US Survey Feet, Drawing Units and Drawing Settings

[pbradburyYWE5N]

I am looking for a straight forward (hopefully) explanation of the items in the Title as it relates to what units features are drawn to in the active file, how it affects attaching XREFs that might have different units and what exactly selecting the "Scale objects inserted from other drawings" and "Set AutoCAD variables to match" does in the file or the attached XREFs. 

For instance, I understand that 2017 was the first version to have US Survey Feet, but does this mean the "Drawing units" under Drawing Settings can be set to this now, or that the "Insertion scale" under UNITS can be set to this now? And why does UNITS have a selection for "Insertion scale" when Drawing Settings also has a "Scale objects inserted from other drawings", why have seemingly the same exact setting in two different places with the ability to possibly have different values for each? And why in some files is the "Imperial to Metric conversion:" selection box greyed out, and not in others? And why do some files I open all in and created originally in 2017, have more options for "Drawing units" and "Insertion scale"? 

How does all of this relate to the assigned coordinated system as well? I've looked through these forums, the Autodesk help menus and looked on the internet and I can't find a straight forward explanation of how all of these settings interplay with each other.. 

I am a previous Microstation user and with that program there was only one location to set a drawings units and the coordinate system is set from the seed file.., so this is very confusing for me to have this option in multiple different places..

Any help is greatly appreciated!

[rl_jackson]

You really only have one location to set units in C3D, that's by going to the drawing name in the settings tab and right clicking to select units,zone and a host of other things. The UNITS command is Autocad related hence C3D being built on top of Autocad. Those settings do affect things but not so much when you use C3D, since the true location to set those is in the settings tab.....

[Pointdump]

Paul,

"And why in some files is the 'Imperial to Metric conversion:' selection box greyed out, and not in others?"

Assigning a Coordinate System locks in that box. In a drawing with "No Datum, No Projection" you can change it.

Dave

[pbradburyYWE5N]

Thanks very much for the info, a couple follow up questions. What exactly does clicking the settings for "Scale objects inserted from other drawings" and "Set AutoCAD variables to match" do?

When I select the "Set AutoCAD variable to match", it automatically changes the "Insertion scale" under UNITS to US Survey Feet, despite the "Drawing units" under the settings tab indicating the drawing units are Feet? So when I XREF in another drawing or insert a block or whatever, to what **** units does it scale the XREFed drawing or the inserted block US Survey Feet or Feet? What exactly are the "drawing units" of the file I'm in US Survey Feet or Feet? Why is this so dang confusing? 

[tcorey]

I can answer a couple of your questions.

Scale objects inserted from other drawings Means that, as you insert styles from from other drawings into this one, and the drawing scales are different, the components of your label style will be scaled to your current units. It changes inches to millimeters and vice-versa.

Set AutoCAD variables to match This setting means that if you change the Scale setting on this tab, various AutoCAD system variables, such as LTSCALE and DIMSCALE will be updated to match. If this box is not checked, changing the drawing scale here does not affect those settings.

As far as inserting/xreferencing drawings into one another, read up on InsUnits, InsUnitsDefSource and InsUnitsDefTarget AutoCAD system variables.

The "Assigned Coordinate System" is used by Civil 3D *(and AutoCAD Map) during functions that are able to convert from one system to another. For example, your client gives you a point file in UTM10-N, but you need to work in CA83-IF. If you have assigned CA83-IF to your open drawing and if you have told Civil 3D that the file you're importing is in UTM10-N, then you will be allowed to check a box that will convert the coordinates from one system to another.

Using AutoCAD Map, you can query information from outside drawings, import GIS data, and attach images. All of those data types can be converted to your current coordinate system.

Welcome to the Autodesk side of the fence. The grass is greener here. 😉

Best regards,

Tim

[Pointdump]

Paul,

"...despite the 'Drawing units' under the settings tab indicating the drawing units are Feet..."

I think that would be better labelled as "Imperial".

Dave

[pbradburyYWE5N]

That makes a bit of sense... so then can I understand that the "Drawing units" in a 2017 C3D file are "US Survey Feet" by default even though it clearly only says "Feet" under the "Drawing units" and "Feet" or "Meters" are my only choices? Does this mean that all the linework and designs I create in 2017 C3D will all be in "US Survey Feet" and if I XREF these files into an earlier version of AutoCAD that is set to just "Feet" that things won't line up? 

