Carto Mixer

The Carto Mixer feature in BlueSpray allows you to quickly great professional looking shaded relief (i.e. hillshade) raster images. The feature also is very flexible in that it contains a number of different processes that you can apply to a Digital Elevation Model (DEM) to create relief images.

To get started, load a Digital Elevation Model (DEM) into BlueSpray. You'll want the image to be the same resolution as you plan on printing. If your DEM is too high a resolution, it will appear "rough" and if the resolution is too low, will will appear smoothed out. Typically the resolution will be 150 to 300ppi for print media and about 100ppi for the Web. Use "Sample" to rescale your DEM so you have the right resolution. You'll also want to crop your raster to the desired area as the CartoMixer will process from the minimum pixel values to the maximum pixel values (i.e. from the highest elevation to the lowest). Don't worry if your DEM includes bathymetry data (i.e. negative numbers) as BlueSpray has a feature to let you simultaneously shade terrain above and below the surface of water.

Right click on the raster layer and select "Transforms: Cartography -> Carto Mixer" and then you can just click "Update" to see a preview of the shaded relief. The black triangles on the right side of the setting panel allow you do open and close the various settings panels.

Note: The settings panels in the Carto Mixer dialog are ordered from top to bottom in the order that they are applied to the DEM. However, we'll explain the panels below in the order of importance (i.e. most of the time I just use the Color Ramp panel).

Color Ramp

Open the "Color Ramp" panel now and select a different "Color Ramp" for your DEM. Then, click "Update" again to see the results. The chart with the red, green, blue curves represents the colors that will be used for each elevation. On the left of the chart is the color for the minimum elevation and on the right is the color for the maximum elevation. Try moving the control points on the curves and then updating your image to see the results. This is just a previous so periodically you'll want to click "OK" to see the final results.

Bathymetry Color Ramp

This is what I do to create shaded relief images on a regular basis. If I have DEM that includes bathymetry data (i.e. underwater terrain) then I will click the "Include" box next to "Bathymetry Color Ramp" and open it's panel. Here I can select a separate Color Ramp that can be used for bathymetry data. Try picking the ramp that goes from black to blue and clicking update.

Elevation Exaggeration Ramp

Sometimes, you'll want to accentuate either the lower elevations or the higher elevations. A common example is when we have some interesting topographic features in the bottom of a valley. If there are high mountains around the valley and we use a linear ramp, these features might not appear at all. Try checking the "Include" for this panel and setting the "Number of Points" to 3. Then move the control point in the middle of the ramp and press "Update". By moving the point around, you'll be able to bring out features at different elevations.

Smooth or Sharpen with Matrix

Sometimes our DEMs contain artifacts from processing that can create undesirable effects in our shaded relief images. The image on the left below has been hillshaded from a DEM that was processed as integer values. This removed the elevations between the integer values making it looks like we have rice farming in the Eel River watershed. The image on the right has been smoothed with a matrix.

Mix inputs

The Carto Mixer allows you to combine three images into one: 1) a color ramp based on elevation, 2) another image as an overlay, and 3) a hillshade. The Mix Inputs feature allows you to change the percent of each image that is included in the final output. Try lowering the Color Ramp value to 0. When you press Update, you'll see that you have a grayscale hillshade. If you put the Color Ramp back to 100 and reduce the Hillshade to 0, you'll just see an image that is colorized based on your color ramp. You can combine these two images with an overlay image and mix them to create the effect you are looking for.

Overlay

The Overlay setting just allows you to specify another raster image, such as a satellite or aerial photo, to mix with the other images. This can be used to make photo realistic images.

Hillshade

The hillshade tool allows you to change the direction and angle of the hillshade. The direction is measured from 0 as north, clockwise back to 360 at north again, just like a compass. The elevation angle goes from 0 at the horizon to 90 degrees directly overhead. The Hillshade settings can be used to create some interesting special effects and highlight areas that have topography aligned in particular directions.

Contract Map

The final settings allows you to apply an overall contrast map to the image. This will allow to you highlight particular areas of the image that are otherwise would be too dark or too light.