Skip to Content

Details for Benchmark: HS5120

N 37° 52.902 W 121° 54.849 (NAD 83)

Altitude: 3864

Coordinates may not be exact. Altitude is VERTCON and location is ADJUSTED. (more info)

Location:
In CONTRA COSTA county, CA View Original Datasheet
Designation:
MOUNT DIABLO
Marker Type:
survey disk
Setting:
set into the top of a round concrete monument
Stability:
Most reliable and expected to hold position/elevation well.

Reference Points

Must Read!

Benchmarks may be on private property or in dangerous locations. Obey local laws. By using the services on Geocaching.com you agree to this disclaimer.

Found this while on a hike today. Good thing I had a flashlight - the mark is at the end of my hiking pole in the picture.

[Photos:]
photo

Climbed Mt Diablo for the first time. Recent rains have the disk covered in dirt but it was otherwise identifiable.

[Photos:]
photocopper bolt

Discovered at the summit of Mt. Diablo.

[Photos:]
photoSurvey mark obelisk
photoReally big disk

Easy to put this one in the Found column. It's all about the benchmark at this spot.

Found while on a hike on Mt. Diablo from Juniper to the Summit. Found this one thinking it might have been a benchmark, and it was.

I was headed to W6/CC-045 Mt Diablo for a Summits On The Air (SOTA) activation with my ham radio. I am KB6CIO. This was a wonderful find which I used as a way point to get my bearings for this amateur radio adventure. My brother, KF7URE, joined in on this grand adventure.

[Photos:]
photoObservation Deck Monument
photoDescription Information
photoIt is right inside that hole at the base.

Very cool place!

Found it on a beautiful morning.

Visited the summit of Mount Diablo and the Initial Point this day. My main goal for the journey, however, was to recover the USCGS disc I had seen in many photos. At this point in my benchmarking career, I did not understand the difference between the main station and the azimuth mark. The government description had me wanting to find the USCGS disc.

When I reached the summit, I asked the rangers where the azimuth mark could be found. Both admitted they had never visited it. The park superintendent also did not know the location. I showed him a tiny photo looking up towards to summit and the water tank. He directed me to the general location and I ended up finding the spot.

Anyways, to make it easier for the "rest of us". The azimuth mark is located well before the summit. If you are heading up, and pass Juniper Campground, you have gone too far. The KEY to the find is the POWER LINE which marches up the summit. AFTER passing the ranger station at the junction, you will go over a crosswalk. Shortly after, the power line will appear from the left at a right hairpin turn. Located at the turn is a gravel pullout and a side driveway marked with "Park Vehicles Only". Park here. Walk down the driveway. The third power pole is past the end of the driveway in a meadow down a dim walking path.
As described, its set in a concrete monument. Good luck!

[Photos:]
photoUSCGS Azimuth Mark MOUNT DIABLO HS5120
Mount Diablo Azimuth Disk Photograph

Found!

[Photos:]
photoIMG_2379

Here with my son. Great views

[Photos:]
photoMarker

On the last excursion of our US holidays we visited this impressive place. I saw the plaque in the upper floor, the lower floor was closed because we arrived after 4pm. Greetings from Switzerland!

[Photos:]
photoPlaque.

Visited while on a family outing on Mt Diablo.

This entry was edited by owlandpussycat on Sunday, 13 July 2014 at 21:43:12 UTC.

[Photos:]
photoIn Mt Diablo
photoAll the way up
photoIt's in there, I touched it

Found while exploring the mountain top.

Exploring Mt.D today with StarPop and GeoKashers. Found this one then did our part to contribute to the gift shop too!

Found the bolt. No picture worth posting. Pretty cool to be able to get down on my hands and knees, reach in, and touch something installed in the 19th century. I'm going to ignore the question of whether the bolt is actually the station. It sounds like California would fall into the ocean if anyone pointed out that the actual station no longer exists.

I wonder what's around the corner. Just a second access tunnel that's closed off now?

We did some trail maintenance on the mountain this morning, then made it to the top of the mountain. Views were obscured by fog, but we spotted this benchmark! We had to get down on our hands and knees, but we spotted it!

[Photos:]
photoHS5120 Benchmark

Found the bolt while caching on the mountain with Papa EGTH. The mark is a brass bolt and not a survey disk.

Always post photos of the benchmarks with your logs. How else do you prove you found them?

[Photos:]
photobolt in the shaft

HockeyHiker19 and I had attended the [url=http://coord.info/GC4TYBP]Mount Diablo Trails[/url] CITO and made sure to make our way to the top of Mt. Diablo so that we could find some benchmarks. This one was easy enough to find although you have to get on your knees in order to see it.

[Photos:]
photoHockeyHiker19 taking a picture of the benchmark
photoThe benchmark itself
photoThe Meridian above the benchmark
photoThe Base above the benchmark
photoMemorial plaque

Found in good condition. Easy to reach, though did not try for Reference Marks this day.

[Photos:]
photoHS5120 MOUNT DIABLO

Up for the CITO and stopped to grab a couple of benchmarks. Pictures attached of the Monument marker and the initial point.

[Photos:]
photoMonument Marker
photoInitial Point
photoIMG_0873[1]

How great to find the initial point for all of Northern California surveys! We're from Oregon and live only a few miles from the Willamette Stone, which serves the same function for all of Oregon and Washington. Great views from the mountain today! Found both the large monument in the top floor and the rectangular indentation (the top of the mountain) on the bottom floor. That indentation is the initial point!

[Photos:]
photoMount Diablo Monument
photoMount Diablo Initial Point

Love to find these benchmarks at historic/notable places! I had no idea that this initial point is where the entire survey grid of Northern California/Nevada is based. Very cool. The ranger at the visitor center told us that the initial point was originally placed at the indentation in the rock at what was at that time the top of the mountain, a few feet away from the bolt. In any case, a most interesting spot. Photos attached.

[Photos:]
photoInitial point - indentation in rock
photoBolt under Obelisk
photoBase Point Marker
photoSurvey Map
photoSurvey Marks Plaque

Wow, what a great day!!!

