Azavea Atlas

Maps, geography and the web

OpenDataPhilly Launches Visualization Contest is undergoing a redesign thanks in part to grant funding from the Knight Foundation.  In anticipation of the relaunch of Philadelphia’s newly designed data portal, Azavea invites submissions of visualizations of Philadelphia’s open data.

The OpenDataPhilly Visualization Contest calls on designers, data scientists, developers and anyone who enjoys exploring and visualizing open data. You are invited to share your data visualization that utilizes open data found on Your visualization can be static or interactive and may include maps, infographics, charts or any other creative visualization of data.

Visualizations that represent creative and visually impactful uses of Philadelphia’s Open data will be selected to be featured on the new OpenDataPhilly website (to be launched in late 2014).

Up to 10 data visualizations will be selected to be featured on OpenDataPhilly’s new website.  Prizes include $500 in Amazon gift cards to be divided among winners. Additional data visualizations may be selected for display on the OpenDataPhilly web site but only a maximum of 10 will receive prizes.  The contest is international and open to anyone. The data visualization must use open data available on The deadline to submit is Sunday, November 30th 2014 11:59pm.

For more information on the contest or to submit your visualization, please visit:

Join Azavea and The Knight Digital Media Center for a Free Spatial Analysis Webinar

kdmc-logoAttention all nonprofits, foundations, data analysts, and data journalists:

I (Tyler Dahlberg) will be presenting a free webinar in partnership with the Knight Digital Media Center on Tuesday, October 28 at 11am PST/2pm EST. The presentation will be about the origin of spatial analysis, how it works, real-world examples of how it has transformed decision making processes and data display, and how you can get started. To join the free webinar (which is limited to 125 seats) please register for Mapping Insights You Never Knew You Had, which will be administered through the required Fuze web conferencing software.

We hope to see you there!

4 Cartography Color Tips Hue Should Know

Recently attending the NACIS Annual Meeting provided significant inspiration on cartography and visual map design.  This encouraged me to assemble some tips on the thoughtful use of color in cartographic design.

1. Never Use the Default Colors

A frequently mentioned recommendation during the conference was to avoid defaults at all cost.  One specific set of defaults to avoid in mapmaking are the default color schemes (and even classification styles) used for symbolizing data in your maps.  John Nelson made this specific warning during his presentation on 20 Unrequested Map Tips (see tip #3 “Defaults are Evil”).  His map below highlights the worst of the worst of relying on defaults in ArcMap.


Map highlights worst of defaults in ArcMap by John Nelson

Consider using the ColorBrewer web tool (Cynthia Brewer’s collection of beautiful color choices for ramped or categorical  data) as an alternative to Arcmap’s uninspired defaults .  You can even import ColorBrewer schemes directly into ArcMap or other GIS or data analysis software of your choice (GDAL, QGIS, R, TileMill, etc). Happily, a favorite web mapping tool, CartoDB, already includes these lovely schemes.

2. Palette Inspiration

Color selection need not be traditional and stuffy.  Inspire yourself to design a more creative color scheme by browsing some existing color palettes and even create your own. Here are a few I like:




Or browse old maps for inspiration:


Isochronic Distances Map of Travel Time in Days from London, 1914

The above map was used as inspiration for the color palette below


3. Logo or Photo Inspiration

Are you designing a map for a client? Try coordinating their company colors with your map design.  Identify the RBG codes of the colors in a logo or site by using a free eyedropper tool (in your Chrome browser or desktop) or add the Eyedropper tool to your toolbar in ArcMap. Now that you have identified a few of the predominant colors in your logo, decide how they will be used in your cartography (would these colors be suitable for categorical, divergent or sequential data?)  You can simply use these colors for inspiration or you can use a color blender tool like this one or this one to create a range from two colors.  Adjust saturation and transparency to suit your mapped data.  Below is a logo, a ramp and a map created using this method.  I decided to just use a palette made from only the blue in the logo but you can also find a divergent palette using both the red and blue here.

Logo of Inspiration: the Philadelphia Phillies Logo:


A palette created from the primary blue of the logo:


Finally, a map symbolized using the blended color palette:

Find the color palette of the above scheme here.

4. Design for Accessibility

Color deficiency or blindness is an important consideration in cartographic design.  Red to Green color palettes are used frequently when mapping divergent data.  The inability to differentiate these two colors causes significant challenges in interpreting data.  Tip #17 from 20 Unrequested Tips and this fantastic blog post does a great job at describing the shortcomings of some color palettes and makes fantastic (and beautiful) recommendations for accessible colors. When selecting your accessible palette, consult Colorbrewer which has an option to select only colorblind safe palettes.

Other areas of consideration for design accessibility for vision impairment include tactile maps which deserve their own blog post, but I’ll say PATCO’s Tactile Transit Map is worth checking out for inspiration. (Routes and stop amenities are uniquely symbolized using tactile features for easy navigation).


It is important to consider how the colors in your maps communicate and whether it is successful in sharing the correct message.  The book How to Lie with Maps by Mark Monmonier devotes an entire chapter on the misleading use of color in maps.  As a cartographer, you have the power to make creative and thoughtful color choices. Use these tips and guidelines to bring careful color consideration and planning to your maps. This will help you communicate better with a wider audience and help your map stand out in a sea of ArcMap defaults.

