Getting GPT Vision To Return Coordinates

[_j]

That is not something that gpt-4 vision can do, alone.

Estimation of measurements in images or PDFs

Obtaining dimensions and bounding boxes from AI vision is a skill called grounding. You can, for example, see how Azure can augment gpt-4-vision with their own vision products. Other AI vision products like MiniGPT-v2 - a Hugging Face Space by Vision-CAIR can demonstrate grounding and identification. Such metrics are needed as a basis for measurement. gpt-4-vision alone might give you a description and be coaxed into extrapolation, but it is unlikely to be reliable.