Owl's Head Bushwhack

[Eric Savage]

I think the evidence is accumulating that the cairn/sign are on the south bump. Whether it's higher or lower or the same elevation as the x4025 bump is of course unknown until someone can measure it. Present day hiker technology may preclude that unless the difference is say 15'-20' or more. However the FTFC may decide (or not) that a spot elevation trumps an open contour. Same argument goes for Scar Ridge (where the canister is not on the x3774 bump), no?

The Owls Head summit issue has not been discussed in the time that I have been on the FTFC but I can ask about it. Even if it turns out that the summit is farther north than the present sign, I'm almost certain that previous ascents will be grandfathered. There are many precedents. If someone does figure out a way to settle this question (a nighttime ascent with laser levels?), I'd love to be part of the "research team." At the very least I'm going to have to plan extra time to walk the ridge next time I go.

As for Scar Ridge, the x3774 bump is considered to be the true summit but is so flat that no one spot can be identified as the highest. As long as you make some reasonable effort to wander around over there, you can count it. The cannister was placed on the other peak only to make it easy to find (it would just be cruel, after having done a bushwhack like Scar Ridge, not to make it as easy as possible to find the cannister). I seem to recall a pretty good herd path leading from the cannister to the 3774 peak.

I also found myself wondering about the highest point on Katahdin but perhaps that's grist for another thread (or just too blasphemous to be discussed ).

 

[DougPaul]

The very fact that you could site on Bondcliff would imnply you were not where the cairn/sign are located. The view there is next to nil. Of course it could have been more open in 1981.

I recall the sight was through the trees, but not how open the view was. It is also possible that I was on the east side of the ridge to get a better view.

Though I hate to admit it, I don't run this particular Circus McGurkis.

I'll forgive you this time, just don't let it happen again.

Note that on another thread (Look Here), the Geocache folks have fixed the location of the cairn/sign at the south bump. Presumably they took a GPS reading when they hid their box there.

Interesting. I just checked the coord--it is the south bump.

(BTW, are geocaches legal in the WMNF? IIRC, they have been forbidden in national parks.)

I think the evidence is accumulating that the cairn/sign are on the south bump. Whether it's higher or lower or the same elevation as the x4025 bump is of course unknown until someone can measure it. Present day hiker technology may preclude that unless the difference is say 15'-20' or more. However the FTFC may decide (or not) that a spot elevation trumps an open contour. Same argument goes for Scar Ridge (where the canister is not on the x3774 bump), no?

I obviously don't know where the sign is since I haven't been there for 24yrs. However, there are some tricks that one can use to make a fairly accurate estimate of the height difference between two locations.

Aneroid altimeters are needed for 2 of the following methods. GPSes with barometric sensors and the auto-calibration turned off will do. Garmin specs 1 ft resolution on their units. (Accuracy of 10 ft with proper calibration (user and/or auto).)

Method 1. Requires 2 aneroid altimeters and 2-way radios. Synchronize the altimeters to the approximate altitude at pt A. Carry 1 altimeter to pt B and compare readings by radio. Might be worth doing twice, with the altimeters switched to minimize the effects of any differences between the altimeters.

Method 2. Requires 1 aneroid altimeter: measure at pt A, then pt B, then back at pt A. (Try to make the travel times equal). Compare altB to the average of altA-1 and altA-2. (The dual measurments at pt A allow you to remove the effects of changes in the atmospheric pressure.) You can do this as many times as you want (or with as many altimeters as you can muster) and use the multiple data points to compute an average and a standard deviation.

Method 3: take a hose long enough to reach between the two locations. Fill it with water (making sure you clear out any air bubbles). Hold both ends up and let the levels settle. The water levels in the ends will be the same and you can compare the local topography to the water levels. (You can drink the water when you are done if you used a clean hose. )

Of course, you could just trust the map and use the GPS to find pt 4025. Sounds too easy, but it would really be amusing if those coord are obviously not at the top.

