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Thursday, January 17, 2008

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Andrew Turner

This can be done using Mapstraction or the GTileLayerOverlay function to have a dual overlay very easily.

In fact, here is a demo doing just that:
http://mapsomething.com/demo/mapstraction/china.html

Another option would be to check out OpenStreetMap and perhaps even OpenAerialMap with OpenLayers for some nice OpenData and Open Software options.

You can then bring in a GeoRSS or KML overlay of important markers:
http://mapufacture.com/maps/1426-LocWeb-2-8-Conference-in-Beijing


Andrew Turner

Here is a map done with OpenStreetMap, free satellite imagery from OpenAerialMap servers and OpenLayers.

http://mapsomething.com/demo/mapstraction/china_osm.html

dret

thanks andrew! that's really cool! i don't want to criticize your work here, but when i zoom in on http://mapsomething.com/demo/mapstraction/china.html, then the map and the satellite images are a bit off, i would say 100m or so (north/south, it is a bit more in west/east direction). the map-based freeway runs right through the satellite-based conference center ;-)

http://mapsomething.com/demo/mapstraction/china_osm.html looks interesting as well, but the quality of the satellite images and the maps is far inferior to the google dataset. again, that's of course easy to say, and thanks again for pointing to that alternative source of geolocation information!

and as mentioned on http://highearthorbit.com/using-google-ditu-maps-with-satellite-imagery-for-china/, you of course get the full bonus points for adding my information from my locweb2008 map at http://tinyurl.com/2xu9zo!

Andrew Turner

You bring up an interesting issue with differences in projections. The "offset" is a result of Google's tiling scheme or rendering. Perhaps this is another reason why they don't have Satellite imagery on their Ditu site.

I recently heard a similar issue arose in Google Earth, where recent satellite imagery is offset from previous releases. Therefore anyone that geolocated their models or markers using Google Earth in certain areas will now find them offset.

As 'neogeography', or ubiquitous geographic tools become more popular, and you run into issues like this with non-expert users they'll be confused. Not an easy problem to solve :)

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