On Tue, July 3, 2018 3:56 pm, mohamet lamine Ndiaye wrote: > I am Mohamet Lamine Ndiaye [..]
Nangadef, I'm happy to hear from you - it has been a long time ! > [..] I think this is the umpteenth time we talk about it Yes, this is a pet issue of mine - I hope that one day I'll understand why you all seem to put so much time and energy into those buildings that I'm not happy about... But hopefully they make other people happy ! > [..] However, it should be noted that in terms of the quality of the > images and the density of the mapping areas, the contributors find it > difficult to distinguish the actual boundaries of the Buildings Yes - and distinguishing between building parts and the whole buildings is a challenge for even the keenest eye. > [..] Nevertheless, this does not preclude the use of these data in > large-scale and highly resilient projects for the populations. Do you have examples of use of that data ? That would help me understand the benefits of mapping buildings even if they are approximate. > [..] Other things, you should know that there are neighborhoods that do > not benefit from subdivision and non-harmonized architecture of some lots > do not promote aesthetics. Indeed, the less orthogonal parts of town are a great challenge. Odette (who is currently doing an internship at my company) told me about her experience updating the cadastre in Ngor - it was a nightmare and they had excellent drone imagery... So for an Openstreetmap contributor with only orbital imagery it is simply impossible to do right - which is why I wonder: instead of that herculean effort, why not settle for a simpler model that provides the same data at a granularity closer to what our resources let us record with adequate quality ? > [..] What is important for me is that we have to start with something > and although these data are of inferior quality, they respond to > operational needs on the ground in case of disaster A landuse=residential with residential=* (currently values of residential=* are mostly "rural" and "urban" but a finer-grained nomenclature could be designed such as "sparse single family", "dense single family", "sparse urban", "dense urban") would provide approximate population impact calculations at a fraction of the effort and without the side effect of producing low quality buildings. Of course, buildings offer much better precision - but only if they are actually precise: if a building is mapped as two rectangles and the two sheds in the courtyard are also mapped as generic buildings, is the result less precise than the surfacic approximation ? Sure, quite a few contributors do excellent work - but there is currently not enough of them available to perform the huge task with high precision everywhere. > if we have data released by the cadastre If you ever get your hands on that, I will be mightily impressed by your advocacy work... So far I failed at getting even a simple list of street references so I find difficult to imagine the day when Senegalese and Malian government agencies will release cadastre and geodesic network. I'm glad that you remain optimist... And after all, before French contributors got their hands on IGN orthophotography and vector cadastre, many of us (including me) didn't think it was possible - and then it happened thanks to the efforts of the optimists and stubborn among us ! _______________________________________________ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
