Azavea Atlas

Maps, geography and the web

Summer of Maps: Lessons in Cartography

This entry is part 2 of 6 in the series Summer of Maps 2014

Summer of Maps logo

Now in its third year, Azavea’s Summer of Maps Program has become an important resource for non-profits and student GIS analysts alike.  Non-profits receive pro bono spatial analysis work that can enhance their business decision-making processes and programmatic activities, while students benefit from Azavea mentors’ experience and expertise.   This year, three fellows worked on projects for six organizations that spanned a variety of topics and geographic regions.  This blog series documents some of their accomplishments and challenges during their fellowship.  Our 2014 sponsors, GoogleEsri and PennDesign helped make this program possible.  For more information about the program, please fill out the form on the Summer of Maps website.


Lessons in Cartography

Summer of Maps focuses on providing spatial analysis services to non-profits in the form of maps.

While I geocoded addresses, performed kernel densities, and converted between vector and raster, none of that means anything unless my maps effectively convey the content. That is, they need to make sense and look awesome. Depending on the ‘where’ and ‘what’ of my maps, I implemented various tips and tricks to make them both beautiful and understandable. One of my mentors, John Branigan, is quite the cartography guru and actually inspired this blog post so I will start with:


1. Lessons from John – When I would bring up a map for John to review, before I had even explained anything he would point out “it’s not projected” or “don’t use red.” His eye for detail is very acute. The following are small tips that make a big difference for the aesthetics of a map.

  • Color – Red can stand out and provide contrast but it also conveys feelings of negativity or danger. On the other hand, green gives off a positive connotation. When I used green for a layer of income I thought it was appropriate because it reminded me of money. As Cynthia Brewer says in Designing Better Maps, “darker colors are used to represent higher data values, and lighter colors represent lower values” (1161). Emphasizing poverty this way, however, does not make sense because the lighter green areas were the ones I wanted to focus on. Instead, I used more of an orange/red to emphasize impoverished census tracts and used a green gradient to emphasize wealth for a fundraising map.
  • Outlines – One of my projects was about New York City, a densely-populated place. My maps could have easily been overwhelmed by the sheer number of census tracts. I avoided this by removing the tract’s outline. This left just the colored polygons, free of distracting boundary lines.
  • Transparency – Another way I was able to convey a lot of information without it getting too “busy” was with transparency. Making a layer 50% transparent lessens the harshness from a strong color while also giving way for other layers to be seen.
  • Basemaps – Basemaps are nice because they give some geographical context. They can also add a lot more like streets, topography, and satellite images. Again, for a place like New York with countless streets, I chose a very simple basemap with minimal labels that would adjust to the scale.


2. Multiple Attribute Symbology – Most of the time a layer is symbolized either by color or size or shape. There are certain instances, however, when you need to show multiple attributes. I came across this for a couple of my maps. For example, I needed to map event locations by the type of event and number of participants. That is, showing a quantity and category simultaneously. I did this by using unique colors for the event type and graduated size for the participation.


3. Labels – It can be important to identify specific features like streets and counties with labels. Unfortunately they can pose problems such as long names, overlapping and simply not fitting where you want them. I counteracted all these complications with the following tactics.

  • Truncate the Label – A layer of community districts was identified by the district code. The code was comprised of a number for the borough and then the district number. I removed the leading number so the label would just be the shortened version.
  • Convert to Annotation – This is a great trick that allows the labels to be manually edited and moved. I was able to place county names where they didn’t overlap other features and rotated them so they fit nicely.
  • Omitting – Using the “one label per feature” instead of “one label per feature part” drastically de-cluttered the Jamaica Bay islands.


4. Extent – Simplify a map by only showing what needs to be shown. I had specific study areas for my projects so any layers that spilled out like a highway were clipped away. Similarly, I removed parts of a density layer that overlapped water.


5. Multiple Data Frames – Including more than one data frame in a map can add detailed views and context.

  • Insets – Maybe there’s an area of the map that is very clustered or is of particular interest. Creating an inset map of the zoomed-in extent avoids squinting!
  • Context Map – A few of my layers were derived from analysis involving various datasets. Instead of writing out many sentences about the process, I made a layout with multiple data frames to visually explain how many layers were added together to produce the main one on display.