My estimates of the location of pt 4025 (WGS-84 datum)
NG TOPO! DRG: ................................... N44 08.636, W071 36.303
Highest point from NG TOPO! DEM: .. N44 08.638, W071 36.305, 4009 ft
Garmin US Topo 24K (DLG): ............... N44 08.642, W071 36.298
(coordinate format: Ndd mm.mmm, Wddd mm.mmm)
(.001 min N = 6 ft, .001 min W = 4 ft)

USGS 24K topo DRGs have an accuracy spec of 90% of the points must be within 40 ft. The DEMs are on a 30m grid.

Just a note: if you are not familiar with the datum, make sure you get it correct. The default for GPSes is WGS-84, USGS topos are labeled--usually NAD-27. (It is settable in the GPS and most mapping software.) I have estimated the difference between the 2 datums in the Whites and came up with 226m.

Maybe we will have to form a VFTT mapping group and actually run an expedition to explore Owl's head summit area...

Doug

 

[Papa Bear]

Method 3: take a hose long enough to reach between the two locations. Fill it with water (making sure you clear out any air bubbles). Hold both ends up and let the levels settle. The water levels in the ends will be the same and you can compare the local topography to the water levels. (You can drink the water when you are done if you used a clean hose. )

Clearly this would be the most fun - maybe use beer. The distance on the map is ~.15 miles = 800'

My estimates of the location of pt 4025 (WGS-84 datum)
NG TOPO! DRG: ................................... N44 08.636, W071 36.303
Highest point from NG TOPO! DEM: .. N44 08.638, W071 36.305, 4009 ft
(.001 deg N = 6 ft, .001 deg W = 4 ft)

Do you mean .001 degree or .001 minute? The location of x4025 and the highest point (NG TOPO) are stated as .002 minutes = .000033 degrees = ~1 inch. Did I miss something here?

Maybe we will have to form a VFTT mapping group and actually run an expedition to explore Owl's head summit area...
Doug

Now you're talking.

 

[Papa Bear]

The Owls Head summit issue has not been discussed in the time that I have been on the FTFC but I can ask about it. Even if it turns out that the summit is farther north than the present sign, I'm almost certain that previous ascents will be grandfathered. There are many precedents. If someone does figure out a way to settle this question (a nighttime ascent with laser levels?), I'd love to be part of the "research team." At the very least I'm going to have to plan extra time to walk the ridge next time I go.

Thanks for the response Eric. I'm of two minds 1) let's get it right and 2) does it really matter? But your interest and willingness to look into things and make things more transparent are very positive. Note from another post that I'm interested in going up there sometime this summer and see what can be determined. I'll try to coordinate that with other interested parties.

As for Scar Ridge, the x3774 bump is considered to be the true summit but is so flat that no one spot can be identified as the highest. As long as you make some reasonable effort to wander around over there, you can count it. The cannister was placed on the other peak only to make it easy to find (it would just be cruel, after having done a bushwhack like Scar Ridge, not to make it as easy as possible to find the cannister). I seem to recall a pretty good herd path leading from the cannister to the 3774 peak.

This is also nice and definitive. I think some folks don't really understand this - they think that it is just another ambiguity. Perhaps a note in the Scar Ridge canister stating "Sorry, you're not quite done yet" would clear that up. Haven't been there yet - I'm planning oin going July 10 with a few others.

Again thanks for being so responsive to us.

 

[DougPaul]

Clearly this would be the most fun - maybe use beer. The distance on the map is ~.15 miles = 800'

But the beer would have to be flat to avoid gas bubbles.

Do you mean .001 degree or .001 minute? The location of x4025 and the highest point (NG TOPO) are stated as .002 minutes = .000033 degrees = ~1 inch. Did I miss something here?

.001 minute. (Realized my error before I logged on this morning, but you caught it before I could fix it... Fixed.)

Nautical navigators rule of thumb: 1 min N-S = 1 nautical mile = 6076 ft.
So .001 min N-S = ~6 ft.
And .001 min E-W @ 44 deg N = ~(6 ft * cos(44)) = ~4 ft.

And the coordinate format was: Ndd mm.mmm, Wddd mm.mmm in case it wasn't clear to anyone.

Doug

 

[DougPaul]

The Owls Head summit issue <snip>

Thanks for the response Eric. I'm of two minds 1) let's get it right and 2) does it really matter?

