Post Echo - Units - Accuracy - Tolerance

I saw David Baldacchino's tweet yesterday sharing a link to a blog post for another software product called FME from Safe Software. The article goes into detail more related to their own product naturally but it does describe the math and computer problems that developers deal with. I found it quite interesting as well as confirming much of what I'd read and been told in the past.

Have a look! It's titled: "FME 2018 Infinity War: How Automatic Tolerance Defeats Infinite Precision without a Snap – but with Anchored Vertices!"

Project Units Matter - Specify Coordinates at Point

When we use the Specify Coordinates at Point (SPaC) it is possible that the units in use will affect your results. For example, this project is using Feet and Fractional Inches (FaFI) but for SPaC to match the available survey info it was changed to Decimal Inches (DI) with six decimal places. After using SPaC the units were returned to FaFI.

Some time later the elevation needed to be changed thus causing us to revisit using SPaC. The following image shows the original values used for SPaC.

Leaving the Project Units assigned to FaFI resulted is this subtle change to the coordinate values.

When the units were revised to match the earlier DI settings the SPaC coordinates are not altered.

Shorter story, be careful with your unit settings when using SPaC.

Revit MEP - Wire Size AWG vs MM

I wrote a post about this subject before. There is an app at the Autodesk Exchange Apps that offers trap door access to revise the bias toward AWG size versus.

It is called Convert Wire Size (AWG to MM) and it sells for $4.00 USD. I haven't used it myself but for those firms that need wire size reported in millimeters squared it may be the solution you need/want until Revit itself allows us to switch the criteria directly itself.

I'll be curious to hear how well it satisfies what engineers are asking for.

Revit 2016 - Piping Units Addition

Plumbing engineers must feel a bit like Rodney Dangerfield's "I'm tellin' you, I don't get no respect!". Here's one for them, subtle though it may be. We can specify Liters per minute (L/min) for piping project units. (woot)

Project Unit Rounding Matters

Let's say for example that you need a metric dimension value in your family and it should be 6.35mm. Let's also say that the family's Project Units are set to zero decimal places. When you enter 6.35mm in the Family Types dialog Revit will round the value to 6.4mm.

When you change the family's units to show two decimal places the value that was stored in the parameter is still the single decimal value (6.4mm). Revit did not store the 6.35mm value but shows the rounded value instead, it stored the rounded value.

If you override the dimension style to show two decimal places (as shown above) but don't alter the Project Units of the family you can enter the correct value (in the dimension string) and the Family Types dialog will still report the rounded value. If you change the parameter value in the Family Types dialog it won't respect a two decimal entry and you'll see the dimension value return to a rounded value.

Short and sweet, if you really want a value like 6.35mm to be honored you need to set the family "Project Units" accordingly.

Fwiw, this is different from the project environment where entering a value that uses two decimal places is honored even if the project units and/or dimension properties do not.

Alternate Units - Seriously?

I encounter the request to show alternate units in Revit every now and then. I see the subject pop up in user forums like AUGI and RevitForum.org too. The superficial response is, "Nope the dimension styles in Revit don't have a "show alternate units" option like other CAD software."

Seems simple enough to me for the software to provide it doesn't it? I'm not a programmer so I won't speak further for them.

Below the surface what's always bothered me is, why???? - Some bureaucratic response? "Just show both units!" Some generic project wide uniformity? -

No this is not some fanboy defense for Revit's lack...I really don't get the notion that we have to provide alternate units for everything. What practical purpose does providing overall building dimensions in both units of measure serve? If the project is to be built in China, or Europe, or the Middle East...do they really care about imperial units? Does the window manufacturer that builds imperial based products care about the metric equivalents? Is the framer going to compare the values before they nail in the studs? Is including both units meant to be "easier" for those team members who can't be bothered to become acquainted with the appropriate unit of measure?

How about providing dimensions that show the units that really matter to the poor sap trying to build the project and leave the rest of the clutter off the drawing? I can understand a manufacturer including both when they are seeking pricing for manufacturing something from a variety of sources including overseas vendors. But then often metric and imperial numbers have some fudging involved to cleanup the numbers (3'-0" vs 900mm doors, shaved 15mm off the imperial size).

Backing up...sure, "please "factory" GIVE us alternate units." But using them in practice still ought to be based on reasonable application versus an arbitrary "just show both", some degree of appropriate use. My $0.025

At this time we've got some "ugly" options.

