Monika Epsefass , Sep 08, 2009; 09:20 a.m.
To work on the ground, pack a thick plastic plane into your bag. It's available at your local hobby market (the plastic covers you use when painting your apartment, for example) - these exist in a bit thicker and sturdier variety. They fold small, weigh near nothing, and are spacious enough for you to lay down on them, if you need to do so.
And get a waterproof jacket at least, if not a waterproof cover to wear on top of your pants.