When Autodesk first introduced the Set Location tool (on the Insert tab) in 2016 we briefly experimented with it, thought it to be confusing at best and ignored it. It was a couple years later when someone sent us a drawing started this way that we determined it to be dangerous at the least.
The user was evaluating one of our add-ons and was reporting that our tool was generating bad results. Naturally it was time to dig deep to find out what was going on. We quickly determined that while they had a drawing with a coordinate system defined as reported by the system variable (and other checks).
Command: CGEOCS
However, an examination of the world coordinates (no UCS active) showed tiny values that were outside of the usable range of the system, we knew something else was wrong. After all, every predefined coordinate system has a well established range of valid coordinates (usually in the thousands) and numbers outside that rectangle are simply invalid, and these certainly were invalid.
Introducing the Voodoo (borrowed term): The unusual thing was that AutoCAD’s coordinate display on the status bar (set to geographic) was reporting latitude and longitude values that were in the neighborhood of being correct and the Bing images underneath appeared to be aerial mapping correct for that location.
So at that point we informed the evaluator that their existing drawing was UNUSABLE and that we couldn’t help them recover all the location work (picking points on the aerial) because the coordinates were all approximate and most importantly, wrong.
Making our own Voodoo: So we decided to try to reproduce this problem and were shocked how easy it was to create GeoGarbage (new coined term). We opened a drawing of an ortho house perimeter (in architectural units inches) with an origin near 0,0,0 and clicked on the Insert tab, Location panel, Set Location drop-down, From Map.
At this point I’m forced to sign in. I have to assume this is required because they pay Microsoft for the Bing maps based on the amount used. We typed in the street address in the field at the top, aerial images appeared. We zoomed in tightly in the view and chose [Drop Marker Here] moving the pin to the center of the house. Approximate lat/long values show at the bottom of the dialog. We chose the [Next] button.
Pretending not to know coordinate systems, we chose a coordinate system that “sounded” right. The system on the dialog said feet but the time zone was wrong and most importantly the drawing unit at the bottom said “Meters”. Playing along, we chose [Next]. It asks me for a point at that location, I pick the approximate center of the house. Then it asks me for a north direction angle, I pick an approximate direction. At this point I’m flooded with Bing images and my location looks right. I right click the coordinate display on the status bar and choose “Geographic” and the lat/long shown is approximate.
The Problem with Voodoo: True mapping simply DOES NOT work that way, you cannot pick a point in a drawing, throw in a lat/long and expect to be georeferenced. While AutoCAD may force the Bing images to follow along you will NEVER be able to merge additional data that is on the proper coordinates nor will you ever be able to export your content to a format like Google Earth. If you send your drawing to true mapping professionals they will inform you that it is unusable, so better hope they were not your (now former) clients you were expecting to pay you.
In true mapping everything added to the drawing comes in at TRUE coordinates for the assigned system (like state plane or UTM, etc). You DON”T GET TO CHOOSE your coordinates, they are what they are based on the system. If you don’t know what you’re doing, enlist the help of a professional surveyor or geodesist.
Reinforcing Statements: If you don’t believe us, take a look at this Autodesk Forum Post on the topic. Pay close attention to posts 2, 6 through 9 where other mapping professionals will confirm that the AutoCAD Geolocation (from Map) tool has problems!
The Bright Side: All other Autodesk projection related tools DO NOT have this problem. The projection related tools in AutoCAD Map3D and Civil3D are solid and accurate. Using the ADESETCRDSYS command in Map3D, or the Assign Drawing System in Civil3D’s ToolSpace > Settings is great, as long as your drawing is on the proper coordinates of the system you are assigning. Also, the underlying projection engine and it’s API (first introduced in version 2014 and finished in version 2015) is solid and accurate. We have done numerous cross checks using other tools (like GDAL) and confirmed matches within tiny decimal variances.