Kevin, as a Vermont resident who is planning several canoe and hiking trips to the Adirondacks (with data collection for OSM), I look forward to having this import as context. Especially when exploring the Saint Regis canoe wilderness, which has a few lakes in OSM, but is otherwise pretty devoid of any sort of detail. Thanks for doing this work!
Best, Adam On Sat, Mar 26, 2016 at 9:58 AM, Kevin Kenny <[email protected]> wrote: > On 03/26/2016 02:06 AM, Russ Nelson wrote: > >> Frederik Ramm writes: >> > I have zero knowledge about the Adirondack[s] >> >> I live here. Imagine a park half the size of Austria, with about 130K >> people living in it, and 200K people visiting it. Give about 30K of >> those people Internet access. Oh, and there are practically no nerds >> living in the park, because there are no high-tech jobs. >> >> It's unlikely that anybody will do much in the Adirondacks whether >> there's an import or not. If there's an import, at least there will be >> something. Something is better than nothing, because at least it's >> less wrong. >> >> Just do the import, Kevin. >> >> I do see an emerging consensus here, and Frederik (to whose opinion I > ordinarily defer) appears to be something of an outlier. I do plan to > go ahead with this, with appropriate warnings, wikification, and a > quick request to the APA's GIS coordinator to confirm that we have > permission to import (we do already, but I want to get the specific > plan blessed). > > It may be some time in coming. Those who know me know that I'm pretty > obsessive about data quality. This job is extremely likely to be a > three-way conflation: what's already there (which, it appears, is > mostly a 'lakes and ponds' file that you imported), the APA data set, > and NHD. Each source has its unique properties. > > What's already there has all the tagging that mappers have done - and > must not be damaged! Nevertheless, there simply is not much in OSM for > the Adirondacks. I'm really working with a big blank spot in the map > here! > > NED has the greatest detail (it was digitized at 1:24000 scale or > finer, for the most part) and has the GNIS names of features. It also > has feature classes that nothing else has, such as rapids, artificial > shorelines, flumes, and so on. Its chief drawback is that there are > objects that are unaccountably missing, in such a way that I suspect a > database glitch happened at the USGS. For instance, the Cedar River > Flow, a fairly sizable lake impounded by the Wakely Dam, is not in > NHD - but the river becomes an 'artificial path' there, which is > typically a flow line drawn through an area feature to keep the flow > lines contiguous. > > The wetlands inventory lacks feature names, and is less detailed (it > was digitized from orthophotos at 1:40000 scale), but has many ponds > and streams that NHD misses. It also has the intermittent or ephemeral > water limits of many waterbodies. In the Adirondacks, these are > important to a hiker. Many trails go through beaver meadows. In years > when the beavers are in residence, the trails may be underwater, and > the hiker must find a route around the pond. Having the high-water > extent mapped is valuable information. The streams that it identifies, > in the few places that I've checked, are there in the field. Alas, it > does not have flowline topology, so conflation with NHD will need a > little bit of patching. > > One bright spot is that the three data sets are well aligned (once the > differences in datum are accounted for). A simple collision check > identifies areal features to conflate. There may be a tiny bit of > manual work for a few places (Indian Lake/Lewey Lake; Long Lake/Park > Lake; Kiwassa Lake/Oseetah Lake/Lake Flower, and so on) where the > boundaries between lakes are indefinite, in that you can take a canoe > from one to another without noticing that you are on a 'different' > lake. > > I'm still working on appropriate heuristics for conflating the linear > features (flowlines, mostly). Again, I have the advantage that there > is very little already in OSM to collide with - at most a few dozen > rivers. What may turn out to be easiest is simply to lift the tags off > the OSM features and apply them to the NHD ones. > > Then there's the area surrounding Duck Hole, which was permanently > changed in Hurricanes Irene and Lee. Now that there is a few years' > worth of orthophoto data available in all seasons, I think the best > thing we could do there is to trace the shoreline from the orthophotos > and add notes that our data reflect the shoreline and river channel > from after the failure of the dam. > > Whatever I do, I plan to leave the features in OSM tagged with enough > information to identify data provenance. This would mean, at the very > least, NHD reachcode and permanent ID, APA object ID, and NWI label, > where these are known, together, of course, with whatever tagging is > present on the features that are already there. > > It would be good to point out that even the 'authoritative' data for > this part of the country is far from the standard that is usually > expected in the developed world. There are even a fair number of > county lines in the Adirondacks that have never been surveyed on the > ground and are marked as 'INDEFINITE BDY.' on the topo maps. > > -- > 73 de ke9tv/2, Kevin > > > _______________________________________________ > Talk-us mailing list > [email protected] > https://lists.openstreetmap.org/listinfo/talk-us >
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