Morro Bay Mysteries

[+cjf]

I held off logging my Morro Bay (San Luis Obispo County, CA) benchmark results for a few weeks because, frankly, I was confused. I kept hoping that the passage of time would make things clear. Didn't happen.

 

The first mystery: FV1654

As you can see by the note I posted, I found several benchmarks on top of Black Hill. I thought I had found the reference marks, took my pictures, and headed down the hill. It wasn't until I got home and started comparing the benchmark photos to the datasheet that I realized something was funny. Benchmark markings were similar, but not the same. Also, there was no NGS entry for 1992, but one of the RMs was clearly cemented in 1992 because it's written in the cement. It was all very odd. I'm still confused.

 

The second mystery: This appears to be a "two for one" visit benchmark. Is it FV1101 or FV0401? What's up with that? Both datasheets refer to the same Centennial Stair monument and the benchmark on top of it. What the heck, I logged them both with a reference to both designations. (The contest is over, so who's counting? )

 

I have a year to mull it all over. I'll be back next fall for the next family campout and can revisit the sites.

 

Colleen

[+BuckBrooke]

cjf,

In response to your first mystery, here is at 2002 log for the station on the "real" NGS datasheet, in the NGS database located here:

 

FV1654 STATION RECOVERY (2002)

FV1654

FV1654'RECOVERY NOTE BY CA DEPT PARKS REC 2002 (DBK)

FV1654'FOUND RM N AND RM SE AND THREE LEAD PLUGS WITH A COPPER NAIL. DID NOT

FV1654'FIND THE STATION MARK BUT IT MAY BE COVERED WITH DIRT. DID NOT SEARCH

FV1654'FOR RM 3. THE STATION IS LOCATED APPROXIMATELY 200 VERTICAL FEET

FV1654'ABOVE THE PARKING AREA. THE STATION IS LOCATED IN MORRO BAY STATE

FV1654'PARK. PARK IN THE BLACK HILL PARKING AREA ABOVE THE GOLF COURSE AND

FV1654'HIKE ALONG A DIRT FOOTPATH TO THE STATION.

 

This recovery basically says what you said. At the location (the station is ADJUSTED horizontally, so right there), there's no disk to be found. The RMs are weird, especially as they're USC&GS disks, which became the NGS in the 1970s. There might have been disks left over into the 1990s, but if the disk was put down in 1992 I would have expected it to be an NGS disk. So, I would call this one not found, and if you log it not found with the NGS you should mention the reference mark stamping.

 

For your second mystery, if you look at the "original" datasheet, look at the class of the station. FV1101 is VERT ORDER - SECOND CLASS 0 and FV0401 is VERT ORDER - FIRST CLASS I. So, you do get a two-fer, as both stations are the same disk. My guess is that someone came through in 1977 and re-leveled the disk to higher accuracies. The NGS isn't going to throw out the original station info, so they added another datasheet.

[mloser]

Colleen,

I had looked at both those recoveries and wondered what was up (not so much with what you said about them but with how the marks were described in relation to what you found).

 

Starting with the FV0401-FV1101 mystery, it appears to me that the mark is the same, but also not the same. For one thing, both descriptions say the mark, named TIDAL 5 in FV0401 and 941 2298 TIDAL 5 RESET in FV1101 is in a concrete block with a 1970 date on it. FV1101's 2004 recovery by the NGS, not part of the Geocaching site's data, says the mark is NOT stamped reset. However, the coords on that mark are adjusted and the description has been rewritten, including the text "THIS STATION WAS OBSERVED IN THE SAN

SIMEON POST-EARTHQUAKE AND HEIGHT MODERNIZATION SURVEY, A CSR PROJECT." so I am betting that they surveyed the mark as a horizontal control point at that time. To me that makes it the "official" mark of the two. Oddly, the 2004 recovery mentions BREAKERS CAFE, which is not described in FV1101, but IS in FV0401 (as BRAKERS CAFE). The survey party had to have been looking at both descriptions when they found this mark. More confusing--the vertical order of the marks is different--FV0401 is First Class, and FV1101 is Second Class. Surveyors can jump in here, but I think that indicates that the mark, if both descriptions are for the same mark, was originally a vertical mark, used for elevation, and when resurveyed in 2004, the FV1101 description was surveyed to a higher horizonal order at that time (it had no horizontal order before).

 

Where does that take us? Well, since FV1101 is surveyed to a high horizontal order, and FV0401 is surveyed to a high vertical order, they are both valid descriptions and PIDS, IF the descriptions match closely enough that you believe the mark(s) are the ones described. This was not the case before 2004, when the NGS resurveyed the mark as FV1101--prior to that it just seemed that the descriptions were duplicates. If I measured and was satisfied that the mark was in the same place as described in 1976 I would submit recoveries for both, noting that they each mark appears to be the same as the other PID, but noting the differences in the horizontal and vertical orders--"NOTE-THIS MARK APPEARS TO BE THE SAME DISK AS FV1101, BUT USED FOR VERTICAL CONTROL", or something like that. I might even get Deb or someone at the NGS involved to help me sort out how to best recover them. (just read BuckBrooke's post and he noticed the different vertical orders, which is also worth noting).

 

FV1654--you found the reference marks, but not the station. A more recent recovery (2002) by California Parks and Recs has the mark as a not found, but the text tells me that the hunt was not very aggressive-- "BUT IT MAY BE COVERED WITH DIRT" isn't quite enough for me to be honest.

