Hello John,
With reference to your moving boulder, just
wondering if that could be in fact moving, i.e.,
not an image based coordinate shift as such. I'm
just thinking that with aftershocks and general
instability, many of these new features are still
sorting themselves out and traveling downhill.
Can DG or Bing make stereo pairs
available? Likely a long shot, but thought I would ask.
Cheers . . . . . . . . Spring Harrison
At 09-05-2015 17:49 Saturday, john o'l wrote:
I've been focusing on landslides and have
located several score that appear recent. Of
these, a few are pre-quake and appear relatively
stable, some are pre-quake but appear
reactivated and many appear to have been
associated with the quake and/or aftershocks.
I've mapped several dozen of these so far. In my
next email, I'll cover why you won't find them
in osm... yet. For this one, I'd like to stick
to post quake imagery and some of its quirks.Â
There is an inhabited hillside that had numerous
landslides, some predate the quake, but most are
presumably related. So far I've mapped about
half of them, those that are largest or appear
to threaten buildings and pathways. There is
Digital Globe imagery available from May 3 and
May 8. It looks like QGIS easily operates with
more than one coordinate system at a time. The
center of a large boulder in the May 3 imagery
(Longitude, Latitude; WGS84 EPSG:3857 x,y) is at
85.85659,27.83609;9557511.789,3228324.329, in
the May 8 imagery it is at
85.85669,27.83656;9557522.728,3228382.865. Mind
you, this is not a complaint, rather it is a
concrete example of the variability with this recent imagery. Â
A more extreme example is a slide that appeared
to be partially blocking a stream in the May 3
imagery
85.90258,27.87818;9562631.312,3233623.303; -- it
was completely obscured by a hillside in the May
8 imagery (probably taken from a more northerly
or northwesterly vantage point.)Â
Downslope (westward) from a likely reactivated
slide located at
85.81987,27.90810;9553423.739,3237391.771 Â is a
remote area that appears very hard hit. The May
8th imagery is mostly clouds, but the May 3rd
imagery shows a blue rooftop at
85.80644,27.90818;9551929.301,3237402.414, it
looks like there are several large boulders in
the immediate area and there is not much left to
tell there were more than 20 buildings nearby.
While the boulders may have contributed, at the
moment I think it is probable that the shaking
itself was mostly responsible for the extreme level of destruction.Â
One advantage of different acquisition angles is
that some features may be discernible on slopes
that don't ordinarily show up very well.Â
Â
Question to the HOT folks -- is there a way to
specify the date of DG imagery we access through
the proxy server?, Some of the May 8 imagery is
starting to come up over the May 3 imagery without me telling it to. Â
Best regards,
John
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