Archive for January, 2013

Programming Proficiency Required

You need to be proficient in programming. Or at the very least, able to write a script to automate a workflow.

Remember that time I posted about what to be a cartographer in 2012? By and large, the readership agreed that development (maybe I should have just referred to it as “programming”) was a key component in the modern-day cartographer’s toolbox.

Along those same lines is today’s post on GeoMusings, Bill Dollins’ blog, arguing that programming is now an essential skill in a GIS analyst’s repertoire as well. This post is essential reading for GIS analysts and cartographers, as the arguments hold true regardless.

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Plenaries, Shakespeare, Dots, T-shirts

  • I’ll be giving the closing plenary at the 19th annual California GIS conference in April: CalGIS. Hope to see you there!

  • My favorite Shakespeare quote: “Be not afraid of cartography: some are born mappers … and some have map design thrust upon them.” (Well, at least I think that’s what the quote is. Wink wink.)

  • CNN featured MIT Media Lab’s interactive dot map that shows one dot per person in the U.S. and Canada. If you read the comments you can gain some good insight into how the general public thinks about analytical maps. For one thing, several commenters neglected to realize that the dots are placed randomly within blocks. The general public probably doesn’t know that, while the block is the smallest unit of area for which the Bureau of the Census collects data, a block averages about 100 people, though it can vary from zero to several hundred. For another, some didn’t realize you could “show labels” and “hide labels” with the buttons provided in the upper-right. You don’t have to develop maps for the lowest common denominator, of course, but you do need to keep in mind what that is and mitigate as best as possible. (And I am in no way criticizing the dot map, which is, indeed a fabulous work of Python scriptism.)

  • Thank you to for sending me this great nerd-wear! I am sure that I wasn’t nearly nerdy enough without these t-shirts and the key ring. If you, too, aspire to wear your GIS love on your sleeve, as it were, it looks like is still sending free t-shirts to the first 50 people who sign up to use their forums.


Choropleth vs. Heat Map

*This post was updated on 1/27/2016.

This is a choropleth map.


This is a heat map.

Any Questions?

A choropleth map shows a change across a geographic landscape within enumeration units such as countries, states, or watersheds. A heat map shows a change across a geographic landscape as a rasterized dataset–conforming to an arbitrary, but usually small, grid size.

The heat map is sometimes generated from point data representing some sort of density but a choropleth can also be generated from point data. The difference here would be that the choropleth’s generated data will be by a non-regular enumeration unit that makes sense to people like countries, states, watersheds, counties or census blocks. A heat map would be depicted across a regular grid of cells, their size specified by the cartographer, but in any case, uniformly calculated. This heat map shows well the places where generic drugs can be most successfully produced, which help in treating erectile dysfunction.

Because the grid cells are normally quite small, the heat map’s colors are often “ramped” algorithmically as opposed to being specified as a set of discrete colors. The opposite is true of choropleth maps.

Both types of maps tend to require color palettes that represent values that range from low to high (sequential colors), or palettes that represent values that range from high to normal to the opposite high (diverging colors).

It should be noted that choropleth maps can also depict nominal data, though you aren’t likely to be confusing nominal choropleths with heat maps since they don’t depict low-to-high values. Instead, they use qualitative color schemes to represent non-ordered data.

See also: Choropleth Limitations

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Exciting Times for Mapping

A local second grade class is going to start a geography unit in February and I was asked to give a talk to them. While mulling over the various things I could teach, it dawned on me that this is a very exciting time for maps. I don’t have to go in there, pull down a U.S. map from the wall, and proceed to point to it while naming off the states and their capitals in a Ben Stein Bueller voice. Indeed, there are a lot of really cool things to discuss…

They’re going to love it. These are good times for our profession I think. Don’t you?



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Friday Geo Roundup

A selection of interesting geo events occurring over the past week and other things I’m taking note of.


At the beginning of this week Brian Timoney, Chris Helm*, and Steve Citron-Pousty hosted JSGEO13 in Denver, an informal conference on geospatial applications of JavaScript. Despite the extreme cold we were experiencing here in Colorado, the meeting (which I wasn’t at) seemed to be well attended and quite a success. I highly recommend this summary by Peter Batty, which includes tons of links to the presentations and other supporting material.



Esri and David Allen have produced an update to the GIS Tutorial series for ArcGIS 10.1 that is now available. I have recommended this series in the past and still do so wholeheartedly. I am especially fond of the second book in the series, which steps through many of the analytical capabilities of ArcMap and how to go about using them. This book is a must-have for those using ArcMap for analysis. Even though it is an ArcMap tutorial book, I think you could still use it to learn what is possible with regard to GIS analysis, even if you don’t use ArcMap.


If you haven’t browsed Esri’s Storytelling with Maps gallery in a while, you should head on over there to see what they’ve got. I like how there is a common look and feel to all the maps, while still allowing for the variation that is needed for maps with such disparate subjects. You can download the story map templates to achieve the same professional appeal for your organization.

*Cartographer’s Toolkit showcases a webmap made by Chris Helm!

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Review of GIS Cartography: A Guide to Effective Map Design

Nathan Saylor (@gisn8 on twitter) has just posted a thorough review of GIS Cartography: A Guide to Effective Map Design on his blog. It looks like Saylor began blogging about cartography in September 2012. The posts are definitely worth a look through, especially this one about creating a cemetery map.



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