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Wrong Scale, Wrong Units IDK???


snakeyes

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So it has been a very long time since I used CAD but its all coming back to me except this. i have come to a firm where they have been drawing everything in model space using DECIMAL units, inches. then on paper space everything is scaled to 1:20 and it all works out to 1" = 20', I've printed and measured and it works. I am used to changing units to Architectural, inches, and drawing 1:1. My issue is when I try to scale it so as 1"=20' nothing works, the drawing becomes so huge it cant be seen. I have gone as far as drawing a line 1 inch and when i set the paper space to 1"=1" it still does not measure correctly.

 

Please someone tell me what I am doing wrong, I'm so lost and getting frustrated.

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1:20 metric is roughly equivalent to the imperial scale of 3/4"=1'-0". It is not the same as 1"=20'.

 

Your paper space viewport needs to have its scale set to 1"=20'. If that scale hasn't already been added to the scale list you need to do that first. There should be no need to set the paper space scale. The default for imperial drawings is 1 inch = 1 unit which is a 1:1 scale.

 

A scale of 1"=20' would be equivalent to 1 paper unit = 240 drawing units. This is how you set it up in your scalelist.

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Check the command -dwgunits (with the leading dash) to see what units you really are working with, and check your dim style to see if there is a linear scale applied. Engineers using vanilla AutoCad have done weirder things than that. IF you have feet as modelspace units, and inches as paperspace units, 1:20 is exactly 1" = 20'-0".

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Maybe I need a refresher course.

 

In all my years doing civil engineering work I've never seen a drawing that purported to be drawn at a scale of one inch equals twenty feet designated 1:20. I've seen hundreds of drawings with the scale designation of 1"=20' or 1"=20'-0".

 

snakeyes: Try this. Make the viewport active. Invoke the Zoom command. Now select the Scale option. When you are prompted to enter a scale factor type in the following: 1/240xp then press the Enter key. What happens? Can you now see your entire line in the viewport? Yes or no?

 

For a list of common imperial architectural and engineering scale factors click on this link.

 

http://www.archtoolbox.com/representation/cad/scalefactor.html

 

BTW...Using the Zoom > Scale method was the very first method used to set a viewport scale when the concept of paper space and viewports were added to AutoCAD. It wasn't until later that scale lists were added.

 

Remember, you want 1 inch in paper space to equal 20 feet. One foot is 12 inches; twenty feet is 240 inches. 240? Doesn't that sound vaguely like a n/xp scale factor?

Edited by ReMark
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In all my years doing civil engineering work I've never seen a drawing that purported to be drawn at a scale of one inch equals twenty feet designated 1:20. I've seen hundreds of drawings with the scale designation of 1"=20' or 1"=20'-0".
When did anyone say they put 1:20 in the titleblock Scale attribute?

 

Civil engineers and Licensed Professional Land Surveyors in the USA work in decimal feet, not inches.

 

The legal requirement around these parts is that recorded drawings must be drawn in a scale of 1 inch equals a list of commonly used multiples of 10 feet. Those so called "metric" scales found in the Acadiso.dwt, have nothing directly to do with the metric system of measurement. They are ratios useful in a base 10 counting system because they are in multiples of 10 units. One base 10 counting system is the metric system of measurement, so these ratios of one unit equals multiples of 10 are particularly useful in the ISO default scale list.

 

Every boundary survey I have ever done for anything that would fit in a 1:20 scale viewport was drawn using modelspace decimal feet, a base 10 counting system, and paperspace inches, with a viewport scale of 1:20. The default scale 1:20 does not show up in the imperial default scale list. One has to add it. It is defined as 1 paperspace unit equals 20 modelspace units, exactly as it is in the ISO template.

 

The OP needs to tell us what the units are after he uses the -dwgunits command to find out.

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This statement is false: "The default scale 1:20 does not show up in the imperial default scale list."

 

Scalelist1to20.PNG

 

I do all my drawings in imperial units and this scale list is the default in the acad.dwt template. Maybe you are using a different version of AutoCAD than I am.

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A 1:20 scale is a ratio typically used as an annotation scale for text placed in model space. Since the OP said he is using decimal units not metric then if he drew a line 20 units long in model space then in paperspace the line would be 1 unit long. I suspect he is using the wrong units for his drawings. I don't own a scale that measures decimal units and I think he doesn't either. Confirm the units for model space and start from there. The origin of the drawing determines the scale.

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The viewport scale factor for 1:20 is not the same as the scale factor for 1"=20'.
Who is talking about scale factors? Besides, it depends on your units, which is my entire point. What's pertinent to my point is what is in the scale list item definition and what are modelspace units.

 

Oh, yeah. This is what I get. This is acadlt.dwt. Why doesn't your window show the little decider buttons up top there? Maybe this is another way LT is made LT, by not flupping up the screen with all them extra ratio thingies.

 

By the way, a ratio such as 1:20 is neither metric nor imperial.

Untitled.jpg

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I mentioned scale factors because the OP talked about plotting from paper space which led me to assume he was viewing the model space drawing via a viewport. For the viewport to plot correctly the proper scale has to be applied.

 

OK...I agree, in this case, 1:20 is a ratio but it is not the same as saying 1 inch = 20 feet.

 

Now that I recall, the only place I have ever seen scale represented on a drawing as a ratio was USGS 7.5 minute quadrangle (topographic) maps which had a scale of 1:24,000. I believe that meant that 1 inch equaled 24,000 inches or 2,000 feet as we commonly referred to it.

Edited by ReMark
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Is 1 drawing unit equal to the 1 of the selected units for the drawing? The reason I ask this is because if you use inches then every thing you draw has to be in inches if you use a ratio instead of a scale. I think that's where the difference is. If you use a scale then you can draw in feet or inches but if you use a ratio then you have to use the same value every time. Am I right here or does it matter if you use different values in the same drawing no matter what kind of scale or ratio your using?

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