[Talk-us] Comparing Tiger 2017 dataset with OSM in a automatedway.

Nathan Mills nathan at nwacg.net
Thu Oct 26 21:12:28 UTC 2017


The tree cover issue is precisely why many states that have seasons have a recurrent leaf-off (sometimes even in IR) imaging program. 

Arkansas has their imagery, along with a raft of other open data, available on Geostor as a WMS service that should be usable in JOSM and also as downloadable data in your choice of extent and format. Oklahoma's is also available somewhere, but I'm not sure where. They lack a statewide data repository, so their data is scattered about various state and university sites.

I know the wiki has a list of imagery sources, but I don't think it has any listed specifically as leaf off. Maybe someday I'll find some time to compile one.

-Nathan


On October 26, 2017 1:00:05 PM EDT, OSM Volunteer stevea <steveaOSM at softworkers.com> wrote:
>I don't know where all of this is going, and wanted to see for myself,
>so I downloaded the California file (the largest one of all) and zoomed
>in on where I live and am most familiar with, Santa Cruz County.  Thank
>you for providing the ten states worth of translated data for us to
>take a look.
>
>What I found was, um, "interesting."  In urban areas, there were indeed
>a few highway=service, service=alley ways which Bing confirms are
>either there, mostly there, or "almost there," as in "slightly offset
>by a meter or three."  However, many of these were also clearly
>service=driveway instead of alley, a subtle distinction, but a crucial
>one, in my opinion (driveway implies access=private).  In more rural
>areas (and by no means is this a hard-and-fast delineation), there were
>many similar entries, but tree cover (2/3 of my county) made these
>impossible to distinguish via Bing.  Also, many had a name= tag with an
>empty value.  I'd rather that simply be no name tag at all, so that
>should be an easy improvement to make in any future/additional
>translations.
>
>There are literally thousands of these in my little county (2nd
>smallest geographically in the state) and it would take many hours
>(days) to go through them one by one and Bing compare, which certainly
>would improve OSM's data here.  (I've done similar tedious visual
>comparisons for thousands of polygons and TIGER review before, it is a
>labor of love!)  However, much or even most of these data would need an
>on-the-ground verification, simply because aerial/satellite data,
>whether fresh or not, have too much tree cover to allow such armchair
>mapping.  And, most of these additional data are very likely in highly
>rural areas which are not only difficult to get to, but are obviously
>on private property and (as is very typical around here on those)
>behind gates or "No Trespassing" signs (which I respect).
>
>So, while I find these a potentially rich source of new and/or better
>additional data, it is with great tedium and difficulty that they might
>be vetted/verified in a proper OSM way (cursory, via Bing, and/or fully
>and correctly, "on the ground").  I'm delighted the exercise to
>translate them into an easily-usable-by-OSM way has taken place, but it
>is with a great deal of caution and indeed trepidation that I approach
>and/or allow any new TIGER dataset "easy entry" into our map.
>
>In short:  eyes very wide open, slow going (if any going at all) ahead.
>If your state is included in the list, and you can zoom into your
>county or city, I'd be curious to hear what others might say after they
>take the half-hour or so I did to look and offer similar impressions of
>these data.
>
>SteveA
>California
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-- 
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