Medieval cartographers were definitely more esteemed and important than cartographers today. Maps were very valuable which is why we have so many.
I've read articles and watched a few short documentary on it, but generally they weren't allowed to share their national, or trade company secrects.
I do know telescopes and calculus really improved things. With greaterbaccuracy, instead of waiting for rare events, far more common events could be used.
The unisolar calendar looks interesting. I have a free one O got from a local pharmacy this year.