# Thread: Dimscalelinear is Squaring itself?

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Originally Posted by RobDraw
Why would it be? Engineering scales are inches = feet not a ratio ( : ) like metric scales.
Architectural Scales are inches (in 16ths) = feet.

EDIT: The bold italic below is wrong. On a Civil Engineering scale the foot is divided into inches, but the inch is divided into tenths of an inch.
In the field, a surveyor measures things in decimal feet, no inches just tenths, and hundredths.

Civil engineering scales are in ratios, 1:1 = one foot = 10/10ths of a foot and 1" = 10/10ths of an inch. They don't do fractions. The rest are 1" (in tenths) = so many feet, 20, 40, 50, 100, 150, etc.

Sorry, I left out the word Civil before. I guess there are other kinds of Engineers, but I thought they all did metric now.

See image, count the divisions.

2. Originally Posted by ilarson007
Yeah, the only other options were 1:50 and 1:100. Neither worked....

I know how to do that, but I guess I just didn't?
It really isn't what works, it's what the industry uses and can verify. White space around a 1:100 is ok if the 1:50 does not fit the paper.

3. We are getting into semantics here.

My point is that metric scales are a ratio using the same units. By definition, a 1:1 ratio cannot mean 1" = 1/10'. Metric scales can use a ratio symbol because they are using the same units on either side of the symbol.

I've never seen a scale like the one in your image but in that case the 1:125 means 1" = 125".

4. The image Dana posted is of a metric scale. I believe the six scales on it would be 1:20, 1:25, 1:50, 1:75, 1:100 and 1:125. See Alvin 740PM plastic metric scale.

http://www.draftingsteals.com/catalo...ic-scales.html

5. Oh, I thought the top scale was inches.

6. Originally Posted by ReMark
The image Dana posted is of a metric scale. I believe the six scales on it would be 1:20, 1:25, 1:50, 1:75, 1:100 and 1:125. See Alvin 740PM plastic metric scale.

http://www.draftingsteals.com/catalo...ic-scales.html
That was a mistake. The scale I meant to post is the first one on this list.

7. Originally Posted by RobDraw
We are getting into semantics here.

My point is that metric scales are a ratio using the same units. By definition, a 1:1 ratio cannot mean 1" = 1/10'. Metric scales can use a ratio symbol because they are using the same units on either side of the symbol.

I've never seen a scale like the one in your image but in that case the 1:125 means 1" = 125".
Whatever metric scales do, imperial surveyors scales are a ratio between a paperspace unit, which is one inch, and one or many modelspace units, which is a decimal foot, not an inch.

Ahhhhrgg!! I was thinking like an architectural person. Architectural 1:1 is full size in model and paperspace. Civil 12:1 is full size in paperspace only, 1:1 in modelspace.

I should not have used 1:1 as an example, and then explained it incorrectly. In the surveyors world, one has to use 12:1 for full size in paperspace since the modelspace units are feet, and I cannot think of anything a civil engineer might have to plot at full size. Nothing would fit on a sheet of paper anyway.

8. Let's, for a moment, forget about AutoCAD using different units in paper space when drawing in feet or meters.

Technically, a ratio does not make sense when using different units on either side of the symbol. In the trade, it may be accepted. I'm not sure about that. By definition, a ratio, is the comparison of amounts of the same thing. Apples to apples, etc. It can be expressed with either the ":" symbol or a "/".

If you apply unit labels to your scenario the expression would look like 1":20'. I've never seen it expressed that way. Always, it's 1"=20'.

Again, we are talking semantics here. I cannot see how expressing it incorrectly would cause anything more than maybe momentary confusion to someone in the trade. But, for a drafter not in the trade, and not knowing better either way, he/she can easily make the mistake that 1"=20' is the same thing as 1:20. I've seen it done before. Technically speaking it is not and getting it wrong can result a drawing that is not 1:1.

9. …he/she can easily make the mistake that 1"=20' is the same thing as 1:20…
Yes, that does happen. It happened to me the first time I tried to AutoCad a survey drawing. However, it is still something that should have been figured out in middle school math, or earlier.

1" = 20', and 1:20 are both expressions of ratios, but 1" = 20' contains information telling you what type of, and how many measurement unit values the ratio represents. 1:20 does not tell you anything about the values it represents, even though it represents exactly the same measurement values in the same proportions as 1" = 20' if modelspace units are feet, and paperspace units are inches. The inch to inch ratio is 1:240 for both these examples.

By the way, 1" = 20' will have to be a custom scale. It doesn't come in the can.

I just spent a few minutes googling up a definition for ratio. While all two or three hundred of them said pretty much the same thing in different ways, the simplest said that a ratio is an expression of a relationship between two values. What that relationship is, is apparently up to the user. None of them said anything about both values must represent the same kind of values. 1:20 only means there are one of these, and 20 of those.

While 1 apple:20 oranges may not make any real sense, there is no reason a ratio cannot have different things on each side. In fact, other than the two most common value relationships we use for the AutoCad scale ratio, inch:inch, and mm:mm, depending on the template used, all the rest are apples and oranges.

It is the purpose to which Autodesk puts its ratio that is confusing to the novice because they don't examine what the ratio actually means to the program itself. Most of us go on for years without ever having to add a custom scale to the scale list. When we do, we discover that we can only enter our values in one way, as a ratio between paperspace units and modelspace units. We can only use an amount of inches or millimeters on the paperspace side, then we have to enter an amount of modelspace units we want one or more paperspace units to represent.

PS. To the casual observer: Never use more than one paperspace unit in a custom scale.

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A scale of 1:20 metric is roughly equivalent to 3/4"=1'-0" imperial.

A scale of 1:100 metric is roughly equivalent to 1/8"=1'-0" imperial.

And a scale of 1:250 metric is roughly equivalent to 1"=20'-0" imperial.

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