Geocachers Spot Another Bogus Summit

[RoySwkr]

Remember the Owls Head situation where the best evidence that the sign wasn't in the right place was the coodinates of a nearby geocache? Now we have the same thing on Eagle Mtn in Jackson NH.

The WMG says the "true summit" is marked by a large cairn but if you bushwhack NW maybe 100 yds you will reach an apparent higher spot in the woods. There is a geocache along this route whose coordinates are SE of the spot elevation on the map indicating that the trail does not reach the spot elevation.
http://mapper1.acme.com/?lat=44.16106&long=-71.19584&scale=11&theme=Topo&dot=Yes

A lot of hikers carry GPS units now but few actually look at the coordinates they get. If every hiker checked the coordinates of every summit they got to, a lot more bogus summits would be discovered and a lot of hikers would learn the limitations of GPS when the supposed summit coordinates did not plot at the obvious highest point.

 

[rocket21]

The WMG says the "true summit" is marked by a large cairn but if you bushwhack NW maybe 100 yds you will reach an apparent higher spot in the woods.

I was up there about a week ago and did said bushwhack - it indeed seemed to be a few feet higher than the ground at the cairn (which was somewhat visible through the trees for visual judgement).

 

[TCD]

I'm not sure how accurate or precise elevations are on the typical hand held GPS, but if you want to do it the old fashioned way, it's pretty easy to use a standard 4' carpenter's level as a makeshift theodolite. I have done this on a hike a few years ago. If you have three people you can get some pretty good readings. One person stands at the target site (say, the cairn) and might hold a pole or some other object in the air as a height scale. Two people use the level at the other site; one to view along the level, the other to level it via the sight glass. It's quite accurate, and wonderfully low tech...

 

[Dr. Dasypodidae]

I'm not sure how accurate or precise elevations are on the typical hand held GPS, but if you want to do it the old fashioned way, it's pretty easy to use a standard 4' carpenter's level as a makeshift theodolite. I have done this on a hike a few years ago. If you have three people you can get some pretty good readings. One person stands at the target site (say, the cairn) and might hold a pole or some other object in the air as a height scale. Two people use the level at the other site; one to view along the level, the other to level it via the sight glass. It's quite accurate, and wonderfully low tech...

Good suggestion, and I carried a hand level with me to Owls Head this past weekend. But, as I suspected, because of all the ups and downs along the 0.2 mile or so between the "old" and "new" summits, too much time would have been required to make dozens of fore- and back-sightings because of the thick vegetation. Perhaps I will try again with a couple of accomplices and take along a collapsible stadia rod when the days are longer.

 

[DougPaul]

I'm not sure how accurate or precise elevations are on the typical hand held GPS, but if you want to do it the old fashioned way, it's pretty easy to use a standard 4' carpenter's level as a makeshift theodolite.

What is important here is the differential altitude accuracy, not the absolute accuracy.

The vertical accuracy of a GPS altimeter* is ~15 meters, 95% of the time under ideal conditions**. Thus the differential accuracy between two measurements would be ~21 meters, 95% of the time. A properly-used good quality barometric altimeter would be more accurate.

* This refers to the altitude from the GPS, not a barometric sensor coupled to a GPS.
** ideal conditions include good skyview, good satellite constellation, etc.

A piece of clear tubing filled with water is another low-tech way of determining the difference in altitude for two points that are not too far from each other.

There was a a lot of discussion on measurement of differential altitude in the big thread on the "summits" of Owls Head: http://www.vftt.org/forums/printthread.php?t=7172

Doug

 

[Kevin Rooney]

Good suggestion, and I carried a hand level with me to Owls Head this past weekend. But, as I suspected, because of all the ups and downs along the 0.2 mile or so between the "old" and "new" summits, too much time would have been required to make dozens of fore- and back-sightings because of the thick vegetation. Perhaps I will try again with a couple of accomplices and take along a collapsible stadia rod when the days are longer.

Thom - another option to a hand level is the small laser level which you can get for as little as $25 at Sears, Home Depot, etc. When laying out the foundation lines for our house, studio and garage, I used a combination of line level on a string, a small laser level and even the tube method Doug mentions using a garden hose. I found the laser level the easiest to use, and it's rather small - not much bigger than a GPS.

 

[Lou Hale]

Why carry a 4' level when a lazer like kevin said or one of these will work

http://www.amazon.com/Stanley-77-187-Pocket-Optical-Stadia/dp/B0007SXI5E

 

[DougPaul]

Re laser levels:
How accurate are these levels?

Depending on the accuracy and range, these devices could be useful or useless for this task.

It is possible that they would have to be used at night to extend the range.

Doug

 

[Dr. Dasypodidae]

Why carry a 4' level when a lazer like kevin said or one of these will work

http://www.amazon.com/Stanley-77-187-Pocket-Optical-Stadia/dp/B0007SXI5E

The hand level that I took to Owls Head last Sunday is essentially the same as that shown in the link. But, it does not see through trees, and one still needs to do a lot of fore- and back-sightings for an up-and-down transect such as that between the two summits on Owls Head. My guess is the project will take at least a couple of hours with at least one other person to carry and mark a stadia rod.

 

[Paradox]

I'm thinking a laser combined with the water filled tube would be an inexpensive and light weight way to do this.

