the DEM to our area of interest and select a suitable sampling resolution to load.
Once the DEM has been loaded into LIME it shows up just like any other model, allowing us to take advantage of the in-built display settings to create stunning terrain visualisations. In LIME v2 there are a few new terrain colour ramps too. Here’s a small gallery for inspiration.
The island of Kinn in western Norway (national lidar data from Kartverket), showing the impressive Kinnaklova split peak (which incidentally is a wonderful hike if you are ever in the area).
Colour coding of aspect (dip direction) of a terrain model (300 m grid spacing) and 10 m contours (OpenTopography). The colours are blended with the terrain relief.
Made in Bergen: visualisation of surface normals to show the relief around our offices (Kartverket).
General surfaces and horizons can also be loaded. Here we are looking at data from Mills et al. (2003) – flat shading, a colourful ramp and full grid opacity gives a “classic” simulation image.
