hmmm ok I need to do some more checking on my mages but it looks like this AOE macro will only work if you target flat terrain on your mini-map.

Based on the fact it looks like the pings change posistion when you alter your minimap zoom I suggest either using max zoom where by 1ping pixel = 1yard or use the below data to calculate your distances.
This data was collected under the assumption that you can only trade or follow another charactor at a max distance of 30yards.

30yards
max zoom(5) = 0,30
1yard = 0,1

30yards
zoom(4) = 0,22
1yard = 0,0.13

30yards
zoom(3) = 0,16
1yard = 0,0.18

30yards
zoom(2) = 0,14
1yard = 0,0.21

30yards
zoom(1) = 0,12
1yard = 0,0.25

30yards
min zoom(0) = 0,10
1yard = 0,0.3