Survey Feet vs. International Feet

RE: Survey Feet vs. International Feet

Gerard Georges — Tue, 06 Mar 2018 22:20:21 GMT

HI Tim;

I know this is an old article. But to get a bit more clarity. are you saying that with V8 using "true Scale" does the conversion factor for you? whereas I have a Feet and inches files and I'm referencing a Survey Feet file that the survey feet file will be scaled down to the 1.000002?

RE: Survey Feet vs. International Feet

caddcop — Mon, 09 Feb 2015 15:11:35 GMT

In the Md SHA's V8 Workspace is a series of mvba macros that are by default configured to open an alert dialog box if any file is opened where the units are not US Survey Feet or Metric. It then offers to run another mvba macro that will correct the units from international feet to survey feet without changing the coordinates of the file. The workspace can be freely downloaded and setup, or you might be able to pull out any mvba files from it to get the parts you need. However, the mvba files are password protected, so it might take some good detective work to determine which files contain which macro.

RE: Survey Feet vs. International Feet

Anonymous — Mon, 15 Jul 2013 16:58:01 GMT

us feet diffrent international feet

RE: Survey Feet vs. International Feet

Dan Rodman — Fri, 17 Feb 2012 20:12:43 GMT

Our organization is transitioning from V7 to V8i and has many V7 files defined in International feet though they should be US Survey feet. U.S. State Plane coordinate values are up in the 2,000,000's of US Survey feet, so confusing the units produces as much as 4 feet of shift. The solution for the site config was to define both feet the same in the units.def file, but then there is the risk of shifts if a file is opened outside of the site config.

The safest thing is to turn True Scale off in the default reference attachment config variable (MS_REF_DEFAULTSETTINGS = trueScale=0).

Here is a test to show why:

(ft = International foot, sf = US Survey foot):

New V8i settings (for active file):

Global Origin = 0,0 ft from design plane center

Resolution = 1000 per US Survey foot

Master Unit = US Survey foot (label = sf)

Sub Unit = custom (1000 unlabeled per 12 US Survey Inch)

I created 2 reference files with units of International feet instead of US Survey feet.

In each I drew a box from XY=2000000,400000 to XY=2001000,401000 (typical coordinate values).

V7 (J) Reference

Global Origin = 0,0 from lower left corner design cube (different than our new GO)

Resolution = 1000 per ft, 1 positional units per (blank sub unit)

Master Unit = ft

Sub Unit = blank

V8i Reference

Global Origin = 0,0 ft from design plane center

Resolution = 1000 per foot

Master Unit = Feet (label = ft)

Sub Unit = custom (1000 unlabeled per 12 Inch)

I opened the active V8i file (sf) in the site config, which uses a units.def that defines international feet as equal to US Survey feet. Then I referenced each file Coincident World (to account for the different Global Origin in the V7 file), once each with True Scale on and off.

Results (site config):

Ref TrueScale Result

V7 on OK (not shifted) – units definition file took care of units inconsistency

V7 off OK (not shifted)

V8i on Scaled 1/1.000002 (shifted SSW ~ 4 ft); Apparently units.def doesn’t apply to resolution?

V8i off OK (not shifted)

Then I opened the same active file outside of the site config. The default config uses the default units definition file, which doesn’t define International feet as equal to US Survey feet

Results (default config):

Ref TrueScale Result

V7 on Scaled 1/1.000002 (shifted SSW ~ 4 ft) – became a problem when custom units def file wasn’t used.

V7 off OK (not shifted)

V8i on Scaled 1/1.000002 (shifted SSW ~ 4 ft)

V8i off OK (not shifted)

The upshot for me is that there is never an unintended scaling, and resulting 4 foot shift, if True Scale is off. This is especially important considering many of our users aren't Microstation experts, and files (with references) may be opened accidentally outside of our site config. For the few times we need to scale a reference from meters or inches, we can set that manually in the reference manager rather than rely on True Scale, or even toggle itsTrue Scale button after referencing to see what scale factor would be applied. Users should always verify reference orientation parameters anyways.

Again, if you're in a similar situation, I recommend the following:

1. Teach everyone about International feet and U.S. Survey feet!

2. Turn off True Scale off in the default reference attachment config variable (MS_REF_DEFAULTSETTINGS = trueScale=0)

3. When referencing, select "Interative" mode and make sure True Scale button is off in reference options.

4. After referenced, verify orientation parameters (scale, rotation, offsets), and toggle the True Scale button on/off to see what scale it would have applied.

RE: Survey Feet vs. International Feet

Tim Hickman — Mon, 20 Jul 2009 20:39:31 GMT

wow - sorry for the delay on this post.

Lets see - you imported your US Survey Feet data into an International foot design ?

Wellll - when you imported the data - how was it done ? Did you attach it as a reference ? and was the reference attached "true scale" ?

RE: Survey Feet vs. International Feet

Kurt Rasmussen — Wed, 27 May 2009 06:22:50 GMT

What if my seed file was set to International feet but all survey data imported was US Survey Feet? What would it take to get them right?

RE: Survey Feet vs. International Feet

Tim Hickman — Wed, 06 May 2009 18:33:19 GMT

Hey Bryan,

Nice ta hear from ya.

So what you are saying is that your V7 file were all converted to international feet.

And you now have data that is in survey feet to be referenced to these files.

Questions:

Do you have survey feet defined in your units.def file ?

What expectation are you looking for when referencing the files ?

DWG decimal units is of no help - what specifically are the DWG file drawn in ? (IE:METERS)

RE: Survey Feet vs. International Feet

Bryan McCary — Thu, 23 Apr 2009 03:51:08 GMT

Nice article Tim

How would you resolve a civil project converted from v7 to v8.0 with the default International ft in the v8.0 units.def?

Then referencing files setup as U.S. Survey Ft?

Throwing into the mix that Architect DWGs in decimal units will also be used.

RE: Survey Feet vs. International Feet

Matt Thompson — Sat, 17 Jan 2009 08:44:04 GMT

Thanks for bringing-up this topic for consideration and offering some explanation. I think it is worth emphasizing that files with unit definitions different than the data added to them can wreak absolute havoc to users "down the line", often without the original creator of the file being aware of any problem because the coordinate values for data in that file appear correct, as you've explained.

While attachment options can be manipulated to cause this file to appear correct when referenced into a properly set-up file, I would say that would be akin to two wrongs appearing to make a right. Just like the addage that two moral wrongs do not make right, the reference file is in fact "wrong", as are the attachment settings used. This situation is much worse than just a "bad workflow" in my opinion.

As you point out, while these sorts of problems are often noticed when the incorrect unit type is significantly different, when the difference is smaller, like that between US survey feet and international feet, there is a greater chance of it not being noticed before real problems are created.

Thanks again for bringing this topic up so that more users are aware of the importance of units definitions of files with respect to data integrity.

~Matt Thompson

RE: Survey Feet vs. International Feet

Sal Cross — Tue, 08 Jul 2008 23:42:31 GMT

Tim,

That was the best explaination of the International feet vs Survey feet I have seen, easy for all to understand.

Thanks