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Georeferencing - Block Insert Scale

Question asked by geonetadmin on Jul 25, 2012
Original User: gknight


I am trying to georeference some floor plans using ArcGIS for AutoCAD.  I am running AutoCAD 2012 x64 with ArcGIS for AutoCAD 300.  The floor plans are drawn in architectural units where one unit equals one inch. 

When I use a local map service with a state plane (ft) coordinate system (2249) - the drawing scales correctly with an insert factor of 0.08333333 (inches to feet). 

When I use an ArcGIS Online map service (meters) with the web merc coordinate system (102100), the drawing does not scale correctly with an insert factor of 0.0254 (inches to meters). See attachments for results in each case.

Once the drawing is properly georeferenced using either a local or online basemap, i will write out a world file so the cad files can be converted and projected on the fly (in ArcMAP for example) from their native coordinates.  The inconsistency in georeferencing with  ArcGIS Online basemaps is problematic. 

Any ideas what might be going on here?

Many thanks,