Me and my 7th-grade students are going to a 3-day trip. It's an excellent opportunity to have some outdoor math games and activities. What games and activities do you suggest? Do you know any source for finding them?
Students can play many estimation games. Students can find objects in nature and then challenge others to estimate the length, weight, and surface area. These can be checked with measuring tools and whoever is closest gets a point. Determining who is closest is also a mathematical exercise.
You can also make a list of things to find (a scavenger hunt) with a range of lengths or weights, e.g. between 5 and 6 inches or between 25 and 30 grams. Give them a time limit to find the items.
One of my students favorite games which can be played when walking in a group is where I pick a number (e.g. 3,050,322, 3/7, -25, or 0.55673) and the students have to guess. I give them no clues to start but they are told higher or lower. Give the class a time limit to find the number. Start with reasonable numbers e.g. a whole number in the thousands and work your way to harder numbers. Always write the number down on a paper in your pocket so they know it's really the number you picked. If they guess the number in the time limit they get a point and if not you do. For some reason they adore this game.
Hope these ideas help.
On one outdoors activity day, we got set a version of the little child's toy with three posts and different size rings made out of numbered tyres. I would consider the reasoning in that a form of maths.
(When the instructor realised I knew how to do it, he insisted we started again without me saying what to do. So I pointed.)