View Full Version : Geospatial Question concerning Country/Population Center Point

01-05-2014, 06:30 PM
I dabble in geographic information systems, specifically with arcmap software and wanted to try out some isotherm maps using data from some of the admixture populations.

My question is: would it be more accurate/appropriate to use the geographic center for a country, the mean population center point (population center of gravity) or something else?

For example, if you look at this map from 23andme results, the centroid for the UK for example appears to be just off the English coast in the North Sea which isn't near the pop center or geographic center.

01-09-2014, 12:33 AM
Thought I would share some of my geospatial "dabblings" with the Eurogenes K13 Admixture data based on my results/values from five K13 populations.

Please realize a lot of assumptions went into creating these maps. For example where to place a point representing a population group. Move the points a little and the results will obviously change.

Also the choice of which interpolation tool affects the map results. I chose the natural neighbor interpolation tool, but others might more appropriate for this type of data. I just don't have enough experience with these tools at the present.

In addition, these maps are not ready for prime time from a cartographic view point. i.e. they need still need some work.

The black bands on the maps represent +/- 5% from my K13 values for:
1. North_Atlantic
2. Baltic
3. West Med (band expanded to +/- 7.5% to create an overlap)
4. West Asia
5. East Med (on next post)

I stopped at 5 groups because my values for the remaining K13 groups was quite small (less than 2% of my makeup). The last map on the next post is a composite all 5 maps at the same time, showing where they all overlap.

01-09-2014, 12:51 AM
Here are the East Med and composite maps mentioned above. Couldn't get them all in one post.


01-09-2014, 01:02 AM
Population centroid seems the most sensible to me, unless all your ancestry from within a population is from a single known spot.

01-09-2014, 01:24 AM
Population centroid seems the most sensible to me, unless all your ancestry from within a population is from a single known spot.

I used the population centroid when I could find it. I have them for all the European countries, but some of these populations are a subset of a country. e.g. where exactly is the population centroid for Southeast England, or North Sweden or South Italy.

For those situations above and for countries where I couldn't find a population centroid, I reviewed population density maps for the specific area and made an educated guess as to the most appropriate spot to place the point.

01-09-2014, 03:12 AM
That seems like a good fallback.