ckhd Posted March 26, 2004 Share Posted March 26, 2004 I need your opinion: I went in search of this benchmark. ER0206. The NGS didn't find it previously because the intersection that the description refers to has been moved about 800' to the East. I knew where the 1934 intersection used to be, and using the description literally drove right to this benchmark and found it within 5 seconds of exiting my car. The coordinates are .002 minutes off N, and exact W. .002 minutes = about 12', my GPS had an estimated error of 13', so I consider the coordinates to be EXACT. The problem I have is that the original data sheet says "STAMPING: X-66 1934". As you can see from these pictures, X-66 or 1934 isn't anywhere on it. Is it the correct benchmark? Why or why not? There isn't another benchmark listed very close to this one either... What are your thoughts? Quote Link to comment
mikeh420 Posted March 26, 2004 Share Posted March 26, 2004 It looks like after it was destroyed or removed, the AZ Highway Dep't realized they still needed that benchmark, so they replaced it with their own. We found a benchmark EW7276, in 1856 "A HOLE WAS DRILLED IN THE ROCK AND LEAD WAS POURED INTO IT AND MARKED WITH A CROSS ON TOP." While we didn't find the described marker, we found a marker "BURBANK I-8" on the same spot, a replacment BM by City of L.A. Dep't of Public Works. Quote Link to comment
+GeckoGeek Posted March 26, 2004 Share Posted March 26, 2004 The markings do not match - at all. It was set in 1934. Lots could have changed since then. Also it doesn't say that it was AZ Highway dept disk. I'd have thought that they would have mentioned that the disk belonged to someone else. The mark uses scaled coordinates which can be several hundred feet off, so the GPS location isn't very convincing. In short, nothing matches. How old is the bridge it's set in? It could have been rebuilt or widened since '34 Quote Link to comment
+happycycler Posted March 26, 2004 Share Posted March 26, 2004 I suspect that you have found an Arizona Hwy. Dept. disk instead of the Coast & Geodetic Survey (CGS) disk. Maybe the bridge was replaced since 1934? In which case the Hwy. Dept. may have placed their own benchmark on the newer bridge. Not all state highway dept. (& other agency) disks are in the NGS database. GeoCaching database is derived from the NGS database. from the NGS data base: ---------------------------- ER0206 ********************************************************** ER0206 DESIGNATION - X 66 ER0206 PID - ER0206 ER0206 STATE/COUNTY- AZ/APACHE ER0206 USGS QUAD - SPRINGERVILLE (1969) ER0206 ER0206 *CURRENT SURVEY CONTROL ER0206 ___________________________________________________________________ ER0206* NAD 83(1986)- 34 07 58. (N) 109 16 18. (W) SCALED ER0206* NAVD 88 - 2125.701 (meters) 6974.07 (feet) ADJUSTED ER0206 ___________________________________________________________________ ER0206 GEOID HEIGHT- -22.52 (meters) GEOID03 ER0206 DYNAMIC HT - 2122.407 (meters) 6963.26 (feet) COMP ER0206 MODELED GRAV- 979,010.0 (mgal) NAVD 88 ER0206 ER0206 VERT ORDER - SECOND CLASS 0 ER0206 ER0206.The horizontal coordinates were scaled from a topographic map and have ER0206.an estimated accuracy of +/- 6 seconds. ER0206 ER0206.The orthometric height was determined by differential leveling ER0206.and adjusted by the National Geodetic Survey in June 1991. ER0206 ER0206.The geoid height was determined by GEOID03. ER0206 ER0206.The dynamic height is computed by dividing the NAVD 88 ER0206.geopotential number by the normal gravity value computed on the ER0206.Geodetic Reference System of 1980 (GRS 80) ellipsoid at 45 ER0206.degrees latitude (g = 980.6199 gals.). ER0206 ER0206.The modeled gravity was interpolated from observed gravity values. ER0206 ER0206; North East Units Estimated Accuracy ER0206;SPC AZ E - 347,740. 295,910. MT (+/- 180 meters Scaled) ER0206 ER0206 SUPERSEDED SURVEY CONTROL ER0206 ER0206 NGVD 29 (??