Choosing symbology for maps can sometimes be a tricky business. When you're plotting the location of restaurants along a route, it's pretty simple - You really only need points since the people viewing it are likely starving. But...what about in cases of emergency? You want something clear and concise, that immediately allows its audience to tell what they're looking at without having to heavily rely on a legend. In cases of fire, it's no different.
The Rim Fire in Yosemite has a been a hot topic here in California lately. Disregarding the bad pun, it really is a huge deal, and there's been a lot of attention placed on how best to alert those it might affect - both within the company I work for and without. There's been a lot of trial and error in general - some of these resulting in some best practices, and consequently, worse.
HEY THERE, "WORST"
Inciweb recently produced the map below to highlight the fire's progression. The different colors show daily movement, including number of acres burned in that day. This information is fantastic to have. However, it isn't very easy to read. There's no discernible pattern to colors chosen, and frankly, there are too many for the average person to keep track of. A random color scheme may have been better suited for a smaller fire that burns out quickly, but it's not the case here.
Although it isn't extremely easy to determine daily burn and acreage with this new version, Simmon's did a great job of showing the overall progression by doing three things.
First, he's chosen a graduated color scheme. The progression is easy to follow, soothing the eye rather than confusing it. The most recent burns are darkest and therefore stand out more. Although every part of the fire is important, it may be more valuable to know what areas have been most recently hit. The color drawing the eye in and then out allows for that importance to be place on the information at hand.
Second - and this may be the most obvious point, one that could go unsaid but darnit, I'm going to say it anyway - is that he chose a color appropriate for the subject! He didn't paint with the colors of the wind, choose all the colors of the rainbow, or even use a graduated color scheme like blue to green. Instead, he chose a scheme that can be instantly recognized as fire.
Finally, he set up the legend so that there is an easy, difficult-to-miss progression of colors. Although the reader is forced to count the days themselves, it helps having a visualization of all the colors leading from left to right (the way normal people read in the first place), flush to one another, with a minimal amount of text.
NICE TO SEE YOU, "BETTER"
What's been beneficial about this map since its release, however, is that others have recognized the issue at hand and have since fixed them. The individual in particular is Robert Simmon, Lead Data Visualizer and Information Designer at NASA's Earth Observatory. His recreation of the map (below) uses the same daily progression pattern as the original, but with more appropriate (and less chaotic) symbology.
"BEST", HOW YOU DOIN'?
Now for the best map! Kidding, kidding - just a different approach. I work in the same department as the Disaster Response Program at Esri. Thankfully, I've had the opportunity to see how focused they are on better alerting the public about situations like this - in terms of software, social media publications, and - you guessed it - symbology. An example (below) takes into account the perimeter of the fire as well as MODIS hot spots, which are areas of extreme thermal temperatures recorded by satellites. The issue here is trying to distinguish the "hot spots" from actual point of ignition as well as trying to ensure that they are not mistaken for the fire itself. To do this, an approach is taken to separate it as a point symbol but keep it the same color as the perimeter. This way, the fire itself is the main focus and the viewer's eyes are eventually lead to the spots. They sort of, you know, blend in. If these points had been issued a different color, or even a halo, they might stand out too much, placing too much emphasis and cause for concern on these locations.
Altogether, relevancy and representation of data are important factors to consider when making maps, but especially when it comes to sensitive information. I'm interested in some alternatives to displaying this type of information. How would you improve or change these maps, or what practices in general would you (or do you) use for your emergency response maps?