Our First Benchmarks... awwwww!

[NothingBetterToDo]

Well, almost 6 months after buying my GPSr, I finally got off my butt and we went out benchmark hunting, starting with one that I remember seeing many years ago which probably was the starting point of my interest in this area. We pulled a couple other nearby marks off of the ngs site, and stopped "impromptu" at a few clearly marked with witness posts alongside the roads we traveled.

 

The marks we found were these: PP2972, PQ0693, PQ0694, AE4682, AE4688, PP1824

 

My inexperience shows in PQ0693, the mark that after 10 years, I still didn't realize was just a reference marker to the actual station which I probably walked right over on the way to the reference mark. Will have to plan another trip (Mankato is 2 hours from my current home, but I went to school there and I wanted to find that mark again, so that's where we went.)

 

I have a few questions for the veterans amongst you all...

 

1) Please check out our finds. Any comments on things to improve / do differently are welcomed.

 

2) After reading through many posts, I've determined not to send my finds to NGS unless there is either no recovery listed within 20 years, if I'm confident of it's (former) location and could not locatie it, or if the description is incorrect or could benefit from updated references. Thoughts on this policy? Should I report them all for benefit of surveyors or am I just wasting the NGS's time?

 

3) I have an Etrex Venture GPS. Works well; all my finds were only off by +/- .005 minutes, and I suspect that some of this error is due to not letting the GPSr "settle", which I've gathered is necessary for better readings. But my elevations consistently showed 10-20 feet lower than expected. Is this normal? I suppose with the given accuracy of a hand-held GPS, this would logically apply to vertical accuracy as well as horizontal.. but it was odd that it was consistently lower. Should I be worried?

 

4) Does NGS ever lay any NEW benchmarks? I understand that the most obvious places.. mountain peaks, hilltops, etc are long ago marked.. but in areas of new development for instance, where modern marks may not exist.. if urban sprawl spreads to these areas, are they surveyed and new benchmarks placed to assist in future development?

 

A final note that's probably of interest only to me, but maybe I'm not the only person that's fascinated by this kinda stuff. If my calculations are correct from wandering around outside the building, and from aerial survey maps, it appears the 45 00.000 N.. midway point between the north pole and the equator.. runs directly through my cubicle at work, within a few feet. Maybe I'll call the NGS and have them set a benchmark in my desk

 

Thanks for listening, and I hope to find many more of these seemingly lonely, unnoticed, yet important little circles in the coming summer!

[+Kewaneh & Shark]

Let me start by saying welcome to the Geocaching and Benchmarking community! Congrats on finding your first benchmarks.

 

Onto your questions:

 

1) Your photos & descriptions are fine. This is, for the most part, a game we're all playing, (although there are possibly benefits in some professional circles), but there are no hard-core set parameters for logging your finds.

 

2) As far as reporting your finds to the NGS, it's completely your call. You'll find the opinions here about that subject to be as different as each benchmark hunter. I very rarely find a benchmark that has changed significantly enough to warant an NGS report. Even if a fair amount of time has passed, say 20 or 30 years. If the surroundings have not changed, and it can still be found using the description, there's no need to report it.

 

Professional Surveyors generally don't use this forum as a tool to search for benchmarks, they go directly to the NGS database, so your logs and comments are used just by geocachers and geo-benchmark hunters.

 

3) Your ETrex is going to have a horizontal error of +/- 10 meters (33-35 feet) and a vertical error of +/- 15 meters (50-55 feet). Vertical accuracies are always lower (worse) than horizontal accuracies. Most times, both horizontal and vertical accuracies will be better than this, but that's all that Garmin (or any other recreational GPSr manufacturer) can guarantee. Don't worry about your numbers being 'off'. (Survey grade GPSr's are much more accurate, but they are also much more expensive.)

 

4) The NGS still does place benchmarks, but not too often. Most surveying for future developments are done on a local level, either by the county surveyor or privately on an as needed basis.

 

In two of your logs, you were curoius about the 'oil' on the marks. I don't know about any oil ever being used to protect them, unless the local jurisdiction has some sort of policy to do so. The caps found in wells like that are usually aluminum so an oil coating would really be no benefit. I would suspect that it was simply condensation from the inside of the well. The next one you find like that, leave the lid off for a few minutes and see if it evaporates, or wipe a bit off to see.

