Summit Benchmarks

[4000'er]

Sorry,

I got side tracked on another project. I will try to set something up this week.

 

[Nate]

Are triangulation stations depicted in any way on USGS maps, or can their locations only be found from their respective datasheets? Also, on Topozone, I've noticed how often there's a triangle near where at "BM" appears on a map, but for the BM's I've tried to locate near my place, I haven't been able to find anything. Do the triangles not accurately depict where the benchmark disks are, did the disks happen to be missing for the three spots I visited, or does not every spot that's noted on the map with a "BM" actually have a benchmark disk planted there? Or it is none of the above?

 

[Papa Bear]

Are triangulation stations depicted in any way on USGS maps, or can their locations only be found from their respective datasheets? Also, on Topozone, I've noticed how often there's a triangle near where at "BM" appears on a map, but for the BM's I've tried to locate near my place, I haven't been able to find anything. Do the triangles not accurately depict where the benchmark disks are, did the disks happen to be missing for the three spots I visited, or does not every spot that's noted on the map with a "BM" actually have a benchmark disk planted there? Or it is none of the above?

Sometimes.

Short answer: if you see a triangle or an "x" on a map, there should be a disk there to find unless it has been removed or destroyed over the years.

But if you find a disk and then look at the map, you may not see the symbol printed there.

Long answer: The USGS used both triangulation stations and bench marks to "control" their maps. Most USGS marks of both types are shown on the maps. The triangulation stations will have a triangle and the bench marks will have "BM x" with the elevation next to it. the 'x' is not the letter x, but is a cross.

HOWEVER, the USGS marks are only a fraction of all marks set by various state, local and other agencies. Many of these others are not on the maps. FURTHERMORE, many of the USGS stations, although they are on the maps, and not in the NGS database. The NGS, the "National Geodetic Survey" (formerly the "Coast and Geodetic Survey") continues to set and maintain many stations (many not on the maps) including it's own and USGS's. On the other hand, the USGS no longer sets or maintains its stations. They were used to make the maps, the maps are made and they are no longer needed. This is a simplified version of a long complicated situation.

So to sumarize:

USGS set many stations, both triangulation and bench marks over it's history and used them to make maps, but no longer makes or maintains these stations.

NGS (formerly CGS) set many stations, some of which are on the maps and continues to set and maintain stations.

NGS also maintains a database of stations which include its own, some of USGS's and some of those of numerouse oither agencies and this database defines an interconnected grid of geodetic points called the National Spatial Reference System.

To quote from the NGS:

NGS is a federal government agency within the National Oceanic Atmospheric Administration (NOAA). NGS is responsible for maintaining the National Spatial Reference System (NSRS) which is the basis for all mapping and surveying in the USA. For more information on NGS visit our webpage, www.ngs.noaa.gov

Incidently, triangulation stations, originally defined by trigonometric triangulation, are now maintained by survey grade GPS by the NGS.

 

[Nate]

Should Geocaching.com have a complete list of all major triangulation stations? I ask because two locale stations that are depicted on Topozone (with the coordinates of 42 25.46N 71 7.12W and 42 25.30N 71 7.49W) are not mentioned at all on Geocaching. But other than that, the website does seem to have fairly complete listing.

 

[Papa Bear]

Should Geocaching.com have a complete list of all major triangulation stations? I ask because two locale stations that are depicted on Topozone (with the coordinates of 42 25.46N 71 7.12W and 42 25.30N 71 7.49W) are not mentioned at all on Geocaching. But other than that, the website does seem to have fairly complete listing.

Geocaching.Com has a snap shot of the NGS database as of 2000 or 2001 (not sure), so marks that have been added more recently are not there. To get data directly from the NGS use this site: http://www.ngs.noaa.gov/cgi-bin/datasheet.prl?Type=DATASHEETS

This gap constitutes only a small number of marks and most mountain top marks were set long before this snapshot.

The bigger issue is what I alluded to above. Many, many marks that were set by USGS (and by many other agencies) never made it into the NGS database for various reasons.

There is still a good chance that you could find these stations on the ground. The triangulation stations are depicted very accurately on the maps but the bench marks are less precise. The real problem is the lack of descriptive text such as that given in the datasheets.

