[Retric]

https://ntrs.nasa.gov/api/citations/20205008318/downloads/20...

NASA’s direct comparisons between New Mexico (55) and Antarctica (160) only showing a relatively modest decrease from earths magnetic field when measured by high altitude balloons, but again very little GCR reaches the surface.

To be clear a very small fraction of GCR is extreme high energy particles which penetrate just fine.

[schiffern]

Hard to say, since that's in grays instead of sieverts. The two can give very different curves.

>again very little GCR reaches the surface

On Venus there would be less shielding than on the surface of the Earth.

The minimum acceptable altitude is ultimately limited by temperature, not pressure or radiation.