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I have a lot of KML files that I created using Google Earth and Google Maps in 2009. These KML represent the boundaries of vine parcels. I created the KML files by drawing the parcel boundaries on the satellite view.

When I was printing the KML file with Google Earth and Google Maps everything was fine in 2009 and in spring 2010. However, now all the KML are not aligned anymore and have an offset of more than 10 meters. You can see an example in the picture :

Did Google change something?

Thanks!

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migrated from superuser.com Oct 4 '10 at 13:33

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3 Answers

up vote 3 down vote accepted

Perhaps tectonic plate shift and/or earthquake activity has moved your land recently. You should get new surveys done!

In all seriousness, yes, they probably did change something. They changed mapping providers for the US, but it's not there maps you are complaining of it's the satelite image alignment. This quite likely got updated, much of their older imagery had alignment problems that have been getting fine tuned as time goes on. It would be interesting to note the difference between google earth's lat/lng coordinates for your parcels and the values on an official land survey. I suspect you will find the updated imagery is much closer.

As for what to do about it, I think you will just have to update your KML files by bulk selecting everything and moving them by some set offset amount and then fine tuning anything beyond that.

Keep in mind how complicated it is to take pictures from space of little things on earth often at oblique angles from a floating platform hurtling through the air, then stitch all the pictures together so they not only match each other but follow the general shape of the land keeping each pixel close to it's real location no matter the elevation ... it's always improving but it's not as an exacting a science as most people assume it is. Even ground based surveys have a lot of work to do to keep in the right place!

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When we get updated satellite imagery for a particular area in Google Maps, we will often get a different offset/alignment for the particular imagery. This is especially true when we get a higher resolution imagery.

You can sometimes see locations in Google Maps where overlapping imagery have different offset/alignment.

I think, it is unlikely to be map projection issue.

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Perhaps they are using a different projection? If you could figure out what projection (or otherwise) was, you could probably run your files through ArcGIS and then export at the new projection system.

You might also try http://gis.stackexchange.com/. (Yes, it is getting ridiculous, I know.)

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