GPS If used right you can tell every thing your dog is doing. He was walking till he hit 800 yards then he ran 35MPH for 200yards so that tells me he didnt see the hogs till he was 800yards out.
Awesome, Those GPS units are great. I saw one utilized in Gonzalez not to very long ago. I asked him where he thought a dog was, he told me, 278 feet over there. then showed me where it had been.