Damn - that's annoying. Sorry!!
https://apps.apple.com/au/app/theodolite/id339393884
I note that a new version was released yesterday. Maybe the pricing changed?
I am certain in was free - I don't think I would have spent $12.99 on this - I would have at least tried to find another one that is similar.
I may have downloaded this app a very long time ago (I mean like 8 years ago), so maybe that's why it just upgraded me for free. I didn't pay that much attention!
Normally I don't spend money on apps unless I know I'm going to use them a lot. This one falls in to the "interesting", but I'll only use it a few times bucket.
I have to say though, it is pretty cool looking and can do quite a bit of interesting stuff, way more than I'll ever use!