Re: [OSM-talk] Why the HOT obsession with low quality buildings in Africa ?
On Mon, July 2, 2018 1:26 pm, Robert Banick wrote: > Many humanitarian groups use buildings as a rough proxy for population Yes, I have had that explanation from multiple sources involved in humanitarian uses of Openstreetmap: from that they can calculate, for example, the impact a a flood. I believe that it is an awfully expensive way to gather that data. A landuse=residential with a density qualifier may do the trick cheaply with the addition of a density qualifier attribute: single family houses, sparse multi-tenant buildings, dense multi-tenant buildings... This is actually the data model used by the government of Senegal at their national level with a street-level granularity. If one wants to go further and count the number of dwelling units, then a node is sufficient (maybe along with an attribute to discriminate single or multi-tenancy) Shapes are of course good for many other uses but, if the actual user requirement that data is gathered for is a population density map, then they are a waste of resources. I'm pretty sure that contributors are happier if their efforts are directed at profitable purposes. ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Why the HOT obsession with low quality buildings in Africa ?
Low quality building mapping is pretty general in Africa, I mentioned Malawi still has some 4,805 duplicate buildings in the HOT mailing list very recently which as a percentage of the buildings mapped is probably fairly low but is still a concern. The problem is one of data quality, is OSM reliable? and if I want to promote a commercial alternative the data quality of buildings in Africa is a weak point of OSM. Can you trust the buildings mapped in OSM? The mappers seem to be mappers for a day or possibly three and having spoken to one or two training is seen as a waste of time they just want to map. I get the impression that mapping buildings is seen as a way of engaging people and bringing something to their attention as much as mapping accurate buildings. Perhaps a better way would be to map the village outline and tag them with the number of buildings on a date? Cheerio John On 2 July 2018 at 07:26, Robert Banick wrote: > Many humanitarian groups use buildings as a rough proxy for population > (density), or to ensure every household is covered during a vaccination > campaign, or simply to navigate. Likely they use them for a combination of > the three. As Phil says, it’s best to read the specific task. > > As a side note, it’s helpful to be more specific than the entire continent > of Africa, which is a very, very large and diverse place. If you can note > individual problematic countries, as Frederic does, it helps us to identify > sources of error or verify there was a legitimate humanitarian or > community-building reason behind any fall in quality. > > On Mon, Jul 2, 2018 at 4:16 PM Warin <61sundow...@gmail.com> wrote: > >> On 02/07/18 18:52, Frederik Ramm wrote: >> >> > Hi, >> > >> > On 02.07.2018 10:24, Jean-Marc Liotier wrote: >> >> churning out buildings like demented stonemasons trying to reach their >> weekly quota >> >> of gamified task-managing ! >> > I recently stumbled upon >> > >> > https://www.openstreetmap.org/#map=15/-6.8958/39.1623 >> > >> > (Tanzania) and had a similar thought. The buildings there are at least >> > square and largely match aerial imagery, but this, too, looked like >> > supercharged one-trick-pony image tracing combined with very little on >> > the ground knowledge (e.g. quite a few roads and tracks clearly visible >> > on the imagery are not traced, and from someone local you'd expect the >> > occasional POI or label). >> > >> > Someone must have buildings very high on their priority list (don't even >> > know if HOT are involved but it certainly doesn't look like local >> mapping). >> > >> > It will be interesting to learn why buildings are so important. Or are >> > they just the lowest-hanging image tracing fruit, or just easier to >> count? >> > >> I have been mapping a few buildings lately - mainly to add addresses to. >> Past mappers have placed a few POI ... but they tend not to be too >> precise - e.g. between buildings or on the footpath. >> Once the building outline is there then you see the discrepancy. And any >> further additions of POI can be guided by the building outlines. >> >> I hope 'my' buildings are a little better that what is described above, >> some of that depends on the imagery, >> some in the pride of workmanship and some on the fatigue of the mapper. >> Certainly any HOT manager who rewards the number of things done should be >> alert to the quality reduction that such motivation brings. >> >> One of the good things about adding addresses .. you notice things like >> the road name is wrong. >> >> >> ___ >> talk mailing list >> talk@openstreetmap.org >> https://lists.openstreetmap.org/listinfo/talk >> > > ___ > talk mailing list > talk@openstreetmap.org > https://lists.openstreetmap.org/listinfo/talk > > ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Why the HOT obsession with low quality buildings in Africa ?