 

Your assumption about the big, cloth cross is correct - it is an aerial panel point used for photogrammetry, and is used to tie the aerial photos together as a common point seen on more than one photo. Surveyors and photogrammetrists work closely together on projects that would be too lage for conventional surveying methods.

 

As far as the 45th Parallel going right through your cubicle... that's pretty cool. (I'm at a nice, round 36d 49.421. )

 

Good luck in your future hunts!

 

Keep on Caching!

- Kewaneh

 

[This message was edited by Kewaneh & Shark on April 18, 2003 at 04:30 PM.]

[+Black Dog Trackers]

NothingBetterToDo -

 

Congratulations on your new hobby!

 

A minor suggestion is along with your mark closeup, to always take a scenery picture around the benchmark, optionally with the mark somewhere in the foreground. This makes the photography more fun, not only for you, but for others looking through a list of marks or looking at the benchmark gallery. Most of us don't include the GPSr in the picture, but it doesn't really matter.

 

By your remarks on your finds, I'm not sure if you realize that some of your finds are for vertical control and some are for horizontal control. Your PP2972 is an example of horizontal control. Under its coordinates, it says "location is ADJUSTED". Its coordinates are probably within a few millimeters of the true value. Your PP1824, on the other hand is for vertical control and you can tell this because, under the coordinates, it says "location is SCALED". The SCALED coordinates could be off from the true value by 200 feet or more.

 

Interesting about your work location right on a latitude. On that same subject, check out this website. Be sure to wear your expedition hat when you click on this!

 

[This message was edited by Black Dog Trackers on April 18, 2003 at 09:36 AM.]

[+chaosmanor]

Let me also welcome you to the BM hunting part of this hobby! We don't have a whole lot of them logged (Sharon isn't too interested in them, so Jim often does them on his lonesome), but they are a fun adjunct to geocaching.

 

Black Dog Trackers has it completely right about "scenic" shots. They not only add to the fun, but they also give a sense of "place" to the BM, and they can serve as a good photo on their own. We just posted a log for GS0339, in the Mojave Desert; check out our photos to see what I mean about this. And future hunters will have something to go by, should they have trouble finding the thing later.

 

As for the co-ordinates, I used to post them, but I no longer bother, for reasons that other replies have stated. Our GPSrs are "toys" compared to what surveyors, etc. use. I can't get our Magellan to repeat to the exact thousandth ten minutes later, so I decided that no one else would find my info of value. But I *have* reported one BM missing. I think that this sort of info is of possible use to the authorities, and the worst that they would do is ignore the info. A found BM but with radically different description is probably not worth the hassle, though; if they felt the need to visit it themselves, they would have. The BM I referenced above is a case-in-point; no logs in 68 years!

 

So many caches; so few pairs of decent shoes

[NothingBetterToDo]

Thanks for all the replies.

 

I definitely see the point about taking pictures of the environment. I never realized until you all mentioned it, but in looking at other people's finds, looking at the pictures of the surroundings is just as fun as the BM itself.

 

In studying all the different data sheets in the past, I did learn the difference between horizontal and vertical controls... but was so engulfed in going on my first hunt that I never once considered which kind I would be visiting (as I mentioned, the fact that my first mark was just a reference, and not the actual mark, completely escaped me..). Thanks for the reminder.. it might have been awhile before I remembered there was a difference.

 

So I won't be concerned with exact coordinates, I'm going to try to seek out some older marks, and I'll focus more on surrounding environment pictures to give everyone an idea of what my little corner of the world looks like.

 

Thanks for your advice!

[Z15]

The position you get with a hand held GPS receiver is close but not exact. You can be as much as 100 meters off in position. NOTE-Some hand held have greater accuracy (WAAS compatible) the others and that is reflected by the higher cost

 

Take a look at THIS PAGE , click on the first link in "How do I Start" paragraph and the requirements to do a high accuracy GPS survey. Also note the some positions (Latitude and Longitude) are scaled. That is because the primary purpose of the bench mark was elevation only. You can see from the link that a lot of time and expense is required to determine a precise position for Lat and Long and having precise elevation marks is critical.