Census Maps FAQ
- How can I go to a particular latitude and longitude?
- How can I save a map view to look at later?
- How can I go to a particular address?
- How can I make the response faster?
- Why don't I see any color?
- Why don't I see much color variation in my percentage figures?
- Why can't I zoom all the way out?
Why is there a horizontal line sometimes?- What do the colors mean?
- Are you going to do X?
- How accurate is the data?
- Are there census overlays for Google Earth?
- Do you take contract work?
- What tools did you use?
- Who helped you?
How can I go to a particular latitude and longitude?
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.
- Use the expert form. There is a place near the end to specify latitude and longitude.
- 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.
- 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.
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.
Why is there a horizontal line sometimes?
It was a bug in gd, the graphics library that I use. I have reported it and fixed my local copy. You should not see that horizontal line bug any more. If you do, please let me know.
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. See my future plans.
Maybe. See my future plans.
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.
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.
See the Credits.
See the Credits.
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