/??/92) 2124.753 (m) 6970.96 (f) ADJ UNCH 2 0 ER0206 ER0206.Superseded values are not recommended for survey control. ER0206.NGS no longer adjusts projects to the NAD 27 or NGVD 29 datums. ER0206.See file dsdata.txt to determine how the superseded data were derived. ER0206 ER0206_U.S. NATIONAL GRID SPATIAL ADDRESS: 12SXC593782(NAD 83) ER0206_MARKER: DB = BENCH MARK DISK ER0206_SETTING: 36 = BRIDGE ER0206_STAMPING: X-66 1934 ER0206_STABILITY: B = PROBABLY HOLD POSITION/ELEVATION WELL ER0206 ER0206 HISTORY - Date Condition Report By ER0206 HISTORY - 1934 MONUMENTED CGS ER0206 HISTORY - 1969 MARK NOT FOUND USGS ER0206 ER0206 STATION DESCRIPTION ER0206 ER0206'DESCRIBED BY COAST AND GEODETIC SURVEY 1934 ER0206'0.8 MI E FROM SPRINGERVILLE. ER0206'AT THE JUNCTION OF HWYS. NO. 60 AND NO. 71. ABOUT 400 FEET EAST OF THE ER0206'INTERSECTION. SET ON THE SOUTH HEADWALL OF A CONCRETE BRIDGE. ER0206 ER0206 STATION RECOVERY (1969) ER0206 ER0206'RECOVERY NOTE BY US GEOLOGICAL SURVEY 1969 ER0206'MARK NOT FOUND. Quote Link to comment
+rogbarn Posted March 26, 2004 Share Posted March 26, 2004 I'll give this one a shot but I'd be interested in what anyone else has to say. I would suspect that you did not find ER0206. I think "X 66" should be stamped on it. The "1934" may or may not be stamped on it. I would also suspect that it should be a CGS disk, not Arizona Hwy Dept. although this is certainly not absolute. Given my suspicions, I would next ask where could it be? Is there a different bridge with a headwall? The location is scaled, so the coordinates are only accurate to 6 seconds. On the other hand, you walked right up to it, based on the description and the placement of the old intersection which suggests you are in the right place. Maybe the bridge has been replaced since 1934? At this point, I would post a NF but YMMV. One thought is to track down disks on the same project. See if you can find T 66, U 66, V 66, W 66, Y 66, Z 66, etc. They should have been placed at the same time. Quote Link to comment
2oldfarts (the rockhounders) Posted March 26, 2004 Share Posted March 26, 2004 (edited) We looked at the benchmark page and think you found a different mark. Was the one pictured in the north headwall of a bridge? Scaled coords are usually not very close to the 'mark'. Altitude was adjusted and is different from what is stamped on the disk in the picture. A lot of headwalls for bridges and culverts have Az DOT marks on them that are not in the NGS database. These marks around here usually have the elevation stamped on the disk. Good luck on finding the right mark. John PS Forgot to add that after looking at the benchmark page map We determined that the problem you're having finding the right mark is due to the highway shown on the map... US 666 !!! Edited March 26, 2004 by 2oldfarts (the rockhounders) Quote Link to comment
+rogbarn Posted March 26, 2004 Share Posted March 26, 2004 jeesh, no replies when I first read it, by the time I post my reply, there are three ahead of me. keep up the good work guys.... Quote Link to comment
ckhd Posted March 26, 2004 Author Share Posted March 26, 2004 South headwall. Exactly as described. In fact, I didn't even look at my GPS until I found the mark. I didn't even realize that the coordinates were so close until I took the pictures and got back in the car. I did find Y66 that had been previously "not found" by the NGS. The disks are not the same. Y66 did have "Y66" stamped in it. I suspect that happycacher is right, and it has been replaced. Oh well, there aren't any other concrete bridges nearby (at least not in the ±6 second range), so I'll just have to log is as a DNF. Quote Link to comment
+happycycler Posted March 28, 2004 Share Posted March 28, 2004 Congrats. on your find of Y66 (ER0208)! I have yet to find one that the pros. had listed as a Not Found! Great Job! Quote Link to comment
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