Subscribe to this thread
Home - General / All posts - Issues importing CAD files
259 post(s)
#03-Sep-19 23:09

I am dealing with Planners who use AutoCAD quite a bit and keep running into the issue with M8 of not being able to import the DWG and DXF files as they are in versions other than 13, 14 or 15. I am dealing with the issue by asking to have them in one of those versions. Sometimes this is an issue. I am not familiar with AutoCAD is it easy to export files in versions 13-15? Is there a better way of dealing with this issue such as having a program that can convert the files? Or some other avenue?

drtees90 post(s)
#03-Sep-19 23:30

Autodesk has a free program called DWG TrueView. You can look at or print CAD files, but will not have the ability to modify the files. You willhave the ability to save the DWG down to an older CAD format. I typically save CAD files back to Version 2000, which is the most recent version that M8 or M9 will read.

That said, CAD files (at least from my experience) will have hundreds of unnecessary layers, blocks, and other leftover bits. They often have internal errors that can also cause troubles. I usually use other AutoCAD-like programs to clean and repair files before saving them down to Version 2000. I am currently using a free version of Draftsight, which will no longer be free as of January 2020. Another program I have not played much with is FreeCAD; an open source CAD program. Winnowing down the number of unnecessary, empty layers, blocks, and formats greatly helps in reducing the sheer number of choices of layers to import. Having DWG TrueView, Draftsight, or FreeCAD running on a second monitor also helps to narrow down which layers contain the information you need to import.

Best of luck with the import.

259 post(s)
#04-Sep-19 00:12

Works perfectly, really appreciate your help, thanks

259 post(s)
#20-Nov-19 22:02

If having done the conversion M8 can't import the fie is it likely that there are some issues with the file itself? I can import it into M9 but only some of the layers have anything meaningful in them.


5,994 post(s)
#21-Nov-19 06:51

9 generally has better dataports than 8, so if 9 can import something but 8 cannot that does not mean there is something wrong with the file. It could just be a better import capability in 9.

259 post(s)
#03-Feb-20 22:47

Am stuck here again. I have imported files into M9 but I need them to use in an existing project in M8. How can I get them there? I can't import them directly to M8 and when exporting the from M9 I need to chose a projection and so far I haven't found the correct one. Previously I have used NZMG and Mt Eden but these are not working. Does anyone have any suggestions? Thanks


9,223 post(s)
#03-Feb-20 23:27

How can I get them there?

Export sounds good. That's good so far.

when exporting the from M9 I need to choose a projection

No, that's incorrect. You never need to choose a projection on export. You might be holding it upside down.

A step-by-step account would be great.

259 post(s)
#04-Feb-20 00:03

I can import the dwg files into M9. It then assigns the projection as pseudo mercator, which is fine for me viewing it in M9 but this is in red so I need to chose a projection and I have no idea what it is. I have tried exporting it in pseudo mercator but it doesn't work in M8


9,223 post(s)
#04-Feb-20 01:15

which is fine for me viewing it in M9...

It's not.

but this is in red

Because it's not fine.

so I need to chose a projection and I have no idea what it is

Start there? Get the projection/datum right in 9.

Then you will have a fixed starting point.

160 post(s)
#04-Feb-20 08:24

concerning the projection:

1. Try to get the information from your planners.

2. Try to get the information from the landsurvey people who draw the initial map.

3. Check the coordinates of some objects in the layers. Sometimes this may be a clue.

4. Could it be NZTM ?

5. I found this old webpage on NZ projections :

Look down for the topic -->"How can I tell what the projection is for existing data?"

I don't know if this may be of any help to you.

Good luck.


5,994 post(s)
#04-Feb-20 07:57

It then assigns the projection as pseudo mercator, which is fine for me viewing it in M9 but this is in red so I need to chose a projection and I have no idea what it is.

DWG format doesn't specify projections, so with any GIS system (Arc, MapInfo, Q, Manifold, etc.) if you want to use a DWG drawing in the correct coordinate system it is you who gets to manually specify what that coordinate system should be. If you don't know, you either have to do some trial and error detective work to help guess the right coordinate system, or you're out of luck.

The good news is that if a DWG shows some sort of geographic setting, like a known island or whatever, it is usually fairly easy by trial and error to zero in on the coordinate system that was used.

Every reasonable GIS has some sort of dialog that is used to assign the initial coordinate system when importing from a non-spatial format that fails to specify what coordinate system should be used.

Here is how to do that in Manifold:

1. Visit the Projections topic.

2. The third heading down, just a few paragraphs into the topic, is "Formats that Do Not Specify Coordinate Systems". That tells you step by step what to do. It's easy, and takes but a moment.

There are also step by step examples specifically for DWG and also for DXF, so it's a good idea to read the DWG topic and the specific DWG example, Example: Import AutoCAD DWG and Georeference , which shows how to work with a well-documented DWG.

For an example of a lucky guess with a poorly-documented DXF (same thing, really, as a DWG... also spatially brain dead...), see the Example: Import AutoCAD DXF and Georeference topic.

In addition to the above, the generic topic that discusses how to assign coordinate systems when the format fails to do so, is: Example: Import a Shapefile.

drtees90 post(s)
#04-Feb-20 23:46

If we are lucky, the drafters that made the CAD file will have referenced their drawing in model space to a known survey point and have used State Plane coordinates. If we are even luckier, the drafter will have used feet (or meters) as the standard unit of measure (sometimes they even tell us what the units are).

