By Andy Woodruff on 23 August 2010
I’m very weary of the hipster obsession with zombies by now. Cut it out, hipsters. So I felt shame the other night as my friend and I sprinted through the dark along treacherously uneven brick sidewalks, running from zombies and loving it.
Not real zombies, or even hipsters—we were responding to an awesome app for Android phones called Zombie, Run! It’s a location-based game of sorts that places a bunch of zombies between you and your destination on the map. When you’re near enough to a zombie, it begins to give chase. You must reach your destination without a zombie catching you and eating your brains. It’s lots of fun and can make mundane trips much more interesting, especially if you enjoy running around like a maniac in public.
But a game like this is also fascinating when you set down your can of High Life and put on your Geographer hat. It directs a kind of spatial behavior that technology more often stamps out in one way or another—wandering. While our gizmos usually tell us exactly where something is and how to get there, here is something that forces a person to stray from the direct path. Assuming the player keeps his eyes open and actually notices the world around him, the game provides an interesting way of experiencing and understanding urban spaces. By acting upon virtual landscape in the physical landscape, the player travels unpredicted paths and enters areas that might otherwise never have been seen.
It’s a little like an exercise in psychogeography, a field I can’t really claim to understand but a central activity of which seems to be the dérive, in essence a sense-driven wandering. But here instead of reacting to the sights and sounds and smells of the real urban landscape, a person is influenced by a random set of obstacles beyond anyone’s control. Such randomness may not lead to an especially deep understanding of the city, but its advantage is in ensuring wandering much more free of human biases—perhaps a better sampling of the landscape.
I have a hobby of going on long walks about town in order to check out areas I don’t know well (or at all) and often to capture a photo or three. Most of the time I end up plotting a general route beforehand to ensure that I hit a few key spots and maximize travel on routes I haven’t taken before. Invariably I second-guess myself after the fact. What did I miss by adhering to this route? What made me choose this route? What made me avoid other routes? So recently on what was only my second visit to South Boston, I let the zombies decide much of where I would walk, leaving me with perhaps not a representative impression of the place but certainly the feeling that I got a moderately more real, unbiased look at the neighborhood. Naturally it was an amusing mapping exercise too.
Here is my great Southie zombie adventure. From the point where I switched on the game (A) I had three destinations in sequence (B,C,D). Blue shows the direct route, and red is the GPS track of my actual route.
Apologies to any of you fine Southie people I hurriedly brushed past to escape a close call with zombies. Good thing none of you were angry Irish mobsters like in the movies.
Praise be to mobile technologies that promote discoveries of space and place instead of conveniently simplifying them.
Tagged Boston, exploration, psychogeography, urban geography, wandering, zombies | No comments
By Andy Woodruff on 20 July 2010
The other day Axis Mapper Dave was working with styled maps in the Google Maps API and made a brief styling mistake—all the small roads disappeared but their one-way arrows remained.
It was actually kind of an interesting perspective on the street system, a stripped-down view of engineered traffic patterns or perhaps a measure of the confusion facing unseasoned motorists. Sure enough that same evening saw me driving in circles because of one-way streets in a place where I’d ordinarily be on foot. And in Madison, Wisconsin, pictured above, in spite of the relatively few arrows on the map it can be surprisingly complicated to cross the isthmus if you don’t start from the right spot. Anyway, with these thoughts in mind naturally I stole Dave’s styling code and tried to blank out everything else to leave nothing but arrows from one-way streets.
Unfortunately it doesn’t seem possible to do this completely with the Google Maps style options, and my samples below involved a little editing to remove yellow streets. I couldn’t figure out a way to make the “arterial” category of streets white without also turning their arrows white. Cloudmade’s style editor, meanwhile, can do that but can’t yet remove street labels. This bare-bones map is the best I could do with Google Maps; the arterial streets are just turned off entirely, leaving a mostly white-and-arrows map at the largest scales.
Whereas I have previously tried to make a map into a musical instrument, I picture these maps as dance steps. It looks easy to do the Brooklyn, but it’d take some skill to dance the Paris. I’m not about to try it myself, but when geography-based dancing sweeps the nation, I demand royalties!
Pictured at top: dance steps in the sidewalk on Broadway in Seattle, by Flickr user DrewToYou.
Tagged driving, google maps, minimal maps, one-way streets | 3 comments
By Andy Woodruff on 10 July 2010
You know you’re a map geek when you’re at Red Rock Canyon outside Las Vegas, walking across ground that is covered with thousands of stones, and what catches your eye is a single little rock that totally sorta looks like a map of Ohio.
(At the time you’re also wearing a t-shirt with a map of Wisconsin on a cow, obviously.)
