What is this used this for?

[Vietti]

A goniometer is also a hand held device for measuring crystal faces to determine a mineral.

 

[Sprocket]

Goniometers are also used for measuring joint angles and range of motion on people.

 

[DKGrimm]

Partially Off-Topic Question for DKGrimm:

Perhaps you can answer a question about a device that was auctioned along with some surveying equipment several years ago.

It was manufacturer-tagged as a goniometer, which I can find described and defined as an elaborate protractor-type device for use with maps and drawings, but it was a large piece of precision engineering in a fancy wooden case that had lots of spirit levels and two telescopes and came with a tripod. How would that device be used in comparison to a theolodite?

--ShopShoe

The word goniometer has yet another use. In radio direction fining receivers, it is a set of coils -- two fixed and one movable -- used to combine signals from two perpendicular receiving antennas to measure the arrival angle of the signal. It was invented jointly by Ettore Bellini and Alessandro Tosi in 1909, and was widely used from the 1920s until the 1970s, when it was gradually replaced by electronic circuits that do essentially the same thing.

DKG

 

[L98fiero]

The word goniometer has yet another use. In radio direction fining receivers, it is a set of coils -- two fixed and one movable -- used to combine signals from two perpendicular receiving antennas to measure the arrival angle of the signal. It was invented jointly by Ettore Bellini and Alessandro Tosi in 1909, and was widely used from the 1920s until the 1970s, when it was gradually replaced by electronic circuits that do essentially the same thing.

DKG

When I initially gave the description, it was relative to the other survey equipment the OP said it was with, generically, a goniometer is anything that measures or facilitates setting angles.