Posts Tagged ‘cartographic line’
Making a map look prettier
Problem: Your map is going to be used for a special purpose and it needs a little something extra to give it that polished, professional look.
On St. Patrick’s Day, the ESRI Mapping Center blog posted one of the award winners of the 2009 International User Conference Map Gallery Competition. The title of the map is “Geo-Geneology of Irish Surnames.” Besides being interested in the subject matter because I am of Irish descent, I think it is a beautiful presentation. So beautiful, in fact, that I printed out two copies on photo paper: one for my office and another as a Saturday party decoration.
I started thinking about the ingredients that make this map look so good. It was made entirely within ArcMap, which means it’s possible take ideas from it that would improve the appearance of any map created on the job. I noticed four things in particular that I have seen on other professional maps hanging on walls, but which I hadn’t tried before. I taught myself how to do them, and now I will teach you.
1. Shaded Relief Background
The map uses a color gradient to display different elevation values. This imparts a subtle texture that makes the background spring to life. I was able to achieve a similar effect using a combination of a hillshade with a carefully symbolized DEM surface. I used the USGS GTOPO30 for this. GTOPO30 is a Global Digital Elevation Model with a horizontal grid spacing of 30 arc seconds–approximately 1 kilometer.
First, I clipped it to my map area in order to make it easier to work with. ArcToolbox’s Data Mangement Tools –> Raster –> Clip function will clip any raster to bounding box coordinates that you either type in directly, or import from a shapefile. Here, I’ve imported the bounding coordinates from a shapefile of the Ireland country boundary.
Now that the DEM has been clipped to a manageable size, creating a hillshade will go much faster. Hillshading is a method of representing relief on a map by depicting the shadows that would be cast by high ground if light were shining from a certain direction. You can create hillshades from the the 3D Analyst toolbar.
When the tool comes up, it will ask for several values which are fine to keep at the defaults, except for the Z-factor. The ESRI Help document on hillshades notes that if the x,y coordinates of your data are in angular units (degrees), the hillshade output is going to look funny. This happens because the elevation values are in linear units, and the length of a degree of longitude changes with latitude. So, if your x,y units are in decimal degrees and your z units are in meters (which is the most common case and the case with GTOPO30, which is in GCS WGS 1984), ESRI recommends using the following table of z-factors:
| Latitude | Z-factor |
| 0 | 0.00000898 |
| 10 | 0.00000912 |
| 20 | 0.00000956 |
| 30 | 0.00001036 |
| 40 | 0.00001171 |
| 50 | 0.00001395 |
| 60 | 0.00001792 |
| 70 | 0.00002619 |
| 80 | 0.00005156 |
Ireland is at about 50 degrees latitude.
The output, which I named “shadow”, is a grayscale shaded relief that looks like the land surface with hills and valleys. We are going to drape it over a color-coded DEM. The hillshade will provide the light-dark values and the DEM will provide the hue values. I found that my hillshade looked the best with the following contrast and transparency percentages. (You can find these settings on the Layer Properties, Display tab).
Now, go back and choose colors for the original clipped DEM (gtopo_1km_Clip1). After a lot of trial and error I got my best results with 6 color classes, ranging from green at the lowest elevations through brown to white at the highest elevations.
2. Gradient Water Bodies
Using a gradient fill to symbolize the lakes creates an effect called “sunglint”. I’d never heard of it before, but it’s easy to to do, and quite pretty. In the Symbol Property Editor, change the Type to Gradient Fill Symbol. Raise the Interval value to something higher than the default 5. This will blend the colors better. You’ll stop noticing the difference much over 50. Now, pick a blue color ramp from the list.
If you want to, you can tweak the pre-made ramps by right-clicking on them and selecting properties. I didn’t like the darker blue end of mine, so I removed it.
Note: If you click properties again, you can change the two colors that make up the ramp, as well as the blend algorithm and the black and white brightness.
3. Coastal Vignette
The Irish map makes dramatic use of this, so that the coastline appears to glow out of the–in their case–green background. Most other maps use a subtler effect of the coast fading into blue water. To create that look, first change your background color by going to the Data Frame Properties, Frame tab.
Then, create multiple copies of your country boundary in your table of contents. Each copy should be symbolized with a white hollow border that has increasing width and transparency as you go down. Here are the settings I used:
4. Colorful Administrative Boundaries
This takes a bit of time, but the result is lovely. The idea is to have each county outlined by a border that’s shaded a different color from the counties surrounding it. The borders need to touch, but not overlap. And, the borders need to fade, like the coastline, but not quite as much. So, how to do it?
Before you start picking colors, you need to solve the overlap problem. (I learned the hard way that this step will undo your color choices). Symbolize by category: province name, then right click on any province in the list and select Properties for All Symbols. Click the Properties button, the Outline button, and then the Properties button once again. Now, change the line Type to Cartographic Line and the Offset to -0.5.
Note: The offest should be negative half the width of your line. My line width is 1.
Now, go back to the first screen and pick your border colors. If you keep the window open and keep hitting Apply, you can check your results as you go to make sure you don’t put two of the same color next to each other.
When you’re finished, make a second copy of this layer, and put it underneath the first in the table of contents. Then, double the border width and the offset. Important: also go to the Cartographic Line tab and set the Line Caps and Line Joints to Round. This will avoid spikes from showing up at wider widths. Fair warning: when you do this, your colors will be all be reset to black, and you will have to go back and fix them one by one. I’m sorry.
It’s totally worth it. Set the transparency on the bottom layer to 50%. And, you end up with:
Isn’t that nice?
Tags: cartographic line, clip, color ramp, hillshade, symbol, vignette