I personally don't care from the standpoint deciding whether earlier ascents were vaild or not (I'm willing to accept them and I never even submitted my claim of having ascended all NH 4K peaks), but I'd be curious from the standpoint of figuring out the ground truth. It would be interesting to check the orignal survey notes used to make the topo, if they still exist. (It would probably require a professional mapmaker's skills.) Accurate surveying of relatively flat treed peaks such as Owl's head is probably difficult and time consuming and I doubt that most map makers care much about checking out all of the 2-3 ft high lumps. Radar maps might be useful (if such maps of sufficient accuracy exist).

Think we could get Washburn to map Owl's head for us?

Doug

 

[Papa Bear]

... It would be interesting to check the orignal survey notes used to make the topo, if they still exist. (It would probably require a professional mapmaker's skills.) Accurate surveying of relatively flat treed peaks such as Owl's head is probably difficult and time consuming and I doubt that most map makers care much about checking out all of the 2-3 ft high lumps. ...
Doug

Look at the old 15' map of the area (surveyed 1929): Here. A couple of interesting points: 1) it has 20' contour intervals vs. 40' on the modern map; 2) there is a spot elevation of 4023', quite close to the more modern valus of 4025'; 3) the high point is roughly east between where the two streams coming off Mt. Lincoln join Lincoln Brook. This is also roughly where the more modern x4025 point lies. (Topozone) OTOH, the south bump on the modrern map (1995) is just south of the southern stream. On the old map this is just the end of the ridge, with no bump plotted.

I know the old maps should not be trusted for real detail, and that the newer maps have sattelite data to supplement photgrametric date, nevertheless it's probable that the cartographers used the old maps as prototypes when they were putting together the newer maps.

 

[DougPaul]

Look at the old 15' map of the area (surveyed 1929): Here. A couple of interesting points: 1) it has 20' contour intervals vs. 40' on the modern map;

Just because a map shows a smaller contour interval, doesn't mean it is more accurate. I've seen (and posted) accuracy specs on the modern topos, don't know what they are on the old topos. And I'm sure the technology has improved. IIRC, most of the US topos are based upon aerial photography plus ground surveying.

2) there is a spot elevation of 4023', quite close to the more modern valus of 4025'; 3) the high point is roughly east between where the two streams coming off Mt. Lincoln join Lincoln Brook. This is also roughly where the more modern x4025 point lies. (Topozone) OTOH, the south bump on the modrern map (1995) is just south of the southern stream. On the old map this is just the end of the ridge, with no bump plotted.

Looks to me like the S bump is just SE of the "O" in "Owl's head" on the 1929 map. Both the summit and the S bump look to be in about the same location re the streams on Franconia and Bond ridges to me (compared to a modern 24K topo).

I know the old maps should not be trusted for real detail, and that the newer maps have sattelite data to supplement photgrametric date, nevertheless it's probable that the cartographers used the old maps as prototypes when they were putting together the newer maps.

It would seem possible, but I don't know what the actual procedure was. Also don't know if satellite data were used. (FWIW, radar mapping can be done from either aircraft or satellite. There is a bunch of shuttle SAR (synthetic apature radar) data, but I don't know what it covers or how accurate it is. Of course there could be more radar data too.)

In any case, I doubt whether the summit of Owl's Head was a point of particular interest to the USGS. This issue only comes up now because
any jerk with a few hundred dollars can locate a point as or more accurately than most maps.

Doug

 

[Papa Bear]

Looks to me like the S bump is just SE of the "O" in "Owl's head" on the 1929 map. Both the summit and the S bump look to be in about the same location re the streams on Franconia and Bond ridges to me (compared to a modern 24K topo)...
Doug

That's not what I'm calling the south bump. That's (the USGS version of) Owls Head. That's this: Topozone. It's opposite the 3rd stream (counting from the north). The so-called south bump (where the summit sign and cairn are located) is opposite the second stream: Here

 

[DougPaul]

That's not what I'm calling the south bump. That's (the USGS version of) Owls Head. That's this: Topozone. It's opposite the 3rd stream (counting from the north). The so-called south bump (where the summit sign and cairn are located) is opposite the second stream: Here

Oops. I measured the distance from pt 4025 to the S bump at 850 ft yesterday (reported in post #19) and at some point since then seem to have shifted my definition (possibly when looking at the old map).

