Tag Archives: analytical

In the bad old days, you may have done some work for a client and got to a point where you just want to make a map for a meeting or a report.  One of the most time consuming parts of making a map from scratch was finding data for rivers, streams, and lakes, then turning each an appropriate blue, making each line the appropriate symbol, then symbolizing each stream segment.  It takes time to find a dataset that is good enough, at the right scale, and that looks good when you are done symbolizing everything.  It may take you hours to find the right data, symbolize, and label everything.

In my past life as a consultant, sometimes I had to start from scratch like this. I spent time finding and downloading appropriate scale data, checking it to see if it looks OK on my map, then symbolizing each stream and lake at least a little bit (most places I have worked don’t need glaciers symbolized) so they show up with the right symbol.  Once that is all set, I haven’t even started labeling each stream, which can take quite a while to get right.

Sometimes to save my clients money I would give up and use USGS DRGs, turning only the blue symbols on.  I often thought wouldn’t it be wonderful if there was some kind of national hydrologic map service on the internet that you can just add to your map and it just works?

Now there is… in the form of the esri Mapping Center Hydro Team Hydro Basemap.  We have made a medium scale hydro basemap of the United States, from 1:147,000 to 1:18,000.  And we think it will make a lot of things easier for our community.

The Hydro Basemap of the United States is based on NHD, but with a focus on analytical cartography.  These maps are made to show hydrologic networks connecting through a system.  What’s known as the ‘Hydro Basemap’ is just the Hydro Reference Overlay plus relief… At times you may have your own relief or basemap and may not need any background behind the rivers and lakes.  For that you don’t want the whole Hydro Basemap, just what’s called the Hydro Reference Overlay. That’s the only difference in the two concepts… the presence of relief.  These two products are close companions to one another.

Gardiner, Maine area, esri Mapping Center Team Hydro Basemap of the United States

Actually the Mapping Center Team has gone way beyond the concept I described earlier.  What we actually built is a hydro basemap, but one that is ready for a multiscale experience.  You can take one of the applications we built such as the High Water Map, then recycle/repurpose the javascript application for your needs, and the basemap is ready for you to use.  Just add your data.

A map created on arcgis.com using the hydro basemap, mashed up with the USGS river gauge service.

As you zoom in and out, streams turn on and off, and labels rearrange for you.  As you zoom in, more and more stream segments appear that are important to your map view.  As you zoom out, smaller streams that would clutter your map view are selected out of the cache and removed.  Streams do not turn off and on indiscriminately or based solely on size or flow, there is a sophisticated algorithm at work here that will prioritize small streams with big important names (such as the upper Mississippi River in Minnesota).  In addition, different parts of the country have different methods of stream prioritization, and these are respected.  There is no one size fits all method to pruning streams as scales change, since different parts of the country have different soils and drainage characteristics. Don’t worry, we have done this for you so you don’t have to.

It’s easy to get used to something like this because (as we like to think at the Mapping Center) it’s how things should have been all along. We at the Mapping Center Hydro Team are proud of this product and would like you to give it a spin, and see how you like it.  We’d like to hear your comment to know how easy this is for you to use.  I wish they had this when I was a consultant.

Special thanks to Michael Dangermond for providing this post. Questions for Michael:  mdangermond@esri.com