 

I don't think anything is out of kilter with that station. The dates on the reference marks are somewhat odd, but if they fit the descriptions they are probably correct but may have been reset at the same location but just not described at that time. The key to finding the station is to get the original datasheet from the NGS, take a tape, a prod of some sort, and maybe a metal detector out and start measuring. At the top of the datasheet is the "box score". It gives distances and directions to various other survey points. Ihe case of FV1654 that box score is huge, but what you want to pay attention to are the two reference marks DA5710 BLACK HILL RM SE and DA5709 BLACK HILL RM N. I think those are the two disks you found (or are the location of them, if they were reset in place). By using the information to the right of the box score you can measure the direction and distance to the station from the RMs and find the likely location for the main station. "BLACK HILL RM SE 8.740 METERS 13418" means that the southeast RM is 8.740 meters from the station at a direction of 134.18 degrees. Correct your compass for the declination of your area (14.276 degrees east, which means you subtract 14.276 degrees from 134.18 to get the magnetic reading) reverse that so that when you are standing at the RM you can measure to the station, then measure the 8.74 meters in that direction. So stand at the RM, check your compass for the direction of 300 degrees, and measure 28.7 feet. Do the same thing with the other RM using the information on the box score. Where the two lines meet is your station! Well, hopefully NEAR that spot, with some slack for sloppy compass readings or poor directional skills. A metal prod might be all you need to find the monument at that point and a metal detector might make all the difference in the world.

 

Edit-another thing you could look for are the old reference marks--tacks and lead bolts. Three are mentioned in the different recoveries but there is no distance given for any of them. Two things to consider that may be make them useful. First, they will be closer than the RM disks, most likely on the nearest rock outcrops to the station. Second, if there were four of them at one time, chances are they formed an X over the top of the station. I have seen that in some cases with older tri-stations. To help you, DaveD, who visits this site, might be able to get hold of the original description, since they are missing from the current one.

 

Whoa that was long! I hope it helps.

 

Matt

 

Edit: P.S. NEVER use the Geocaching datasheets. They are about 4 years out of date. Always download the latest sheets from the NGS site.

Edited October 20, 2006 by mloser

[+rogbarn]

Edit: P.S. NEVER use the Geocaching datasheets. They are about 4 years out of date. Always download the latest sheets from the NGS site.

According to this thread, Jeremy stated that the CDs were purchased in January 2001, so, the data is almost 6 years out of date. Despite on and off discussions about getting the database updated, it has never happened.

[+cjf]

Gentlemen,

I always use the NGS datasheets downloaded to GSAK. (For proof, witness my cry for help prior to my Morro Bay Weekend: NGS Datasheet Page - California Down? ) I must confess that sometimes the datasheet details make what's left of my brain go numb.

 

Next year I'll climb up Black Hill will additional gear - tape measure, probing device (perhaps I need to finally spring for a metal detector?), and appropriate relatives gleaned from family campout to assist in search. It was just me and my dad this year. My dad and I must have looked awful funny up there this year. I'd have him stand on an RM and point in the same direction as the arrow on the RM. I'd go to the other RM and start walking in the direction of my arrow. When I reached the point where my dad was pointing at me I started looking in the dirt for the main benchmark. Next year I'll grab an uncle or two, perhaps a husband, bribe daughters....... I'll have a whole slew of people up there standing and pointing!

 

I'm just glad to know it wasn't just me and that something was a little odd about those benchmarks.

 

BTW, Breaker's Cafe mentioned in FV0401-FV1101 is now Dorn's. Great place to have dinner (and a grab a benchmark or two to boot!).

 

Colleen

[DaveD]

FV1101 and FV0401 are the same mark. I have sent a note to make the appropriate correction. Thank you for helping us keep the National Spatial Reference System data as up to date as possible.

[mloser]

Dave!? All my great thinking on why they have been kept as different PIDs and you just up and say "they are the same". Dang!

Any luck finding the original description for FV1654 that mentions the WMs?

 

Colleen,

It is great to have someone to hold the other end of a tape, which has only happened to me a couple of times. I end up running the measurements by myself and have gotten decently good at it. It gets more difficult if thre are obstructions between the station and RM but I have adapted. I have no other real choice. If you can prepare, there is nothing better than using a compass and tape to get a precise location for the mark. The arrows are not always 100 percent accurate and at the very least they are only as accurate as tiny arrows on a disk can be.

[+cjf]

FV1101 and FV0401 are the same mark. I have sent a note to make the appropriate correction. Thank you for helping us keep the National Spatial Reference System data as up to date as possible.

You're welcome! (How cool is this? A "thank you!" I cut and pasted it into my GSAK notes for these/this benchmark as a momento.)

 

Colleen,

It is great to have someone to hold the other end of a tape, which has only happened to me a couple of times. I end up running the measurements by myself and have gotten decently good at it. It gets more difficult if thre are obstructions between the station and RM but I have adapted. I have no other real choice. If you can prepare, there is nothing better than using a compass and tape to get a precise location for the mark. The arrows are not always 100 percent accurate and at the very least they are only as accurate as tiny arrows on a disk can be.

Duly noted. All the helpful advice about Black Hill also copied into GSAK notes so it's there for next year.