The RDA has standardised arena dimensions, marker distances, scoring & penalties, and saluting & presentation for 2020 onwards. That information is published below, and each page may be clicked to enlarge for viewing, or downloaded for printing at A4.
The two drawings below are for a standard 50m x 25m arena (ie Sands Farm):-
The two drawings below are for a standard 60m x 30m arena (ie Hartpury):
Normally, Chalvington will be set out to a standard 60m x 30m, unless forthcoming competitions dictate otherwise.