Well north line actually ...

Ended up:
1. going from screen point (stored on style blackboard by a tool)
2. to a world point
3. to EPSG:4326
4. marching a little wasy up (0.1 of a degree)
5. back to a world point that is slight north of step #2
6. figuring out the theta between #2 and #5
7. calculating how far to walk in world units for 20 pixels
8. using the a bit of trig to produce a unit 20 pixels away
9. and then drawing the line ...

Next up a style contribution to let you choose something other then a line.
Jody

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