Sure it's laborious. I said "most accurate," not "easiest"!kepPNW wrote:Oh wow. That was my first thought, but then, "no way, really?"adamschneider wrote:It's not jargon; I mean literally drawing a new track manually on top of the "real" track(s). I reduce the opacity of the existing tracks and use them as a rough guide, but rely mostly on the aerial imagery whenever possible.kepPNW wrote: Tracing? Sounds like something I oughta be familiar with, maybe by another name?
Why do you feel that's more accurate than what the GPS records? Seems incredibly laborious. Like what we were doing back in the 80's when GIS were still mostly theoretical. I mean, I can sure see the appeal of tracing along visible trails, but the flipside of that is that the image rectification isn't all that wonderful or the feature has moved (happens!) over time.
GPS readings can be complete crap at times; we all know this. Often I do an out-and-back hike, and my "out" track is 20 meters away from my "back" track. Sometimes they line up for a while, then one drifts off to the west for a while, then it comes back when another satellite comes into view, or because the GPS gnomes got off their lunch break, or who knows why. You see this even when you're standing still.
If I had a really good signal all day, sometimes I'll simply edit the track I recorded: I move obviously wild points back in line, and I delete the tangled knots that form when I take breaks. But I've come to realize that editing existing tracks can take even more time than just drawing a good clean line on top of what's there.
As for the accuracy of the aerial photography... well, for one thing, in my experience, it's more accurate than most GPS tracks — and it's way better now than it was even 10 years ago. Also, when I'm tracing a clean track, it's usually because I want to get an accurate idea of the distance traveled, rather than the exact position within 2 meters. If the photography for a parcel of land is mis-aligned, oh well... the relative distances are still the same.
Obviously, tracing works best for hikes in open country where the trails are visible from above. Of course, that's when you're also likely to get a good GPS reading... unless you're in a valley, or next to a cliff. Cliffs are even worse than trees when it comes to screwing up your GPS. (When you're under trees, your GPS has trouble and you can't see anything on the aerial photos, so true precision is a lost cause there.)