The Arena

There are two sizes of arenas: small and standard. Each has letters assigned to positions around the arena for dressage tests to specify where movements are to be performed.

Small Arena:

The small arena is 20 m by 40 m.
The letters are A-K-E-H-C-M-B-F.
This arena is used for children’s level dressage.
A number of mnemonics devices are used to remember this sequence, such as the phrase
"All King Edwards' Horses Can Make Big Fences."
Letters also mark locations in the middle of the arena: Moving down the centre line, they are D-X-G, with X in the centre.

Standard Arena:

The standard arena is 20 m by 60 m.
The letters are A-K-V-E-S-H-C-M-R-B-P-F.
It is commonly believed that these letters were chosen because the German cavalry had a 20 x 60 meter area in between the barracks which had the letters posted above the doors.
The letters on the long sides of the arena, nearest the corners, are 6 m in from the corners, and are 12 m apart from each other. The letters in the middle of the arena are D-L-X-I-G, with X marking the centre line.

The letters and there meanings:

PPferdeknecht(Ostler or Groom)
EEdling/Ehrengast(Chieftain or Honoured Guest)
BBannerträger(Standard Bearer)
SSchatzkanzler(Chancellor of the Exchequer)
HHofmarschall(Lord Chancellor)

Standard dressage arena, 20 m by 60 m:

Dressage Arena