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musicman82 - Apr 17, 2010 12:45 am - Voted 10/10

Great work

This is a fantastic article - thanks for sharing this info!



peakhugger - Apr 17, 2010 10:30 am - Hasn't voted

Re: Great work

Thanks Tim. Glad you enjoyed it - I just had to share what I'd learned.


silversummit - Apr 17, 2010 11:46 am - Voted 10/10

Sounds like a thorough but very readable article

which I really enjoyed reading. It also rings close to home since my dad worked for the US Geological Survey here in DC and then in Reston, VA creating precise instruments of different types from drawings for scientists. He loved the geodes and other samples they would bring back to him from their travels as mementos of their work, some from mountains far away.

Again, an excellent contribution to SP!


peakhugger - Apr 18, 2010 12:57 am - Hasn't voted

Re: Sounds like a thorough but very readable article

Thanks! I found it impressive the precise tools folks were able to manufacture in the 1800s, especially when the measurements with those instruments still stand today (give or take a few inches). My Grandfather was once given an old surveyor's theodolite (he was a collector of various western artifacts) and I remember being amazed in its intricacy, even at the age of 10.

Arthur Digbee

Arthur Digbee - Apr 18, 2010 1:24 pm - Voted 10/10

nice article

and fun to learn about the "benchmarks" other than USGS.

I saw a weird one on top of Deer Mountain in RMNP -- the Bureau of Reclamation!


peakhugger - Apr 18, 2010 9:59 pm - Hasn't voted

Re: nice article

That is an odd duck. As MOCKBA states below, everybody was looking for vertical control, and a highly visible summit is a pretty ideal spot.

Dmitry Pruss

Dmitry Pruss - Apr 18, 2010 1:49 pm - Voted 10/10

Very well written

Thanks for the effort! We are blessed here with numerous surviving markers from the 1871 transcontinental survey, and for a while I seriously engaged in the hobbyist recovery of the oldest benchmarks, like the 1870-1880s crosshair bolts and turn-of-the-20th century triangle-stamped bolts.

Some of the other old survey markers are harder to find because the GLO / BLM records haven't been digitized yet. Up in the mountains of the West, there are many 19th century US Mining Monuments but finding them takes serious gumshoe work with the longhand records of the BLM archives.

Lastly, a lot of 20th century BMs in the Western mountains were set up for vertical control for settlement of irrigation dams. So their placing has been typically done by BOR or USDA.

Our state's highest Kings peak (actually its South summit which was thought to be the highest before the age of satellites) has only a "target" silhouette listed as an USGS BM, but it also had several control disks not listed in their database, placed by the irrigation authorities.


Noondueler - Apr 18, 2010 8:56 pm - Hasn't voted

Re: Very well written

Keep on rockin' Mockba!


peakhugger - Apr 18, 2010 10:04 pm - Hasn't voted

Re: Very well written

I have a feeling one could dig forever and still learn more about the surveys of the last 200 years (and find markers!) Interesting to hear that the south summit of Kings Peak was once thought to be higher...
Thanks for the review and the tidbits on GLO/BLM and BOR marks.


Dean - Apr 18, 2010 2:20 pm - Voted 10/10

Interesting addition

As one who truly loves benchmarks, I appreciate your addition. Thank you.


peakhugger - Apr 18, 2010 10:05 pm - Hasn't voted

Re: Interesting addition

You're quite welcome. Cheers!


CrazySanMan - Apr 19, 2010 7:25 am - Voted 10/10

Great article

I really learned a lot from your article. Thanks!

clearcut - Apr 20, 2010 3:39 pm - Hasn't voted

more info

I work for the USGS and did 9 years of topo field mapping. FortMental is correct. Nearly all elevations on mountains with a BM were established using vertical angles from transits from several locations on established leveled BMs. the closest level line is probably the West Rosebud Creek, the Beartooth highway or the highway going past Cooke City. The mountain top BMs many times are not on the highest point because of loose rock etc or it was placed for the best view to other BMs to tie into(Mt Wood maybe). The elevations on mountains nowadays are established using photogrametric stereograph equipment and aerial photos. This does not mean they are more accuate just easier to do. Any elevation on mountains that do not show either a triangle(horizontal) and or a BM deliniation were probably established stereographically. I don't know why the 1986 Grainte Pk map no longer shows a VABM(vertical angle) on the top unless it no longer met horizontal accuracy standards.


suddendescent - Apr 20, 2010 7:11 pm - Voted 10/10

I guess that with advancements with science more accuracy is to uncover

Thanks for exposing the subject matter about as completely as it can get considering what isn't mentioned namely the bulging resulting from the combination of lunar and solar attraction without mention of the consequences of rotational velocity creating centrifugal expansion(whose effect is maximised at the equator), to put everything back in perspective !

Excellent article !