Please note also: the datasheets (when you get them) will give locations for triangulation stations (horizontal control stations) and for bench marks (vertical control stations). The locations for the tri stations are super accurate (probably sub-centimeter) but that for BMs were just taken off topo maps based on the descriptions. I've seen these off by 1/2 mile or more - whoever did the transposition from the maps sometimes just got it wrong. On the datasheet you will see the word "adjusted" next to the accurate ones and "scaled" next to the ones taken off a map. There is also a link given on the datasheet (http://www.ngs.noaa.gov/cgi-bin/ds_lookup.prl?Item=HOW_SUP_DET) which explains this all.

The situation for elevation is similar. Those elevation values marked "adjusted" are quite accurate and "scaled" (as before) are taken off of a map.

Generally speaking, a horizontal control station (triangulation station) has accurate location (adjusted) and inaccurate elevation (scaled). Vertical control stations (bench marks) are just the opposite. The reason is the method of measurements are quite different for the two types.

A few (very few) stations have accurate locations and elevations and you will see the word "adjusted' after both the location and the elevation value. These were measured twice - once by triangulation to get the location and again by differential leveling for elevation. With the use of highly accurate GPS, these double duty stations will become more common, since the GPS units can measure both quantities. These uinits are surveyors grade and it often takes several days of measurements followed by after-the-fact calibration at the home base, and bear little resemblance to the hand held units you and I are likely to have.

 

[Nate]

Not to pick on Geocaching.com or the NGS listing, but in some subsequent poking around I found they they don't have a complete listing of benchmarks and triangulation stations. After all, they don't list the triangulation station that's on New Hampshire's Mount Tremont (which is depicted in Topozone and is readily observable to this day). Further, I stumbled upon a benchmark today, #5 FC, which is located on the sidewalk at about 42 24.84N 71 7.20W (this BM was installed by the Mass. Highway Dept.), and which is not mentioned or depicted anywhere.

But, my nitpicking aside, these two online sources certainly seem adequate enough.

 

[Nate]

Also, I keep meaning to ask, what purpose does the azimuth disk serve (especially in light of the fact that their distance from the station disk can very so much)?

 

[Papa Bear]

Not to pick on Geocaching.com or the NGS listing, but in some subsequent poking around I found they they don't have a complete listing of benchmarks and triangulation stations. After all, they don't list the triangulation station that's on New Hampshire's Mount Tremont (which is depicted in Topozone and is readily observable to this day). Further, I stumbled upon a benchmark today, #5 FC, which is located on the sidewalk at about 42 24.84N 71 7.20W (this BM was installed by the Mass. Highway Dept.), and which is not mentioned or depicted anywhere.

But, my nitpicking aside, these two online sources certainly seem adequate enough.

Geocaching.com is not a real issue since they simply reproduce the NGS data, albeit at a point in time. They are primarily interested in Geocaching and the web owners only tolerate benchmarking but they are not interested in expending new effort to keep the data up to date.

NGS on the other hand is tasked with maintaining a database of high quality information. There are a number of reasons that certain marks don't get into their database:

- the agency that set the mark never submitted it to the NGS

- the survey that was done did not follow the NGS standards

- the cost of doing the high quality survey (and paperwork) was too much.

This may have been the case with your Mass Highway Dept. disk. The agency may have seen no value in submitting to the national database since it's purpose was for building or fixing a highway or whatever, and was a primarily local issue. This need not imply that their work was in any way inferior.

There is actually a link on the NGS web page directed to surveyors interested in submitting data. Interesting reading.

In the old days, things were cheap and lots of work got done and put into the database. As time went on, agencies (like the USGS, or Mass Highway Dept.) got narrower in their focus and did not care if their stations were in a national database as long as it suited their own needs. They made maps (or built highways) and they weren't trying to help build a national interconnected network of geodetic stations.

The other thing to remember is that the NGS no longer has the manpower to go out and set marks and check them every few years. Like many agencies that used to depend on lots of manpower, they now rely on newer technology (GPS) and must do it with considerably reduced forces. Much of the reporting on the condition of old marks which they used to do, is now done by volunteer groups (like us) and private contractors.


