To sort out location will need:
Bright objects visible at large distances
Objects above or below the plane – so not as
obscured
Ways to measure distances to those objects
Ways to see material other than stars
Gas, dust, ???, mass distribution
Ways to map motion of objects in our Galaxy
Examples of other Galaxies
The Shapley-Curtis debate:
Are spiral nebulae external galaxies or a type of object within
our own galaxy