Are you going for a bike ride? :)

The area around Atna has many nice trips for bicycles. Friisvegen is great. Round trips can be made From Atna via Vinjevegen, to Trønnes and then the road on the east side of Glomma to ungå RV3, possibly a longer trip via Imsdalen to Imsroa. The long trip can be laid via Ringebu and then Venabygdsfjellet back, down to Enden and Atnadalen back to Atna Camping.

Clothing adapted to the weather
Tent if one wants to make it a trip with accommodation
Food, drink, primus or the like (remember the fire ban).