Scaling with reference DIM

Some background:

-I'm a former AutoCAD user but looking for and opensource alt. that can do simple manipulations such as scaling .dwg or .dxf for use in energy modeling software.

-A lot of times I'm getting PDF's and converting those vector drawings into .dxf I then need to scale these drawings.

-The energy modeling software that I'm using (IES VE) requires an obnoxious level of precision within its 3D modeling application; approx. scaling factors (like from a CAD software rounding a dimension in the thousandth decimal place) can cause headaches later on in the energy modeling process.


What I'm trying to do:      

I need to scale a .dxf of an unknown scale to a known one. ie. CAD allows you to scale to a reference dimension. So, if I have a floor plan I that calls out a 20' dimension I can do the following in AutoCAD:
 -> draw a line that is 20'
 -> use the scale reference command (with the drawing elements selected)
 -> select the unscaled 20' dimension from the drawing
 -> then select the end points of the 20' line I drew

CAD then scales everything so that the 20' from the imported drawings equals the 20' line I drew.

Is this functionality available in LibreCAD? I've gone through a lot of FAQ posts and can't find this capability.

https://wiki.librecad.org/index.php?title=Measure_Areas

Thank you for the response.

The method outlined seems to be for a rasterized image; I'm not able to get it to work on a vector line drawing. I only see the scale option if it's an image.
Also, this method seems to be relying on determining scaling factors, which I'm trying to avoid as that can cause issues within the 3D modeling platform, I will be using these files in.  

The AutoCAD functionality SIM to what I'm looking for is:
scale (sc)
 ->reference (r)

Someone mentioned a scale reference command "szr" in a LibreCAD forum but that command isn't available as a default in my copy of the program. That post was also oddly worded, and the poster may have been saying it as something they wish the program had. (https://github.com/LibreCAD/LibreCAD/issues/1338)

Hi,

jlackie wrote

-The energy modeling software that I'm using (IES VE) requires an obnoxious level of precision within its 3D modeling application; approx. scaling factors (like from a CAD software rounding a dimension in the thousandth decimal place) can cause headaches later on in the energy modeling process.

See in Options -> Current Drawing Preferences -> Units if the precision you need fits in one of the offered by Librecad.
Also check Options -> Application preferences -> Defaults for the units

I need to scale a .dxf of an unknown scale to a known one. ie. CAD allows you to scale to a reference dimension. So, if I have a floor plan I that calls out a 20' dimension I can do the following in AutoCAD:
 -> draw a line that is 20'
 -> use the scale reference command (with the drawing elements selected)
 -> select the unscaled 20' dimension from the drawing
 -> then select the end points of the 20' line I drew

What I'd do with the tools I know in LC:
Mesure the line that should be scaled to 20, supposing it currently measures 100
Select all  the entities to be scaled (drag left with a green rectangle selects anything the rectangle touches, dragging right with a blue rectangle selects anything that is fully inside the rectangle, same as Autocad)
Tools -> Modify -> Scale,
Specify reference point, is not important for the matter currently.
write in the popup box 20/100 which is the measure that should have the drawing / the measure it currently has
Hit Enter

Re-measure the line and check if all has been scaled right, specially check the precision.

HTH
Pere