How do I export from GIS to DWG at true scale

CaraO_Brien · ‎10-13-2020

Hello,

I am trying to export from ArcGIS Pro to DWG. I am able to export all the layers I need by using Tools, Conversion Tools, To CAD, Export to CAD, but when I open the DWG file in AutoCAD the data isn't to true scale. I'm not sure if this is a CAD units issue or GIS export issue, but I'm getting batty looking at it. Any help would be so much appreciated!

Thanks,

Cara

ThomasHoman1 · ‎10-13-2020

Hi Cara,

Can you provide examples of the discrepancy? Ideally this would include GIS as well as DWG data and some discussion on the observed discrepancies.

Regards,

Tom

CaraO_Brien · ‎10-14-2020

Hi Thomas-- Thanks. So in GIS I am exporting straight from the Map. It is currently scaled at 1:4,800 (if that matters). To test, I am just exporting one layer to a new output file. In the environments I have specified the WGS 1984 Coordinate system, as well as a crop to current view extents. In the output DWG file, a feature that in reality is app. 310' registers as 117 units in my drawing. When I open the DWG, the file is set to inches. When I change it to feet, the length changes (obviously) to just over 9". I have a feeling the problem lies in my CAD file.. but I'm not sure which settings to tinker with to get the scale correct.

DawnMcCall · ‎10-14-2020

I would double-check your drawing units or Scale up or down in cad by 12. This is usually a feet to inches problem.

Thanks,

Dawn

CaraO_Brien · ‎10-14-2020

Hi Dawn, Thanks. I have a feeling you are right about the drawing scale (I addressed it a little in the reply above to Thomas). Scaling up by 12' does not seem to be the solution (a segment of street that in reality is app. 300' registers as 117 units in my DWG)... but my DWG file is defaulting to opening in inches. Could you provide any insight on the appropriate settings/units? Thanks!

DawnMcCall · ‎10-14-2020

Hi Cara,

Have you seen this?

https://knowledge.autodesk.com/support/autocad/learn-explore/caas/sfdcarticles/sfdcarticles/Changing-units-of-existing-drawing-from-inches-to-decimal-feet-in-AutoCAD.html

But 117 units to 300’ doesn’t seem correct.

I would also test by creating a shapefile and using the command in AutoCAD to bring the shapefile in. This will give you coordinate system options and preserve your dataset. The important thing to know when importing polygons is to check the polygon as closed polylines option at the bottom. You can also choose the data option to bring in attributes, to help you determine which segments you are looking at.

Hopefully, this maintains your length.

Good luck

Thanks,

Dawn

CaraO_Brien · ‎10-15-2020

Thanks, Dawn! I'll look into that now. What I noticed is that depending on the coordinate system of the drawing, the CAD export has a different scale. For example, in WGS 1984-- the export is in meters (It is the incorrect coordinate system for my map I believe... but) the DWG segment measured at 117 units, the same segment (when the drawing was in the 1984 projection) in GIS measured at 384'ish feet (which is 117 m), and then when measured crudely in google earth, the correct length is app. 320'. I can't discern what is happening when I export the map when it is set to its (I believe correct) coordinate system, 1983.. but the units are tiny. .001 for a segment that measures 320' in GIS and in google earth. Do you have any thoughts on this? I may drop this observation in a new question as well.. to see if I can get any traction.

Thanks!

StanHennigh · ‎10-20-2020

First question is what flavor of Autocad is she using? If there is not a Coordinate system in play in the DWG, that could be the issue. I’m pretty sure it has to do with either feet to inches or imperial units to metric conversion. Also, the scale that she is at in Arc Pro is probably a factor as well.

JOSH CLAWSON

DESIGN TECHNOLOGY MANAGER - CIVIL

CaraO_Brien · ‎10-21-2020

Hi Stan. Thanks! I'm using AutoCAD 2021-- but only the trial version for now. In ArcPro-- I'm exporting from the Maps tab. Sometimes I'm viewing it at a scale sometimes not... although it doesn't seem to matter what scale my map view is in for the export-- those are always consistent. Wrong... but consistent. I think you may be on to something with the coordinate system.. but have never dealt with coordinate systems in AutoCAD. Previously to using ArcPro.. I used arcMap at a different organization. Of course, I also had a different version of CAD so its tough for me to understand what the issue is. Could a problem be that all of my layers in the drawing do not have the same coordinate system? The data I put into ArcPro is not incredibly consistent.. with some layer even appearing to have an incorrect coordinate system applied even when I first put them into my map (getting some parallelogram building footprints that should be rectangles.

ANNIERSCOTT · ‎04-27-2021

Did you get this figured out? I'm having what sounds like the exact same maddening problem. I looked through the comments, but have not been able to figure out the issue yet. Thanks!