Mapping Center

This post, is to announce the release of a map template for historical GIS called Historical GIS:  Boston 1775. If you’ve never given historical GIS a second, or a first thought, you might find the contents interesting and maybe even applicable to your work. Consider that the vast majority of GIS data is historical, even if it’s only a few minutes old. Read More...

From time to time we've had to create some building footprint data. A colleague was in my office yesterday looking at the map to the right, and remarked that he thought that adding building footprints to maps "humanizes" the map. An interesting observation, and one that I'm not inclined to argue against.

We've learned a few tricks for making haste with little or no waste to produce building footprint data. Read More...

I frequently come across data which has lost data links (a red !). This occurs when the data has been moved or no longer exists, thus breaking the link. On some occasions, even after I tracked down the data and repaired the data source, the symbology still didn’t draw -- it exists, but the wrong field is listed on the Layer Properties Symbology tab. Usually the draw category (Value field) has defaulted to a non-matching field. Simply changing the Value field does not do the trick. Read More...

The vertical change in the elevation of the land surface, when determined over a given horizontal distance-along a road or stream, for instance-is known as its slope (Figure 1). There are three primary ways to quantitatively express the slope between two points. In each, the lower the slope value, the flatter the terrain, and the higher the slope value, the steeper the terrain. The slope values may be expressed as a ratio, as a percentage or as an angle. Read More...

Have you ever wondered where a feature class came from as you've browsed over one of your geodatabases in ArcCatalog? I think most of us have, and probably more often than we'd like to admit. In the example shown here to the left, I made these datasets a few weeks ago, and I have no idea what "GN" means, and if or how I selected, simplified, or dissolved the data.

There are a couple of things we can do to avoid that puzzled feeling: standardize your feature class naming convention; standardize your geoprocessing.  With the naming convention, I started doing the right thing here, but failed to follow through and leave myself the necessary clues. The data in the image above was also the result of a complex workflow, so rather than start with that, let's cover the basics. 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...

This final part of the series will cover using cartographic representations for dashed lines, like the red and white cased lines in the image at the left, and for creating cul-de-sac or squared off ends to streets.  Both of these effects will build on the examples in the previous two portions of this series with one exception.  Because we will be using cartographic representations for the streets, we will be better able to manage line caps and therefore will not need to use the Dissolve tool to dissolve the streets by name, type, and z-level.  The removal of this step is significant because now an extra dataset is not required just to have cartographic quality streets; everything needed for a high quality cartographic depiction of streets can be stored in attributes. This should come as good news to those of you who have mentioned to us, many times, that managing additional datasets for the sake of cartography is not only a data management, but a political hurdle, that you would just as soon not have to deal with. Read More...

Symbolizing road overpasses or underpasses typically requires that you perform two data preparation steps.  First, identify which roads overpass other roads.  This may be very simple intersections between two roads, or it may include many other roads when dealing with complex highway interchanges.  Second, represent the interchanges clearly.  This task may mean simply changing feature or layer drawing order, or it can also mean knocking out or masking portions of underpassing features.  The image to the left shows the underpassing highway being masked by an overpassing street and railroad. Read More...

We received a suggestion to write a blog entry on this topic from Anna Schwabedal, who is a technical sales representative for ESRI Germany.  Anna gave us a rough idea of how this works and I was able to use that when this topic came up through Ask a Cartographer recently, and I've worked on it a bit more since in order to write this. Read More...