Frequently Asked Questions

Obama victory map FAQ

• Why do you show Walmart and health food store locations?
• Why do you show ZIP code locations?

Cartograms

• How did you make the cartograms?

General answers

See the data page.

Why did you do this?

Originally, I did a mashup of U.S. Census Bureau information for California with Google Maps for an Information Visualization class. And I got hooked.

Can I hire you?

Absolutely. My preferences (in order) would be for a full-time job, in British Columbia, working on maps, in Java, but I'm quite willing to do maps consulting in the meantime. I'm particularly strong in making tiles of polygons.

Who else could I hire?

For polygon work, if you didn't want me, I'd first send you to John Coryat. He's better at some things and I'm better at others.

What other projects allow displaying lots of polygons?

• The GeoCommons project by FortiusOne allows user-generated choropleth mapping.
• The Polygonzo project aims to do polygons very fast on the client side, but isn't quite released yet as of Jan 2009.

Why do you spell 'colour' with a 'u'?

I live in Canada now, and feel that it is important to use the spelling of the place that I live. I also decided I wasn't going to switch back and forth much -- that I would use the 'u' unless I was addressing only people in the USA.

Why don't you have much data for Canada?

Sigh. In the US, any data collected by the federal government is, by US law, in the public domain. In Canada, data collected by the government is owned by the government. While I have heard that Stats Canada is starting to release some of its data, I need to look at the licensing very, very carefully to see if I can use it. Partly, there is a clause in the Google Maps API where I have to avow that I own the data I map and that I give Google the right to redistribute it.

What are your future plans?

See my future plans.

Obama victory demographics map answers

Fivethirtyeight.com had talked about the Starbucks-to-Walmart ratio when talking about which states were likely to votes which way. The Starbucks locations do correlate extremely well with Obama votes, but I have not gotten authorization to use that dataset, alas. I did find health food store locations, and am using that in place of Starbucks, but neither it nor the Walmart locations seem to correlate (at least visually) as well as Starbucks did. Hopefully I will get authorization someday...

Why do you show ZIP code locations?

Because they show, in a very visceral way, just how empty the American West is. From Dallas West, the population density falls off quite dramatically. M.E.J. Newman has some great cartograms of the elections that help show how few people there are in "red" states, but it's still difficult to internalize how empty the West is. I encourage you to play with the population density maxValue colour control to get a sense of how the population is distributed. The population densities in cities can be ~50,000 people per square mile, while in many rural Western counties it is less than 10 people per square mile.

Census tract maps answers:

For most of my maps, you can use one of the following. For the Blacks and Prisons in California map, I don't have a way right now.

1. Use the expert form. There is a place near the end to specify latitude and longitude.
2. Edit the URL in your browser by hand. Look for something like lat=-122&long=37 and change those latitude and longitude coordinates to the ones you want.
3. Use the Google Map zoom tool on the upper left hand side to zoom out, move to where you are interested in, and zoom in again.

How can I save a map view to look at later?

In the standard maps, look for a link at the top of the right sidebar that says, "Link to this view". Save that link; it will take you right back to where you were.

This doesn't work in the Blacks and Prisons in California map yet.

How can I go to a particular address?

You can't yet. Google added a service to translate from address to latitude/longitude after I did most of the work on my standard maps; I haven't yet gotten around to incorporating that.

How can I make the response faster?

Clear out your browser's cache. That will let you keep more of the map tiles in memory.

The Blacks and Prisons in California map is just slow to load, it's not you.

Why don't I see any color?

If you don't see much color, that's probably because the area you're looking at has low values compared to the min and max. For example, if you are looking at rural Kansas, the population density is much much lower than 20,000, which is the max density for the densitry map.

Urban areas have concentrations of up to 100,000 per square mile, while very rural areas are usually less than 200 per square mile.

Try replacing the max value directly in the URL and see if that makes it better, or use the expert mode.

Why don't I see much color variation in my percentage figures?

Percentage figures frequently don't have a lot of variation. In particular, the male-to-female ratio doesn't vary much (except for prison tracts). You will probably need to narrow the min/max spread.

Try replacing the min/max values directly in the URL and see if that makes it better, or use the expert mode.

Why can't I zoom all the way out?

The farther back you go, the more computationally expensive it is to generate the maps. (The maps also get less interesting as more of the tracts are obscured by the road network.) At some point, I might turn those on, but I'm not planning on doing so soon. As a result, I don't think it's particularly useful to allow you to zoom out, so I disabled it. Note that you can switch to one of the other maps, zoom out, move, and zoom back in.

What do the colors mean?

That depends a little on what is being plotted. Always, however, bigger values are darker reds; smaller numbers are lighter.

If there are fewer than 10 people total in a census tract (as happens sometimes for airports), I color that tract grey.

The level where the red maxes out is in the "max" field of the URL; the level where it is full-white is in the "min" field of the URL.

I will have a color bar/legend eventually.

How accurate is the data?

I don't know, and I don't really have the resources to make definitive judgement of the quality. If you are just poking around for your own interest, they are probably accurate enough. If you want to do research-quality work, you really should use a professional-grade system like ArcGIS. My maps system won't ever be better than ArcGIS, only cheaper and more accessible.

Ultimately, the data comes from the U.S. Census Bureau, so it can't be any better than the Census Bureau. Along the way, it passed through the offices of ESRI, which packaged it up in a way that made it much easier to deal with.

In general, from what I can tell, it looks reasonable in most cases. By that, I mean that for the areas that I am personally familiar with, things mostly make sense. East Palo Alto has high Latino and Black populations. Milpitas and Cupertino have large Asian populations. Mountain View has lots of rental units, etc. HOWEVER, there are some areas that look really strange to me. I've documented some places that don't look quite right.

Are there census overlays for Google Earth?

I don't have any on webfoot.com, but my friends over at Juice Analytics have overlays for some census data as well as general Google Earth resources.

Do you take contract work?

Yes, but I have work right now that is keeping me busy. I could probably handle about ten hours more per week, but no more.

If you need some work done, send email to me.

What tools did you use?

See the Credits.

Who helped you?

See the Credits.

Ducky Sherwood