Mapping Center

We got a good question on Ask a Cartographer this morning.  The gist of the question was how to go about symbolizing street centerlines so they could be drawn using line symbol widths that reflected, at scale, the actual width of the road (as shown in the image to the left). This is a good cartographic solution because varying the line width adds hierarchy to the roads -otherwise it would be hard for you map reader to know which are wider or more heavily used. Read More...

I've spent the last few months immersing myself in ArcGIS 9.3, particularly ArcGIS Server and ArcGlobe in order to create some map and globe services and see how they work in ArcGIS clients, Google Earth, and Virtual Earth. These services need to look good and draw fast. One factor that can dramatically influence drawing performance is whether projection-on-the-fly is being used.  Projection-on-the-fly will slow your map down, anywhere from 30% to 1000% slower (depending on the coordinate systems involved). Read More...

I have recently "invented" a method for simplifying polygon map layers, which seems to give reasonable results. Probably many others have invented it before me, but I would like to present it in order to receive comments and advice on setting the appropriate parameters.

My task was to produce a national soil map suitable at 1:1,000,000 scale on the basis of a 1:200,000 map. The best method would probably be to have a geologist or soil scientist make a complete re-production for the new scale - but we needed a less expensive method. The challenge was to find a technique that would not totally erase soil types represented as many small polygons covering more than half of the area in some regions. Read More...

If you're making a map that is either a large format print map or a map that will be served via ArcGIS Server, squeezing every bit of wasted time out of drawing performance is critical. Don't get tired of sitting there drinking extra cups of coffee watching the word "Drawing", all your layer names, and that little blue globe. If you're finding it stressful to explain when updates will be coming, or the timing for caching the map you are serving, or your map services generate complaints about poor performance, then try the two tips in this entry. Read More...

I've often had the situation where I wanted to use a raster data source as a single-color map background layer, but the cell size or other data processing output resulted in a 'blocky' or 'pixelated' appearance to the data at the map scale I need.  A simple raster-to-vector data conversion served only to recreate the boxes or 'saw-tooth' or 'stair-step' lines from the original raster. The ArcScan extension has tools that reduce or remove this problem, and create an output vector data layer with smooth polygon boundaries or more naturally sinuous lines. Read More...

Which are the 30 or 500 most important of Minnesota’s famous 10,000 lakes?  Next, think about that question from the point of view of making a zoom-able map of the U.S. and how many lakes need to be shown as you zoom in.  That question boils down to how to decide which polygons to show.  Not all polygons are created equally, some are roughly round, some are banana shaped (like ox-bow lakes) some have lots of prongs (like a reservoir formed by U.S. Army Corps of Engineers dam), some are long and twisty like a pretzel. Read More...

In the United States, the Public Land Survey System (PLSS) is a way of subdividing land. The USGS topographic map symbols for displaying PLSS data are an excellent way to symbolize PLSS data on not only topographic maps, but because the topographic symbols are  so well recognized, the same symbols can be used on many other kinds of maps. In the image to the left, the "plus" marker symbol shows where a found corner is located, however, if no corner has been found, then no marker should be shown, leaving a gap that signifies the doubtful location of the corner. Next we will describe how to use cartographic representations to symbolize township, range, or section lines to leave a gap at the corners, allowing corners to be added (as point features) or gaps to be shown. Read More...

When an elevation raster dataset contains values for both topography and bathymetry, often the best solution to this is to split it into two new rasters:  one for the topography and one for the bathymetry. The reason is that symbolizing this data is difficult. This is because a color ramp that contains appropriate hues for both bathymetry and topography must be adjusted so that it shows the shoreline exactly in the right place, at zero elevation. Read More...