Creating Custom Color Ramps in ArcMap
Creating eye-catching visualizations for your printed maps, or online web applications is key to catching your viewer’s eye and holding their attention. Through the creation of your own custom color ramps, you can better visualize your data to suit your needs. Here, I will show how you can create two custom color ramps for topobathy LiDAR data that has been “split” into two separate rasters – one for bathymetric data and one for topographic data.
I will be building on the skills learned in the blog posting Visualizing Topobathy Digital Elevation Models (DEMs); if you haven’t read this yet, a quick review is recommended, however you DO NOT need topobathy LiDAR (or elevation data) to create your own color ramp. Custom color ramps could be useful for any type of raster dataset, although I have found these most useful with elevation data, or even for use with vector data, such as land use data.
The method shown below is just ONE of the ways you can create custom color ramps. There are a few different algorithm options offered to users – HSV, CEI Lab and Lab LCh. Here, I will be using the CIE Lab algorithm for my first ramp, and then the HSV algorithm for my second color ramp. Esri describes the color ramps this way:
“There is very little difference between these algorithms when the from and the to colors are of the same or very similar hues. But when the hues for the from and to colors are different (Hue is different by 40 or more on a 0-360 scale), the algorithms produce different results. The ‘hsv’ algorithim traverses the hue difference in a purely linear fashion, resulting in a bright ramp where all intermediate colors are represented. For instance, a ramp from red to green would include orange, yellow, and yellow-green. The ‘cie-lab’ and ‘lab-lch’ produce a more blended result. Thus, a ramp from dark green to orange would not contain a bright yellow, but instead a more brown and green-gold or green-brown intermediate color. The advantage of the ‘cie-lab’ algorithm is that the colors of the ramp are visually equidistant, which can produce a better ramp.”
To start, add some raster data to ArcMap. In this case, I’ve added two rasters for Assateague Island National Seashore, one representing bathymetric elevations, and one representing topographic elevations.
First, I will create the custom color ramp for my bathymetric elevations. Since these represent areas that are under water, I want my color ramp to have varying shades of blue, from light to dark. This will be easier to create than a color ramp for my topographic areas.
- Open your Layer Properties dialog box by double clicking your raster layer in the Table of Contents.
- Select the Symbology tab.
- On the Color Ramp drop down, right click and select Properties.
- Ensure that Algorithm is set to CIE Lab.
- In the Colors area, select two different shades of blue.
- First, ensure that the “dot” (see below) next to Color 2 is selected. This will allow you to select two colors to blend together.
- For Color 1 I selected a light blue, and for Color 2 I selected a darker blue.
- Adjust the brightness until you reach your desired color mix.
- Click OK to save.
- This color ramp will now appear in your dropdown. To permanently save this, right click within the color ramp drop down again, and select Save to Style.
- Select an appropriate name for your color ramp.
- For example, I selected Topobathy Split – Bathymetry for mine.
Now, I will work on creating a color ramp for my topographic elevations. This will be more complicated, because my goal is to have varying colors to “represent” the different types of landscape on Assateague Island. My goal is to have marsh areas represented by greens, brush and dune areas to be represented by browns, and beach areas to be represented by yellows.
To simplify this, I suggest starting with an existing color ramp. I found it useful to first select the color ramp titled “Elevation #1”. You can determine the color ramp names by right clicking in the drop down, and selecting Graphic View from the menu (see screen capture above).
Once this is selected, right click and select Properties for the Elevation #1 ramp.
The dialog that opens appears slightly different. This color ramp is made up of 7 different HSV algorithmic color ramps. Because I know I want my new color ramp to have three distinct colors, I started by deleting 4 of the existing color ramps. To do this, select one, and then click Remove (I chose to delete the bottom 4 color ramps – see below for details).
The three remaining color ramps provide me with a good foundation to start with. Since I know that elevations are represented in the ramp from low to high (left to right), and I know that marshes will have the lowest elevation on Assateague Island, I will start by modifying color ramp A (see above).
To begin editing color ramp A, double click on it. The first thing you should do is ensure that only Color 1 is selected. Use your brightness sliders to adjust your ramp. See below for how I formatted mine:
When you are satisfied with your new color ramp, click OK.
Next, I moved into the modification of color ramp B to represent the beach elevations (I felt like it was safe to assume that generally beaches are higher in elevation than marshes, but lower in elevation than dunes/scrub areas).
Here, I also ensured that only Color 1 was selected; I then selected a light yellow and adjusted my brightness sliders until I was happy with the result (below).
Finally, I moved into the modification of color ramp C to represent the dune and scrub elevations. Because I wanted to transition from dune areas (which I associate with a sandy, yellowish color) to scrub areas (which I associate with drab brownish color) I decided to use the CIE Lab algorithm, and to blend these two colors together. The result is below:
When I finished, I clicked OK to exit both dialog boxes. I then saved my new color ramp using the name “Topobathy Split – Topography.”
Applying both of these color ramps to their appropriate rasters, the resulting image looks fairly realistic and almost life-like. Below, find a zoomed in view of the southern tip of Assateague Island National Seashore.
This blog posting was developed with the support of a competitive grant (cooperative agreement number P09AC00212; task agreement number P13AC00875) from the National Park Service in partnership with the North Atlantic Coast Cooperative Ecosystems Studies Unit.