Re: [OSM-talk] How can we measure the completeness of the map statistically
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 wer-ist-roger wrote: > Am Donnerstag 26 Juni 2008 schrieb Frederik Ramm: >>> * Another hypothesis is that more complete areas of OSM will >>> have a higher level of edit activity. >> Then there are those who say that an area that's complete doesn't >> require any edit activity... > > That is right that "complete" areas might not gany much edits (or maybe no > edits at all) but you can see that on the edit history you will get a > submit-curve that has a lot of edits within a timeperiod until you get at > thet point it's getting less end less till you have almost no edits at all. > > So a calculation should allways include the history of submitted changes. > Indeed, that curve of much editing -> less editing should be a factor in the completeness measure - an area with much activity in the past + some more recent would be good, an area with no edits at all for 2 years is ripe for a check-over, an area with no history is clearly not good. Landuse=field is perhaps an example of the exception that proves the rule? I still think it would be useful for an overlay to exist for mappers to mark up where they consider done, perhaps that & an auto-layer should combine to make a more visible 3rd layer of completeness where they agree? We could start by filling this public layer with coastline data & mark the seas as done, at least - unless we want to get full marine data in as well? Mark -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFIZmF7JfMmcSPNh94RAj8AAJwKi2OWzcWKzHoKkBDSszfF73hrMQCcCtm6 oYevRaoNA00yrTvL7Qqnk3M= =P35M -END PGP SIGNATURE- ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
Re: [OSM-talk] How can we measure the completeness of the map statistically
On Friday 27 June 2008, Edward Johnson wrote: > I'm very intrigued by your work Freek. Thanks :-) > I'll get working on trying to reproduce something like this for the UK If you can wait for a few days, I can make some for the UK too (busy finishing my exams a.t.m.). > and then try to use the map > generated to compare with OSM. See if the hypothesis does hold that more > complete areas are edited more. Because of course as you say a fully > complete area should not be edited at all. Difficult... In the Netherlands it might be easier because we have the AND data as a "background" to compare to: the number of edits in different areas can probably be compared by dividing them by the amount of AND data for the areas, which is again approximately what I'm doing for the blue-green-red maps. For other areas you really need another external source to compare to. Some ideas: - VMAP0 has some city boundaries I remember (and cities also have a special colour on landsat imagery); data density in cities will be higher than in rural areas, on average. - Some governments publish road-length statistics, someone used these to generate a top-10 of most complete municipalities before the AND import: http://wiki.openstreetmap.org/index.php/WikiProject_Netherlands/Statistieken Interestingly, these statistics generated some healthy competition among Dutch participants at the time. I think we should just work out some of the different methods (from fully automated based on different sources to manual tagging) and see which work best. Probably manual and automated methods will just coexist in the future. -- Freek ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
Re: [OSM-talk] How can we measure the completeness of the map statistically
Am Donnerstag 26 Juni 2008 schrieb Frederik Ramm: > > * Another hypothesis is that more complete areas of OSM will > > have a higher level of edit activity. > > Then there are those who say that an area that's complete doesn't > require any edit activity... That is right that "complete" areas might not gany much edits (or maybe no edits at all) but you can see that on the edit history you will get a submit-curve that has a lot of edits within a timeperiod until you get at thet point it's getting less end less till you have almost no edits at all. So a calculation should allways include the history of submitted changes. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
Re: [OSM-talk] How can we measure the completeness of the map statistically
> * 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. I have done approximately this some time ago. See my post in an earlier thread on completeness measures: http://lists.openstreetmap.org/pipermail/talk/2008-May/026284.html In the meantime I created the images for the Netherlands weekly and put them in an animated GIF file: http://www.vanwal.nl/osm/density/nl_500_080425-080619.gif On the Dutch tile server we also added a layer showing recent changes, overlayed over aerial imagery, see http://tile.openstreetmap.nl/~rubke/fietskaart/?zoom=9&lat=52.00&lon=5.07&layers=0B000FFTT (Only zoom level 7-10; the placenames can be turned off in the layer menu.) Although the amount of recent changes is not a measure for completeness, I think it shows nicely what we can do using automated image generation, and the method can easily be adapted to show different kinds of statistics. -- Freek I'm very intrigued by your work Freek. I'll get working on trying to reproduce something like this for the UK and then try to use the map generated to compare with OSM. See if the hypothesis does hold that more complete areas are edited more. Because of course as you say a fully complete area should not be edited at all. Ed http://edwardmjohnson.wordpress.com/ ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
Re: [OSM-talk] How can we measure the completeness of the map statistically
Hi, > * Another hypothesis is that more complete areas of OSM will > have a higher level of edit activity. Then there are those who say that an area that's complete doesn't require any edit activity... Bye Frederik -- Frederik Ramm ## eMail [EMAIL PROTECTED] ## N49°00'09" E008°23'33" ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
Re: [OSM-talk] How can we measure the completeness of the map statistically
On Thursday 26 June 2008, Edward Johnson wrote: > * 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. I have done approximately this some time ago. See my post in an earlier thread on completeness measures: http://lists.openstreetmap.org/pipermail/talk/2008-May/026284.html In the meantime I created the images for the Netherlands weekly and put them in an animated GIF file: http://www.vanwal.nl/osm/density/nl_500_080425-080619.gif On the Dutch tile server we also added a layer showing recent changes, overlayed over aerial imagery, see http://tile.openstreetmap.nl/~rubke/fietskaart/?zoom=9&lat=52.00&lon=5.07&layers=0B000FFTT (Only zoom level 7-10; the placenames can be turned off in the layer menu.) Although the amount of recent changes is not a measure for completeness, I think it shows nicely what we can do using automated image generation, and the method can easily be adapted to show different kinds of statistics. -- Freek ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
[OSM-talk] How can we measure the completeness of the map statistically
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 ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
