It Sort of Makes Sense

[kevin_standlee]

Part of the work I'm doing on The Big Project involves plotting the geographic centroid of each US state and picking out a city to stand for that state's centroid. This doesn't always work well for odd sized states. It appears, for instance, that the geographic centroid of Maryland is Washington DC.

Comments

[mishalak.livejournal.com]

Why would you be finding the center of each state and not of a population based region? A number of states (Colorado) aren't really well grounded in the behavior of the population or geography. Colorado, Washington, and Kansas/Missouri, frex.

[kevin-standlee.livejournal.com]

Because we're in a hurry and location centroids are easier. We know they're terrible. I don't have to pick the exact centroid, but it's at least a notional center of the state. We hate doing this in states like California, which are really at least two "states" for logistical purposes; however, the client insists on us quoting a single rate good for anywhere in California to (say) anywhere in Florida.

[mishalak.livejournal.com]

Makes sense to me. Though a bit of a nightmare for you.

[kalimac.livejournal.com]

"Centroid" is, like, a center point balancing the competing claims of population, geography, transportation, and commerce?

So what did turn out to be California's centroid, anyway? Was it LA (or in the LA area) or did the competing claims of south and north put it at some odd spot between them, like SLO or Fresno? What about other states with a heavy population crunch towards one corner, like Michigan, Illinois, or South Dakota?

Come to think of it, if confidentiality requirements don't prevent you, post the whole list. It'd fascinate us geography geeks.

[kevin-standlee.livejournal.com]

No, the centroid in this case is only the geographical one and ignores population, transportation, and commerce. That's why it's not very good. I went through the list myself -- there are, after all, only fifty states -- and picked a city near the physical centroid.

California's centroid for this purpose is Fresno. I've also sometimes used Bakersfield. California should be two states, and indeed, when we're doing analysis where we aren't constraint by an overbearing client, we do break California, Texas, and Florida into multiple regions reflecting demographic reality.

Unfortunately, you also end up with things like Nevada's centroid being near Tonopah. The only time this method works okay is for the regularly-shaped states that placed their capitols near their centers.

I found the raw centroid points file online with a Google search last night, but forgot to bookmark the location, and now I can't turn it back up again. I must be using slightly different search terms than last night. After >14 hours working on the project at a stretch, I wasn't necessarily at my best. But it is out there if anyone wants to take a crack at finding the file, which is named "s_16mr06.zip" and contains a dBase file. I think my employer would probably consider the file I created, which is slightly more realistic, to be proprietary.

[sfrose.livejournal.com]

http://www.nws.noaa.gov/geodata/catalog/national/html/us_state.htm ???

But it is out there if anyone wants to take a crack at finding the file, which is named "s_16mr06.zip" and contains a dBase file.

That seems to have a file for each state's centroid LON and LAT.

And in doing a google search to find an ap to locate the locations, I found this:

http://www.maptech.com/support/forums/messages.cfm?threadid=1101&threaded=no&CFID=820102&CFTOKEN=93740132

(I was curious whether Hawaii's centroid would end up in the ocean or on land..._

[kevin-standlee.livejournal.com]

Yep, that's it. Good job.

When you look at the specific points, you realize how useless some of them are. That's why I had to go through and pick a city that was at least on a main highway. The "notional centroid" has to correspond to a specific 5-digit zip code because we're using to calculate average shipments.

[(Anonymous)]

I curious how that works for Michigan. I'm guessing it's in the middle of some forest in the northern lower peninsula where nobody lives.

[kevin-standlee.livejournal.com]

It's near Mount Pleasant.

[(Anonymous)]

If it's near Mt. Pleasant that probably means you only looked at the lower peninsula and ignored the upper peninsula entirely.