Regarding the "tidal" effect; studies have indicated that there is significant expansion to observe inland...

I remember (either reading or watching on TV) a feature dwelling on such a subject matter whereby many contradictory claims were advanced either giving more prominence to a peak on it's podium of glory or less which for an example like Everest could have lead to "devastating" results LOL !

Although, it's obvious that the purpose of such investigations is to assure that accuracy prevails unchallenged...

Nowadays satellites can accurately judge elevation by triangulation such as is observed once trying to accurately determine the geographic location and altitude of a GPS device using 3 sources and comparing the return signal time while taking into account the angular differences (giving different signal time returns) for satellites emplaced at the same altitude and at a different geographic location . Although such a task can also be accomplished by use of a radar beam (such as a maser which is typical of Radarsat) which with one satellite without use of any ground equipment which will use the emitted beam from such a satellite and wait for a return signal which in accordance to time gives a good indication of altitude. The microwaves from such radarsats bounce off rock and -as is well understood once putting a cup of water in amicrowave oven- are absorbed by objects containing water including living tissue... Such a means of measurement is typically used to precisely give differences of elevation on other planets. Extremely "Hard" return signals (such as what was uncovered on Venus ) indicates solid metal.

Mind you , previously it took an experienced climber risking loss of life and limb to put a benchmark on a summit...Nowadays, a helicopter does the job without any hassles...

Anyways, what counts for most is the sensational aspect of the topography best uncovered with rapid changes in elevation -which is properly rendered with current maps- as opposed to the elevation itself expressed with the goal of assuring that a certain measure of objectivity prevails once considering the quest for accuracy...

By the way; after quick inspection of some landsat winter images from Quebec I was lead to believe that some mounds (such as from the lower north shore) could, despite the unappealing grades , lead towards some interesting surprises...

Mark M

Mark M - Apr 21, 2010 8:11 am - Hasn't voted

Very nice!

Great Article. Thanks!


suddendescent - Apr 23, 2010 7:24 pm - Voted 10/10

By the way;

Considering the acknowledged fact that the earth despite being deemed as a sphere is actually flattened at the poles, this leads us to understand that despite the impressive nature of antarctic summits which culminate at a height of over 15000 feet , such summits with due consideration for the flatness of the poles are actually 20000 leagues under the acknowledged frame of reference once considering the perfect sphere which for the earth is best described by the sea level... !

With regards to the flatness of the poles , I was lead to beleive that such a reality resulted from the rotational velocity of the spinning sphere which considering the presumption of a molten interiour immediately below a superficial crust created such a distortion...But then the effect could be more gradual if the molten interiour is much further down...Imagine an asteroid hitting at ahigh velocity at the equator...I guess it could potentially disintegrate a planet...

John Kirk

John Kirk - Apr 27, 2010 3:07 pm - Voted 10/10

Caveat of elevation revision

It's important to keep in mind measures of prominence become problematic when applying new elevations. There is no data source for what the saddle elevation revisions should be (how often is a benchmark at a saddle?), so prominence figures are being inflated when saddles are not revised. From a peak listing perspective referencing prominence, until maps are redrawn with new contour lines reflecting the change in datum (unlikely), elevation adjustments should be taken with a grain of salt.

Gary Schenk

Gary Schenk - May 5, 2010 10:44 am - Hasn't voted

Nice Article

A quite nicely written article. Just one comment, the differences between NGVD 29 and NAVD 88 elevations are not because the 29 values were "wrong" or inaccurate, but because the basis of these datums are different. 88 elevations are derived from the center of the earth using a modern mathematical model of the earth's surface. 29 elevations were based on seal level as reported at several reference benchmarks around the country. And as you noted, sea level varies from location to location.


MountainHikerCO - May 5, 2010 2:56 pm - Voted 10/10

Interesting read

I think we can sometimes get too hung up on wanting hard definitions when there are several variables. Yet we still want to come to terms with our own climbing logs!

Here in Colorado we have our lists of fourteeners and thirteeners. The discussion is often about what is a separate or ranked summit. While summits commonly have a benchmark or spot height, the saddle elevations are often interpolated from the contours. Is there a 300’ drop or not? If we “discover” or demote a ranked summit that changes the high 100 list! Traditional fourteeners El Diente & North Maroon have been demoted on 300’ lists while Challenger & Ellingwood have been added.

A couple years ago some friends and I surveyed unranked thirteener Drift Peak. There was suspicion it could be a ranked high 100. Here is my trip report on

We also plan to survey North Massive which Roach lists as “soft ranked.”


CheesySciFi - May 29, 2010 9:36 pm - Voted 10/10

Fine article

Given that we use USGS topo maps so much in our adventures, it makes sense that we have an article about USGS benchmarks. This is a very interesting look at the history and techniques of surveying. Not that I'm biased, being an employee of USGS after all!

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