I would like a way that we can say accurately how complete any area is, without
relying on other users to have said its complete. Ive come up with a few
hypotheses and posted them on my blog (http://edwardmjohnson.wordpress.com) of
ways which we can start to do this.
* A complete map will have all of the roads in an area, but we cannot
obtain stats on the amount of road in every area we may wish to test in
OpenStreetMap. So an accurate way to predict the length of road in any area
would be useful. My hypothesis is that the length of road in a given area is
dependent upon population density. That is to say I expect that urban areas
will have less road per person than rural areas.
* For areas where OSM has aerial imagery I would like to compare the
complexity (ie file size) of the Yahoo! jpeg and the corresponding OSM tiles.
The hypothesis is that areas with very small aerial jpeg files (because they
are simply one colour like the sea or vast expanses of desert) will have few if
any entries on OSM, whereas areas with large file sizes (cities) will have a
large density of nodes and ways in OSM and therefore large tile size. I do not
have the technical knowledge to test this so any help would be great.
* Another hypothesis is that more complete areas of OSM will have a higher
level of edit activity. If no-one has ever edited an area then it may be
unlikely that the map is complete there, obviously however there may just be
nothing there, so this test could be used in conjunction with the Yahoo!
Imagery test stated before. If we could produce some sort of heat map showing
which areas are edited most frequently and monitor it over time this could
certainly show us some interesting trends.
* This is an attempt to solve the problem of missing roads. I would think
it unlikely that there would a road which is completely cut off from others, or
that there would be an entire settlement of roads not connected to rest of the
country’s road network (as in the Madiera example shown below again). The
hypothesis is that every road is connected to at least one other road of equal
or higher classification. So if in OSM there are roads that are not, then maybe
there are missing roads. This testing may require a lot of calculations and may
not return that many missing roads. If some one can think of a way to do it
simpy then I would very much like that input.
Any other ideas of how we can measure completeness statistically?
Ed
http://edwardmjohnson.wordpress.com
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