[HOT] #1915 - Sri Lanka Floods: Eastern Kelani River Basin instruction contradiction

Russell Deffner russell.deffner at hotosm.org
Mon May 23 13:32:51 UTC 2016

Hi Alan,


Yes, sorry – hard to write this short and sweet.


Basically east of Ambulgama both Bing and Mapbox imagery source ‘changes’; in particular the ‘hi-res’ tiles of Mapbox (i.e. beyond zoom level 17) is not available.


So, you’ll be able to see the buildings better in Bing. So I’ve been accomplishing tracing by either just leaving Bing as is, trace the buildings, then switch to Mapbox and drag them to line-up, as we’ve still checked and although the offset is ‘less’ between Bing and Mapbox, Mapbox is still in better alignment.


Another ‘fancier’ way to do this is check to see if the roads are lined up with the Mapbox imagery, if so, you can adjust the Bing Imagery first, then trace off that and you’ll be all lined up.


But Mapbox is also more recent imagery, so there might be new construction.


In other words, you really should be using both imagery sources for this area to ‘get the best picture’.




From: Alan Bragg [mailto:alan.d.bragg at gmail.com] 
Sent: Monday, May 23, 2016 7:11 AM
To: hot at openstreetmap.org
Subject: [HOT] #1915 - Sri Lanka Floods: Eastern Kelani River Basin instruction contradiction


​I'm afraid I don't understand the instructions for task #1915.


 "Either use Bing to trace features and then align it with Mapbox or use Mapbox to trace and then align it with Bing imagery.​"


The second half of the above sentence seems to be the exact opposite of the first half.

Can someone please clarify. 


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