On Thursday, August 05, 2010 06:32:04 pm you wrote: > On Thu, Aug 5, 2010 at 6:10 PM, James U <[email protected]> wrote: > > I have to say that after importing a large amount of NHD data (most of NC > > and MN) that it is of varying quality, as was the preexisting water > > related data already on the server. In general, I agree with Ian that > > it is higher quality (both resolution and accuracy) than the preexisting > > data that largely consisted of quickly drawn Yahoo traces. I saw very > > little evidence of on the ground surveying of these features and don't > > think the import will hinder most people from participating in OSM writ > > large. > > On the other hand, my (extremely limited) experience is that the > aerial water traces for Disney World were superior to the NHD import > (so I quickly deleted all the dupes from NHD). But the swamps were a > lot more useful, since you can't really tell if something's swampy > without physically going there. I love how all these "islands" > suddenly made sense: > http://www.openstreetmap.org/?lat=28.29&lon=-81.5191&zoom=14&layers=M
You are certainly correct that there are many examples of other imported waterbodies and streams that _are_ better than NHD, this is why I strongly recommend that importers of the data do a careful scan of the data and when there are duplicate features to try to use a high quality aerial photo to make a judgment of which is the better data. For some features, such as multipolygon lakes with islands, I have mixed and matched different parts of the NHD and the previously uploaded feature (sometimes you can tell where mappers got tired of tracing). In some cases, for example in dams where water levels fluctuate and aerial photos might represent a low water phase, the NHD may have better data that are representative of the level that the reservoir is maintained at. _______________________________________________ Talk-us mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk-us