Using the corrected definition of the S bump, I agree that it does not show on the old map.

And I still agree that Kevin's track looks like it ends at the S bump.

Doug

 

[Papa Bear]

Oops. I measured the distance from pt 4025 to the S bump at 850 ft yesterday (reported in post #19) and at some point since then seem to have shifted my definition (possibly when looking at the old map).

Using the corrected definition of the S bump, I agree that it does not show on the old map.

And I still agree that Kevin's track looks like it ends at the S bump.

Doug

Doug,
I think we've got the facts on the maps down at this point. Next we need to find out the facts on the ground. Once I get back from my NH and Maine hiking in mid July. I'll ask for interest in a joint trip up there to check it out.

So everyone: get your maps, compasses, altimeters and GPSes into shape and look at your calenders for a late July / early August mapping trip to the Unamed Peak above Owls Head.

 

[NH_Mtn_Hiker]

So everyone: get your maps, compasses, altimeters and GPSes into shape and look at your calenders for a late July / early August mapping trip to the Unamed Peak above Owls Head.

Sounds like a plan.

 

[DougPaul]

Doug,
I think we've got the facts on the maps down at this point. Next we need to find out the facts on the ground. Once I get back from my NH and Maine hiking in mid July. I'll ask for interest in a joint trip up there to check it out.

Sounds reasonable to me.

So everyone:

get your maps, compasses, altimeters and GPSes into shape and look at your calenders for a late July / early August mapping trip to the Unamed Peak above Owls Head.

If you/we get enough people, we can trample all that offending vegetation down and really be able to see the lay of the land. It might improve the views too.

Doug

 

[Papa Bear]

If you/we get enough people, we can trample all that offending vegetation down and really be able to see the lay of the land. It might improve the views too.
Doug

Excellent plan. And you can bring the 900' long hose and flat beer.

 

[DougPaul]

Excellent plan. And you can bring the 900' long hose and flat beer.

OK, you can fill at one end and I'll drink at the other "to remove the bubbles".

Doug

 

[DougPaul]

Papa Bear,

One other thought with respect to the methods that I described for estimating altitude difference in post #24.

The non-water hose methods all use *only* the aneroid barometer function of the GPSes. (The GPS part could be turned off.)

There is a general technique called DGPS (differential GPS) which uses a reference GPS at a known location to measure variations in the GPS satellites and in the signal transmission. This information is then used to increase the accuracy of a rover GPS by correcting some of the errors in the measued satellite signal arrival times. Techniques such as this are used to obtain millimeter or centimeter accuracies in surveying. (WAAS (wide area augmentation system), available on many consumer GPSes, is a form of DGPS.)

There is a simplified version sometimes called "poor man's DGPS", which seems logical, but doesn't work. This technique uses two regular GPSes--one takes two simultaneous GPS readings and subtracts the reference position from the rover position to get the rover position relative to the reference position. The hope is that the posiiton errors will cancel out, but unfortunately, many of them do not and the two GPSes may not even be using the same set of satellites. (Real DGPS makes the corrections on the measured satellite signal arrival times, not the resultant positions.)

Doug

 

[Papa Bear]

Papa Bear,
There is a general technique called DGPS (differential GPS) which uses a reference GPS at a known location to measure variations in the GPS satellites and in the signal transmission. This information is then used to increase the accuracy of a rover GPS by correcting some of the errors in the measued satellite signal arrival times. Techniques such as this are used to obtain millimeter or centimeter accuracies in surveying. (WAAS (wide area augmentation system), available on many consumer GPSes, is a form of DGPS.)

There is a simplified version sometimes called "poor man's DGPS", which seems logical, but doesn't work. This technique uses two regular GPSes--one takes two simultaneous GPS readings and subtracts the reference position from the rover position to get the rover position relative to the reference position. The hope is that the posiiton errors will cancel out, but unfortunately, many of them do not and the two GPSes may not even be using the same set of satellites. (Real DGPS makes the corrections on the measured satellite signal arrival times, not the resultant positions.)

