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How to Read

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I have found a few local brass monuments based on the directions to the benchmark. But I have not figured out how to read them. If I were to stumble on one in the great out of doors, say on a cache trip, how would I be able to find out what BM it is?


What data is contained on BM?


What is a witness post? What are they made of? icon_confused.gif

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is mark it with a waypoint and when i get back do a search on the coordinates. It is also helpful to get any ID numbers that may be stamped on the marker. If there are a couple listed close to the coordinates you may have to go to the data sheets and match up numbers and descriptions.

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Sorry, I didn't see the other question. A witness post is a marker at or near the BM making it's location easier to find. In surveying, Witness posts were corner markers for property lines, sometimes they used boulders or trees. Out where I am in farm country witness posts are very often close to the BM's since all are not for elevation.

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Originally posted by SC-Yankee:

Here's a pic of one type. There are many and there is a thread somewhere here where someone posts a lot of different ones.http://img.Groundspeak.com/benchmark/lg/3839_100.jpg


Assuming I find the one in the picture just by stumbling around in the woods. And I forgot to bring by gps,r. What do I use on the disk to find the bm and what index do I go to for more info on the bm?

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Good question Geofred. I'll try to answer as best I can. First I would copy all the info on the disk,take note of the coords, then returning home look on the BM location page and try to match it up with the one you found. I would try putting in the zip closest to where you found the BM and looking at all the ones regestered nearby. In the case of this one it is named SHADY and is well marked. Some have names like this or some identifing mark or number ie:309-A, or 2027 etc. I would think that the best way to go about it would be to look for a listed BM in the area you want to hunt and then look for that one specifically. Doing a reverse hunt may prove disappointing. If I can find the other thread I will post a link for you.

Hope this helps.

PS: I found one just the way you are talking about. It is in the middle of the town at the RR crossing. I have looked for a match and haven't found one as yet. I assume it is not on any present registered list but then you know what they say about people who assume icon_smile.gif

PPS: Team 5-oh!(posted above)has a very good idea on making it easier to identify a BM. It is what I tried for the one I found and led me to my assumption.


[This message was edited by SC-Yankee on August 16, 2002 at 08:49 AM.]

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I have a forest service map, really I do, and it shows BM as bench marks. Usually there is a 4 digit number. I am looking for BM5212, bm5180, bm 5091 which are all with the National Grasslands of Eastern Colorado. I cannot find them in the database. I entered BMXXXX and LLXXXX to no avail. When I entered approx. co-ords I go locations for things my map calls Horizontal Control Stations indicated by small equilateral triangles with a dot in center.


How to go from map to land with a BM #?

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First, bear in mind that not all benchmarks you find on the ground or that appear on a map (USGS, military, forest service, whatever) will appear in the database on the geocaching.com site or in the NGS database. There are many entities placing these survey marks, and thus many of the marks will be in local, regional, agency, etc., databases, not the ones you're looking at.


Don't be alarmed if you don't see something like 'AA1234' on the disk. The PID (permanent identifier, I think it stands for) does not appear on the disk itself. What's stamped on the disk (other than boilerplate identifying who placed the mark, etc.) is called the designation, and you can find this at the top of the official datasheet or a few lines down the page as it appears on geocaching.com. If you do see something that looks like a PID (i.e., two letters and four numbers) on the disk itself, it probably isn't, and you shouldn't be confused.


What I would probably do it see if your mark is in the database is to enter the coordinates on the benchmark home page and see if something nearby looks familiar. But don't be discouraged if you don't find it in the database, because there is a very good chance you might not find it for reasons mentioned above.


Good luck!

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