[josm-dev] [Talk-us] Poor JOSM Yahoo imagery solution?

[andrzej zaborowski]

2009/11/24 Frederik Ramm <frederik at remote.org>:
> Alan Mintz wrote:
>> Is anyone working on a solution to the poor Yahoo image quality in JOSM
>> (compared with Potlatch, browser, etc.)? This pic shows the striking diff
>> between the same area at the same scale in JOSM and in Potlatch:
>> http://sites.google.com/site/am909geo/osm-1/BadYahooImagery.jpg?attredirects=0
>
> Interesting. When I call up this area in JOSM, or indeed using any
> standard "Yahoo Map API" example, the image URLs that are retrieved look
> like this:
>
> http://maps1.yimg.com/ae/ximg?v=1.9&t=a&s=256&x=22784&y=13251&z=1
>
> That's the best zoom it gives you (z=1, smaller being better). So JOSM
> plays according to the rules of the Javascript API. However using
> Potlatch, which presumably uses a Flash API, the map tiles requested
> look like this:
>
> http://us.maps3.yimg.com//aerial.maps.yimg.com/img?md=1204827325&x=45569&y=26502&z=19&r=1&v=1.7&t=a
>
> and have a better resolution - z=19, higher being better in this scheme.
>
> The key to fixing this in JOSM would be finding a way to get the
> high-res imagery through the Javascript interface. So if anyone would
> manage to modify any of the examples on
>
> http://developer.yahoo.com/maps/ajax/
>
> to actually give you the high-res image then we could use that knowledge
> to improve JOSM. (I'm cc'ing this to the JOSM-dev list.) - We are not
> allowed to cheat our way out of the Javascript API, sadly, which means
> we cannot retrieve the tiles directly even if we knew how to.

I have heard on IRC that Potlatch bends the API slightly to get these
images.  However, the only area Yahoo has better resolution than z=1
is the US where the imager comes from another source (calles USGS I
think) that can be used as a WMS directly so there's little gain from
being able to get it through Yahoo.

Regards