Summer of Maps: An ‘Atypical’ Approach to Analyzing Tree Canopy Cover

This entry is part 1 of 6 in the series Summer of Maps 2014

Summer of Maps logo

Now in its third year, Azavea’s Summer of Maps Program has become an important resource for non-profits and student GIS analysts alike.  Non-profits receive pro bono spatial analysis work that can enhance their business decision-making processes and programmatic activities, while students benefit from Azavea mentors’ experience and expertise.   This year, three fellows worked on projects for six organizations that spanned a variety of topics and geographic regions.  This blog series documents some of their accomplishments and challenges during their fellowship.  Our 2014 sponsors, Google, Esri and PennDesign helped make this program possible.  For more information about the program, please fill out the form on the Summer of Maps website.


An ‘Atypical’ Approach to Analyzing Tree Canopy Cover

As part of Azavea’s Summer of Maps program, I elected to work with TreePeople, a Los Angeles based environmental non-profit with a goal of ensuring the sustainable future of L.A. by expanding and maintaining the city’s tree canopy. I have always had an interest in sustainability, so I jumped at the chance to work with such an environmentally-focused organization. TreePeople was seeking GIS analysis to further understand the relationship between public health and socioeconomic characteristics in the city of Los Angeles with the city’s tree canopy cover (TCC). Their aspirations for the project were to understand in which neighborhoods of L.A. they should focus their resources, according to the correlation. Before I even began looking for pertinent data sources, I performed some rudimentary research on the health and societal benefits of trees, especially on the West Coast and in a city infamous for its air pollution problems.   I was pleasantly surprised to learn that many scientists have found evidence stating that trees can help people to live healthier, happy lives. A recent article published in The Atlantic found that the U.S. TCC averts $6.8 billion in health care costs each year, simply by existing.


Besides their environmental effects, in which trees remove carbon from the atmosphere – they are often used as offsets for carbon emissions – many scientists understand trees to have positive psychological effects on the human population, including decreased depression due to the presence of greenery, and decreased crime rates. In their publication in Landscape and Urban Planning, Troy, Grove, and O’Neil-Dunne (2012) found that in Baltimore, a 10% increase in TCC was associated with a 12% decrease in crime. While some scholars are not fully on board with some of these findings, more and more evidence is pointing towards the positive aspects of having trees in our residential and urban centers.   Due to the fact that Los Angeles is stricken with severe air pollution problems, one can expect that certain respiratory conditions, like asthma, are very prevalent in the region. In a world where 7 million people die from air pollution every year, according to the World Health Organization’s March 2014 publication, it is crucial that all measures to reduce pollutants are taken, which includes planting trees. Taken from the above listed The Atlantic article, scientists found that in 2010, the presence of trees in the United States prevented 850 human deaths and nearly 670,000 cases of acute respiratory symptoms, like asthma. If more trees were to be planted, a situation similar to the crime correlation in Baltimore could potentially result.   Using this information on what variables are thought to be directly influenced by the presence of trees, we began searching for data specific to the Los Angeles region. Using the data that was provided by TreePeople and finding our own on various websites, such as the site of the California Office of Environmental Health Hazard Assessment (OEHHA), we were able to obtain numerical figures for 10 variables, broken down into smaller geographic areas of the city of Los Angeles, including census tract and health district levels. With the help of TreePeople, we ranked our variables according to their importance and proposed correlation to TCC:

Variable Name








Minority races


Traffic density


Linguistic isolation






Low birth weight


Educational attainment


Using the assigned weights, we used the Weighted Sum tool in ArcMap 10.2 to mathematically combine all of the rasterized factors into one layer and determine which parts of the city had the highest need – where the highest values (out of 100) were found. What resulted was the following, where the dark reddish-brown color indicates the priority areas with the highest need.

Weighted Sum map


From this map, we were able to determine the neighborhoods in the city that contained the highest values, broken up by neighborhood council delineation, as established by the Los Angeles government. TreePeople will use these designations to determine where they want to focus their efforts to increase tree canopy by planting trees and increasing awareness. We found that the top 5 ranked neighborhoods were all located in South Los Angeles and Downtown Los Angeles, but that there were two neighborhoods in the Panorama City and Winnetka areas that also demonstrated a high need for tree plantings, which we chose to study as well.

Top 5 neighborhoods

Finally, once we had reached this point, it was time to add in the original tree canopy cover data that we had been given by TreePeople. One might believe that starting with this data set would have been the most logical way to tackle this GIS project, but I find that understanding the situation in more depth and then using the tree canopy cover to confirm the findings produces a more comprehensive result.


