[Talk-us] USGS Large-Scale Imagery degraded this month :(
david.t.kewley at gmail.com
Sun Dec 18 19:43:46 UTC 2016
For a lot of my satellite imagery tracing, I've found it very useful to go
back and forth between Bing and USGS Large-Scale Imagery, which provides at
least 1-m resolution across the U.S., and in some areas (e.g. urban areas)
provides nice 1-foot resolution orthoimagery that aligns very well in my
local area with Bing imagery.
Well, I should say "provided", past tense. For the past couple of weeks or
so, I've noticed that the the USGS LSI has seemed to degrade in many of my
local imagery tiles, and I've finally looked into why that might be so.
For example, at this location, today (current state of imagery tile
caching, perhaps mostly local to me?)
when using USGS LSI, I see the NE, NW, and SW imagery tiles look fine, but
the SE tile is much lower quality, clearly from a different set of imagery.
I could swear this area was formerly seamless with the good imagery.
It looks like this month's degradation is probably a downstream effect of
Before USGS made this change, I saw identical imagery if I used iD's
built-in USGS LSI, versus using the following setting in Custom imagery in
The OSM built-in USGS LSI was faster than this custom link, I believe
because the custom link is dynamic (not cached by whoots), and it takes two
round trips, a lookup by iD to whoots, then by whoots to USGS, and probably
a dynamic conversion by whoots. I'm not an expert in this, so could easily
have some of this wrong.
USGS LSI seemed faster -- perhaps it was static on the backend, or cached
better or something. The OSM built-in USGS LSI imagery appears to be served
by openstreetmap.us, though I know none of the details of how it's served.
Anyway now per the above announcement link, the *USGS_EROS_Ortho* URL is
deprecated, and is no longer served, and it seems like the following whoots
dynamic lookup imagery is the appropriate one, based on the
USGS-recommended replacement for the deprecated imagery:
Indeed when I use this in the Custom imagery setting in iD, I see the same
degraded imagery that the built-in USGS LSI setting now gives me.
Can anyone shed further light or corrections on any of this? Any idea
whether it's technically possible and legally permissible to have
openstreetmap.us serve the older, better USGS LSI instead of the newer,
worse stuff? If so, upon further discussion I'd probably support such a
move, and possibly even offer to help with the conversion. :)
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