"Jóhannes Birgir Jensson" <[email protected]> writes: > Well the current issue in Iceland is a error of 50 cm between 1993 and > 2016 due to crust movements. So it's less than 2 meters but more than > one cm.
That's interesting and a useful data point for later discussion about the points that my message said this discussino isn't about! > What is your accuracy limit if 2m is just unacceptable but a > centimeter is? There are several issues that must be addressed over time for improved accuracy. I am not claiming that any particular accuracy is required and I am very definitely NOT suggesting that OSM adopt accuracy requirements for data. I am not following where "1 cm" came from in this discussion and don't think it is relevant. (I do think that asking the question of how to get to 1 cm eventually is interesting, but I see that as a separate issue.) My point is that our current definition of "WGS84" has ~2m of fuzz *intrinsic to the definition* because (as discussed at length on the proj list) saying "WGS84" means "these coordinates are in one of six datums and I am not telling you which". There is no need for OSM to have this definitional uncertainty, and I think that is both the biggest issue and the easiest to address. Regardless of the definition, it is clear that there will be data of varying accuracy in OSM. I am not objecting to that reality, or asking that OSM adopt accuracy standards. There seems to be a shared norm that more accurate locations of nodes are preferred to less accurate locations. I think there's also a shared belief that wildly inaccurate nodes are not helpful; if I added a POI that was 10 km off (in an area where there are many things between the mapped location and the real location), then that is probably a bad thing to have done. But if I add a POI that is 100m off, someone might fix it, but I don't expect they would tell me that I should not have added it. Certainly this is true at 10m error (the lack of outrage; it might or might not get improved). So about the narrow issue of the definition of OSM's coordinate system, do you prefer leaving it defined as "WGS84", so that coordinates have to be treated as having an intrinsic uncertainty of several meters changing it to "WGS84, and in particular the revision currently in use by GPS", allowing one to treat the datum as relatively precise and thus only question the accuracy of the coordinates themselves? something else? Note that the second option allows one to transform e.g. precise coordinates from a geodetic control point to add to OSM. (Yes, I realize one could transform to a particular realization anyway.) In all seriousness, I cannot tell if you object to this first step, or are making comments about some later step that might happen, or at talking about the issues of OSM perhaps adopting accuracy requirements (not on the table!0, or something else. _______________________________________________ talk mailing list [email protected] https://lists.openstreetmap.org/listinfo/talk