Many humanitarian groups use buildings as a rough proxy for population (density), or to ensure every household is covered during a vaccination campaign, or simply to navigate. Likely they use them for a combination of the three. As Phil says, it’s best to read the specific task. As a side note, it’s helpful to be more specific than the entire continent of Africa, which is a very, very large and diverse place. If you can note individual problematic countries, as Frederic does, it helps us to identify sources of error or verify there was a legitimate humanitarian or community-building reason behind any fall in quality. On Mon, Jul 2, 2018 at 4:16 PM Warin <61sundow...@gmail.com> wrote: > On 02/07/18 18:52, Frederik Ramm wrote: > > > Hi, > > > > On 02.07.2018 10:24, Jean-Marc Liotier wrote: > >> churning out buildings like demented stonemasons trying to reach their > weekly quota > >> of gamified task-managing ! > > I recently stumbled upon > > > > https://www.openstreetmap.org/#map=15/-6.8958/39.1623 > > > > (Tanzania) and had a similar thought. The buildings there are at least > > square and largely match aerial imagery, but this, too, looked like > > supercharged one-trick-pony image tracing combined with very little on > > the ground knowledge (e.g. quite a few roads and tracks clearly visible > > on the imagery are not traced, and from someone local you'd expect the > > occasional POI or label). > > > > Someone must have buildings very high on their priority list (don't even > > know if HOT are involved but it certainly doesn't look like local > mapping). > > > > It will be interesting to learn why buildings are so important. Or are > > they just the lowest-hanging image tracing fruit, or just easier to > count? > > > I have been mapping a few buildings lately - mainly to add addresses to. > Past mappers have placed a few POI ... but they tend not to be too precise > - e.g. between buildings or on the footpath. > Once the building outline is there then you see the discrepancy. And any > further additions of POI can be guided by the building outlines. > > I hope 'my' buildings are a little better that what is described above, > some of that depends on the imagery, > some in the pride of workmanship and some on the fatigue of the mapper. > Certainly any HOT manager who rewards the number of things done should be > alert to the quality reduction that such motivation brings. > > One of the good things about adding addresses .. you notice things like > the road name is wrong. > > > ___ > talk mailing list > talk@openstreetmap.org > https://lists.openstreetmap.org/listinfo/talk > ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Why the HOT obsession with low quality buildings in Africa ?
On 02/07/18 18:52, Frederik Ramm wrote: Hi, On 02.07.2018 10:24, Jean-Marc Liotier wrote: churning out buildings like demented stonemasons trying to reach their weekly quota of gamified task-managing ! I recently stumbled upon https://www.openstreetmap.org/#map=15/-6.8958/39.1623 (Tanzania) and had a similar thought. The buildings there are at least square and largely match aerial imagery, but this, too, looked like supercharged one-trick-pony image tracing combined with very little on the ground knowledge (e.g. quite a few roads and tracks clearly visible on the imagery are not traced, and from someone local you'd expect the occasional POI or label). Someone must have buildings very high on their priority list (don't even know if HOT are involved but it certainly doesn't look like local mapping). It will be interesting to learn why buildings are so important. Or are they just the lowest-hanging image tracing fruit, or just easier to count? I have been mapping a few buildings lately - mainly to add addresses to. Past mappers have placed a few POI ... but they tend not to be too precise - e.g. between buildings or on the footpath. Once the building outline is there then you see the discrepancy. And any further additions of POI can be guided by the building outlines. I hope 'my' buildings are a little better that what is described above, some of that depends on the imagery, some in the pride of workmanship and some on the fatigue of the mapper. Certainly any HOT manager who rewards the number of things done should be alert to the quality reduction that such motivation brings. One of the good things about adding addresses .. you notice things like the road name is wrong. ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Why the HOT obsession with low quality buildings in Africa ?
Hi, On 02.07.2018 10:24, Jean-Marc Liotier wrote: > churning out buildings like demented stonemasons trying to reach their weekly > quota > of gamified task-managing ! I recently stumbled upon https://www.openstreetmap.org/#map=15/-6.8958/39.1623 (Tanzania) and had a similar thought. The buildings there are at least square and largely match aerial imagery, but this, too, looked like supercharged one-trick-pony image tracing combined with very little on the ground knowledge (e.g. quite a few roads and tracks clearly visible on the imagery are not traced, and from someone local you'd expect the occasional POI or label). Someone must have buildings very high on their priority list (don't even know if HOT are involved but it certainly doesn't look like local mapping). It will be interesting to learn why buildings are so important. Or are they just the lowest-hanging image tracing fruit, or just easier to count? Bye Frederik -- Frederik Ramm ## eMail frede...@remote.org ## N49°00'09" E008°23'33" ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
[OSM-talk] Why the HOT obsession with low quality buildings in Africa ?
Active in Senegal and Mali, I have noticed that changesets tagged with tasking-manager HOT projects produce very large numbers of buildings. Those buildings appear to be of very low quality. I wonder: who uses this data ? If it is only necessary to assess that people live there, then a landuse=residential is sufficient If it is necessary to count the number of dwelling units to infer population, then a node is sufficient (maybe along with an attribute to discriminate single or multi-tenancy) If the geometry is actually necessary, then I wonder if anyone is satisfied with those semi-random shapes that, with some optimism, may be identified as being in the vicinity of actual buildings (most of the time) Enthusiastic contributors expend an awful lot of effort in flooding the map with low-quality buildings. I have seen ruins, building parts, walls, vague shadows on the ground, rubbish heaps, market stalls, cars and trucks all tagged as buildings - and I'll charitably keep from commenting on the geometric quality of those that attempt to map actual buildings (and I'll leave aside the issue of HOT leads requiring the use of outdated imagery such as Bing instead of ESRI World in Bamako). Is it the most useful way to channel the energy of inexperienced contributors ? I often find myself wishing that HOT leads introduce them to Openstreetmap through Osmose quality control rather than by churning out buildings like demented stonemasons trying to reach their weekly quota of gamified task-managing ! ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