It started off EARLY with a fun gathering at the [url=http://coord.info/GC4494W]BUNDLE UP: BREAKFAST & GEOCOIN BONFIRE!!![/url] event. Then, the crew of [b][red]BooDogMama[/red][/b], [b][purple]Paracelsus[/purple][/b], [b][blue]Jimlips[/blue][/b], [b][orange]NightKnight[/orange][/b], and [b][green]I[/green][/b] was off to finish a Downtown Sacramento multicache! Somehow, we immediately transported ourselves through space and got to Mount Diablo right after the Sacramento cache Thank you SOOO much, [b][red]BooDogMama[/red][/b], for inviting me to tag along on your #3000 ! What an accomplishment![b][green] The attached pic is from sticking my camera in a whole and asking the bolt to say cheese.

~ecrane b#70
Davis, CA USA

[Photos:]
photoHS5120-Summit of Diablo
N 37° 52.900 W 121° 54.850

Found the copper bolt in the base just below the plaque. The disc at the top is not accessible at this time due to construction. Visited while geocaching and hiking in the area.

[Photos:]
photobolt in it's hole
photoplaque

Oaknest and I found this monument and benchmark while visiting Mt. Diablo. We also found other caches in the area.

[Photos:]
photoMount Diablo monument

Came up with greenusagi and flowerisland and found this benchmark.

Cool to find this benchmark @Mt. Diablo today with Mask2011 & greenusagi, Thanx.

Enjoying the view from the top of Mt Diablo this morning with flowerisland and mask2011.

Found with CarlottaP

wow amazing views from that awesome spot

made the trip up here and dint have time to chase down the multi but have to at least get the BM

Found while hiking to the Mt. Diablo Summit.

It was a super clear day, we could see clear to the Golden Gate bridge.

Visitng the area and just had to visit the "Initial Point", the place where it all began, the basis of the majority of Public Land Surveys for California and All of Nevada.

Found it, as did many touring folks...

For a land surveyor, finding this marker is like taking a pilgrimage to Mecca, since this monument is 0,0 for the majority of our great state. Found it in the access hole. I am sure that most visitors think that the large stamped marker on the second floor is the monument. I would not want to have to tie into this monument because of all the obstructions. It is an odd quirk of this website that all monuments are called benchmarks. By definition (per NGS Data Sheet) this is not a benchmark because it has no vertical order component. It does have an elevation on the Data Sheet, but it is not of an accuracy sufficient for surveys and should therefore be referred to as a monument.

Found with no problems!

[Photos:]
photoOn top of Mt. Diablo

Found in good shape and don't expect it to go missing anytime soon.

Came up to Mount Diablo geocaching and this benchmark was a bonus....

[Photos:]
photoDSC01607

Found on our trip up the mountain.

seen this many times over the years didn't realize it was a survey marker.

I visited this place April 21, 2009. In the park literature it stated this was a geocache but I can't find that cache's website so I'm logging it as this benchmark cache.

Found while visiting the Mt. Diablo Summit.

We found the survey marker and the azimuth mark in good condition. We could not search for reference mark 1 and reference mark 2 because the trap door to the third (top) story is locked. The azimuth mark is 1.1 miles southwest at N 37 52.190 W 121 55.661.

As noted previously, there is some disagreement regarding the location of the Mount Diablo initial point. In his 1996 book Initial Points of the Rectangular Survey System, C. Albert White argues that the bolt was placed at the initial point. White's reasoning is based on Davidson's 1858 report. In his 2001 Record of Survey (RS 2582), John W. Pettley argues that the bolt was placed about 3 feet from the initial point. Pettley's reasoning is based on Ransom's 1851 field notes, Cutts' 1852 report, and Pettley's own 1987 field survey. Unfortunately, the surviving depression in the rock is not conclusive. However, the NGS datasheet notes that, as early as 1938, Lukens also argued that the bolt was 3 feet from the initial point and that the rock had been cut away. In 1993, the Northern and Southern California Sections of the American Congress on Surveying and Mapping, the Mount Diablo Surveyors Historical Society, the East Bay, San Mateo/Santa Clara, Monterey Bay Chapters of the California Land Surveyors Association, and the Northern California Surveyors Joint Apprenticeship Committee helped install a new plaque that identified the rectangular depression as the Mount Diablo initial point.

[This entry was edited by ltleelim on Tuesday, June 24, 2008 at 5:54:22 PM.]

Interesting survey marker. Had the most fun finding the azimuth with our new friend Michael.

[Photos:]
photoMOUNT DIABLO marker, CA
photoMOUNT DIABLO location, CA
photoMOUNT DIABLO plaque, CA
photoMOUNT DIABLO AZ marker, CA
photoMOUNT DIABLO AZ location, CA
photoMount Diablo initial point
photoThe Mount Diablo Survey Marks plaque

Hard to miss!

biggest dang thing I ever did see ! Found it on bike trip to CLayton via the Deer Flat road

Took photos of both the base inside the visitor center, and the bronze plaque above (which turns out to be a clue for a multi-cache too). I'll post the photos in a week or two.

This site is BM rich.

Came across this benchmark while visiting Mt. Diablo. I understand that this is the single probably the most important benchmark for surveying in California.

Hiked some of the trail and drove to the top. Clear day to the east; I could see to the Sierras.

[I found this accidently while hiking with my friends]

Found it while working on a multi-geocache GCMAF4. Thanks

Found during a trip to the top of Mt. Diablo via motorcycle. Too much fog/haze to see much from the top, but the road was fun!

This was actually the first part of the multi-stage cache Higher.

Found it while working Geocache GCMAF4 ;-)

(edited to set the correct date)

I wonder why they covered up the viewing/plumbing spot on the third floor with the plaque? The plaque is certainly very nice but it's not the benchmark and now you can only access the mark from the side opening on the first floor. Nice location and a unique benchmark in any case and worth seeing.

[This entry was edited by Team Nazgul on Thursday, February 16, 2006 at 10:01:46 PM.]

[Photos:]
photoOpenings in base of obelisk
The benchmark is the bolt.

