Data is shown in wrong location in a GIS software when exported from AutoCAD Map 3D using command Mapexport

[boriskosic]

Hello,

I using using the mapexport function to export the data from AutoCad MAP 3d 2024 to KML or MIF file. When I check the coordinates in the Autocad MAP 3d the coordinates are OK but if I do export and then import KML into Google Earth the location is displaced. 

I am using the coordinate system Hong Kong Grid 1980 in AutoCad MAP 3d and for export I convert coordinates to LL84. The drawing is Hong Kong (AUtoCAD MAP 3D) but in the Google Earth is placed somewhere in Thailand. If I check the coordinates in the exported *.kml file  they are wrong.

I have already followed the instructions on this page: https://www.autodesk.com/support/technical/article/caas/sfdcarticles/sfdcarticles/KML-file-is-shown-... 

This instructions didn't helped. Any other idea what could be wrong ? 

Thank you!

[ChicagoLooper]

<<The two most common reasons export procedures fail are (a) the source drawing isn't properly georeferenced and (b) you have assigned an inappropriate coordinate system to your drawing's modelspace.>>

Hi @boriskosic 

To effectively troubleshoot your issues, do these two things:

1. Turn on Bing Hybrid Map in your drawing. If your drawing is georeferenced correctly, then Bing imagery will be consistent with your linework. If the imagery is not, then your drawing is not properly georeferenced and you must take corrective action. 
2. Take screenshots of the 3 tabs named Selection, Data and Options of the MAPEXPORT procedure so your export settings can be analyzed. Upload those screenshots so the forum can evaluate them.

[Pointdump]

Hi Boris,
Welcome to the Autodesk Forums.
More details please. What data are you using? Which coordinate system are you using? In MAPEXPORT what format are you saving?
Dave

[ChicagoLooper]

Hi @boriskosic 

Make sure your drawing is in WCS (World Coordinate System) before you perform MAPEXPORT. If it's not, your exported output will NOT be geospatially accurate.

An easy way to determine whether you're in WCS is to look at your UCS icon in lower left corner. If there's a square then you're in the WCS system. If the square is missing, you'll need to put your drawing in WCS before MapExport. Once you've completed the export you may return to your Customized User Coordinate System. 

Examples:

1. This drawing is in WCS.

2. This drawing is NOT in WCS.

3. This drawing is in WCS.

[boriskosic]

Hi @ChicagoLooper and @Pointdump ,

thanks for the quick reply. I am a beginner with the any maybe I am just missing some step. I've got the *.dwg from the customer  (since it is confidential I sadly can share the *.dwg file ) even if it would be easier to show my issue. 

@ChicagoLooper - please find the attached screenshots and the answer to first question below:

If I turn the Bing Hybrid map on the drawing is not aligned with the real map. I tried to fix this with : geographiclocation function in Autocad Map 3D. The coordinates were correct in AutoCad but not in the export. I assume the drawing is not georeferenced properly. Can you please elaborate on corrective action ? 

@Pointdump : 

I got the *.dwg drawing from the user and they told me to use the "HK1980 Grid" coordinate system and I set it to  :

- code: HongKong80b.GridSystem

- ESPG code: 2326

In mapexport I am saving to *.kml or *.mif.

[Pointdump]

Boris,
"I tried to fix this with : geographiclocation function in Autocad Map 3D."
GEOGRAPHICLOCATION is meant for use in Vanilla AutoCAD, not Map 3D or Civil 3D. It usually breaks any georeferencing. Best to use MAPCSASSIGN.
Dave

[boriskosic]

@ChicagoLooper thanks for a detailed explanation. I have to drawings but (one was wcs and other not). What is weird is that the export is the same for both.

[boriskosic]

@Pointdump first I used MAPCSASSIGN and since the coordinates were still not ok I tried to fix it with GEOGRAPHICLOCATION. Then the drawing was aligned with the real world in AutoCad but still not KML export.

[ChicagoLooper · Accepted solution]

Hi @boriskosic 

You are correct. Your drawing is not georeferenced.

Do you have the original drawing you received from the customer? If you do, open that drawing and assign HK1980 Grid. Don't move, scale or rotate any objects in the drawing. Next, turn on Bing Hybrid imagery. Bing Hybrid should be consistent with the linework. If it's not, then there are three likely possibilities:

1. The drawing isn't in HK1980 and you must do research to find which one the original author used. Be careful accepting the coordinate system provided by the sender/customer, he may not be the original author and may only provide you with guesses. 
2. The drawing was modified by someone who took it out of its proper coordinate system. You'll need to UNDO the bad work in order to return the drawing to its original condition. This might be difficult and might even be impossible.
3. The drawing was never georeferenced to begin with. This means someone gave you bad info. 

[boriskosic]

Hi @ChicagoLooper,

thank you for the detailed answer. I attached the screenshot of the drawing (I am sorry but I needed to blur out the details.) where we have:

- full building on the top right (with red ellipse)

- multiple representations of the the same area(those are the same areas of the building in red ellipse) marked with blue ellipse

I am wondering if is possible to align this drawing to real world on my own ? Perhaps with the ALIGN or similar function ? Before going back to the customer.

[ChicagoLooper]

@boriskosic 

If you are dealing with coordinates, especially surveyed coordinates, I wouldn't recommend using ALIGN command, it defeats the reason why you (or someone else) paid for the survey in the first place.

If you are going back to 'the customer' then go back and get what you need and what you deserved--don't settle for a workaround or another command that replaces the real-deal coordinate system. It doesn't matter if famous celebrities use the command or if an entire country uses a command. Nothing replaces the actual coordinate system when it's assigned to a drawing to make everything right.

<<BTW, your uploaded blurry images don't help your cause. If you provide the site address, anyone would be able to SEE your site using Google or Bing maps. You may pretend it's private but any bird, plane, helicopter, drone, parachuter, hang-glider, bat or flying insect would be able to view your sight without issue.>>

You should upload the ORIGINAL, the real-deal, drawing so it can be analyzed. You may remove any or all mtext if you wish. It's critical to upload the actual geometric building footprints in their actual real-deal locations.

To answer your question, yes. You can use align at your own peril.

[boriskosic]

@ChicagoLooper  and @Pointdump thank you were much for your support. It helped a lot. I appreciate it! 

Have a nice day!

Best regard,

Boris