Also, many folks have simply mentioned the "drawing units" for AutoCAD, what does this refer to? The setting you see under the Settings tab, or the Insertion Scale you see when you type UNITS? And could the drawing units for AutoCAD and C3D be different?

Thanks for any final information!

[cwr-pae]

---

@pbradburyYWE5Nwrote:

Also, many folks have simply mentioned the "drawing units" for AutoCAD, what does this refer to? The setting you see under the Settings tab, or the Insertion Scale you see when you type UNITS? And could the drawing units for AutoCAD and C3D be different?

---

Drawing units generally refers to the dimension units set by UNITS command. One thing I have been frustrated with for 8+ years of C3D, people not setting the UNITS to feet and leaving the default of inches.  Makes for some weird block/xref insertion results.

[Pointdump]

Paul,

"Does this mean that all the linework and designs I create in 2017 C3D will all be in 'US Survey Feet' and if I XREF these files into an earlier version of AutoCAD that is set to just 'Feet' that things won't line up?"

Yes. Until 2017, Xref's came in only as International Feet.

"...could the drawing units for AutoCAD and C3D be different?"

Yes. It's prudent to always check the Settings Tab (C3D Units) and the _UNITS Command(AutoCAD Drawing Units) to make sure they match.

Dave

[Anonymous]

We have DWGs from over the years created/drafted in AutoCAD 2004, 2014 and 2016 with drawing units(-DWGUNITS) set to value 2(feet), but more specifically that option is in international feet to my understanding. There has never been a US Survey Feet option for drawing units. The data collection of points(x,y,z) that we receive from the field is in US Survey Feet. We then insert that data into model space and draft the Survey data. Now the difference between US Survey Feet and International Feet is very small so we have overlooked this difference for some time, but we have run into an issue now with a client who uses Microstation and they have informed us that when we gave them our DWG file that contained information in Florida State Plane Coordinates, that we were slightly off from their file. I believe this is due to not being in US Survey Feet.

We have Civil 3D 2016 and it has the option for drawing units to be set to US Survey Feet. So i have 3 sets of questions:

1) I know you can just switch the drawing units to US Survey Feet in C3D, but will that correct the issue? And if not, is there a way to take old DWGs that were created/drafted in AutoCAD 2004, 2014 and 2016 with drawing units set to International Feet and convert them to new DWGs with US Survey Feet as the drawing units? And will that correct the issue of being slightly off from the DWGs that were done in US Survey Feet?

2) When i insert point data(x,y,z) into model space with 2 DWGs with different drawing units, since AutoCAD works in a unitless Cartesian plane will they be the same or not? Is the drawing unit just a unit of measure? And again, does that mean you can just switch "on the fly" between drawing units with respect to question #1?

3) Can you insert a Wblock of the DWG with drawing units set to International Feet into a DWG with drawing units set to US Survey Feet and have it correct the difference?

Also, does AutoCAD 2017 and greater (non Civil3D) have the option to set drawing units to US Survey Feet as well?

Thank you for your time,

Terry

Orlando, FL

[_Hathaway]

If  you are bypassing the survey database when inserting survey points to your drawing the points will be on whatever system they are in in field. If they were obtained on Florida State plane in US Survey feet your coordinates are on that system.  Your field data must match your office data so all drawings will need to be set to match the field data.  You can simply change the drawing coordinate system to the correct system IF you are bypassing the survey database when inserting points to your file.

If you are using the survey database, which is by far the best method, your data will get converted from the survey database coordinate system to whatever coordinate system your drawing is in.  If they done match, things will shift.  We only work in two states and two coordinate systems so it is very easy to ensure each database matches the drawing.

[Pointdump]

Terry,

Welcome to the Autodesk Forums.

"...drawing units(-DWGUNITS) set to value 2(feet)..."

Don't use -DWGUNITS. Instead use UNITS. Then you'll see the US Survey Feet:

"...does AutoCAD 2017 and greater (non Civil3D) have the option to set drawing units to US Survey Feet as well?"

Yes, my above screen shot is from Vanilla AutoCAD 2018.

"...is there a way to take old DWGs that were created/drafted in AutoCAD 2004, 2014 and 2016 with drawing units set to International Feet and convert them to new DWGs with US Survey Feet as the drawing units?"