One of the more elaborate BMs I have found :-)

[Photos:]
photoDSCN1608.JPG
photoObelisk
It is back there somewhere :-)

Saw it.

Great drive and view.

Found as described.

[Photos:]
photoMount Diablo Benchmark Location
Disk set into the top of round concrete monument

I've visited this benchmark before, atop Mount Diablo, before I was a geocacher. Today, we came up here today with SnoWake and Dingo specifically so I could log it. This is my first benchmark, too, and it sure is a good one! The view from up here is amazing.

Found the mark in the hole at the base of the shaft as described in the 1971 recovery note. My interpretation of the recovery note leads me to believe that the bronze plaque at the top of the shaft is not the mark nor is it one of the reference marks. I did not make a diligent search for the reference marks while there but they are probably on the outside of the building.

Shaz the surveyor thought it was cool to see what she refrences on most of her maps

[Photos:]
photoGeo2.jpg

Was not looking for this benchmark, but found it and logged it.

Found as described

[Photos:]
photoMt Diablo

Nice easy 2fer today. Was up here doing Devil's Pulpit cache with Z & thought since we were here we might as well log this one too! Nice & warm inside the Tower.

[Photos:]
photoSurvey Marker in Tower on Mt. Diablo
Nice & warm in here!
photoClose up of Numerals on Marker
photoClose Up of Numerals II
photoMarker w/ GPS
photoSecond Floor Observation Tower
photoView Looking West From Inside Tower Mt. Diablo
Nice foggy day down there but not @ 3800ft. :)

Great view from on top. A rather "civilized" survey marker.

Up atop the mount caching with 4wheeler today.

Tower was locked up but spotted a disk and plaque on the side of the octagonal shaft through a window.

[Photos:]
photoOctagonal shaft with plaque

Sadly, the door to the first and second floors was locked. All I could see were the third floor monument and, looking through a first floor window, the octagonal shaft and the historical plaque.

Found it as very adequately described by B. Thomas.

[Photos:]
photoMt. Diablo, CA - Some of the history
photoMt. Diablo, CA
The building houses the Initial Point
photoMt. Diablo, CA - Monument found on 3rd floor.
photoMt. Diablo, CA - Sign found on 1st floor.
photoMt. Diablo, CA - Initial Point resides in the hole

A Google search on "Mt Diablo Initial Point" (include the quotes) yields a great deal of fascinating information. Be advised, however, that Pettley's thesis (that Ransom and Cutts established two different initial points) has been challenged by C. Walter White in his book on the 38 Initial Points. I find White's arguments persuasive. Regardless, a visit to the site cannot but inspire respect and even awe for the history of the GLO rectangular survey system, especially before the advent of our present day satellite survey technology. Heroes all! . . . . patrick & shirley

[Photos:]
photoView of tower
Built by the CCC with WPA supervision in 1939 with much maintenance and mods since. This tower replaced several previous memorials and commercial tourist buildings on site.
photoShaft positioned over the station mark

It was cold on 12/22/2002, too.

[Photos:]
photoElev 3800 ft

Not too much trouble finding this one. Can you believe there was SNOW up here today??

[Photos:]
photoSnow!
Buddy Mike tosses a snowball for Dingo - what is this, Tahoe?

A bit of a hazy day, but a nice bike ride, nonetheless.

Well, this is a pretty easy one to find. I did stumble across a traditional monument 3/10ths a mile away on one of the trails leading to the summit, but it's not in the database.

A major survey point for the State of California.

The site is still accurately described by NGS of 1971. A stone building of three stories covers the summit site specified for HS5120. The first floor has a few square feet of summit rock, flooring, and a concrete obelisk from floor to ceiling. The obelisk has a vertical shaft to the 2nd and 3rd floors for a plumbline, a shoebox sized alcove at foot level with small floor level openings on west and north sides to observe an imbedded bolt. The bolt is the survey mark for the plumbline.

On the second floor the obelisk terminates at waist height and is capped by a 1 foot diameter plaque by the State Park. This memorial plaque gives coordinates N 37 52.54, W 121 54.48. The plaque blocks the plumb shaft to the third floor. The third floor is the survey observation floor, accessible by a locked pulldown ladder. Apparently, 1946 benchmarks are located offset on the stone window sills. The metal roof is capped by a pre-WW II Sperry rotating aviation beacon.

The ranger says that HS5373 in the parking lot is used for surveys.

bthomas

[last edit: 11/21/2003 8:14:35 PM PST]

[Photos:]
photoMt. Diablo, 2nd floor plaque
photoSummit obelisk, 1st floor.

One of the more impressive benchmarks that the wife and I have visited. Nice view, too.

Documented History (by the NGS)