 

[Dr. Dasypodidae]

A piece of clear tubing filled with water is another low-tech way of determining the difference in altitude for two points that are not too far from each other.There was a a lot of discussion on measurement of differential altitude in the big thread on the "summits" of Owls Head: http://www.vftt.org/forums/printthread.php?t=7172
Doug

So, although no doubt more accurate, I am thinking that a water level might not be very efficient for measuring the difference between the Owls Head summits if one needs to make 20 or more 50-ft measurements over the 0.2 mile distance? And, even a small-diameter 50-ft tube would require a fair volume of water, which I suppose one could drink when finished.

 

[DougPaul]

So, although no doubt more accurate, I am thinking that a water level might not be very efficient for measuring the difference between the Owls Head summits if one needs to make 20 or more 50-ft measurements over the 0.2 mile distance? And, even a small-diameter 50-ft tube would require a fair volume of water, which I suppose one could drink when finished.

It might not be the fastest method, but it is cheap, low-tech, easily understood, and fairly accurate. And of course, it can go around trees and corners.

One could probably use a 100-200 ft tube to reduce the number of individual measurements. The longer the tube and the smaller diameter the tube, the longer it would take to settle.

The amount of water wouldn't be too bad: a 3/8 inch id tube 100 ft long has a volume of ~2.2 liters.

Doug

 

[Paradox]

It might not be the fastest method, but it is cheap, low-tech, easily understood, and fairly accurate. And of course, it can go around trees and corners.

One could probably use a 100-200 ft tube to reduce the number of individual measurements. The longer the tube and the smaller diameter the tube, the longer it would take to settle.

The amount of water wouldn't be too bad: a 3/8 inch id tube 100 ft long has a volume of ~2.2 liters.

Doug

I have a couple 25' lengths of tygon that used as a level to build my workshop. Shooting the laser across the meniscuses (menisci?) with the laser, to a tree far ahead would minimize the amount of water and tubing one would have to use.

 

[JOD]

if it really matters

If it really matter do it the right way. One may rent an auto level and rod for $30 a day. They only charge you for the days you actually use it. Even if you have it 3 days over the weekend and you are honest you will be charged for the 1 day use. The rod is fiberflass and collapsable to about 5' it isn't too heavy. The tripod is aluminum again not too heavy. The auto level is small enough to fit in a day pack. It only takes two people to run the levels bring a field book to record the levels and you can run the calcs while having lunch. Running levels for 0.2 miles shouldn't take that long.

Let me know how it works, and have fun! I really think this is all getting too anal for hiking. Whatever rocks your boat.

 

[Dr. Dasypodidae]

Let me know how it works, and have fun! I really think this is all getting too anal for hiking. Whatever rocks your boat.

Owls Head is not just "hiking," but rather one of most disputed summit elevations and locations in the Northeast!

Thanks for these two ideas (including water level details from DougPaul), which both sound feasible and more accurate than using my hand level and/or surveying altimeter.

 

[Paradox]

My knee should be fully recovered in another 2-3 weeks. I would like to nail this down once and for all with Dr. D and others then. As long as were all on the level this should be fun.

 

[Dr. Dasypodidae]

My knee should be fully recovered in another 2-3 weeks. I would like to nail this down once and for all with Dr. D and others then. As long as were all on the level this should be fun.

I am not sure how well the water level will work in sub-freezing temperatures, but let's keep an eye on the weather.

 

[DougPaul]

Re accuracy of laser levels:
Did a bit of searching. http://www.google.com/search?hl=en&q="laser+level"+accuracy&btnG=Google+Search&aq=f&oq=
1/4 inch at 100 ft and ranges of 100 ft or less seem pretty typical for construction-grade laser levels. To get maximum range, one has to use a digital receiver. I suspect the cost of the better ones is prohibitive for this application.

It looks like the units are somewhat delicate--about like a digital camera, according to one comment. (It is, after all, a precision mechanical-optical device.)

So it looks like the accuracy of construction-grade or better is adequate for this application. Don't know about the $30 units.

Doug


Some data:

http://shopping.msn.com/specs/stanl...:stanley-cross-line-laser-level-model#-77-152
5/32 in at 30 ft (=1/2in at 100 ft), range 30ft?, $110

http://www.surveyingtrade.com/laser.htm
1/4 inch at 100 ft, range 30m without detector (100m with)

Trimble precision laser http://www.trimble.com/ll500.shtml
1600 ft (500m) range, accuracy 1/16 in at 100 ft, $1500
requires a digital receiver.

 

[DougPaul]

I am not sure how well the water level will work in sub-freezing temperatures, but let's keep an eye on the weather.

You can use automotive antifreeze in it. Just make sure that you mix a single batch prior to filling the tube so it all has the same density. (It is poisonous, so don't drink it or dump it out in the field. Animals like the sweet taste of ethylene glycol and have been known to drink it.)

Ethanol mixed in with the water will also reduce the freezing point and will be consumable after the fact. (You might want to use medical grade tubing if you plan on drinking the contents...)

Salt or calcium chloride would work too. (Salt is a terrestrial plant poison, don't know about calcium chloride.)

Doug

 

[HockeyPuck]

A lot of hikers carry GPS units now but few actually look at the coordinates they get. If every hiker checked the coordinates of every summit they got to, a lot more bogus summits would be discovered and a lot of hikers would learn the limitations of GPS when the supposed summit coordinates did not plot at the obvious highest point.

Such as the N Slope of Sandwich Dome is listed as the Carroll County highpoint but probably the 4th highest point in the county...

...Or Waumbek East (might) be higher than Waumbek.. Personally I believe the elevations are within inches of each other and way too close to judge with primitive GPSr tools.