Possible scaling factor lockout

When working on a project, I use a photo as a background to reproduce it as faithfully as possible.
However, in order to use the actual measurements, I have to vary the scale ratio of the primitives used to adapt them to the photo.

In other words, a dimension measured on the photo must correspond to the actual dimension regardless of the size of the photo in the background.
Since the scale ratio returns to 1 when I add a new primitive, I ask you:
Is it possible to lock a scale factor (other than 1)
so that I can correctly size each primitive used without having to re-enter the scale?

Thank you for your help.

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Yes I would like to advocate for improvements to a workflow where matching to reference images is crucial.