While analyzing solely TCC does not pick out the same 5 neighborhoods as an analysis of correlated variables does, the 5 neighborhoods that we had originally selected are on the lower spectrum of TCC, and provide TreePeople with different neighborhoods to investigate that they otherwise may have missed out on by simply analyzing the map of TCC. Using this ‘different’ method to complete the project shows that one’s first instinct is not the only way to take on a project, and that more communities may benefit in the long run from an atypical analysis. It is important to look at a project from multiple dimensions in order to fully understand and complete it.

FOSS4G North America 2015 Program Committee Chairman Announcement

I’m honored to announce that I will be taking the position of chair of the program committee for FOSS4G North America in 2015. The open source geospatial landscape is rich with new ideas and technologies as well as advancements and applications of well established projects and practices. I’m excited to work with the community and guide the program committee through calling on participants from all corners of our slice of the open source world to share with us the news from the forefront of geospatial technology, to build a meeting of the leaders of our field, and to create an informative, exciting program. Thank you to Andrew Ross and the rest of the conference committee for entrusting me with the task of ensuring this conference program is a great one.

The FOSS4G North America conference will be taking place from March 9th to 12th (save the date!), and will be held alongside EclipseCon. It will be held in California, in a town called Burlingame which is minutes from the San Francisco International airport.

As part of the community, I would love to hear any input on what topics you’d like to see in this year’s conference or qualities you think this conference program should have. Email me at and let’s start a discussion.

Trees, Green Stormwater Infrastructure, and…Arduinos? Come to EcoCamp!

ticketleap_bannerMy colleague Amelia Longo and I are hard at work – we have just seven days to go before Philly EcoCamp starts next week! EcoCamp – a combination of workshops, an unconference, and a hackathon - will be the most comprehensive event Azavea has ever organized. At three days, it’s even longer than the NASA Space Apps hackathon we hosted last year! We’re making  awesome t-shirts; we’ve confirmed an excellent, LEED-certified venue in Friends Center; we have a full slate of eight technology and environmental workshops; and we’ve received some great unconference sessions, hackathon ideas, and, of course, data! There’s still time to register  if you want to be a part of EcoCamp next weekend!

Azavea’s involvement in environment and sustainability work runs deep. GIS for sustainable communities is the tagline on our business cards. One of our longest-running and most successful projects has been the spatial analysis applications and expertise we provide for the Philadelphia Water Department’s green stormwater management programs . The Coastal Resilience mapping application we recently released with the Nature Conservancy provides important environmental planning tools, and we were just awarded an SBIR grant from the Department of Energy to develop more climate change modeling tools. Our flagship open source product, OpenTreeMap, promotes and facilitates urban forestry – a key sustainability strategy for reducing a city’s pollution, carbon footprint, and managing stormwater runoff.

We also happen to love civic hackathons. The proliferation of open data from governments and other organizations combined with the ingenuity of civic hackers and groups like Code for Philly presents an amazing potential for analyzing our world and the environment we live in.

So it should come as no surprise that after straddling these two communities ourselves for so long, we decided it was high time to bring more environmentalists and technologists together. Philly has had hackathons in politics, transportation, space science, accessibility, digital humanities, education, and loads of other fields. Why not the environment? Philly is home to organizations like the Sustainable Business Network, Grid Magazine, Pennsylvania Horticultural Society, Philadelphia Water Department, Philly Nexus, Clean Air Council, Mayor’s Office of Sustainability, and Solar States – all leaders in sustainability. Aside from some very notable examples, the potential for collaboration between environmental experts and civic hackers in our city is ripe but relatively untapped.

We’re organizing EcoCamp to change that. But fostering real cross-domain collaboration requires more than getting people in the same room – we need to build capacity and create a space where technologists and environmentalists can speak the same language and consider the same challenges together. I’ve been to too many hackathons where technologists and subject matter experts start out collaborating on Saturday morning, only to diverge later. At the end, in part thanks to this frequent disconnect, some hackathon projects don’t have a “home” – an organization or users for whom the project fills a need and will actually use it. None of this is good news if we want our civic tech efforts to be inclusive and meaningful.

So we’ve incorporated a full day of workshops and an unconference into EcoCamp, alongside the hackathon. A diversity of perspective and expertise builds better hacks, and we hope these elements of the event will encourage that. Our environmental workshops will give participants a core understanding of environmental issues in our region, by going outside and pruning trees, exploring urban forestry science, delving into building energy data, and understanding green stormwater management . Our technology workshops will work the other side of the equation – teaching fundamentals of data visualization, crowdsourced mapping, online GIS, and electronic sensors. We hope this combined set of knowledge and skills building will provide ideas for hackathon projects and empower everyone to contribute.

