Sparse noise units documentation

[k1o0]

Saw the 'WHAT UNIT' in the sparse noise table definition:

IBL-pipeline/ibl_pipeline/behavior.py

Lines 229 to 230 in fe3d00b

	sparse_noise_x_pos: longblob # x coordiate on screen of sparse noise stimulus squares (WHAT UNIT?)
	sparse_noise_y_pos: longblob # y coordiate on screen of sparse noise stimulus squares (WHAT UNIT?)

The answer is degrees visual angle. In other words the x positions are in degrees azimuth, where 0 is the centre of the visual field, -ve is the left; y positions are in degrees altitude, where 0 is the centre of the visual field and -ve is below the centre.