"Dynamic" Labels & StyleMaps

I've been unhappy with how Google Earth handles labeling of shapes - the Placemark KML object is pretty good at containing a single shape, but breaks down when handling multiple shapes. Placemark elements contain the name and description elements, but only Point elements pick up on these. As I have talked about before, you can't label a Polygon without using a Point. I started to use the MultiGeometry to group together Polygon elements that belong to one geography (i.e. when a County has a couple of noncontiguous shapes). The annoying part is that I needed to add a Point for labels to show up.

When dealing with complex geographies, like Block Groups, having the labels show up the entire time doesn't work very well. For example in the last map I shared, there are ~4,300 Block Groups in WA and having the labels all show up doesn't work very well because they overlap and make it quite confusing. You can play with breaking out the labels into a different Placemark and perhaps a folder structure at the County/County Subdivision level might help, but it still isn't perfect because you would have to hunt and peck for what you were looking. In looking through the KML spec, I was excited to find the StyleMap element. The StyleMap element provides a mechanism to have a Placemark respond to mouseover/click/highlight events. You can define a Style element for both normal and highlight classes. I thought this would be a great way to provide a label: when a user moves their mouse over a geography (e.g. Block Group, County Subdivision, County) the label could show up - the normal style would have it transparent and the normal would have it opaque.

Well, turns out it doesn't quite work that way. Unfortunately, the only thing that sparks the transformation is the user moving their mouse over the icon of a Point: the style doesn't change if they mouseover the label or any of the Polygon elements in the Placemark. What is odd, however, is that all of the elements of the Placemark do respond to the new style when you mouseover the icon.

What you'll see below are maps of Median Household Value (variable H85 MEDIAN VALUE (DOLLARS) FOR ALL OWNER-OCCUPIED HOUSING UNITS [1] from Summary File 3) by County Subdivision. I'm not entirely happy with my new labeling, but it works such that when you mouseover the icon at the center of the polygon, the name of the County Subdivision shows up and the border is highlighted in white. I like the effect, but I am not happy with how I have to have an icon show up. In the maps below, the more red an area/shape, the higher the median household value - the greener, the lower the median household value. In the 3D maps, each $1,000 of value adds one meter of height.

Movie:


Screenshot (notice how Leavenworth-Lake Wenatchee is highlighted):

Follow up to Median Household Value for Washington

I just recently discovered the TimeSpan element in KML and thought it might be an interesting way to animate the maps. To try this out, I add this to the maps I discussed in my previous post. The dates are arbitrary, but I gave each block group a date starting from the one with the lowest median household value and ending with the block with the highest. You can see the effect in the following video which animates the drawing of each of the block groups: building all of them up in order and then removing them in reverse order.



In Google Earth you can control many aspects of the animation, including the speed at which it moves through dates. I think this may be an interesting way to make the maps come alive a bit more.

New KMZ!

Today I'm going to share a KMZ of a new variable that I've been working on. I wanted to experiment with more complicated variables, beyond Median Household Income, to really push the flexibility of the code I'm writing. The migration variables of summary file 3 from the Census are fascinating and fit the bill. They allow one to understand how people are moving about the country and include quite a bit of granularity. I'm going to share 7 states worth of data: Connecticut, Maine, Massachusetts, New Hampshire, New York, Rhode Island, and Vermont. Before I share links to the actual file, I want to be sure to share some important definitions, data sources, and notes.

What is mapped?

• There are many migration variables, but for this example I've chosen to use two. I used the Population 5 years and over: Total - P024001 variable which represents the number of people in 2000 over the age of 5 and used it to divide the Population 5 years and over: Different house in 1995 - P024003 variable. The resulting percent should represent the number of people, over the age of 5, who didn't live in the house they lived in during the 2000 Census in 1995. Put it simply, the percent of people who moved in the last 5 years. The migration data provides a much more detailed breakout of where the people that moved came from, which I hope to work further with.
  
• The data is presented broken out by county: the taller, the more blue a county is in the file the higher a percent that moved - the shorter, the more green, the smaller percent that moved. The actual percent can be found in the description for each polygon, however it is multiplied by 1,000 there so the actual value is what is found in the description divided by 1,000.
• In New England, the region in the provided KMZ, Tompkins County, New York has the max value at ~ 58%. This means that ~ 58% of people in Tompkins County moved since 1995. There are many counties at the low end: Hamilton County, New York is quite low at around ~30%, but so are Aroostook County, Maine and Orange County, Vermont, both around ~33%.
• You'll also note how the counties are organized into folders within the KMZ file. This is a recent improvement to the KMZ generation process. I've also modified the code to follow the best practice of referencing repeated styles by ID (each polygon references a base style and only overrides what it needs to) - I thought this would save a lot on file size, but it didn't because ZIP was quite efficient at compressing the bits that were repeated again and again.
  

How about a quick tour of the map?
[YouTube seems to like to cut down the length of videos, so this may feel a bit choppy - not sure why it is doing this]


Where is the data from?

• I downloaded the data from the FactFinder Download Center.
• The County boundary files came from a Census website: 2000 County Cartographic Boundary Files.
• The Census boundary files include data the denotes cut outs when a polygon should not cover an area. These are denoted with a -99999 ID in the Census boundary files. While I read these in, I have not decided the best way to handle them so that data is not represented here: in other words, some of the polygons may inappropriately cover an area.

Notes/Disclaimers:

• This is a preliminary release.
• Turn off Terrain for best viewing.
• Rotate, fly around, change the viewing angle to get a real sense of the visualization!
• Commercial use of this file is prohibited. If you are interested in using this file commercially, please drop an e-mail to censuskml [at] [Gmail].
• I do not warrant in any way, the accuracy of these maps. Use at your own risk.

Files:

• 2000 Census New England Migration Data.kmz

Please pass along any feedback/thoughts/inquires via comments!

Getting better color schemes...

I'm making good progress in finding color schemes that actually make sense. As a sneak peak, I've posted a video of a tour over the median household income data from the 2000 Census by County. Green is low median income and red is high (the other way around, which may be more logical there is just way too much red on the screen). The main hurdle I am working on now is how to reduce the file size. The file shown in the movie is ~7 mb.



Here are some of the color schemes that I have put together by hand (enough of the auto-hex code generation that led me to a random walk across hues & saturations). The movie above uses the scheme third from left.