[HOT] landslides and imagery

Prabhas Pokharel prabhas.pokharel at gmail.com
Mon May 11 14:10:40 UTC 2015


Another email to add to the list for those interested in doing landslide
mapping:
We at KLL were forwarded this landslide risk assessment layer:
https://www.google.com/maps/d/u/0/viewer?mid=z6HUO2aILzmQ.kGtOdlu45GXY&usp=sharing
which comes from here:
https://sites.google.com/a/umich.edu/nepalearthquake/landslide-maps

It may help those of us interested in finding lanslides have some areas of
high risk where they could start looking.

cheers,
Prabhas

On Sun, May 10, 2015 at 11:50 AM, Springfield Harrison <stellargps at gmail.com
> wrote:

> 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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>>
>
>
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-- 
Prabhas Pokharel
http://prabhasp.com
twitter/skype/facebook/whatever: prabhasp
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