[OSM-dev] Assembling imagery: to mosaic or not

[Peter Wendorff]

Hi Paul,
IMHO for osm editing purposes multiple distinct sources are better.
The first reason is to give a proper source tag, the second one to check
for updates only where necessary when one source imagery set changes.
On top of that continuity breaks in the imagery IMHO it should be clear
for the mapper that this is due to different image sets, image dates and
so on.

regards
Peter
(mapping from imagery sometimes but not hosting any)

Am 03.01.2014 23:19, schrieb Paul Norman:
> I host various sources of imagery for the benefit of local users. One 
> fairly typical scenario is where I have two sources of imagery covering 
> an area. Although I create layers for each source, I'm not sure what to 
> best put as a source for the list in the editors. The two options are to 
> add a number of discrete sources, or to add a layer mosaicking them 
> together, and displaying what the best source is at any one point. 
> 
> One mosaic
> - Does not requires users to switch between layers at edges
> - Technically more difficult to implement
> - More fine-grained control over what layer is default when all the 
>   sources are better than Bing, but doesn't work as well when some 
>   sources are better and others are worse
> 
> Multiple sources
> - Requires users to load up more imagery sources to view the area, and 
>   when coverage overlaps to load the sources in the right order so the 
>   better sources appear on top
> - Requires no additional work to implement
> - Setting what layer is default does not work well for overlapping 
>   sources where both sources are better than Bing
> 
> I'd like the thoughts of others, particularly those who host imagery for 
> editors where they have overlapping sources 
> 
> I am currently leaning towards setting up a mosaic of the 8-12 sources. 
> These include:
> 	
> - Latest available Landsat8 (~3-6 months old, given BC clouds), 15m/px
> - 2013 Surrey imagery, 10cm/px
> - 2010 Surrey imagery (covers some blanks in 2013), 10cm/px
> - 2012 Vancouver imagery, 10cm/px
> - 2012 Kelowna imagery, 10cm/px
> - 2012 Nanaimo imagery, 10cm/px	
> - 2009 Nanaimo imagery, 30cm/px
> - 2009 DataBC GVRD West imagery, 10cm/px
> - 2009 DataBC GVRD East imagery, 20cm/px
> 
> 
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