Even with mentorship and training, a hackathon still isn’t for everyone. Don’t feel like hacking? Can’t stay the whole weekend? Want to thresh out an environmental question with like-minded individuals? Show off an initiative your organization is championing and get feedback? In the great tradition of other unconferences like PlanningCamp and TransparencyCamp, on Saturday we’ll have plenty of breakout rooms for anyone to lead a session on any topic. It’s way more fun than a traditional conference!

We’re striving to make EcoCamp exciting for everyone that wants to learn, do, or talk sustainability and technology. There are just a few days left to register – you don’t want to miss out!

Good Planning Begins with Good Data: Mapping Tools for Community Organizers


Recently I had the opportunity to co-teach an elective, Good Planning Begins with Good Data, for the Citizens Planning Institute.  The Citizens Planning Institute, organized and operated by the City of Philadelphia’s City Planning Commission, has a mission “to empower citizens to take a more effective and active role in shaping the future of their neighborhoods and of Philadelphia, through a greater understanding of city planning and the steps involved in development projects.”  CPI teaches community organizers and activists about the role of good planning and implementation to enrich their communities and neighborhoods in which they live.  CPI provides two programs yearly which enroll about 25 students each.  Each program includes a rigorous application process and a curriculum of core and elective courses.

The three hour elective course, Good Planning Begins with Good Data, discussed how data informs better decisions and the importance of collecting and presenting data accurately.  The course had the highest enrollment and interest of any elective ever offered by CPI and included the current program’s students as well as many alums.  There was clearly an unmet need among Philadelphia’s community organizers for instruction on locating, assembling and presenting data in meaningful ways.

In order to demonstrate the key principles of our topics, the course focused on the case study of a hypothetical vacant lot in North Philadelphia that had potential to be converted to a community garden.

Mark Wheeler of the City Planning Commission discussed available City resources for accessing planning, zoning and property data such as:,, OPA Property Search and more.  Lauren Gilchrist described how to access key census data tables using American FactFinder and analyze and aggregate the data with key Excel commands.  She also described the best methods for creating web and in person surveys for collecting data.

The portion of the course that I taught was on the available tools for mapping data as well as the best way to engage experts in the arena of mapping data.  Below is a Q and A featuring the most interesting topics and questions from my talk:

Q: Why bother mapping your organization’s data?

A:  Visualizing data is a powerful way to tell your story.  Maps are easier for your constituents to understand than a huge database of information.  And by mapping your data, you can expose hidden patterns and relationships in your data.

Q: What is spatial data?

A: Spatial data is data that defines a geographic boundary or location.  This data comes in many forms: it can be point data such as addresses of constituents, it can be boundary data such as census tracts with demographics.  It can also be grid-based such as land cover or aerial imagery.

Q: How should I format the data I collect?

A: When you collect data, be sure to store it in a spreadsheet such as Excel.  Assign a unique ID to each record and store address information in separate columns (address, city, state and zip).  Keep the document as clean and simple as possible.  This guide is helpful in understanding how you should prepare your data if you plan to map it.

Q: What desktop and web mapping tools exist?

A: The most popular desktop mapping tool is Esri’s ArcGIS desktop software which has discount licenses available for home or nonprofit use.  QGIS is also a great option for desktop GIS. It’s open source software with a lot of geoprocessing tools.

 A great tool for learning QGIS is the QGIS Training Manual.  Desktop tools can have a steep learning curve but generally have greater processing power.

Web tools offer another range of mapping capabilities and can generally be easier to use but have a pricing structure that ranges from free to an expensive monthly fee.  CartoDB is a fantastic tool with a free tier that can be used to quickly make a map.

Q: How can I engage experts to assist me in mapping?

A: Understanding a bit about how spatial analysis is used to answer questions is helpful when determining the analytical needs of your own organization.  Preparing your data using the recommendations described above (or this guide) can be really helpful to a consultant who will spatially enable your data. Azavea offers fantastic spatial analysis and mapping services for our clients.  Hopeworks, a nonprofit in Camden, also does interesting spatial analysis work while providing training opportunities to high school students.

Q: What pro bono and civic services exist to contribute to my work?

A: The Summer of Maps program is a great resource for nonprofits needing spatial analysis services.  Civic hackers such as Code For Philly and area Hackathons may also be interested in provide assistance in mapping the data your organization has if it serves as a civic resource to others.