[OSM-talk] New tool: Generate coastlines from Landsat imagery

Darryl Shpak darryl at shpak.ca
Sat Aug 4 14:14:57 BST 2007


Alex L. Mauer wrote:
> Darryl Shpak wrote:
>   
>> Hi all,
>>
>> I've just checked in Lakewalker...
>> If you have questions or suggestions, feel free to email me directly or 
>> look for me on #osm.
>>     
>
> Very nice.  I only noticed one problem with it, aside from the inherent
> inaccuracy of the landsat images: It tends to create what the validator
> plugin for josm sees as duplicate nodes and segments.  That is, it will
> create a node, then a segment to another node, and then a segment to a
> third node at the exact same location as the first node.
>
> I don't know how feasible that is to fix though.
>   
I'm aware of this. It normally happens when the tracer returns along the 
same path it traveled before. I think I can solve it by nudging every 
node a small amount to the left. It actually doesn't cause any serious 
problems with the renderers, but it would be nice ti fix.
> One other thing is that at least in my area, the yahoo imagery seems to
> be much more accurate.  Would it be feasible to have it use that
> imagery, or does the color add too much complexity?
>   
Color is feasible (I'm using it for another Landsat-imagery tool that 
I'm writing), though it has a few problems: water can be blue, green, or 
brown, depending on where you are, and clouds get in the way (the IR 
imagery sees through them). However, as Joerg Osterstag pointed out, the 
license could be a problem...the way I understand the license, this 
wouldn't be permitted.
> Thanks
>
> -Alex Mauer "hawke"
>   
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