Globelink Issues - Unwanted Scaling

[barrie.sharp]

I have imported a location from google earth. I have measured between two landmarks and get a different reading for both (Revit:220m, Google:197m). The google measurements seem to tie up with site surveys which means the import is getting scaled up in Revit. This is a bit of a problem since I'm using google to do a rough site map. :(

Also, I tried publishing to google and the plugin says that I need google earth installed... I have:?

It acquires ok!

[barrie.sharp]

I have attached an example showing a footprint from a measured survey overlayed on the imported google image. As you can see, they don't match up. Within google earth, the rooftop meaures 20m × 12.5m which corresponds with the size of the footprint.

So why is my google image in revit larger than it should be? Can anyone recreate these results?

I have always found google to be very reliable for measurements, it would be a shame if revit can't match scales.

[emily.clark]

Barrie,

This is a know issue with Autodesk and they are currently working on this issue. Here is the reasons this is happening.

The difference is caused by the tolerance during transforming Google Earth data into the Revit coordinate system. Google Earth works on a globular curved system, whereas the Revit system is based on flat coordinates.

When the data is translated into Revit, the piece of the curved surface is stretched into a plane in Revit. To maximize the accuracy, it is recommended to zoom as far into Google Earth before acquiring the data.

Another workaround in Revit is to ungroup the image group created during acquiring. You can adjust the image to be exactly the correct size, based on a measurement line in Google Earth if needed.

The development team is currently reviewing more recent versions of Google Earth to see where the map data acquirement or API can be improved upon.

Regards,
Emily Clark
Ideate Technical Support Team

[barrie.sharp]

That's a fantastic explanation! Thanks. Is there a site or blog to track the progress of developments?