Azimuth marks are used to establish an absolute direction when a survey is done from a triangulation station. The way a survey was done is that a theodolite (basically a telescope with a very accurate compass circle) would take readings of a number of other stations in the area. The result would be accurate angles between the station and the stations which were sighted (accurate to less than a second of arc). But they also needed an absolute measurement of direction. The azimuth station was set some distance away and the line connecting it to the triangulation station was surveyed using astonomical measurements of the north star so it would supply the needed calibration. So when doing a survey, they would start with the azimuth station and then procede around the circle and measure all the other stations. (then they would do it again backwards for error checking).

After they did this same thing at all the other stations, they would run the whole thing through a least square calculation and solve for all the triangles, and thus establish the location of all the stations. So in affect, each station depended on all the others. (You can also see how this method bears on your other question.)

Now they measure each point with a GPS, and things are much simpler.

 

[Nate]

A final note for those who have been following along on this thread: I've done some further checking on Topozone, and while there are a great number of triagulation stations and benchmarks it doesn't depict, it seemed to show all the triangulation stations that are on mountain summits, so it's a good place to check to see if a mountain you're planning on hiking next weekend has any disks on it (which tend to be ones that either have fairly open summit areas or used to have a fire tower). Then again, if you want to know where all the reference markers and azimuth disks are (once you know they're there), it can become cumbersome to then look up the all the location details on Geocaching.com or NGS, especially for a prolific weekend of peakbagging. But, that's the price to be paid in to ensure you don't miss seeing anything while on a mountain.

 

[Raymond]

I don’t have as many as I thought I had either, but here is my entire meager collection (ten photographs).

The third (Catamount Mountain in the Adirondacks) and tenth (Doubletop Mountain in Baxter State Park) are best. Doubletop’s is labeled ‘‘McNair.’’ The two Colvin bolts I’ve photographed, Noonmark and Dix, are kind of small, but you can click on any photo to enlarge it.

I can’t figure out how to have them simply appear here on this page as others have done.

 

[RoySwkr]

Do the triangles not accurately depict where the benchmark disks are, did the disks happen to be missing for the three spots I visited, or does not every spot that's noted on the map with a "BM" actually have a benchmark disk planted there?

PB seems to have skipped this one so I'll try.

> Do the triangles not accurately depict where the benchmark disks are

They do within the limitations of the map scale, but you may not be where
you think

In one case I remember, the marker was near the side of the road but the
road had been moved and the marker was of course next to the old road.
Then the directions were given from the post office which was now in a
different building.

> does not every spot that's
>noted on the map with a "BM" actually have a benchmark disk planted
>there?

Every spot should have had some sort of marker once, but it need not have
been a brass disk, read the datasheet to see what it was. For instance
while there is a brass disk on Mt Monadnock, the main survey point is
actually a nearby drill hole. Also some points were originally located
below the ground surface which will be noted on the datasheet. Other
points may have been buried or removed.

 

[Papa Bear]

I don’t have as many as I thought I had either, but here is my entire meager collection (ten photographs).

The third (Catamount Mountain in the Adirondacks) and tenth (Doubletop Mountain in Baxter State Park) are best. Doubletop’s is labeled ‘‘McNair.’’ The two Colvin bolts I’ve photographed, Noonmark and Dix, are kind of small, but you can click on any photo to enlarge it.

I can’t figure out how to have them simply appear here on this page as others have done.

Raymond

Here's a few more you are welcome to use - just download the images. Each has a thumnbnail and a bigger one if you click:

Snow (Hundred Highest)


Moxie - set in 1902! (sorry a piece of my hat got into this one)


Mt. Mansfield


The Traveler


Carragain



I also have a ton more peaks on or near the US Canadian border, but they all look mostly the same. They were all set in 1915 - 16 which is pretty old. They are:

Layton
Bump
Moran
Smith
Dennison
East Saddle (Fish)
Twin Peaks (Nicollet)
Salmon
Trumbull
Prospect Hill (Pros)

PM me if you want any of them. They all look basically like the one on your site for Boundary Peak.

 

[Papa Bear]

...
Doubletop’s is labeled ‘‘McNair.’’
...
I can’t figure out how to have them simply appear here on this page as others have done.

Hi Raymond again.

MCNAIR

McNair is interesting. A number of Maine peaks in and near Baxter have a McNair. Most seem to have been set under fire towers. On another forum I asked my NGS guy about this:

Recently, a friend was hiking in Baxter State Park in Maine (home of Katahdin) and climbed Doubletop Mountain, a nice climb about 5 miles west of Katahdin. Among his pictures, there was a shot of a USGS triangulation station stamped "MC NAIR 1929".

