Benchmarks

[+neohiocacher]

I would like to start searching benchmarks with my GPS.

Is there available maps showing benchmarks and thier coordinates like the caches?

The benchmark section shows maps with the specific benchmark but what I am looking for is a map overview that shows all benchmarks.

Thanks

[+G & C]

If there is, I have yet to find it.

 

Part of the fun of finding BMs for me is the fact that they're harder to locate. The coords are rarely right on the money, and you usually have to follow a set of clues that were written in the 60's and earlier.

[+GeoGeeBee]

There is no such map on this website. The benchmarking section of the forum has a lot of information on other tools one can use to display benchmarks on a map.

[jholly]

Going to another website, try scaredy cat.

[+G & C]

Going to another website, try scaredy cat.

 

Wow, that's pretty cool. Thanks for sharing!

[+neohiocacher]

Thats what I am looking for. Perfect!

Thanks

[+GeoReapers]

I found one the other day that had moved a tenth of a mile. Seemed as though it was on a bridge, then they moved it and forgot that they did that.

 

EDIT: That sounded a lot more interesting and intelligent in my head before I wrote it.

Edited April 29, 2011 by GeoReapers

[2oldfarts (the rockhounders)]

Anyone can find a lot of info on the benchmarking forum also.

Edited April 30, 2011 by 2oldfarts (the rockhounders)

[Keystone]

I am moving this thread from the Geocaching Topics forum to the Benchmarking forum.

[+Student Camper]

If there is, I have yet to find it.

 

Part of the fun of finding BMs for me is the fact that they're harder to locate. The coords are rarely right on the money, and you usually have to follow a set of clues that were written in the 60's and earlier.

 

Actually, the coordinates for most benchmarks are "right on the money", these coordinates have been surveyed to very close tolerance,

The challenge for locating many benchmarks is that the mark has been there for 100 years or more and are often hidden by natural events or destroyed by vandals and modern development.

You are right, in general, they are harder to locate.

[+agentmancuso]

I found one the other day that had moved a tenth of a mile. Seemed as though it was on a bridge, then they moved it and forgot that they did that.

 

EDIT: That sounded a lot more interesting and intelligent in my head before I wrote it.

 

Been there.

[+shorbird]

If there is, I have yet to find it.

 

Part of the fun of finding BMs for me is the fact that they're harder to locate. The coords are rarely right on the money, and you usually have to follow a set of clues that were written in the 60's and earlier.

 

Actually, the coordinates for most benchmarks are "right on the money", these coordinates have been surveyed to very close tolerance,

The challenge for locating many benchmarks is that the mark has been there for 100 years or more and are often hidden by natural events or destroyed by vandals and modern development.

You are right, in general, they are harder to locate.

 

You can figure out how close the coordinates are for finding benchmarks by noting if the coordinates are "Scaled" or "Adjusted." Your GPS will probably come within 20 feet of "Adjusted" coordinates, whereas "Scaled" coordinates can be as much as 1/4 mile off.

[+LSUFan]

 

Actually, the coordinates for most benchmarks are "right on the money", these coordinates have been surveyed to very close tolerance,

The challenge for locating many benchmarks is that the mark has been there for 100 years or more and are often hidden by natural events or destroyed by vandals and modern development.

You are right, in general, they are harder to locate.

 

Really, it depends on the 'type' of benchmark you are searching for, as to whether it will have exact coordinates. In actuality, the majority of marks published in the NGS database are going to have scaled coordinates (off by as much as 600+ feet), but extremely accurate elevation numbers....since these types were placed for elevation purposes. As time goes by, many of these elevation benchmarks are getting accurate horizontal coordinates published for them. Here are some excerpts from the FAQ section that may help explain this:

 

Kinds of Benchmarks

 

Benchmarks can be divided into two general groups. The first group, "vertical control points" are objects that mark a very precise elevation above the standard datum plane (usually referred to as elevation "above sea level"). The second group are the "horizontal control points" - objects with precisely established latitude and longitude. At this point, we should explain that "benchmark" is a generic term that is used here at Geocaching.com to refer to all geodetic control points. In the surveying profession, however, the term bench mark (usually two words) is used specifically for points of known elevation, or vertical control. When the benchmark is established at known latitude and longitude, it is described as horizontal control. The generic terms favored by professionals to describe horizontal control are station or mark, rather than "benchmark".

 

What is the difference between "Location Adjusted" and "Location Scaled?"

 

Simply put, "location adjusted" means that the published coordinates are very accurate, and "location scaled" means that the published coordinates are not very accurate. The published positions for benchmarks with adjusted horizontal coordinates were computed using advanced surveying techniques and are far more accurate than even the finest handheld GPSr can get. The position of a benchmark with "scaled" coordinates was derived by a human in an office by estimating the location of the mark on a topographic map with a scale (ruler). As such, they can be off by 600 feet or more from the actual position though deviations in the 100 - 150 foot range are more common. Your handheld GPS may be very helpful in finding benchmarks with adjusted horizontal coordinates, but can be nearly useless for finding benchmarks with scaled horizontal coordinates. The good news is that only vertical control points have scaled horizontal coordinates. Trying to use your GPS "GOTO" function to find a benchmark with scaled horizontal coordinates will usually lead to frustration and failure.

 

How can I determine whether a particular mark is "Location Adjusted" or "Location Scaled?"

 

* On a Geocaching benchmark datasheet, the second line under the coordinates will say either "location is ADJUSTED" or "location is SCALED".

* On the 9th line of an NGS benchmark datasheet, to the right of the latitude and longitude coordinates, will be either the word ADJUSTED or the word SCALED. (Don't confuse this with the next line down, which tells whether the vertical elevation is adjusted or scaled.)

 

EDIT: Shorbird explained it while I was typing my post up. Sorry for the duplicate

Edited May 2, 2011 by LSUFan