For the Love of Maps

nacis_2014_pittsburghLast week, Data Analytics Project Manager Sarah Cordivano and I attended the North American Cartographic Information Society conference in beautiful Pittsburgh. After searching around for some of the best GIS and mapping related conferences to attend, NACIS was one of the mostly highly recommended, and I think it lived up to its reputation.

The conference started off with Practical Cartography Day, an entire day of sessions devoted to real-life examples of map-making. The talks touched on a diverse array of topics in mapping, which made it particularly valuable. If these talks were scheduled on topic-area specific tracks, I probably would have missed some interesting examples and discussions. One of my favorite speakers on Practical Cartography Day, John Nelson, offered his 20 Unrequested Map Tips. It’s really great advice for those just starting out in cartography, especially in academia, where often the ArcGIS defaults are the only thing taught. It made me reflect on how important user interface and design is to cartography and how that education is really lacking within today’s GIS programs.

Some other sessions and talks that were particularly good:

    • Alan McConchie of Stamen Design gave out a bunch of good tips for manipulating custom CartoCSS. It’s a must-see for anyone who uses Tilemill and wants to learn some cool tricks for customization.

    • Exemplifying the challenge of customizing maps, Nicki Dlugash of Mapbox talked about the design challenges in creating a basemap of the entire world styled optimally at all zoom levels using OpenStreetMap data.

    • Though not strictly map-related, Miles Barger of the US National Park Service presented on a recent project to create a 3D model of the Grand Staircase, a major geologic feature in Utah. He touched on the need to “fiddle” with settings to create the perfect diagram and also started a bit of controversy (mostly from one attendee) when he suggested it’s okay to manipulate or exaggerate features for the purpose of creating a user-friendly design.



  • Also of the US National Park Service, Mamata Akella presented on the beautiful custom maps and tools the park service has been working on. They’ve put everything on GitHub (except the internal stuff, of course).

  • Patrick Kennelly, of Long Island University, showed the results of using a three dimensional helix model to visualize daily temperature data over time at over 250 weather stations across the US. Patrick and his team used the Blender API for data manipulation.

  • During the Transportation Maps session, Nate Wessel, student at the University of Cincinnati, presented his bicycle map of the Cincinnati area. Contrary to the typical government produced bike map based on subjectivity of conditions, Nate based his map on more objective conditions agnostic to the type of rider, such as elevation change, speed limit, and road condition. Nate’s map was also a runner up for the student competition.

In addition to attending the conference, Sarah and I also presented on some topics of personal interest. I introduced General Transit Feed Specification data and gave some examples of how to the data is being used in mapping and analysis today. Sarah talked about the importance of open data and open source tools which brought up a lively discussion of how the issue relates to cartography and spatial analysis. Overall, the conference had a nice balance between real-world and academic examples of cartography and analysis. Next year, the conference will be in Minneapolis and it’s definitely a must attend for anyone who loves maps.


Five Ways Your Foundation or Nonprofit Can Get Started With Spatial Analysis

Taking advantage of new technology in your foundation or nonprofit can sometimes be a difficult process. Fortunately, the Knight Digital Media Center (KDMC) hosts a series of workshops across the US for nonprofit foundations to learn about technology. I was able to speak at the most recent KDMC workshop in Charlotte, North Carolina, along with Amy Gahran, independent journalist, Dan X. O’Neil, Executive Director of the Smart Chicago Collaborative, and Sarah K. Goo, creator of the Pew Research blog Fact Tank.

In my workshop I talked about five ways nonprofits and foundations can get started with spatial analysis, and I used three case studies from Azavea’s Summer of Maps program to help.

The bicycle crash maps I made last summer for the Bicycle Coalition of Philadelphia fostered a public conversation about crash reporting policies, raising awareness about an issue the Bike Coalition cared about. The spatial analysis work I completed for the Greater Philadelphia Coalition Against Hunger as a Summer of Maps Fellow helped amplify their door-to-door efforts and target their limited advertising dollars. Finally, 2013 Summer of Maps Fellow Lena Ferguson’s work for DVAEYC had a huge impact, helping win one million dollars in grant money to improve early childhood education programs in Philadelphia.

Your foundation or nonprofit may be interested in taking advantage of spatial analysis to raise your profile, amplify your message, and target your efforts. Here are five steps you can take to get started:

  1. Take the Maps and the Geospatial Revolution class at Coursera to learn more about spatial analysis. The course is online and free, and takes about five weeks to complete. Have a data analyst in your organization take it too.
  2. Collect address-level data about every interaction your organization has with clients and the public, because addresses need to be in a specific format to be put on a map. Here are some best practices for preparing and maintaining your organization’s address data.
  3. Check out TechSoup to find discounted licenses for ArcGIS, or download the free and open-source alternative, QGIS. You may not be ready to use a GIS desktop software now, but having one on hand will enable an analyst, consultant, or intern to get started working on spatial analysis right away.
  4. Check out the presentation, sample maps, and some resources I collected for the workshop with this Bitbucket of links.
  5. Tell each of your grantees (if you’re a foundation) to do steps 1-4.

The five steps above should help your organization leverage the power of spatial analysis. You may already have questions about your data. If so, consider applying to the Summer of Maps program. Your organization will have a chance to receive pro-bono spatial analysis from Azavea-mentored Fellows. If you’d like to learn more about spatial analysis or Summer of Maps send me an email at