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March 01, 2005


Julian Elson

In addition to your (correct) remark that other gridded maps are needed (or at least on my wish-list) for things like elevation, land use (and perhaps more demographically oriented things like life expectancy and GDP per capita as well), I think time series would be useful, it would be interesting to see time series for these gridded population maps as well. It would be neat to see changes in population density by seeing one map for 2005, one for 2000, one for 1995, etc. (I think yearly increments might be too much, but every five years would be good). Overall, one would expect such a map to get slightly redder year by year, due to increasing population (unless the scale itself were adjusted), but it would be interesting to see the areas that got whiter. The U.S. Great Plains might be such a case, and I wonder what other areas would appear to be "emptying out."

João da Costa

"Now, if only I can find links with information on other geography-related phenomena, e.g. weather patterns, forestation, elevation, land use, etc."

Actually such information exists.
Look at for general topographic data. This is well known by people working with Geographic Information Systems (GIS).
General geographic information at a world scale was assembled first by the US Defense Mapping Agency's (DMA) through the 1990's and later adapted and used by other organizations. The scale used was 1:1.000.000 and most of that information is public. But there is also information at a more precise scale that is kept private for security (military) reasons.
Elevation data is now public at a "pixel" resolution of 90mx90m derived from the NASA Shuttle Radar Topography Mission of the year 2000 (see; the USA kept for itself the original data at a "pixel" resolution of 30mX30m).
I'm a frequent user of GIS related systems since 1990 and I notice a gradual but clear shift from national or local to regional and global geographic databases with a wide spectrum of thematic layers. Some of those data you can buy (in CD or similar media; for example or download from the Internet. For an optimal exploration of this information some operational knowledge of GIS software is needed (look at the Wikipedia article
The students I tutored recently in preparation of their theses at the main university in Maputo used the Shuttle Topography Data for hydrological modelling of certain international river basins that flow from neighbouring countries into our shores Mozambique. Cross country geographic data are crucial in such studies.

Abiola Lapite

"Look at for general topographic data."

Seems interesting, but it says on the page that the data's only accessible by those with a Princeton IP address.

João da Costa

"Seems interesting, but it says on the page that the data's only accessible by those with a Princeton IP address."

I was only trying to explain where the whole thing came from.
The data initially known as "Digital Chart of the World" was later refined and polished in a knew mapping agency (known as "National Imagery and Mapping Agency", NIMA) and the finished product was named "Vector Map Level 0", VMAP0.
You can download these data from the following link:
This is what we call basic (but a lot of stuff!) topographic data.
Other thematic layers as for example land coverage, soil classification or population spatial distribution must be found elsewhere.
A lot of people made/make money encapsulating the original VMAP0 stuff with other thematic layers and selling the resulting products in the Internet or otherwise.
For example:

Note -
In a way what is happening in the geographic arena is similar to what happens in the biological arena with the sequencing of the human genome (or other species genome!) that is public data on the one end and the finished product that come from the diverse laboratories (public or private) analyzing further said genome and in the process yielding new discoveries like, for example, new farmaceutical drugs.


"Overall, one would expect such a map to get slightly redder year by year, due to increasing population (unless the scale itself were adjusted"

You'd fix world population at 1 and graph the share of world pop at each place. That would be interesting. Especially if you could do it over a long span of history, like say using Maddison's data (however imperfect his estimates may be) which go back to 1 AD
( (there's other data which goes back even further)

Somewhat relatedly, this is also interesting:

(I think original title for that paper was "Why are one third of people Indian and Chinese?")

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