• Add the alternate values as an override suffix to each dimension (make that really really ugly).
• Change the unit of measure for the project dimensions and plot the set again (PDF only hopefully) It does nothing to resolve "messy" conversion numbers like the door example above.
• Add additional dimensions that don't show the "lines" and adjust the dimension value so it is next to the others (pretty darn ugly but at least tied to real elements/values).
• Provide and use alternate dimension styles that show the appropriate units for what is being communicated and based on where the project will be constructed. (maybe you can sense my preference here?)
• Use API to add/update alternate unit suffix for us, don't know if API actually permits this though. Programmers confirm/deny?

Level Annotation - Elevation Units

Here's a quick video showing how to change the units of a Level annotation for elevation.

No time for a video, want to dash in and try to do it? Take these steps (added per Rusty's comment):

1. Select the Level
2. Examine it's Type Properties
3. Find the Symbol Family it is assigned to
4. Close the Type Dialog(s)
5. Scroll to the Families category in the Project Browser
6. Select the family the Level is using under the Annotation Symbols category
7. Right Click > Edit
8. Select the Elevation label, click Edit Label
9. Select the Elevation parameter in the list
10. Click the Format button, Un-Check Project Units
11. Choose another setting
12. Save the family and load it into your project

You should save this family as a new type in your office standards folder.

Units of Measure - Data Entry

When you enter a length value Revit will accept the value regardless of the project units your project is using as long as you provide a unit of measurement symbol.

For example, if you are working in a metric project and the base linear unit of measure is millimeters you can type 2500 and Revit will assume that you intended it to mean 2500 millimeters. If you type 2.5m however Revit will forget the millimeter assumption and use Meter as your unit.

If you are in an imperial unit project you can still enter a metric value by including mm, cm, m etc. Same is true in the reverse...in a metric project enter 12' 6" and you'll get the soft metric (mathematical) equivalent of 12 feet and six inches.

This "thinking" can usually be applied to other units of measure as well, in different parameters.

Hard Boiled Dimensions

A recent thread at AUGI and then an echo of the question at a client office prompts me to write this one. The question is, "Can we show both metric and imperial units in the same dimension string?" More specifically the client request was to provide for "Hard Metric" and the imperial value at the same time.

Regardless, sorry, the answer is no. You cannot automatically show both imperial and metric dimensions in the same dimension string. Even if you could show them both Revit could not provide the "Hard metric" value because this is not a consistent conversion.

In an attempt to be clearer, the concept of "Hard" metric values is the alteration of actual dimensions to a "normalized" or nominal metric equivalent, for example: 36 inches = 900 mm or 8 inches = 200 mm. Conversely "Soft" metric is the literal mathematical equivalent dimension or as in the previous example: 36 inches = 914.4 mm or 8" = 203.2 mm.

If it helps you could think of the normalized metric value as "hard" to do while the mathematical conversion is "easy" or..."soft". My interpretation of this is based on reading a number of governmental sites that discuss the use of this practice. Fwiw, I have heard it described exactly the opposite way, hard is soft and soft is hard, hmmm isn't that a Zen thing? Regardless there is a different approach for each.

With regard to Metric versus Imperial project templates and choosing which to start with...consider that an imperial project can be switched to metric easily...to soft metric. Easy, however, the content will STILL refer to imperially named families. As a practical matter a truly metric project should begin with a metric template and use metric content so that schedules report 200 mm walls not 8" walls or Single Flush 900x2100 doors instead of 36x84 doors, for example.

As for the display of either unit of measure in documents...my cynical side wonders who really wants or needs this? In my North American tunnel vision I don't see a real need to show both even though a local jurisdiction may require it. Despite being told since I was a young lad that we are going to "go to metric"...we still haven't. In a practical way our trades don't really need it and in fact may just be confused by it. An exception might be where the actual material involved is truly specified and supplied according to metric specification. Surely this doesn't require an entire set of documents to adhere to such requirements?

Well enough assumption...what to do if you must? You could consider metric plans and imperial plans, completely separate views. Document it fully as if metric were the only appropriate unit of measure, do the same for imperial.

or...you can place a string using one and then place another string either above or directly on top of the previous string and then move the text off to the side "next" to the other. Sure looks like it is the same string when it is printed out but "we" know better. There are a few ways to replicate the dimensions quickly, such as copy/paste aligned. Still quirky and definitely extra work.

Personally I kind of like the idea of duplicating a view with detailing and then switching all the dimensions to a metric formatted version. Either way just keep in mind that you won't get Hard metric, just Soft.

What I like better still is the ability to provide alternate dimension unit display, much like the "step-brother" AutoCAD perhaps? It probably isn't all that hard to do, just needs doing? If it gets done this post will be pointless eh? Here's to pointless posts!