1/1/1876 by CGS (MONUMENTED)
1/1/1852 by CGS (GOOD)
DESCRIBED BY COAST AND GEODETIC SURVEY 1852 (RDC) THE STATION WAS NOT OCCUPIED. OBSERVATIONS WERE MADE TO THE FLASHING RED BEACON LIGHT ABOUT 40 FEET ABOVE THE STATION MARK.
1/1/1935 by CGS (GOOD)
RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1935 ABOUT 30 MILES EAST OF BERKELEY AND OAKLAND, ABOUT 15 MILES BY ROAD EAST OF WALNUT CREEK, AND ABOUT 15 MILES BY ROAD NORTHEAST OF DANVILLE, ON SUMMIT OF MOUNT DIABLO, MOST PROMINENT LANDMARK IN VICINITY AND A STATE PARK. AT WEST END OF PARKING SPACE ON SUMMIT IS MOUNT DIABLO, AIRWAY LANDMARK BEACON (SEE BELOW). AT EAST END OF SUMMIT IS SMALL WOODEN OBSERVATION TOWER BUILT OVER ROCK OUTCROP WHICH FORMS HIGHEST PART OF SUMMIT. FROM THIS POINT SUMMIT BREAKS OFF STEEPLY IN ALL DIRECTIONS EXCEPT WEST. STATION IS UNDER NORTHWEST PART OF THIS PLATFORM, 3 FEET NORTHWEST OF CONCRETE PIER WHICH IS AT CENTER OF PLATFORM AND AROUND WHICH RANGE FINDERS ARE CENTERED. IN 1852 STATION WAS MARKED BY HOLE ABOUT 2 INCHES IN DIAMETER AND 1-1/2 INCHES DEEP IN CENTER OF BOTTOM OF ANOTHER HOLE 8 INCHES IN DIAMETER AND 6 INCHES DEEP. IN 1858 A 1/2-INCH HOLE WAS DRILLED IN ROCK. IN 1876 COPPER BOLT WITH CROSSLINES ON TOP WAS SET IN SOLID ROCK. OVER THIS WAS PLACED PIER WITH 3/4-INCH COPPER BOLT MARKED WITH CROSSLINES CEMENTED FLUSH IN TOP. IN 1892 HOLE AT INTERSECTION OF CROSSLINES IN UPPER BOLT WAS FOUND ECCENTRIC TO TRUE STATION, AND CENTER WAS RE-MARKED WITH NEW CROSSLINES 3/16 INCH SOUTHEAST OF HOLE. IN 1922 TOP OF PIER FOUND IN RUINS AND MARK RECOVERED DESCRIBED AS 1/2-INCH COPPER BOLT WITH CROSSLINES IN TOP SET FIRMLY IN, AND PROJECTING 1/8 INCH ABOVE BEDROCK. OLD PIER HAD THREE OPENINGS AT BASE TO PERMIT ACCESS TO MARK. PIER WAS REPAIRED, AND ON IT WAS PLACED CONCRETE CAP 20 INCHES HIGH, MARKING TOTAL HEIGHT OF PIER ABOUT 4 FEET. IN CENTER OF CONCRETE CAP WAS HOLE 6 INCHES SQUARE TO PERMIT ACCESS TO MARK. IN 1935 REPORTED THAT BRICK AND CONCRETE PIER HAD OPENING ON NORTH SIDE TO PERMIT ACCESS TO MARK AT GROUND LINE. PIER WAS REPORTED TO EXTEND 3 FEET ABOVE OBSERVATION PLATFORM. IN 1876 VERTICAL-ANGLE PIER WAS BUILT 144.74 FEET WEST OF STATION. BRICK LATITUDE PIER, 27.7 FEET SOUTHWEST OF VERTICAL-ANGLE PIER AND 167.82 FEET WEST OF STATION. AND TRANSIT-INSTRUMENT PIER, 32.5 FEET SOUTHWEST OF VERTICAL-ANGLE PIER. IN 1922 ONLY BASE OF VERTICAL-ANGLE PIER WAS FOUND. GRADING OF SUMMIT MAY HAVE DESTROYED OTHER OLD AUXILIARY PIERS. IN 1922 REPORTED THAT TWO STANDARD REFERENCE DISKS WERE SET IN SOLID ROCK, BUT DATA FURNISHED FOR THREE REFERENCE MARKS AS FOLLOWS--NO. 1, 2.41 METERS (7.9 FEET) FROM STATION. REFERENCE MARK NO. 2, 3.05 METERS (10.0 FEET) FROM STATION. REFERENCE MARK NO. 3, 17.14 METERS (56.2 FEET) FROM STATION. IN 1935 NO. 1 WAS RECOVERED IN GOOD CONDITION, REPORTED TO BE UNSTAMPED. IN 1931 NO. 2 REPORTED UNDER OBSERVATION PLATFORM. NO. 3 NOT RECOVERED IN 1932. MOUNT DIABLO, FLAGPOLE (SEE DESCRIPTION THEREOF) IS 14.70 METERS (48.2 FEET) FROM STATION. MOUNT DIABLO, AIRWAY LANDMARK BEACON (SEE DESCRIPTION THEREOF) IS 65.51 METERS (214.9 FEET) FROM STATION.
1/1/1938 by CGS (GOOD)
RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1938 (LAM) A COPY OF STANDARD OIL BULLETIN PUBLISHED BY THE STANDARD OIL COMPANY OF CALIFORNIA WAS SENT TO THE U.S.C. AND G.S. WASHINGTON OFFICE BY LEWIS A. MC ARTHUR, PORTLAND, OREGON. THIS BULLETIN CONTAINED A DESCRIPTION OF MOUNT DIABLO AND PHOTOGRAPHS WHICH SHOW THE TRIANGULATION STATIONS THEREON, MOUNT DIABLO, MOUNT DIABLO, FLAGPOLE, AND MOUNT DIABLO, AIRWAY LANDMARK BEACON. ANOTHER LETTER FROM MR. MC ARTHUR DATED APRIL 20, 1938, IN REGARD TO THE INTERSECTION OF THE MOUNT DIABLO MERIDIAN AND THE MOUNT DIABLO BASE LINE STATES-- CAPTAIN LUKENS SAYS THAT CUTTS IN 1852 REPORTED THE ORIGIN OF THE LAND SURVEY ON MOUNT DIABLO WAS 3 FEET FROM A COAST SURVEY STATION. HE IS OF THE OPINION THAT THE ROCK WHICH CONTAINED THE LAND OFFICE POINT HAS BEEN CUT AWAY, AND THAT THE POINT IS LOST. HE IS OF THE OPINION THAT IT WAS NOT IDENTICAL WITH THE TRIANGULATION STATION.
