A beginners Guide to Benchmarks!

[Mike&Melanie]

Ok first off a BM may not be an easy thing to find. Benchmarks are often located in places that can be difficult and dangerous to get to. I am a survey tech for a civil engineering firm and can tell you from experience. Some are often located in the center of roads, not wise to try these without the proper safety equiptment vests, cones, etc. Some benchmarks are much easier. Often they are located in the Right of Way. Commonly refered to as the parking. The space between the road and the sidewalk and usually near the intersection. The are also located at the corners of property. There are or should be survey markers at the corners of every property. These are called lot corners and are most likely an iron rod. Some will have caps on them. Caps vary but are typically yellow or orange. the will say something like CDA #15890 or PLS #15980 CDA would be the Firm that surveyed it and the number is the ID number for the Surveyor that signed off on the placement. PLS stands for Professional Land Surveyor. There are also markers at the corners of larger pieces of land a Plat corner which could be similar to a lot corner. These would be at the corners of a housing development for example. Even larger pieces called sections have corners too. These could be caped rods, Iron I shaped beams or even benchmarks. The problem with trying to find these is when they are not in someones yard they are in someones field or the middle of nowhere. They may have been placed 50 years ago and never found again. They are often under a foot or two of dirt. Or even under a road, in which case you won't be able to find it. Suryeyors use what are called ties to help find them. A tie will give the distance to nearby objects like trees and powerline poles. These objects will often have nails in the shape of and X on them. They also use GPS that is accurate to 100ths of a foot. Then they will use a metal detector to see if there is anything there or close by. Then dig at that spot to see if it is there. If you try using a metal detector and a shovel in your search for benchmarks be careful. There could be buried utility lines and you don't want to damage the marker.

[+BuckBrooke]

Greetings, Mike&Melanie, and welcome to the benchmarking community. You've stated you're a surveyor by profession, and we hope that you will contribute to the discussions we have in this forum.

 

Please take the time to look at the FAQ for the Benchmarking group; many members of this community who are surveyors or have recovered a number of benchmarks (for the NGS or not) have contributed to that document.

 

A growing site of information for benchmarkers is holograph's benchmarking wiki, which contains quite a collection of resources for those following this hobby.

 

In regards to the benchmarks that we search for on www.geocaching.com/mark, this is a copy of the NGS database. As such, only a minute fraction of the disks are corner markers, quarter corners, etc. Most were put down by the NGS, USC&GS, state or city agencies. For example, most of the stations in my area in Albuquerque are New Mexico State Highway Commission disks.

 

There is also a National Geodetic Survey discussion forum, to which Dave Doyle and others at the NGS regularly contribute.

 

As an introduction, I'm a physics graduate student, measuring parallax to find the distance to a particular type of evolved star for my dissertation, and thus have some understanding, if not quite hands-on experience, with the techniques used in surveying.

 

Again, greetings.

Edited January 27, 2007 by BuckBrooke