When we think of an Military Ambulance, or a Military Hospital, Casevec Helicopter or a Hospital Ship, the foremost identifying mark we recognise is the "Red Cross". This is actually a clearly defined international sign that was originally agreed upon in the 1889 Geneva Convention to signify non-combatant, and non-partisan, humanitarian and medical services. All signatory nations agreed to observe the neutrality of any members of any Armed Force displaying the Geneva Cross, and in return declared that any unit or body displaying the Geneva Cross would not actively or passively engage in warlike actions. To readily identify units with such protection, a clearly marked symbol needs to be displayed. The agreed symbol was initially formed by reversing the flag of Switzerland to create a red cross on a white background. Like any official international symbol, an agreed "Standard" to describe that symbol was required.
The Standard adopted to describe the Geneva Cross is "A red cross formed by five red squares arranged horizontally and vertically placed on a white background of either circular or square shape. The circle will have a diameter of five times the measured dimensions of the red squares, while the square background will have dimensions of five by five times the dimensions of the red squares".
Confused? If the "red squares" are 12" square, forming a cross 3'x3', then the white circle will be 5' diameter, or a white square 5'x5'. If the "squares" are 18", the Cross will be 4'6"x4'6" on a white circle/square of 7'6"x7'6". The dimensions will always remain proportional.
Anyway, to cut a long story short, pictured below are examples of a "Good" Geneva Cross (although the cross is a little large for the circle), and a "Bad" Geneva Cross.
Hopefully this will be of assistance to someone repainting an Ambulance, or any other medical equipment.