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

Paul Norman penorman at mac.com
Fri Jan 3 22:19:58 UTC 2014


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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