AutoCAD thinks map in viewport is at 1:530, but it is actually drawing at 1"=530' --> dynamic scale bars don't work

[tcrossman]

I am working in AutoCAD Map 3D ... I have a viewport that is drawing a map in a projected coordinate system in International Feet from model space (of an XREF drawing) at 1"=530'.  This is what I want.  I can measure an inch in paper space and see that it is 530' in model space; however, when I try to add a dynamic scale bar, it is completely the wrong size.  When I add the scale bar, the dialog indicates the "Scale Ratio" to be 1:530, i.e. 1"=530" or 1" = 44.17', but the viewport is drawing the map at 1" = 530' (which, again, is what I want.)  When I LIST the properties of the viewport, the viewport scale is similarly given as 1"=44.17'.  Is there a way simply to tell "the system" that the viewport is at 1"=530'--i.e. just to dictate the scale--without changing how the map is drawn?  I do not know how the the drawing of the map and the system-perceived scale got out of synch.  I just need to fix it, pronto, and meet specifications by including a dynamic scale bar.  I have tried everything that I know of to try.  In case it is of use, here is a screen shot of the button bar at the bottom of my screen:

Thanks to all.

[pendean]

Share a portion of your DWG file with the problem still in it please.
Also post a screenshot of your ABOUT command pop-up please.

[tcrossman]

I was afraid you would say that ... I may not share these drawings, as they are security-sensitive information from a client.  Here is my ABOUT dialog:

In case it gives a clue, I did try changing the "Scale Ratio" in the dynamic scale bar dialog to 1:6360 (which is what I am after), and the scale bar comes out the correct size; however, the map in the viewport then zooms way out to a tiny mass in the middle of the screen.  There seems to be some other internal scaling being applied to the viewport.

[pendean]

This is not the MAP forum: I'll ask to have you moved to the correct forum over here

In the meantime.... Open a DWG file with no issues at all like this, like your template file, that does not exhibit the issue with other maps, then INSERT your problem file in it at 1:1 scale and see if you can recreate the issue there (looks like you have a inches vs feet issues).

[tcrossman]

Thank you very much for the consult and the move to the Map forum.  I shall work on doing what you suggest.

[ChicagoLooper · Accepted solution]

Scale in paperspace is one of, if not the easiest concept to misunderstand.

If your viewport scale is 1 inch equals 530 feet then your scale is 1:6,360. That's not easy to understand because most users (doesn't matter if plain vanilla user or Map3D user) believe viewport scale is the same as scale. They're not.

For whatever reason, e.g., this is the way it was explained to me during first day orientation, this how we do it in our office, we weren't taught correctly, etc. etc., etc., 1"=530' for your viewport is not your scale. While your viewport scale may be 1"=530' your scale in an imperial drawing will be 1:6,360.

Viewport scale is 1" = 530'

This means one inch in paperspace =  530 feet in modelspace. Why? Because the " means inch and the ' means feet. We use the symbols " and ' to eliminate confusion when describing VP scale. In your specific case, your viewport scale indicates inch on the left of the equal sign and feet on the right of the equal sign. You are using UNITS and the units are not the same on the left and on the right of the equal sign.

SCALE is 1:6360 

This indicates one unit in paperspace equals one 'drawing 'unit in modelspace. Since your modelspace is using international feet your modelspace drawing units will inherit, or adopt, the units of your assigned coordinate system. Since 530 feet = 6360 inches (530x12) your scale is 1:6360. BTW, there are no UNITS in scale, it's merely a ratio. Ratios, in the math world, don't have units.   

So why is the ratio 1:6360 and not 1:530? Because the drawing units in paperspace are always in inches so the ratio must refer to inches too. You can't have a mathematical ratio that has inch on the left of the colon and feet on the right of the colon. The 'ratio' must be inches:inch OR feet:feet OR yards:yards OR miles:miles, etc.

<<If you remember your 7th grade math class, units on the left will 'cancel out' the units on the right provided they are the SAME UNITS.>>

If you mix the units, for example inches on the left and feet on the right, it's no longer a math ratio, it's a description.

Where does the 1"=44.17' come from?

That's obviously an error. If you have properly assigned a coordinate system that uses international feet (as opposed to US feet and as opposed to meters) then your modelspace drawing units will be international feet--that's just the way it is, and always will be, if you're assigning a coordinate system in Map3D or in Civil3D. No exceptions. Your drawing units in modelspace always adopt the units of your coordinate system.   

You, or someone with access to your drawing, accidentally (or unknowingly) changed modelspace drawing units from International Feet to Inches. This means 530 feet has now become 530 inches and 530 inches is equal to 44.17 feet (530/12).

If you 'can measure an inch in paper space and see that it is 530' in model space' then, congrats, your drawing is scaled correctly. Your issue is the scale bar, not the viewport scale and not scale. To resolve your issue, use your own scale bar (not OOTB) so you can manually input your scale. Or, as an alternative, you can easily create an attributed scale bar with a FIELD. A properly used field in the attribute of your scale bar will dynamically respond to your viewport's zoom factor. 

[tcrossman · Accepted solution]

> ... You, or someone with access to your drawing, accidentally (or unknowingly) changed modelspace drawing units      from International Feet to Inches ...

I believe that is indeed the source of the problem.  I have been a GIS analyst and cartographer for close to 25 years, so I do understand dimensionless scales vs. architectural and other "scales." Give me a dimensionless scale any day; however, I do still struggle with the way CAD approaches scale.  I am not a formally trained CAD technician, and I know just a little bit more than enough CAD to be dangerous.  I could certainly be the source of the problem, but, if so, I certainly did it unknowingly.  I am working with existing files that are given to me to rework and enhance for the purpose and to the specs at hand.  In such situations, it is a risky business to go changing basic parameters like drawing units and coordinate systems without a thorough understanding of the files that one starts with ... which, admittedly, I may not have had.  Using a custom scale bar with a field sounds like just the thing here.  (I now have neither the time nor the budget to go about rebuilding the problem drawing.)  I'll learn something new in the process, too.  Thanks!

[tcrossman · Accepted solution]

"... looks like you have a inches vs feet issue ..."

That is indeed the problem.  I will track it down ... and thanks again for the move to the Map 3D forum.  I should have known better.