[Talk-us] mapRe: (Second attempt) Potential data source: Adirondack Park Freshwater Wetlands

Adam Franco adamfranco at gmail.com
Sat Mar 26 20:22:36 UTC 2016


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 <kkenny2 at nycap.rr.com> 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
>
>
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