1/1/1946 by CGS (GOOD)
RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1946 (SPH) SINCE THE 1935 RECOVERY OF THIS STATION A LARGE CONCRETE BUILDING, WITH OBSERVATION TOWER, HAS BEEN ERECTED OVER IT. A FLASHING, RED BEACON LIGHT, ABOUT 40 FEET DIRECTLY ABOVE THE STATION MARK, IS ON THE APEX OF THE TOWER. THE STATION MARK, UNSTAMPED, IS A BRASS BOLT, 1/2 INCH IN DIAMETER, PROJECTING 1/2 INCH ABOVE THE BASEMENT FLOOR OF THE TOWER, WHICH IS THE SOUTHERN PART OF THE BUILDING. A TAPERED, OCTAGONAL, CONCRETE SHAFT, HOLLOW IN THE CENTER, HAS BEEN ERECTED OVER THE MARK AND EXTENDS INTO THE SECOND STORY OF THE TOWER. TWO OPENINGS, 8 INCHES SQUARE, ARE AT THE BASE OF THE SHAFT AND AT THE LEVEL WITH THE MARK. OBSERVATIONS MUST BE MADE FROM THE THIRD (TOP) STORY, AND A ROUND OPENING, 10 INCHES IN DIAMETER, IS IN THE CENTER OF THE FLOOR TO ENABLE PLUMBING TO THE MARK. OBSERVATIONS WERE MADE FROM A 4 FOOT STAND 7.5 METERS ABOVE THE MARK. REFERENCE MARK NO. 1, STAMPED MT DIABLO NO 1 1946, IS A STANDARD DISK SET IN THE OUTSIDE PART OF THE SOUTH WINDOW SILL. IT IS ABOUT 1 METER HIGHER THAN THE FLOOR OF THE OBSERVATION ROOM. REFERENCE MARK NO. 2, STAMPED MT DIABLO NO 2 1946, IS A STANDARD DISK SET IN THE OUTSIDE PART OF THE WEST WINDOW SILL. THE AZIMUTH MARK, STAMPED MT DIABLO 1946, IS A STANDARD DISK SET IN A CONCRETE CYLINDER, 11 INCHES IN DIAMETER, PROJECTING 6 INCHES ABOVE THE SURFACE OF THE GROUND. IT IS SLIGHTLY SOUTH OF THE CREST OF THE RIDGE, ABOUT 1/2 MILE SOUTHWEST OF THE STATION, 1.6 MILES NORTHEAST BY ROAD FROM THE JUNCTION OF THE ROADS FROM DANVILLE AND WALNUT CREEK, AND 0.1 MILE WEST OF THE ROAD ENROUTE TO THE SUMMIT. IT IS 16 FEET NORTHWEST OF THE THIRD TELEPHONE POLE WEST OF THE ROAD TO THE SUMMIT. THE STATION CAN BE REACHED BY FOLLOWING ROAD SIGNS FROM THE VICINITY OF WALNUT CREEK OR DANVILLE.
1/1/1948 by CGS (GOOD)
RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1948 (CTH) THE STATION WAS RECOVERED AS PER THE 1946 DESCRIPTION. ALL MARKS WERE IN GOOD CONDITION.
1/1/1951 by CGS (GOOD)
RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1951 (JCE) THE 1935 DESCRIPTION OF THE STATION AND MARKS WAS IMPOSSIBLE TO CHECK BECAUSE OF EXTENSIVE GRADING AND BUILDING, ON THE STATION HILL, SINCE THAT DATE. A NEW DESCRIPTION FOLLOWS-- THE STATION IS LOCATED ON THE SUMMIT OF MOUNT DIABLE AND IN THE BASEMENT OF A LARGE STONE AND CONCRETE BUILDING. THE STATION IS OBSERVED FROM THE GLASS INCLOSED LOOKOUT TOWER WHICH IS REACHED BY TRAP DOOR FROM THE LOOKOUT PLATFORM ON THE ROOF OF THE BUILDING. ON THE SUMMIT OF THE LOOKOUT TOWER IS AN AIRWAY BEACON AND FLASHING RED LIGHT. THE STAND MAY BE CENTERED BY MEANS OF A PLUMB BOB AND 30 FOOT STRING. A KEY TO THE TRAP DOOR MAY BE OBTAINED FROM THE STATE PARK HEADQUARTERS ON THE WAY TO THE STATION. A KEY WILL ALSO BE NEEDED TO PROVIDE ENTRANCE TO THE BASEMENT AND ACCESS TO THE STATION MARK. THE STATION IS THE CENTER OF A SQUARE HEADED BOLT WHICH IS SET INTO A DRILL HOLE IN SOLID ROCK. THIS MARK IS SURROUNDED BY A CONCRETE PILLAR WHICH IS ABOUT 8 FEET IN DIAMETER AND ABOUT 15 FEET IN HEIGHT. OPENINGS, AT THE BASE OF THE PILLAR, PROVIDE A VIEW OF THE STATION MARK. REFERENCE MARK NUMBER 1 IS A STANDARD DISK, STAMPED MT. DIABLO NO 1 1946, SET INTO A DRILL HOLE IN THE STONE SILL OF THE LOOKOUT TOWER. REFERENCE MARK NUMBER 2 IS A STANDARD DISK, STAMPED MT. DIABLO NO 2 1946, SET INTO A DRILL HOLE IN THE STONE SILL OF THE LOOKOUT TOWER. NO AZIMUTH MARK WAS SEARCHED FOR OR RECOVERED.
1/1/1957 by CGS (GOOD)
RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1957 (RLE) THE STATION MARK, REFERENCE MARKS 1 AND 2 AND THE AZIMUTH MARK WERE RECOVERED AS DESCRIBED AND IN GOOD CONDITION. A LARGE CONCRETE BUILDING WITH A THREE STORY OBSERVATION TOWER HAS BEEN ERECTED OVER THE MARK. A FLASHING RED BEACON LIGHT, ABOUT 40 FEET DIRECTLY ABOVE THE STATION MARK, IS ON THE APEX OF THE TOWER. THE STATION MARK, UNSTAMPED, IS A BRASS BOLT, 1/2 INCH IN DIAMETER, PROJECTING ABOUT 1/2 INCH ABOVE THE BASEMENT FLOOR OF THE TOWER, WHICH IS THE SOUTHERN PART OF THE BUILDING. A TAPERED, OCTAGONAL, CONCRETE SHAFT, HOLLOW IN THE CENTER, HAS BEEN ERECTED OVER THE MARK AND EXTENDS INTO THE SECOND STORY OF THE TOWER. TWO OPENINGS, 8 INCHES SQUARE, ARE AT THE BASE OF THE SHAFT TO ENABLE PLUMBING OF THE MARK. OBSERVATIONS MUST BE MADE FROM THE THIRD (TOP) STORY. A ROUND OPENING, 10 INCHES IN DIAMETER, IS IN THE CENTER OF THE TOP FLOOR TO ENABLE PLUMBING TO THE MARK. OBSERVATIONS WERE MADE FROM A 4 FOOT STAND ABOUT 7.5 METERS ABOVE THE MARK. REFERENCE MARK NO 1, A STANDARD DISK STAMPED MT DIABLO NO 1 1946, IS SET IN A DRILL HOLE IN THE OUTSIDE CONCRETE WINDOW SILL. IT IS ABOUT 1 METER HIGHER THAN THE FLOOR OF THE OBSERVATION ROOM. REFERENCE MARK NO 2, A STANDARD DISK STAMPED MT DIABLO NO 2 1946, IS SET IN A DRILL HOLE IN THE OUTSIDE CONCRETE WINDOW SILL. IT IS ABOUT 1 METER HIGHER THAN THE FLOOR OF THE OBSERVATION ROOM. THE AZIMUTH MARK, A STANDARD DISK STAMPED MT DIABLO 1946, IS SET IN THE TOP OF A 12 INCH CONCRETE CYLINDER PROJECTING ABOUT 6 INCHES ABOVE THE SURFACE OF THE GROUND. IT IS SLIGHTLY SOUTH OF THE CREST OF THE RIDGE, 0.1 MILE WEST OF THE BLACKTOP ROAD LEADING TO THE STATION AND LOOKOUT TOWER AND 17 FEET NORTHWEST OF THE THIRD POWERLINE POLE WEST OF THE BLACKTOP ROAD LEADING TO THE STATION. TO REACH THE STATION FROM THE INTERSECTION OF STATE HIGHWAY 21 AND DIABLO STREET IN DANVILLE, GO EASTERLY ON DIABLO STREET FOR 0.75 MILE TO A FORK AND SIGN MT. DIABLO 14. TAKE THE LEFT FORK AND GO 1.1 MILES TO A FORK AND SIGN MT. DIABLO 13. TAKE THE RIGHT FORK AND GO 0.6 MILE TO A THREE WAY FORK AND SIGN MT. DIABLO 12. TAKE THE CENTER ONE OF THREE FORKS AND GO 8.8 MILES TO A POWERLINE, A TRACK ROAD AND THE AZIMUTH MARK 0.1 MILE WEST ON THE TRACK ROAD. CONTINUE ON THE BLACKTOP ROAD FOR 2.8 MILES TO THE STATION AND LOOKOUT TOWER.
1/1/1960 by CGS (GOOD)
RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1960 (IRR) THE STATION MARK, AZIMUTH MARK, AND REFERENCE MARKS NUMBER 1 AND 2 (SET IN THE CONCRETE WINDOW SILLS OF THE OBSERVATION TOWER) WERE RECOVERED IN GOOD CONDITION AND THE 1946, 1951, AND 1957 DESCRIPTIONS ARE ADEQUATE. AN UNSTAMPED REFERENCE MARK DISK ABOUT 48 FEET FROM THE STATION IN AZIMUTH ABOUT 78 DEG WAS REMOVED FROM A CONCRETE FLAGPOLE BASE PRIOR TO THE REMOVAL OF THE BASE BY THE STATE DIVISION OF BEACHES AND PARKS.
1/1/1962 by CGS (GOOD)
RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1962 (IRR) THE STATION MARK, AZIMUTH MARK, AND REFERENCE MARKS WERE RECOVERED IN GOOD CONDITION AND THE PREVIOUS DESCRIPTIONS ARE ADEQUATE.
1/1/1963 by CGS (GOOD)
RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1963 (LGB) THE STATION MARK, REFERENCE MARKS 1, 2 AND THE AZIMUTH MARK WERE RECOVERED AS DESCRIBED AND FOUND TO BE IN GOOD CONDITION. NO LOCAL DISPLACEMENT OF THE MARKS WAS NOTED. THE DISTANCE AND DIRECTION TO THE REFERENCE MARKS WERE CHECKED AND FOUND TO BE CORRECT. THE 1957 DESCRIPTION IS ADEQUATE EXCEPT FOR THE TO REACH. THE FOLLOWING IS A NEW TO REACH TO THE STATION. TO REACH THE STATION FROM THE INTERSECTION OF STATE HIGHWAY 21 AND DIABLO STREET IN DANVILLE, GO EASTERLY ON DIABLO STREET FOR 0.75 MILE TO A FORK. TAKE LEFT FORK AND CONTINUE EASTERLY FOR 1.1 MILES TO A FORK. TAKE RIGHT FORK AND CONTINUE EASTERLY FOR 0.6 MILE TO A FORK AT THE ENTRANCE TO MT. DIABLO STATE PARK. TAKE LEFT FORK AND GO NORTH AND EAST UPHILL FOR 3.7 MILES TO A LOCKED GATE. (THIS GATE IS LOCKED AT 10--00 P.M. IN THE EVENINGS THE KEY CAN BE OBTAINED FROM THE MT. DIABLO STATE PARK COMMISSION.) PASS THROUGH THE GATE AND CONTINUE NORTH AND EAST UPHILL FOR 4.7 MILES TO A POWERLINE, A TRACK ROAD AND THE AZIMUTH MARK 0.1 MILE SOUTH ON THE TRACK ROAD. CONTINUE NORTH AND EAST UPHILL FOR 2.8 MILES TO STATION AND LOOKOUT TOWER. THE SAME KEY WILL FIT THE LOCKED DOOR TO GET TO THE STATION MARK THAT IS USED TO GET THROUGH THE LOCKED GATE. OBSERVATIONS MADE FROM A 4 FOOT STAND INSIDE OF THE LOOKOUT TOWER.
