+elvis3068 Posted May 13, 2007 Share Posted May 13, 2007 Hello, This is my first post. I've been doing some caching for a couple years now, but have really gotten excited about the hobby since my daughter now likes to go out with me. The benchmarks appeal to both of us, so we're focusing our attention in this area. LZ1902 was given coordinates that were fairly close to our home. We got up there and the coordinates are in the middle of our town's university's baseball field. So, no marker. We read the benchmark history and it suggest the azimuth marker is in another part of town. Sure enough, it is right where the history suggests it is, but the thing that I was confused about is that it's .67 miles from the coordinates. I think I understand the azimuth is a direction aid if there is a problem with other markers (which by the way have been destroyed when the stadium was built). The arrow on the marker DOES point right to the stadium. My two rookie questions are this: why would the coordinates be given so far away from where the marker actually is? how frequently can I expect this to happen? Thanks! Quote Link to comment
Papa-Bear-NYC Posted May 13, 2007 Share Posted May 13, 2007 (edited) Hello, This is my first post. I've been doing some caching for a couple years now, but have really gotten excited about the hobby since my daughter now likes to go out with me. The benchmarks appeal to both of us, so we're focusing our attention in this area. LZ1902 was given coordinates that were fairly close to our home. We got up there and the coordinates are in the middle of our town's university's baseball field. So, no marker. We read the benchmark history and it suggest the azimuth marker is in another part of town. Sure enough, it is right where the history suggests it is, but the thing that I was confused about is that it's .67 miles from the coordinates. I think I understand the azimuth is a direction aid if there is a problem with other markers (which by the way have been destroyed when the stadium was built). The arrow on the marker DOES point right to the stadium. My two rookie questions are this: why would the coordinates be given so far away from where the marker actually is? how frequently can I expect this to happen? Thanks! My strong suspicion is that everything is correct. The Azimuth marker is a separate disk which iis used to site to from the main station. Once the surveyor has got the Azimuth mark sited (they usually put a pole or a light above the disk so it could be seen with the surveyors equipment) then they have the two things the need: 1) the location of the station and 2) a highly accurate orientation. From theses they can lay out their project, etc. The datasheet has a "box score" which tells how far and in what direction this azimuth is. Here's your box score: LZ1902|---------------------------------------------------------------------| LZ1902| PID Reference Object Distance Geod. Az | LZ1902| dddmmss.s | LZ1902| BLOOM RM 1 14.569 METERS 02843 | LZ1902| BLOOM AZ MK 1670755.5 | LZ1902| KW2999 BLOOMSBURG MAGEE CARPET STACK APPROX. 2.7 KM 2021443.9 | LZ1902| KW2998 BLOOMSBURG MAGEE CARPET TANK APPROX. 2.8 KM 2042645.0 | LZ1902| KW3001 BLOOMSBURG RAD STA WHLM S MAST APPROX. 4.2 KM 2311443.1 | LZ1902| BLOOM RM 2 22.702 METERS 31031 | LZ1902|---------------------------------------------------------------------| It says the marker you found is at bearing 167 deg 7 min 55.5 sec from the station. Take this in reverse (add or subtract 180 deg) and you can get the bearing from the azimuth mark back to the station. They didn't specify a distance in the box score because they didn't measure it (but they did give diections for finding it - you are lucky to get that). They care about the bearing (hence the name "azimuth' mark) not the distance. So the location of the azimuth mark is unspecified. It'specified only in relation to the station . Congratulations for finding it. Now back to the station. Your GPS says it's in the ball field. Perhaps it's burried or destroyed. You could ask the maintenance folks at the University if they know about it. There are also two more items in the box score that can help: the reference marks: RM1 and RM2. Here they give accurate distances (to the millimeter) and slightly less accurate bearings. You can search for these figuring the distance and bearing from the station and perhaps find one. If you find either of them, you now have a more accurate idea of where the station is than the GPS will be able to show. If you have a tape, you can measure back the 14.569 M (about 47' 9 7/16") from RM 1 in the right direction (use you compass - correct for magnetic declination) or the same procedure from RM 2 and you might find the station. Unless of course it's 2' below the pitcher's mound. HOWEVER if you read further in the history, the 1972 entry says the station was destroyed when they built the ball field. Tough luck But remember, sometimes these reports are wrong - a few of us have found marks which had been reportred destroyed. But you do have an azimuth mark that's probably an "orphan" so to speak. But destroyed or not, get a mental picture of how a triangulation and its "helper" disks (reference marks and azimuth mark) relate to one another. Unfortunately an azimuth mark without its station disk is no find. Sorry. But sooner or later you'll find everything for a particular station, then you'll see how it all hangs together. Welcome to the hobby. Papa Bear Edited May 14, 2007 by Papa-Bear-NYC Quote Link to comment