Doug

I'm a little familiar with DGPS and WAAS. WAAS is available on most current models from Garmin., etc. And a number of users have said they have been able to sync to the WAAS source in the Whites.

Are you saying WAAS enabled GPS would not work on a project such as Owls Head, or just that "Poor man's DGPS" wouldn't work?

I was assuming we would take WAAS enabled "digital" readings as well as barometric readings. I have read accounts of running a long sequence (say every few minutes for an hour) of readings using WAAS and taking averages to get good altitude readings.

 

[DougPaul]

I'm a little familiar with DGPS and WAAS. WAAS is available on most current models from Garmin., etc. And a number of users have said they have been able to sync to the WAAS source in the Whites.

Being able to receive WAAS signals is one thing, if they help is something else. The WAAS satellites are geosynchronous (unlike the regular GPS satellites) and are therefore low near the SE, S, or SW horizon. Thus, they can be hard to receive in many places in the hills and/or trees.

WAAS was designed to help airborne aircraft where signals are generally pretty good. Ground use can actually degrade the accuracy--by actual experiment. (Don't believe the EPE (error) ouput by the GPS--it is a just a lower bound based upon some idealized assumptions.) I normally leave WAAS turned off. (It can also shorten the battery life.)

Are you saying WAAS enabled GPS would not work on a project such as Owls Head, or just that "Poor man's DGPS" wouldn't work?

In post #38, I'm saying that "Poor man's DGPS" doesn't work reliably anywhere. And in the previous paragraph, I'm adding that WAAS can help or hurt--and you can't tell the difference in normal usage. I wouldn't bother with it.

I was assuming we would take WAAS enabled "digital" readings as well as barometric readings. I have read accounts of running a long sequence (say every few minutes for an hour) of readings using WAAS and taking averages to get good altitude readings.

Comment on WAAS above. (BTW, GPS altitude errors are on the order of twice the horizontal position errors.)

Averaging to get a better position estimate is a good technique--some GPSes have built-in position averaging. (Some Magellans do it whether or not you want it, some Garmins allow you to specifically ask for it when recording a waypoint. IMO, the Garmin scheme is better.) I have seen long-term plots of error vs time. Some errors are short term noise (under a minute), some persist for periods up to hours, probably due to changing satellite positions. (The satellite positions repeat every 12 hours.) Practical averaging can reduce the short-term noise.

Late night positions tend to be more accurate than daytime positions. The night-time atmosphere and ionosphere are more predictable than the daytime.

IMO, the most reliable and accurate method for measuring the absolute position is the GPS without WAAS and for the absolute altitude is the auto-calibrated barometric altimeter. (I auto-calibrate in the car on the drive up and while hiking in and generally am within 10 ft of the published summit altitudes.) If you want, you can record a waypoint twice--once with WAAS and once without. (Make sure you record which-is-which.) You will have no way of knowing which is more accurate... If you cut down all the trees near Owl's Head summit, you could expect ~10m accuracies (without WAAS)--but there is also the possibility that some of the low elevation satellite signals will be blocked or reflected by the surrounding ridges. (Lincoln is 18 deg above the horizion from Owl's Head, so it can definitely block satellites.)

Don't use battery save mode--use normal mode.

Also don't forget to record the GPS height-above-ground when taking an altitude measurement. (And I'm not sure if the recorded waypoint altitude is the barometric or GPS altitude. Might want to record it with pencil and paper.)

My earlier post (the one including the water hose) covers my suggestions on how to best estimate differential altitudes. (Make sure you turn the auto-calibration off when doing this.)

The next step would be to use a survey-grade GPS. However this starts to become expensive and would probably require more training than either of us possesses.

Doug

 

[Papa Bear]

Another GPS trace

Here's another GPS trace posted by Bob Hayes of this weekend's trip. It seems clear now that the summit is at the southern bump, not the x4025 bump.

Bob's GPS trace

Bob: does your unit record the altitude? It might be interesting to see what it shows for your route (and for the summit), especially since the route passes over several benchmarks which could help with calibration.

 

[spencer]

PB,

look at the rest of Bob's pics on his website. He took a closeup of the screen showing 4033 feet.

nice work getting the info, Bob!

spencer