Twinway - Bondcliff Trail Info Needed

[kltilton]

Hi all,

I was wondering if anyone has any GPS tracks from any hikes that have been done on the Bondcliff Trail or the Twinway. I am particularly interested in the low points between Guyot and Bond and South Twin and Bond. I am curious as to what the col depth seems to be based on handheld GPS observations. If anyone is willing to share any info it would be greatly appreciated. Thanks.

 

[Mike P.]

no GPS but the low spot on the trail may not be at the col. The trail does not always stay at the highpoint of the ridge but wanders from side to side.

The trail may dip 200 feet below Guyot's summit but the top of the ridge doesn't...

 

[RoySwkr]

Good point MP.

Finding the actual col in wooded areas to take a reading at may be tougher than the survey from there to the peak which can mostly use the trail. And several cols may be close enough to the magic number that it requires a more accurate survey - the USGS contours are probably as accurate as a GPS.

Based on my GPS elevations, E Hancock 4020 may belong on the Trailwrights list but I bet it will be a long time before anyone does an accurate survey there

 

[DougPaul]

And several cols may be close enough to the magic number that it requires a more accurate survey - the USGS contours are probably as accurate as a GPS.

Based on my GPS elevations, E Hancock 4020 may belong on the Trailwrights list but I bet it will be a long time before anyone does an accurate survey there

The one-sigma vertical error of a consumer GPS is ~42ft (12.8m) assuming a good skyview. http://www.edu-observatory.org/gps/gps_accuracy.html So the error on a difference between GPS measurements is ~59ft. Thus you would have to measure a dip of 259ft or more before a conclusion of "the dip is >200ft" becomes very believable. (The exact amount would depend upon how reliable you want the conclusion to be.)

A good barometric altimeter rushed back-and-forth between the two points for several interspersed measurements would probably be more accurate.

Seems to be this was discussed in more detail in one of the threads about the "new" summit of Owls Head.

Doug

 

[RoySwkr]

A good barometric altimeter rushed back-and-forth between the two points for several interspersed measurements would probably be more accurate.

It used to be that professional surveyors used high-grade altimeters for ~2' accuracy for designing septic systems etc., KT presumably knows more than I do about this

The "cohp" discussion group is also presently debating this topic, they say that professionals can acquire a differential GPS system for roughly $40k

 

[DougPaul]

The "cohp" discussion group is also presently debating this topic, they say that professionals can acquire a differential GPS system for roughly $40k

Yeah, I think some of them are in that ballpark. I think you can also rent them. You also have to know how to use it.

With the appropriate gear, long data acquisition times, and post processing, it is possible to get accuracies on the order of 1 cm.

Not worth $40K to me to determine if a dip is 200 or more feet...

Doug

 

[kltilton]

My idea is if the col depth seems to be close to the 200' depth based on handheld GPS observations, I may have the ability to use survey grade GPS equipment to survey the low points of the cols and the summit of Guyot (or both summits for that matter). This would involve a lot of work and effort, but it could be an interesting little experiment. One obstacle that can arrise is that the GPS equipment only works so well in thick wooded areas, but if there is an open area close by GPS surveying could be performed there and differential leveling could be employed to reach the true low point.

This is probably a pipe dream, but something that could be done with a little effort and help.

 

[wardsgirl]

I think this is what you are looking for. Although I don't have the track all the way from Mt. Bond, here is a track of Bondcliff Trail and the Twinway from the Guyot Campsite Spur to S. Twin, as produced by a Garmin GPXMap 60 CSX. The track file is in GPX format with the track data in Excel format. (I can provide this in a couple other formats, if needed.) Does this help?

 

[RoySwkr]

This is probably a pipe dream, but something that could be done with a little effort and help.

It would be great if you could do this. As I recall the Twinway W from Guyot drops in the open a long ways but not towards the col, so differential levelling might be needed but it would be fairly level

For a practice trip how about the Lafayette-Lincoln col, that one is pretty open? Of course Hancock-S Hancock and Bond-W Bond are all in trees.