We are not always that lucky. We will get CAD files that are in architectural units (fractional inches) and may not even be referenced to a known survey point in model space. The layers will be hanging out in the middle of somewhere and will be too large by a factor of 12.

If the CAD file contains a layer portraying a parcel boundary, I can usually reference the imported layers manually. I will place points on the layer containing the parcel boundary, then copy those points and save them as a separate drawing layer. These points will remain on the clipboard. Creating a separate file with the points ensures that I do not lose work. I will place control points on all the corners of the parcel in both the CAD layer and the projected parcel layer. Once the corners are paired up with control points, I reference the CAD layer to the GIS parcel layer. Next step is to delete the control points marking the parcel corners on both the CAD layer and the parcel layer.

The next step is tedious, but all the really hard work has been done. I simply have Manifold put control points on the points I previously placed on the CAD parcel drawing.

  • Open up an unreferenced CAD layer;
  • Paste-Append points on the clipboard onto the unreferenced CAD layer;
  • Have Manifold create control points on the pasted points (make certain that the same has been done on the registered CAD layer);
  • Register the unreferenced CAD layer to the referenced CAD layer;
  • Delete the control points from the newly registered CAD layer;
  • Delete the pasted points from the newly registered CAD layer;
  • Rename the newly registered CAD layer so that I know that it has been referenced.

I am certain that a script would accomplish this much faster if I had the time to really learn how to write the script.


5,994 post(s)
#05-Feb-20 08:31

Trial and error in 9 can be remarkably fast, if you need to do that. Usually people who do drafting use metric units in Europe and feet or inches in the US. OK. Using the metrics settings in dialogs, you can set the units as well as coordinate systems and scales and offsets by drilling down through Repair Initial Coordinate System, and see how the drawing moves about in comparison to a "known good" layer, like Bing streets. As long as you use the Repair... system, you can tinker as long as you want and you're not actually reprojecting any data, so there's no risk of damaging the data.

Usually, CAD drawings will either show some geographic features, like islands in the examples I cited, or they will be highly local, just showing the layout of a few blocks of a proposed development, a few parcels, the layout of a factory, etc.

If the drawing is obviously geographic, then I guess Latitude / Longitude and if that doesn't work I try whatever is the local State Plane projection for that location, or Pseudo Mercator, adjusting offsets and scales as need be until the thing lines up.

If the drawing is local, I'll tell it to use Orthographic centered on where it is supposed to be, and using a spherical Earth. I can then tinker with metrics (offsets and scales) until it lines up.

The above assumes "North Up" drawings. If they are not "North Up" then I'll use Hotine so the drawing can be rotated to how it is supposed to be.

To do the above you of course have to learn how to drill into dialogs and to set metrics. But that's easy to do with a bit of trial and error to see the effects different settings have, and once you get used to those it's remarkably quick to get drawings to line up through trial and error.


144 post(s)
#04-Sep-19 00:50

Hi Ian, is also a good source when i comes down to deal with CAD data.

The Future of Spatial Data // //

259 post(s)
#10-Feb-20 01:38

Really appreciate everyones help. I had already tried a few of the suggestions with no luck thus my post. Will go a bit deeper and see how I get on. Thanks again

259 post(s)
#10-Feb-20 23:39

I have got one of the drawings reasonably close to where its supposed to be (have attached a screen shot in M8). I have assigned NZGD/Mount Eden circuit in M9 then exported the drawing then imported it to M8. Do I need to play around with this in M9 so its position is correct in M8 or can I now adjust it manually in M8? Which is the best approach?

My other post about not being able to import the image files into M9 is for this project. I was going to use those as the reference for these drawings but am not able to import them at this stage.



9,144 post(s)
#11-Feb-20 06:43

You can adjust it either in 9 or in 8, it does not matter much where you do it because you can transport the projection in both directions. If you adjust the projection in 8 (using Assign Projection), you can export it as XML named after the original file, then re-import the original file into 9 and 9 will read the projection from the XML. 9 automatically exports the projection as PRJ which 8 can read.

259 post(s)
#18-Feb-20 03:19

Managed to get the CAD files in a proper projection and can import them into M9 and export them and import them in M8 and they sit just where they should in my existing project. However, I have one layer that is not getting all of the data from 9 to 8. When I open it in 9 I can see all of the drawings but after exporting from 9 and importing to 8 less than half of the areas showing in 9 are present in 8. I'm not sure where to start to look for possible causes of the problem, can anyone give me some suggestions? Thanks


9,144 post(s)
#18-Feb-20 08:10

Which format are you using to transport data from 9 to 8? It would help if you shared example data with objects that fail to transport.

259 post(s)
#18-Feb-20 21:07

Shp files. All of the other layers have been fine, its just this one. I can't really attach the original dwg file but I can attach the shp file I exported but not sure if that is any use. Have attached a screen shot of the file in 9 and the shp file exported from 9.


259 post(s)
#18-Feb-20 21:53

Turns out the data was there, I had just missed it as it was a very tiny grey dot on the edge of my screen, zoomed out at 3,800,000:1


9,223 post(s)
#18-Feb-20 23:56

This shows why Manifold 9 is designed to amplify the display of tiny data, at tiny scales. If there is data anywhere, we can always see it.

To do something similar in Manifold 8, we need to apply custom formatting. For example, fat area boundaries or line width. (Points are usually OK.)

Manifold User Community Use Agreement Copyright (C) 2007-2019 Manifold Software Limited. All rights reserved.