Tagged nevada, ohio, rocks | 2 comments
By Andy Woodruff on 22 June 2010
City skylines are one of my favorite types of scenic view. When planning to visit a new city, or even when looking to take some photos of a familiar city, I like to do some online scouting of good spots for a skyline view. I can recall several years ago browsing Google Earth, panning around and tilting the view to see terrain and guess at good vantage points. But by now Flickr users probably have just about every vantage point covered, so a more fruitful search can be done by looking at geotagged photos.
Out of curiosity I threw together some maps to show where most of the skyline views are, as defined by photos tagged “skyline” on Flickr. They are done in a sort of heat map style where brighter red and yellow indicates a higher density of photos, but they are neither real heat maps nor real density surfaces; rather they are many overlapping, mostly transparent dots, blurred a bit and mapped to a heat-like color gradient. There are no great insights that you can’t get from searching Flickr’s own maps, but it’s not bad for purposes like mine. I even learned of a new spot to check out locally; so it totally worked!
Here are some of the most photographed cities in North America, according to these guys. I did skip a few, but they tended to lack enough “skyline” tags to make for an interesting map.
New York: The brightest lights here are observation decks (the Empire State Building and Rockefeller Center), where one can view the skyline from the sky’s perspective. New York has such an abundance of skyscrapers that it’s difficult to take in the whole skyline at once from the ground, but that’s no reason not to see the views that people are favoring along the East and Hudson Rivers.
San Francisco: This city is made for scenic urban vistas. I recognize Coit Tower and Alactraz here, and can see that Treasure Island affords a nice view, but there are also some concentrations closer to the center of the peninsula that are beyond my knowledge of the city.
Chicago: All things considered, Chicago gets my vote as the best skyline in the country. There are several predicable popular spots here, such as the Museum Campus, the Sears Tower (or whatever it’s called now), and the John Hancock Center. But most interesting is the hotspot on Millennium Park, and specifically on the Cloud Gate sculpture, a.k.a. “The Bean.” This is presumably one of the only spots among any of these cities where the majority of skyline photos are of a reflection.
Seattle: Seattle gives San Francisco a run for its money in terms of ideal scenic geography, with lots of hills and coastline. Head to Gas Works Park, the Space Needle, Queen Anne Hill, or, um, that area along the water to the southwest whose name I don’t know. Interesting to note here, as well as in San Francisco, are series of photos that follow ferry routes.
Boston: It’s a difficult skyline, with the two tallest landmark skyscrapers being in an otherwise smaller section separate from the main downtown skyline. Nevertheless there are views to be had. The Prudential tower and the Longfellow Bridge stand out the most here, the latter probably because its panoramic view is so often seen from subway trains coming up for air as they cross the river. Looks like people aren’t fully appreciating the glory of the BU Bridge, though.
Toronto: Toronto’s skyline has the privilege of being visible at great distances across Lake Ontario. Locally, though, the CN Tower is brighter than anything else on this map, but there are also some notable spots along the water’s edge in various locations. Of all the cities here Toronto is probably the least familiar to me; perhaps some readers can identify locations on this map.
Vancouver: My recollection is that Vancouver’s skyline is expansive but not terribly distinctive. But like the other west coast cities, its topography and coastline provide vantage points. The brightest points on the map are actually on land near the downtown area, but views across various water features prevail overall. I know the Stanley Park views and a couple of those to the west, but am otherwise unfamiliar.
Philadelphia: Of course the favored view is the one from the art museum, and of course all those photos are of somebody doing a Rocky impression.
Tagged Boston, chicago, cities, flickr, new york, philadelphia, san francisco, seattle, skylines, toronto, vancouver | 11 comments
By Andy Woodruff on 16 June 2010
Geometry riddle: When is a square not a square?
Answer: When it’s in New England.
Above (click for greater bigness) with the stupid title is a series of minimal street maps I traced to show the varied actual shapes of a selection of so-called “squares” in the central Boston area. Urban spaces come in all shapes, as you can discover with this nifty tool, and a city square in any part of the world is by no means guaranteed to be a literal square, but New England’s style of square is peculiar (at least in this country) in its especially confused geometry. Unlike many places where a square is most often defined by a public open space or civic structure, here a square is typically defined by an intersection of two or more—usually closer to 4 gazillion—thoroughfares and/or other streets. The square’s name further applies to a business district around that intersection, and sometimes to an entire neighborhood. Thus the squares strongly define much of the local geography and organization of Boston and its close surroundings, as you can see in the diagrammatic Unmapped Boston poster. They are many things, but rarely are they square. You’ll also find some Circles and Corners around town, but they tend to be a bit more true to their names.