1/1/1969 by CGS (GOOD)
RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1969 (WFF) THE STATION WAS RECOVERED AS DESCRIBED AND THE DESCRIPTION TO REACH THE STATION IS ADEQUATE. AIRLINE DISTANCE AND DIRECTION FROM NEAREST TOWN ABOUT SEVEN MILES NE OF DANVILLE.
1/1/1969 by CGS (GOOD)
RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1969 (CAA) THE STATION MARK, REFERENCE MARKS 1 AND 2 AND THE AZIMUTH MARK WERE RECOVERED AND FOUND IN GOOD CONDITION, DUE TO CHANGES IN THE ROADS A NEW AND COMPLETE DESCRIPTION FOLLOWS. TO REACH FROM THE POST OFFICE IN DANVILLE WHICH IS IN THE DANVILLE SQUARE SHOPPING CENTER, GO EASTERLY FOR 0.1 MILE TO HARTZ AVENUE, TURN RIGHT ON HARTZ AVENUE AND GO SOUTHERLY FOR 0.1 MILE TO THE JUNCTION OF DIABLO ROAD, TURN LEFT ON DIABLE ROAD AND GO EASTERLY ON DAIBLE ROAD FOR 0.7 MILE TO A FORK (PASSING UNDER INTERSTATE HIGHWAY 680). TAKE THE LEFT FORK AS PER SIGN MT DIABLO 14 FOR 1.7 MILE TO A FORK. TAKE THE RIGHT FORK AS PER SIGN MT DIABLO 13 FOR 0.9 MILE TO A FORK. TAKE THE LEFT FORK AS PER SIGN MT DIABLO 12 FOR 3.85 MILES TO THE ENTRANCE TO THE MT DIABLO STATE PARK. CONTINUE FOR 3.1 MILES TO A JUNCTION AND A RANGER STATION ON THE LEFT. TURN SHARP RIGHT AS PER SIGN SUMMIT AND GO 1.75 MILES TO WHERE THE ROAD MAKES A SHARP CURVE TO THE RIGHT, A POWER LINE ON THE LEFT AND A TURN AROUND,(TURN LEFT ON THE TURN AROUND AND GO FOR 0.05 MILE TO THE END OF TURN AROUND, CONTINUE AHEAD DOWN GRADE FOR 0.1 MILE TO THE AZIMUTH MARK). CONTINUE ON MAIN ROAD FOR 2.8 MILES TO THE SUMMIT, ROCK LOOKOUT HOUSE AND STATION. STATION MARK, UNSTAMPED, IS A BRASS BOLT, 1/2 INCH IN DIAMETER, PROJECTING ABOUT 1/2 INCH ABOVE THE BASEMENT FLOOR OF THE TOWER, WHICH IS THE SOUTHERN PART OF THE BUILDING. A TAPERED, OCTAGONAL, CONCRETE SHAFT, HOLLOW IN THE CENTER, HAS BEEN ERECTED OVER THE MARK AND EXTENDS INTO THE SECOND STORY OF THE TOWER, TWO OPENINGS, 8 INCHES SQUARE, ARE AT THE BASE OF THE SHAFT TO ENABLE PLUMBING OF THE MARK. OBSERVATIONS MUST BE MADE FROM THE THIRD (TOP) STORY. A 10 INCH OPENING (ROUND) IS IN THE CENTER OF THE TOP FLOOR TO ENABLE PLUMBING TO THE MARK. REFERENCE MARK 1 IS A STANDARD DISK, STAMPED MT DIABLO NO 1 1946, IS SET IN A DRILL HOLE IN THE OUTSIDE WINDOW SILL. IT IS ABOUT 1 METER HIGHER THAN THE FLOOR OF THE OBSERVATION TOWER. REFERENCE MARK 2 IS A STANDARD DISK, STAMPED MT DIABLO NO 2 1946, IS SET IN A DRILL HOLE IN THE OUTSIDE WINDOW SILL. IT IS ABOUT 1 METER HIGHER THAN THE FLOOR OF THE OBSERVATION TOWER. AZIMUTH MARK IS A STANDARD DISK, STAMPED MT DIABLO 1946, IS SET IN THE TOP OF A 12 INCH ROUND CONCRETE CYLINDER, PROJECTING ABOUT 6 INCHES ABOVE THE SURFACE OF THE GROUND. IT IS SLIGHTLY SOUTH OF THE CREST OF THE RIDGE, 17 FEET WEST OF A POWER LINE POLE. REFERENCE MARKS ARE TO CLOSE TO FOCUS ON. HEIGHT OF LIGHT ABOVE STATION MARK 24.74 FEET. AIRLINE DISTANCE AND DIRECTION FROM NEAREST TOWN 8 MILES NORTHEAST OF DANVILLE.
1/1/1971 by NGS (GOOD)
RECOVERY NOTE BY NATIONAL GEODETIC SURVEY 1971 (WMJ) THE STATION MARK, REFERENCE MARKS 1 AND 2, AND THE AZIMUTH MARK WERE RECOVERED AND FOUND IN GOOD CONDITION. THE DISTANCE AND DIRECTION TO THE REFERENCE MARKS COMPARED FAVORABLY WITH THE 1935 DATA. DUE TO CHANGES IN THE AREA A COMPLETE NEW DESCRIPTION FOLLOWS-- THE STATION IS LOCATED ABOUT 15 MILES NORTHEAST OF DANVILLE, 15 MILES EAST OF WALNUT CREEK, ON THE SUMMIT OF MT. DIABLO AND IN THE CENTER OF THE FIRST FLOOR OF THE MT. DIABLO LOOKOUT TOWER. TO REACH THE STATION FROM THE INTERSECTION OF HARTZ AVENUE AND DIABLO STREET IN DANVILLE GO EASTERLY ON DIABLO STREET FOR 0.75 MILE TO A FORK AND SIGN, MT DIABLO 14. TAKE THE LEFT FORK AND CONTINUE EASTERLY ON DIABLO STREET FOR 1.1 MILES TO A FORK AND SIGN, MT DIABLO 14. TAKE THE RIGHT FORK AND GO EASTERLY ON DIABLO STREET FOR 0.7 MILE TO A FORK AND SIGN, MT DIABLO 12. TAKE THE