+RazorbackFan Posted May 13, 2007 Share Posted May 13, 2007 Hello, The coordinates listed were for the location of the triangulation station disk, which as you noted has been destroyed. The triangulation station disk is a point from which angles can be measured to other items that can be easily seen and identfied in the distance. Azimuth marks can sometimes be hard to find because they usually don't have lat/long information. Usually all you have is an angle and maybe a distance from the triangulation station disk to the azimuth disk. This information can be found in the "box score" in the data sheet (see below). LZ1902|---------------------------------------------------------------------------------------------| LZ1902| PID Reference Object Distance Geod. Az | LZ1902| dddmmss.s | LZ1902| BLOOM RM 1 14.569 METERS 02843 | LZ1902| BLOOM AZ MK 1670755.5 | LZ1902| KW2999 BLOOMSBURG MAGEE CARPET STACK APPROX. 2.7 KM 2021443.9 | LZ1902| KW2998 BLOOMSBURG MAGEE CARPET TANK APPROX. 2.8 KM 2042645.0 | LZ1902| KW3001 BLOOMSBURG RAD STA WHLM S MAST APPROX. 4.2 KM 2311443.1 | LZ1902| BLOOM RM 2 22.702 METERS 31031 | LZ1902|---------------------------------------------------------------------------------------------| If you look at the data sheet you'll notice the position for this station is listed as "ADJUSTED". When you see this, you can have high confidence that the disk is going to be right where the coordinates say it is. This is usually the case for triangulation stations as their exact position is important. However, if you see a "SCALED" position then you might not be as fortunate. These coordinates were interpolated from a map and may be subject to a small ammount of error. Hope this helps! Welcome to benchmarking! RazorbackFan Quote Link to comment
+Black Dog Trackers Posted May 14, 2007 Share Posted May 14, 2007 elvis3068 - Papa-Bear-NYC and RazorbackFan have given you excellent responses to your post. I just wanted to add that usually an Azimuth mark is set rather far from its triangulation station. Reference marks (much closer) are used to help locate their triangulation stations but an azimuth mark is not for helping locate the triangulation station. Instead, the azimuth mark is established for giving a local orientation to true North (as opposed to magnetic north). In order to offer the best precision in its job of giving a local orientation, the azimuth mark should be rather distant, but still visiible, from the triangulation station. Quote Link to comment
+elvis3068 Posted May 14, 2007 Author Share Posted May 14, 2007 elvis3068 - Papa-Bear-NYC and RazorbackFan have given you excellent responses to your post. I just wanted to add that usually an Azimuth mark is set rather far from its triangulation station. Reference marks (much closer) are used to help locate their triangulation stations but an azimuth mark is not for helping locate the triangulation station. Instead, the azimuth mark is established for giving a local orientation to true North (as opposed to magnetic north). In order to offer the best precision in its job of giving a local orientation, the azimuth mark should be rather distant, but still visiible, from the triangulation station. Papa Bear, RazorbackFan, and BlackDog Trackers, Thank you for the detailed responses. I think I am finally understanding how all the pieces come together. So, the triangulation station is the "top dog" so to speak, with the reference and azimuth markers helping locate that one? By the way, in this particular case, the azimuth station would have been in clear sight (before they put up the new library a few years back) even though it was so far away, so that makes sense too. All this makes the hunt even more intriguing to me. Thanks for the info. I am looking forward to a really fun summer. Quote Link to comment
ArtMan Posted May 14, 2007 Share Posted May 14, 2007 Just one additional note about azimuth marks. Typically they are located a half-mile or so from the main mark ("station"), though this can vary considerably. The box score section of the NGS datasheet will give the direction, but not the distance. Sometimes the narrative will give further information, including distance and how to get there — "to reach" in their parlance, but I have rarely if ever seen coordinates given for the azimuth mark, unless that disk is itself a benchmark with its own PID, which is sometimes the case. Incidentally, the datasheets you can access via the link on each Geocaching.com benchmark page are badly outdated. They were captured around 2001 and have not been updated. Many benchmarks have more recent NGS recovery reports, which can be very helpful. The latest versions are available at the NGS website. Click on the "datasheets" link near the top of the page. -ArtMan- Quote Link to comment
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