Any locals out there can probably find fault with my selection here or with the extent of the individual square maps, but I’ve tried to capture the central intersections of many of the major players. The collection can always grow! Entertain yourself by trying to identify each square before consulting the list under the title. (Squares from Boston, Cambridge, Somerville, and Brookline are included.)
To everyone else: Sorry, I know you don’t care. But this city is just so mappable! (And in a way, undermapped.) You should come visit.
Previously: Squares can also be difficult to drive through, and they make good logos.
Edit: don’t hate me for this, but I’m in experimental stages of posting junk like this for sale at Zazzle, just in case anybody takes pride enough in their squares to put this on a t-shirt or poster. Something more professional and less desperate-looking will occur over time!
Tagged Boston, minimal maps | 11 comments
By Andy Woodruff on 8 June 2010
The latest issue of the The Cartographic Journal (of the British Cartographic Society) contains a paper written by Robert Roth, me, and Zachary Johnson entitled “Value-by-alpha Maps: An Alternative Technique to the Cartogram.” The value-by-alpha map is something I have touched on here several times over the past year and a half (as has Zach on his blog), and about which I spoke at last year’s NACIS conference in Sacramento. With the publication of this paper, it’s high time I explained what it’s all about.
Value-by-alpha maps (hereafter shortened to VBA), like everything noble and good, have their roots in somebody complaining about something on the internet—me, about election cartograms. Seeking an alternative to what I think are ugly and unreadable election results cartograms, I worked with my Axis Maps dudes to create a 2008 U.S. election map that used transparency rather than size to vary the visual impact of map units, thinking that avoiding the distortion of these units into unrecognizable sizes and shapes would make the map easier to read.
Rob Roth, a stellar Ph.D. candidate and shameless county collector at Penn State (studying under The Beard himself, the illustrious Alan MacEachren) became interested in further developing the idea academically and enlisted my Axis Maps partner and radical raw milk zealot Zach Johnson (who wrote his master’s thesis on cartograms) and I to collaborate on the now-published Cartographic Journal article. We were all graduate students at Madison together once upon a time, and we make a good team—striking a perfect balance between study, practice, and chili-eating.
Enough backstory. I’ll summarize at moderate length the idea and what we wrote.
WTF is a value-by-alpha map?
First things first: value-by-alpha is essentially a bivariate choropleth technique that “equalizes” a base map so that the visual weight of a map unit corresponds to some data value. Whereas cartograms accomplish this by varying size, VBA modifies the alpha channel (transparency, basically) of map units overlain on a neutral color background. Thus shapes and sizes are not distorted (except necessarily by the map projection, of course), but the lower-impact units with lower alpha values fade into the background and make for a map that is visually equalized by the data.
Solving Johnny’s Cube
To make a case for the limitations of cartograms, we point to Zach’s graduate work that compares several different types of cartogram designs. Zach developed a typology that describes cartograms in terms of three characteristics: shape preservation, topology preservation, and density equalization (basically a measure of how accurately the area corresponds to the data value; we’ve modified this to visual equalization to include more than just size variation). Depicted as a stylish and highly respectable cube, his typology reveals a back corner that is unattainable for cartograms, as none can be perfect in all three regards. Value-by-alpha, by leaving size and topology alone, allows us to nearly “solve” Johnson’s cube.
VBA works by wordplay
We must note that although creating VBA maps involves modification of transparency, the maps do not in the end symbolize via MacEachren’s visual variable transparency, which is more like a masking of one layer by another that is not aligned to it. Rather it’s two color variables, one of the late Jacques Bertin’s original graphic variables and a later addition—color value and saturation. In the end it is as though each map unit’s color was adjusted in value and saturation. “Value-by-alpha,” then, is an infinitely clever name (chosen by Rob) that refers to both numeric value (as in “value by area,” a term for cartograms) and color value.
Design considerations
On to the practical advice. There are basically three components to consider in the design of VBA maps: the modifying color, the equalizing variable, and the variable of interest.
The modifying color is the color that modifies the original unit color as its alpha value changes, i.e., basically the map’s background color. White or black are the only colors that make much sense here, as anything else will confuse hues and muddle the value and saturation too much. There is some difference in the way white and black affect value and saturation, but they both essentially map an overall “lightness” to the data (just in opposite directions). Black tends to make for a more striking map, I think.
The equalizing variable is the one that is symbolized by alpha and thus visually equalizes the map. First of all, this variable needs to be one of consequence to the variable of interest in order for the visual weighting and VBA altogether to make sense (e.g., counties with more voters are of more consequence to election results). With that out of the way, we recommend classifying the variable into five to seven classes. That number is pushing the limits of what can be visually distinguished, but we are suggesting some compromise for an improvement in aesthetics. To avoid units that are completely invisible, the lowest class shouldn’t have an alpha value of zero, but rather something in the 10–15% vicinity, from there stepping up to 100%. To assist with geographic context, we also suggest adding an outer boundary to the map units taken together.
