Getting relative positions from the real world

Hi, I’m trying to build an accurate representation of my house so I can plan a future extension.

I can model the house accurately without issue but the issue I’m facing is I’m trying to model a hilly and undulating back garden and separate garage-like building in relation to the house.

The only solution i can find is to use a laser measure from a fixed point in the garden (e.g. from a prominent tree) and measure 3 points on the house which are quite far apart (e.g. top left corner of upstairs window, bottom right of door frame etc…) to give me essentially local GPS co-ordinates (not sure what these might actually be called) - using them i can then create 3 spheres from my house model and where all 3 sphere circles collide/connect, is where the fixed point was I was measuring from.

This is quite time consuming and feels somewhat inaccurate, is there a better way anyone knows of?

Your profile says you are using SketchUp Pro. Which version of SketchUp Pro are you using, though?

You could do the processing of your laser sightings faster and more accurately using a trilateration extension. For example, mine.