221 Document gridscan coordinate systems

[rtuck99]

This addresses #221 and improves documentation about the reporting of the Zocalo Results

See also DiamondLightSource/dodal#958

It also fixes an issue where the bounding box returned in the XRayCentreResult is off by 0.5 of a grid-box, however I don't think this impacts anything as this attribute isn't used yet.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.89%. Comparing base (91d755e) to head (631e3d7).
Report is 1 commits behind head on main.

Additional details and impacted files

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i24 SSX	72.69% <ø> (ø)
hyperion	96.88% <ø> (ø)
other	94.24% <ø> (ø)

[olliesilvester]

Thanks! I think this part of the code is always going to be confusing, but it's much more understandable after your changes

[olliesilvester]

As discussed the entire logic here is quite hard to explain via comments, but I think this helps to explain the 0.5

Suggested change

	centre_of_mass_mm=xray_centre,
	bounding_box_mm=(
	# Bounding box coordinates give position of the centre of the box, subtract half a box size to get the start of the box
	bounding_box_mm=(

[olliesilvester]

Whoops, didn't mean to delete line 294 in this suggestion