I use Epicollect, but mostly just for picking GPS coordinates on site.
Once I am in front of my computer, I will download the points on a spreadsheet, make some averages, and calculate the distance of each tree (or other feature/building) from my reference point which is one of the corners of the orchard.
From there I plot the points on AutoCAD to get the drawing of the orchard. The difference in latitude gives the distance in the north-south direction, while the difference in longitude gives the distance in the east-west direction. There are online calculators that will give you those distances from 2 GPS coordinate points (but for my part I calculate them myself in the spreadsheet).
The use of AutoCAD for this is surely overkill, but I have it and I am used to it, so it is the easiest for me. Any other simple vectorial drawing program should do the job just as well.
One thing you need to know, GPS coordinates can be quite off, like easily 10 to 15 meters imprecision (unless you have professional equipment). The way to improve on this is to take many records on the same point and make the average. When I have something like 10 records for a point, the precision is greatly increased. Note that these records need to be taken not just one after the other because in that case you are always on the same satellite which is at the same location. The recordings should be taken over a period of many hours/days, so that each record is independant from the others.
Claude
Jolicoeur OrchardZone 4 in Quebec