[Talk-us] scanned USGS Topo Layer?

[Richard Welty]

On 12/2/13 9:51 AM, Ian Dees wrote:
> The "USGS Scanned Topos" layer is a cached layer based on the three
> layers here:
>
> http://raster.nationalmap.gov/ArcGIS/rest/services/DRG/TNM_Digital_Raster_Graphics/MapServer
>
> I don't see a good way to check metadata for the scanned quads.
> There's information about the "Large Scale Imagery" layer, but not the
> scanned topos.
>
it'd be good to try to figure a way out to do that, although
i realize it may not be feasible. the problem is that when
you're looking at a quad and you don't know the age of
the data, it's hard to assess it's value vs other data you may
have in front of you.

i currently have the 2003 GPS traces the ATC supplies for the
Appalachian Trail north of Salisbury, CT which differ from
what the USGS quad layer shows. it is almost certainly the case
that the USGS quad is out of date by decades and the ATC data
represents the current trail routing, but i'd love to eliminate
that 1% of doubt.

i guess what it comes down to is that the USGS quads are good
for topo data but otherwise they're basically historic documents.

richard

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