Yes, Xref'ing or Inserting allows you to scale.

Dave

[Anonymous]

Thank you

[Anonymous]

Thank you Dave

[jamesmac1201]

Please refer to the following link:

https://www.caddmicrosystems.com/blog/2018/09/ussurveyfeet-vs-feet-autocad/

Has anyone ran into any issues going from "Feet" to "US Survey Foot" in the Units?

[_Hathaway]

Very interesting link Jamesmac1201!  I think Autodesk is causing more confusion with this entire setup, especially with the multitude of locations to set units.

We are on Civil3d 2018 and have been for a while now and luckily have not experienced any of the issues that can easily occur in this Feet/US survey feet dilema.  We work exclusively in state plane so this would affect us drastically if an issue were to occur.

We keep our drawing units in feet but have each of our drawings and survey databases set to our State Plane Zone: USA Idaho, NAD83 Idaho State Planes (can someone tell Autodesk this make them look like they don't know what they are doing when this is worded as State Planes!!!!!!) , West Zone, US Foot:

Using this setup we have had zero issues Xrefing older pre 2017 files to 2018.  I assume this is because our drawing units are set to Feet which matches the pre 2017 files which are also set to feet.  As a  test i changed a current drawing to US Survey Feet units and Xref'd a pre 2017 file and voila' the 0.9999999 scale factor was introduced which causes the pre 2017 files to end up in the wrong location.

Until i can find good justification to change the drawing units to US Survey feet we will keep things as-is.  I feel their is way too much danger in setting our files to US survey feet and nothing to gain.  This is quite confusing for those that are supposed to know what's going on.  This would be a nightmare for those that dont'!

[jamesmac1201]

Thanks for the reply. I, as of today, just found out about this. Our company skipped over release 2017, so we were unaware of this critical update. Our in-house surveyors will now be implementing this option in newer topographic drawings. This will also include creating a new template which has the US Survey Foot selected as the unit (we typically work in imperial units). For existing drawings (like the ones I'm working on now) will stay as is (UNITS are set to FEET). One important note: if the option "Set AutoCAD variables to match" option is selected, your UNITS will be changed to US Survey Foot, if set to FEET.

Most companies, that I'm aware of, typically use state plane. And to add to that, our company, due to our elevation (over 5,000 ft), uses a ground factor as well.

The main key is to be sure each drawing has the units set correctly. Troubles arise when xrefing a drawing into another with different units AND not knowing about the "Set AutoCAD variables to match" option.

Here is an example:

Drawing "A" has a 100 SF rectangle in it at X: 1,000,000 / Y: 1,000,000. Drawing "A" has the UNITS set to FEET. Also in the Drawing Settings, the Drawing units is set to Feet; the Imperial to Metric conversion option is set to US Survey Foot; and no other options are selected

Drawing "B" has a 100 SF rectangle in it at X: 1,000,000 / Y: 1,000,000. Drawing "B" has the UNITS set to US Survey Foot. Drawing Settings are the same as above.

Drawing "A" is open and Drawing "B" is xrefed into it. Drawing "B" rectangle will be shifted.

Now, let make a quick change to Drawing "A". First, Detach Drawing "B" (there will be no xrefs in Drawing "A"). Go to the Drawing Settings and select the option "Set AutoCAD variables to match", then select OK. Next, xref in Drawing "B" again. The drawing will now line up.

If you go to the UNITS in Drawing "A", it will now be changed from FEET to US Survey FOOT. Selecting the option "Set AutoCAD variables to match" changes the units from Feet to US Survey FOOT.

This is critical because let say Drawing "A" represent a 2D linework drawing and Drawing "B" represent a topography. The topography drawing is being scaled to match the 2D linework drawing and that's not good.

[_Hathaway]

Great post! We're just going to keep our Units set to Feet. For us, that is the much simpler, safer option as all drawings will be able to be Xref'd without any scaling issues.

[jamesmac1201]

Finally, I created this document to aid our techs in dealing with dissimilar units from drawings. It may be of some value.

[Anonymous]

I'm not sure that's accurate... i've also noticed strange things when xref'ing and it is directly related to the UNITS settings (which seem to sometimes override or are not honored when xref'ing) so my point is i think UNITS does affect things and their not talking with each other.... but maybe thats discussed on down.... i'm about to read more