Benchmark Hunters??

 

I realize this site is mostly concerned with the navigation aspect of GPS usage, helping solve equipment issues and sharing interesting POI information. The wealth of subject matter provided here is just fantastic and many contributors have devoted a lot of time and effort in posting content. For that I am grateful and wish to say thanks!!

I’m not sure if this subject is appropriate for this site or not but I thought I’d ask anyway.

There has been very little discussion at all on NGS Benchmarks here and the posts that have been made are somewhat misleading. Here are a few facts:

During the 1930’s and 40’s, the US Coast and Geodetic Survey, now a department under NOAA, undertook the monumental task of placing over 700,000 benchmarks along highways, railroads, bridges, curbs, sidewalks and other permanent structures across the US. Some benchmarks date back to 1879 when surveyors began placing them and recording data. Benchmarks are used as base surveying points and are the reason we have such accurate maps to load into our GPS units.

Most, but not all these benchmarks are 2.5” diameter bronze disks stamped with identification markings set in a permanent structure. Some are chiseled markings in stone or concrete structures. A benchmark can also be the point of a church steeple, water tank or radio antenna.

Highly accurate methods were used to record ELEVATION data for these marks to within ¼ inch! Latitude and longitude were not recorded to the same degree of accuracy and the majority of these marks use position information scaled from known objects. Relatively few of these marks have been “blue booked” or updated with coordinates obtained from highly accurate GPS equipment.

Sadly, these time ravaged monuments are slowly disappearing. NOAA employs a team of surveyors who constantly locate and restore them but budgetary constraints limit the effort. All of us complain at one time or another about the mistakes and inaccuracies of our GPS maps. This is due in part to the aging and inaccurate benchmark infrastructure.

This is where benchmark hunters enter the picture. With the proliferation of handheld GPS receivers out there and the demise of selective availability, the average person with a handheld is in a position to be able to provide NOAA and the NGS with far more accurate position information for the majority of these benchmarks.

Yes, geocachers hunt benchmarks and post information on the geocaching.com website. I applaud their efforts but few take the time to report the data to the NGS in the proper format. They tend to treat benchmarks like they do geocaches and do it mostly for entertainment.

More information on benchmarks is available here: http://geodesy.noaa.gov/

Should anyone come across one and wish to report a “recovery” it can be done by going here: http://www.ngs.noaa.gov/cgi-bin/datasheet.prl The information needed is stamped on the benchmark disk or can be obtained by entering the coordinates on the website.

Sorry for the long winded treatise on the subject. My original question was simply to see if there are any fellow benchmark hunters on the site.

Interesting

I've come upon a few benchmarks in some of the out-of-the-way places my job has taken me in the past. I knew what they were, but did not know NOAA or anyone else would be interested in having a set of GPS coordinates. I've even used the elevation data to re-calibrate my trusty 60CS. Next time I find one, I'll be sure to report it.

Thanks,

Shooter

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Shooter N32 39 W97 25 VIA 1535TM, Lexus built-in, TomTom Go

I have encountered many of these...

I have encountered many of these Benchmarks in my travels, and do understand what they are, as well as their importance and function. I have always appreciated and respected them, since I understand the monumental (no pun intended) task required behind properly placing them all, where ever they may be, not to mention the vital need for their proper maintenance.

What I did not know, is how much value there would be in many of us helping the system by recording and reporting our findings out in the field, as you have suggested we do using our hand-held GPS-units. This is very good info!

--I thank you for this well done post, which I think is definitely relevant here.

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~Jim~ Nuvi-660, & Nuvi-680

Elevation Data

Shooter wrote:

I've come upon a few benchmarks in some of the out-of-the-way places my job has taken me in the past. I knew what they were, but did not know NOAA or anyone else would be interested in having a set of GPS coordinates. I've even used the elevation data to re-calibrate my trusty 60CS. Next time I find one, I'll be sure to report it.

Thanks,

Shooter

The Garmin 60 CSX is a great handheld. Very rugged and a good hand fit. I should have held on to mine. I’m always looking for newer and better equipment but I’m finding newer is not always better. I still use my old GPS III+ for benchmark hunting. None of the newer units I’ve tried can equal the position averaging performance of the III+.

If you’re using information from the stampings on a bronze benchmark disk for accurate elevation data, you have to be careful. Most benchmarks disks do not indicate elevation. The numbers are usually a date the mark was monumented and a reference number. If you found one that specifically states “elevation above sea level”, then you’re ok.

Geocaching.com has a great page with pictures of the various types of benchmarks:
http://www.geocaching.com/mark/gallery.aspx

If you use the stamped reference number to access the data sheet on the NGS website, be aware the elevation data shown is not above sea level. It is the height above the geoid which is the theoretical “smoothed out” shape of the earth. This number can vary greatly from sea level elevation especially in mountainous areas.

Geocaching.com also offers a great tutorial on benchmark hunting:
http://www.geocaching.com/mark/#horizontal

Monumental Effort for Sure!

jimcaulfield wrote:

I have encountered many of these Benchmarks in my travels, and do understand what they are, as well as their importance and function. I have always appreciated and respected them, since I understand the monumental (no pun intended) task required behind properly placing them all, where ever they may be, not to mention the vital need for their proper maintenance.

What I did not know, is how much value there would be in many of us helping the system by recording and reporting our findings out in the field, as you have suggested we do using our hand-held GPS-units. This is very good info!

--I thank you for this well done post, which I think is definitely relevant here.

I have been told by old timers in the surveying community that the enormous amount of time and effort used to place benchmarks in the 30's and 40's is equal to that of the effort to put a man on the moon in the 60's!

As a boy I remember surveyors from the NGS erecting a 200 foot tower with a light on top over a benchmark. They then used a transit at night many miles away to get a level line of sight on the light in order to create another mark. This process was used over and over hopscotching all over the country.

logged a few

When I first started caching I logged a few, and when the company I worked for shut down our smokestack which was a benchmark was torn down so I notified them about that. There was another local company that had a water tower that was also a benchmark. When they tore it down I also logged that one with the NGS.

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Anytime you have a 50-50 chance of getting something right, there's a 90% probability you'll get it wrong.

towers

bdhsfz6 wrote:
jimcaulfield wrote:

I have encountered many of these Benchmarks in my travels, and do understand what they are, as well as their importance and function. I have always appreciated and respected them, since I understand the monumental (no pun intended) task required behind properly placing them all, where ever they may be, not to mention the vital need for their proper maintenance.

What I did not know, is how much value there would be in many of us helping the system by recording and reporting our findings out in the field, as you have suggested we do using our hand-held GPS-units. This is very good info!

--I thank you for this well done post, which I think is definitely relevant here.

I have been told by old timers in the surveying community that the enormous amount of time and effort used to place benchmarks in the 30's and 40's is equal to that of the effort to put a man on the moon in the 60's!

As a boy I remember surveyors from the NGS erecting a 200 foot tower with a light on top over a benchmark. They then used a transit at night many miles away to get a level line of sight on the light in order to create another mark. This process was used over and over hopscotching all over the country.

I read an article awhile back that those towers with the lights you mentioned were probably part of a system the government used for transporting the mail cross country. Along with the towers there were giant concrete arrows pointing to the next tower. There were some pictures with the article showing the pad the towers were on and the arrows. It would be interesting to find one of those.

Here is a link to one such site.
http://tinyurl.com/ml33bs8

--
Anytime you have a 50-50 chance of getting something right, there's a 90% probability you'll get it wrong.

Very interesting article

.

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Nuvi 2460LMT.