A Sleep mat is a very important item in your camping equipment. Many campers feel that because they do not provide much comfort they are not worth the space they take.
Actually they are worth every inch of space they take, and they are so light that the weight is not really a consideration.
Sleep Mats for Ground Insulation
Although a sleep mat, or camping mat, will make the ground a bit more comfortable to sleep on, softening any bumps and irregularities underneath you, this is not their main purpose.
Most of your heat loss during the night is to the ground through conduction.
Although your sleeping bag will reduce this, it is not very effective because your body weight flattens the bag underneath you reducing its insulating properties.
This is overcome by using a sleep mat.
Even when sleeping off the ground on a metal framed camp bed or in a hammock, a sleep mat is still a very important part of your camping equipment.