Circa 1999, I was a member of a search and rescue team through the explorer scouts. We got to carry milspec GPS devices on a hike once, because the forestry service wanted accurate maps of some trails. We were under strict orders not to deviate from the trail or tamper with the devices. Very fun cloak&dagger atmosphere for what was otherwise a lovely walk in a park. Hilarious that the need for such missions was obviated a few months later