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"Find nearby benchmarks"

Zombie Food
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So I found cache GC1HN58 yesterday afternoon and within a few feet there is a benchmark. I'm really new to benchmarking so I'm not sure how to really look these up but when I click the "Find nearby benchmarks" link the closet on is almost two miles away :laughing: so I don't know where to log this particular one.


The benchmark disc has GWM38 stamped into it but I don't know what that means. I'm so confused!!


Can someone please help me figure out what I'm doing and why I am an idiot?

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The marks in this database are limited to those that meet the National Geodetic Survey's accuracy standards for either horizontal position or elevation. Furthermore, there are quite a number that meet those standards, and are in the NGS's files, but not in the Geocaching database, which is eight or ten years old. Untold thousands of other marks are out there, having been set by states, counties, cities, or by individual surveying firms marking property boundaries--among other possibilities.


Is the stamping you quoted all there is on the mark? Is there no agency information around the outer edge? Can you get reliable consumer-grade handheld coordinates? A photo?


These additional pieces of information could help you, and readers of the thread, figure out where to head with inquiries.



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It was very similar to the other benchmark disks I've seen except instead of the Geodetic Survey it is stamped with the US Geological Survey around the edge and 1941 under the GWM38.


As far as coords go I didn't think to set my eTrex on it to get those (like I said I'm a newb) but the cache listing has coords of N 37° 01.989 W 119° 43.309. I have to assume those are pretty accurate but I can't vouch for them because the cache owner supplied them and I didn't have to break out the GPS to find the cache. The benchmark is literally four feet from the cache.


Here's a link to the photo I took of it...


Mystery USGS benchmark

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A clarification that has often been made in these forums might be useful again here. The U. S. Geological Survey and the National Geodetic Survey are separate agencies. Quite a few Geological Survey disks meet the NGS accuracy standards and may be found in the NGS database, but the vast majority do not and may not.



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Can you tell me where I could find this coordinate search function you speak of?






'Find A Benchmark' from the sidebar on any Geocaching.com page, then click on 'Other Search Options'.


EDIT:punctuation malfunction


Many Thanks AZCachemeister. I didn't know that you could do that from gc.com's site. I appreciate you sharing that information. I've always used the ngs site below, then clicked on "Datasheets", then selected the retrieval method I needed. Do you know if gc.com's search just shows the ones in their database or links back to the ngs database? I guess I can go try it out for myself to see.



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Geocaching.com's search function only shows results from its own database. Even if you click on "Original datasheet" from a Gc.com benchmark page, you get the datasheet that was in existence when Gc.com took their snapshot of the NGS database.


Searching for datasheets on the NGS website is the only way to get the latest datasheets. However, Gc.com searches can be helpful, too, because geocachers may have posted useful reports about the mark.



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Great find! Although many of the USGS disks aren't included in the NGS database or geocaching.com, you can find where many of these are by checking out the topographical maps. The one you found is on the Madera Quadrangle. From its location on the map I'm guessing it is located on the Northwest abutment of a bridge over a small creek/stream on O'Neal Road.


Click this link to see the topographic with your benchmark on it. When the map comes up select USGS Topo from the pull down menu at the top right of the map and then zoom in all the way to see the map. The red push pin is the location of the coordinates that you gave. The BM 457 tells you there is a benchmark located at the X that is 457 feet above sea level.


If you scroll the map North you'll notice there is another benchmark located just to the Southeast of the intersection of O'Neal Road and Bellview Road. I have found many benchmarks in my area using this method. It is a little more challenging, because you don't have a written description to help you out. You can log your finds on Waymarking.com in the U.S. Benchmarks group. It is a sister site of geocaching.com and you can sign in using your geocaching.com username and password.


Welcome to benchmarking! I hope this is the first of many finds for you!



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The U.S. Geological Survey (USGS), an agency in the Dept. of the Interior has the responsibility for producing our national topographic maps. They completed the monumental task of complete national mapping of the 1:24,000 scale map series (about 55,000 maps) in the early 1990's. USGS would often set survey monuments to help "control" the map. Maps are produced from aeronautical photos mosaiced together. In order to provide accurate location, orientation, scale and elevation to a flat map of a curved surface, it is required to have numerous points that can be identified on the photographs for which the coordinates/elevations are well known. The marks set by USGS were a vital part of this operation. In the days when mapping surveys were conducted primarily by line-of-site methods, these marks helped save money by helping to ensure a network that cartographers could rely on for mapping update procedures. With the rapid developments in surveying and mapping technology, especially GPS, USGS sees little need to setting new marks or maintaining the old networks. Unfortunately the data for tens of thousands of these marks set by USGS were never submitted to NGS for inclusion in the National Spatial Reference System. Due to major reductions in staff and the changing nature of mapping requirements, it is highly unlikely that USGS will ever automate these data.
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