OK, here's my take on this. I hunt coyote in both hardwoods and open country, ie: river bottoms and Sand Hills. When in open country, the best luck I've had is calling with the wind behind my back. This projects the call much further than if you calling into the wind. Granted, longer shots are taken with this method due to the chances of getting winded. But in the wide open spaces of Nebraska, coyotes can hear your calls all the way from South Dakota...ok, maybe a slight exageration on my part but you know what I mean. We're talking miles and miles of grass...no trees, no bushes....just grass. Many of the coyotes will follow the gulleys and valleys..and just before they think they're getting within visual of the prey, they'll pop over a rise. That's when daddy gets home.
In Hardwoods, I've noticed that no matter what position I take, the trees, hills and other obstructions bounce my call. At least I think they are. I dont think the coyote can get a real good idea of where the dying critter is with the sound waves banging back and forth between the trees. I use a scent in that scenario, a little pee pee here, a little pee pee there. Gives them a better idea where the prey is. I havent fiqured out how they can tell direction by smell and not by hearing....but they are coyotes. Shots tend to be MUCH closer in the hardwoods, I use a shotgun while working the river bottoms.
"I Hunt, Therefore I'm Broke"