The variable of interest is the variable being mapped with color and weighted by the equalizing variable. Because the alpha modifications introduce a lot of subtle variations in color, we advise a fairly limited number of data classes (unmodified colors) in this variable, specifically only two or three variants of each hue. For a sequential scheme that generally means two or three classes, and for a diverging scheme it means four to six. As always, ColorBrewer is the place to look for color schemes, a few of which are ideal for avoiding inherent lightness differences in hues that could upset the map’s intended visual hierarchy.
Below are some example color and alpha schemes, taken from ColorBrewer specs. Each is labeled with numbers that correspond to the intended visual hierarchy, where 1 should stand out the most, 2 the next highest in the hierarchy, and so on. Note that several colors may be meant to exist at the same level.
For the faint of heart
Cartograms are good for shock value. They’re an in-your-face radical perspective on a world you thought you knew, and they can really make a point. As a carto-curmudgeon, I remain meta-amazed by the amazement with which cartograms are received. We think that VBA can be a good choice when you want to show similar information but also want to be able to recognize what the hell you’re looking at. So when no shock is required, or it would hinder the intended map-use tasks, perhaps value-by-alpha can be your friend.
Limitations
Let’s be real—even I’m not convinced that VBA is broadly useful. We are proposing it and providing some theoretical support, but it is untested and carries important known limitations. It cannot be a universal replacement for cartograms, and we don’t want to imply that it is.
First, color value and saturation are not the most effective visual variables for encoding numerical data, certainly less so than size, which is what cartograms use. Furthermore they can’t as easily be tied to direct mathematical scaling as cartograms might. What all that means is that we can’t expect users of VBA maps to extract numerical estimations with much success, so the technique is best reserved for big-picture purposes, not precise comparisons.
Second, VBA is incapable of an important use of cartograms, which is to emphasize units that are small in area but thematically important, for example some of the European countries in the population cartogram below. VBA can only reduce the visual presence of a map unit, emphasizing the important ones only by diminishing the surroundings. Small geographic units may remain difficult to interpret.
Third, we can’t ignore varied unit sizes in a VBA map, just as in any choropleth map. Larger areal units carry a higher visual impact even if they are thematically less important, which is why some sort of standardization is generally encouraged on choropleth maps (e.g., mapping population per square mile instead of total population). Cartograms don’t have this problem, of course, because unit size represents thematic data, not geographic area. We didn’t really explore standardizing by area in VBA maps, but it may result in a more appropriately equalized map. However, standardization of the equalizing variable further hinders user estimation of data values in the map. For example in the election map equalized by population density below, it’s correctly visually equalized, but it’s not easy to compare one county’s impact to another’s because it requires calculating some combination of color and size.
Finally, there are display media issues that don’t exist with size variation in cartograms. The subtle variations in brightness and saturation in VBA are very difficult or impossible to hold constant in digital media. A map can look perfect on one screen and completely black on another. We got some feedback along those lines on the original election map. When you can’t control the display medium, a cartogram might be a better bet.
In action
Here I am obliged to point out that we’ve built value-by-alpha functionality into indiemapper, the Axis Maps web-based cartography application. Zach programmed most of that feature about an hour before my NACIS talk last fall. Otherwise, making a VBA map is simple: either programatically adjust alpha values of enumeration units or in a more graphical approach create layers for both the variable of interest and the equalizing variable, and use the latter to mask the former.
To close, it is worth providing an example of the value-by-alpha technique besides the election theme of everything posted so far. Below is a version of a map made by Rob Roth and Jin Chen at Penn State for some research they’re involved with. With a diverging color scheme it shows cervical cancer mortality rates by US county, above and below the national rate. Instead of using a VBA map to equalize by some variable of magnitude, this map uses it to display a measure of statistical reliability. A county’s alpha value corresponds to a score that indicates how reliably it lies in a cluster of elevated cervical cancer mortality, resulting in the spotlight effect on those important regions. Before I do more injustice to this work, check out the fully detailed poster (PDF) available on Rob’s ludicrously thorough online CV.
Paper citation
Roth RE, AW Woodruff, and ZF Johnson. 2010. Value-by-alpha Maps: An alternative technique to the cartogram. The Cartographic Journal. 47(2).
It is probably not permissible for me to post the paper online, but anybody who has read this far is probably an academic with access to the journal.
Tagged Academic, vlaue by alpha | 8 comments