I looked it up in the NGS database, searching in the BSP area. Initially I found a survey marker on Horse Mountain, which I had never heard of. I checked where it was and it seems it is a peak overlooking Grand Lake Metagamon, near the road into BSP from the north gate. But it was something like 10 miles from Doubletop. But then I looked further (search for Designation "MCNAIR" in Maine) and found that there are no less than 6 stations in northern Maine, and the datasheet for all of them say "A U.S. GEOLOGICAL SURVEY DISK STAMPED MC NAIR 1929", and all of them are on mountain tops under fire towers, including Horse Mountain, Beetle Mountain, Norway Bluff, Big Spencer, Sobunge Mountain and Deboullie Mountain. And this list must be just part of the story since it didn't include Doubletop (not unusual - many USGS marks are not in the NGS database). Seems like Mr. Mc Nair, whoever he was, was a busy guy in 1929.

I've checked the original USGS horizontal control records. The survey chief of party was a Mr. E. L. McNair who was responsible for a fairly large network survey during 1929. Unfortunately the USGS data sheets do not indicate what was actually stamped on the disks so we must rely on the later recovery information from USC&GS.

So here are the makings of a new peak list: All peaks with a "MCNAIR 1929" benchmark. Anyone?



Pictures in your post

First you must have the photo on the web somewhere. Cut the URL with a Control-C

Method 1: click the little icon at the top of the edit window that looks like a mountain on a yellow background in a small square. It will ask for a URL. paste it in and you're done.

Method 2: I do it by hand so I can also link the image to a larger version. Put in the text:

[*url=*Large Image URL*][*img*]*Thumb nail image URL*[*/img][*/url]

Now I put all those asterisks there so this forum won't try to display the line I just typed. Put in that text without the *s and with valid URLs for you little and big images and you are in business.

 

[Raymond]

Thanks, Papa. It was actually the person who started this thread, 4000'er, who was looking for the photos. I was just offering what I could.

I think I tried doing what you suggested for posting the photos, but I just had a blank spot when I clicked the Preview button. The individual photos on one of my Web pages don't seem to have individual Web addresses, and having just one picture on a page (as I tried with two of those photos) doesn't work either. Maybe it has something to do with them being posted on a .Mac page, I don't know.

 

[Papa Bear]

Thanks, Papa. It was actually the person who started this thread, 4000'er, who was looking for the photos. I was just offering what I could.

I think I tried doing what you suggested for posting the photos, but I just had a blank spot when I clicked the Preview button. The individual photos on one of my Web pages don't seem to have individual Web addresses, and having just one picture on a page (as I tried with two of those photos) doesn't work either. Maybe it has something to do with them being posted on a .Mac page, I don't know.

If the URL does not point to an image (.jpg or one of the other types) it won't display. So for example you cannot display a whole web page with the [*img*] directive.

OTOH, you can generally get the URL of imbedded pictures. Using firefox, you right click the picture and then click on the "Copy Image Location" option from the pull down.

Here's one from your site (Catamount) for which I did that just now:

Here's the actual URL (minus the "http" and the "://"): "homepage.mac.com/ramerkh/.cv/ramerkh/Sites/.Pictures/Photo%20Album%20Pictures
/2006-12-04%2002.08.06%20-0800/Image-1558508E837E11DB.jpg-thumb_269_202.jpg"

I don't know how to do it with IE, never use that unless I absolutely must. Maybe an IE guru can help here.

The other approach is to dig the picture URL out of what ever tool you used to create the page. It's got to be somewhere (in fact I just displayed it, so it's there! ).

BTW: your picture (Catamount) is of a "Reference mark". Notice the arrow. The arrow actually points to the actual triangulation station, which is what surveyors care about and which is the point shown on a map.

 

[Nate]

Mentioning the benchmarks on Doubletop and Moxie leads to a good point, which is that even when it comes to mountain tops, Topozone isn't quite a complete source, since it does not depict either. But, it seems pretty close for summit areas.

 

[Raymond]

Thanks again, Papa.

I was wondering why that arrow didn’t seem to be pointing north.