RIGHT FORK AND CONTINUE EASTERLY ON DIABLO STREET FOR 0.95 MILE TO A FORK AND SIGN, DIABLO SCENIC BOULEVARD= MT DIABLO 12. TAKE THE LEFT FORK AND CONTINUE EASTERLY ON DIABLO SCENIC BOULEVARD FOR 4.0 MILES TO THE SOUTH GATE RANGER STATION. CONTINUE UPHILL ON THE SURFACED ROAD FOR 3.25 MILES TO RANGER HEADQUARTERS ON THE LEFT. TURN SHARP RIGHT AND CONTINUE UPHILL ON THE MAIN ROAD AS PER SIGN, SUMMIT 4.5, FOR 1.85 MILES TO A GRAVELED SIDE ROAD LEFT. (TO REACH THE AZIMUTH MARK, TURN LEFT AND GO SOUTHWEST ON THE GRAVELED ROAD FOR 0.05 MILE TO THE SOUTHWEST END OF A PARKING AREA. CONTINUE SOUTHWEST ON A TRACK ROAD FOR 0.05 MILE TO A POWER POLE AND THE MARK.) CONTINUE UPHILL ON THE MAIN ROAD FOR 3.0 MILES TO THE SUMMIT OF THE MOUNTAIN, A LOOKOUT TOWER AND THE MARK AS DESCRIBED. THE STATION MARK IS A 1/2-INCH IN DIAMETER BRASS BOLT THAT PROJECTS 1/2-INCH ABOVE THE GROUND FLOOR OF THE LOOKOUT TOWER. A TAPERED, OCTANGONAL, CONCRETE SHAFT WITH AN 8-INCH OPENING IN THE CENTER HAS BEEN ERECTED OVER THE MARK. TWO OPENINGS IN THE BASE OF THE SHAFT ENABLE PLUMING OF THE MARK. OBSERVATIONS MUST BE MADE FROM THE THIRD STORY OF THE TOWER. A 10-INCH HOLE IN THE FLOOR ENABLES THE PLUMING OF THE MARK. REFERENCE MARK 1 IS A STANDARD DISK STAMPED MT DIABLO NO 1 1946, CEMENTED IN A DRILL HOLE IN THE OUTSIDE CONCRETE WINDOW SILL OF THE BUILDING. IT IS ON THE SOUTHEAST SIDE OF THE BUILDING AND ABOUT 3 FEET ABOVE THE OBSERVATION ROOM FLOOR. REFERENCE MARK 2 IS A STANDARD DISK STAMPED MT DIABLO NO 2 1946, CEMENTED IN A DRILL HOLE IN THE OUTSIDE CONCRETE WINDOW SILL OF THE BUILDING. IT IS ON THE WEST SIDE OF THE BUILDING AND ABOUT 3 FEET ABOVE THE OBSERVATION ROOM FLOOR. THE AZIMUTH MARK IS A STANDARD DISK STAMPED MT DIABLO 1946, SET IN THE TOP OF A ROUND CONCRETE MONUMENT THAT IS 12-INCHES IN DIAMETER AND PROJECTS 6 INCHES ABOVE THE GROUND SURFACE. IT IS 17 FEET NORTHWEST OF THE THIRD POWER LINE POLE WEST OF THE SURFACED ROAD. AIRLINE DISTANCE AND DIRECTION FROM NEAREST TOWN--15 MILES NORTHEAST OF DANVILLE
1/1/1973 by NGS (GOOD)
RECOVERY NOTE BY NATIONAL GEODETIC SURVEY 1973 (CLN) THE STATION MARK, AZIMUTH MARK, AND REFERENCE MARKS 1 AND 2 WERE RECOVERED IN GOOD CONDITION AND THE PREVIOUS DESCRIPTIONS ARE ADEQUATE. AIRLINE DISTANCE AND DIRECTION FROM NEAREST TOWN--6 MILES NORTHEAST OF DANVILLE
1/1/1977 by NGS (GOOD)
RECOVERY NOTE BY NATIONAL GEODETIC SURVEY 1977 (CA) THE STATION WAS RECOVERED IN GOOD CONDITION AS PREVIOUSLY DESCRIBED. THE 1946, 1951, AND 1957 DESCRIPTIONS ARE ADEQUATE. THE REFERENCE MARKS WERE NOT SEARCHED FOR.
3/3/1988 by NOS (GOOD)
RECOVERY NOTE BY NATIONAL OCEAN SERVICE 1988 (FRD) THE STATION WAS RECOVERED AT THIS DATE. REFERENCE MARKS 1 AND 2 WERE RECOVERED IN GOOD CONDITION. THE 1971 DESCRIPTION IS ADEQUATE EXCEPT THAT OBSERVATIONS ARE NOT POSSIBLE FROM THE THIRD STORY WHICH IS NOW A RADIO ROOM. A MONUMENT HAS BEEN ERECTED ON THE SECOND FLOOR WHICH PREVENTS PLUMBING THE MARK FROM ABOVE.$DESCRIBED BY T.K. PORTA
1/1/1990 by LOCSUR (GOOD)
RECOVERY NOTE BY LOCAL SURVEYOR (INDIVIDUAL OR FIRM) 1990 (BRH) THE STATION WAS RECOVERED IN GOOD CONDITION AS DESCRIBED.
7/15/1992 by GREENW (GOOD)
RECOVERY NOTE BY RONALD GREENWELL 1992 THE STATION WAS RECOVERED IN GOOD CONDITION AS DESCRIBED.
1/1/1997 by USPSQD (GOOD)
RECOVERY NOTE BY US POWER SQUADRON 1997 RECOVERED IN GOOD CONDITION.

Control Text

  • The horizontal coordinates were established by classical geodetic methods and adjusted by the National Geodetic Survey in March 1994. The horizontal coordinates are valid at the epoch date displayed above. The epoch date for horizontal control is a decimal equivalence of Year/Month/Day.
  • The NAVD 88 height was computed by applying the VERTCON shift value to the NGVD 29 height (displayed under SUPERSEDED SURVEY CONTROL.)
  • The Laplace correction was computed from DEFLEC99 derived deflections.
  • The geoid height was determined by GEOID99.

Advertising with Us

Return to the Top of the Page