There many methods for displaying contour lines in visualization and GIS software programs. In most cases, representing terrain data with standard contours or hillshading techniques are sufficient. In other cases, you may want a more artistic technique to help emphasize specific features in the data or to make the map more pleasing to the eye. One of these techniques is using the Tanaka method for creating illuminated contours. I recently read an article about how to create illuminated contours in ArcGIS and couldn’t resist trying to replicate the results in Surfer's mapping software.
The Tanaka method applies a northwest light source to a contour map. The contour lines then change in color and width based on their relationship to the light source. Contour lines facing the light source are drawn in white while those in the shadow are drawn in black. The contour lines facing the light source (or facing away from it) are thicker, and the contour lines in the orthogonal direction are thinner. A more detailed explanation of the method can be found online at: http://www.mbmg.mtech.edu/pdf/gis_illum.pdf
While Surfer's mapping data software cannot change the width of the contour lines and create a contour map as in the true Tanaka method, you can alter the colors based on the light source and create a very similar effect.
The same map is displayed using various techniques. A map with a Tanaka-style effect is shown at the top, a map showing standard hillshading is shown in the lower left, and a map showing standard filled color contours is displayed in the lower right. All maps are created in Surfer 13.
To create a map with a Tanaka-style effect in Surfer, you start with a grid file. If you do not have a grid file (a.k.a., a raster), you can either:
In addition, the grid file should have a relatively high resolution. I find that a grid file with around 2000 grid nodes minimum works well. If you do not have sufficiently high grid resolution, then the “contour lines” do not look as defined in the resulting map. If you have a grid file, but it is a low-resolution grid file, then you can increase the resolution by following the steps below. Click here to download the grid NEDGrid_CO.grd which we will use in this example.
Once you have a high resolution grid, you can follow the steps below to create the Tanaka-style contour map:
Create stunning illuminated “contours” in Surfer with the modified grid file using an image map with hillshading.
Although the map created in Surfer is not an illuminated contour map using the true Tanaka method (as the contour lines do not change thickness depending on their orientation to the light source), it is still a very beautiful alternative to displaying contours with standard hillshading.