Reference Marks

[Cavalier53]

Just getting started with benchmarking. I have a question. If I find a reference mark, should I expect the benchmark to be relatively close? Here is my dilema. Original data sheet for benchmark (KX2093) led me easily to reference marks, however, there are NO reference points listed between reference marks and benchmark. There are no landmarks in common. See below.

 

KX2093''REFERENCE MARK NO. 1, A STANDARD DISK STAMPED OWENS NO 1 1958, IS SET

KX2093''IN A SQUARE CONCRETE POST FLUSH WITH THE SURFACE OF THE

KX2093''GROUND. IT IS 31 FEET NORTHWEST OF THE NORTH CORNER OF HOUSE, 17 FEET

KX2093''EAST-SOUTHEAST OF A GRAVEL DRIVE AND 2 FEET WEST-NORTHWEST

KX2093''OF A POWER LINE POLE.

KX2093''

KX2093''REFERENCE MARK NO. 2, A STANDARD DISK STAMPED OWENS NO 2 1958, IS SET

KX2093''IN A SQUARE CONCRETE POST WHICH PROJECTS 3 INCHES. IT IS 62

KX2093''FEET WEST OF THE SOUTHEAST GATE POST, 14 FEET SOUTHWEST OF THE CENTER

KX2093''OF A GRAVEL ROAD AND 2 FEET EAST-SOUTHEAST OF A POWER LINE

KX2093''POLE.

KX2093''

KX2093''AZIMUTH MARK IS A STANDARD DISK STAMPED OWENS 1958, SET IN A SQUARE

KX2093''CONCRETE POST FLUSH WITH THE SURFACE OF THE GROUND. IT IS 96

KX2093''FEET SOUTHWEST OF THE NORTHEAST END OF GUARD RAIL, 39 FEET NORTHEAST

KX2093''OF THE SOUTHWEST END OF GUARD RAIL AND 28.5 FEET NORTH OF

KX2093''THE WEST ONE OF TWO 8-INCH TREES.

 

What would be my best course of action as guard rail mentioned no longer exists? And, I'm sure those trees have grown since 1958.

[GH55]

Just getting started with benchmarking. I have a question. If I find a reference mark, should I expect the benchmark to be relatively close? Here is my dilema. Original data sheet for benchmark (KX2093) led me easily to reference marks, however, there are NO reference points listed between reference marks and benchmark. There are no landmarks in common. See below.

 

***

 

What would be my best course of action as guard rail mentioned no longer exists? And, I'm sure those trees have grown since 1958.

 

Look again at the NGS Datasheet: KX2093

 

In the "box score" (right above "Superseded Survey Control")you will find the distance and direction to each of the RM's from the station. Direction only to the AZ mark. If you start from the RM's and measure the given distances in the reciprocal directions, you should get close to the station mark. The one point in approximately the correct direction where the two measurements meet should be the location of the station.

 

As for the AZ mark, you may just have to guess where the guard rail should have been, and rely on the given azimuth from the station.

 

I think.

[mloser]

First off, ignore the azimuth mark for the time being. It is the least important of the marks listed. You chopped the main station off your data and it is what you want to find most.

 

The station is described as:

KX2093'

KX2093'STATION MARKS ARE STANDARD DISKS STAMPED OWENS 1958. THE SURFACE DISK

KX2093'IS SET IN A SQUARE CONCRETE POST FLUSH WITH THE SURFACE OF THE

KX2093'GROUND. IT IS 98 FEET WEST-NORTHWEST OF THE NORTH CORNER OF A TIN

KX2093'BUILDING, 68 FEET EAST-NORTHEAST OF THE NORTH

KX2093'CORNER OF A BOARD GATE AND 42 FEET SOUTHWEST OF THE CENTER OF A

KX2093'GRAVEL ROAD.

If either the building or gate remain you can use those to find the mark. I am guessing neither remain because the mark was not found in 1991. You should be able to get to within 10 feet or so of the station with your GPSr though, and might find enough reference points to guide you to the mark. I am sure the road is now paved but often they paved gravel roads exactly where they were, so the centerline may be accurate enough to use as a measuring point.

 

Your key to finding one mark once you have found anotehr is the "box score" near the top of the datasheet:

KX2093|---------------------------------------------------------------------|

KX2093| PID Reference Object Distance Geod. Az |

KX2093| dddmmss.s |

KX2093| CX5137 OWENS RM 1 28.717 METERS 24510 |

KX2093| CX5136 OWENS AZ MK 2932239.5 |

KX2093| CX5138 OWENS RM 2 21.156 METERS 33955 |

KX2093|---------------------------------------------------------------------|

 

This should give enough information to find the station if you have found a reference mark (or vice versa). The information given is the distance from the station to the reference mark in meters and the direction to the reference mark in degrees minutes seconds. If you find a reference mark you can use the box score to reverse direction to the station. For instance, if you locate RM 1 you know that the main station should be 28.717 meters away at 65.1 degrees (245 degrees 10 min minus 180 degrees, because you are heading the opposite direction TO the station and not FROM the station to the RM). Add in the declination for your area, which is about 9.3 degrees west of geological north and you should be looking at 74 degrees. Get your compass and start walking, either measuring or pacing the distance.

 

Note that both reference marks are close to power poles. Often power poles stay very close to where they were originally placed, even if the road changes, so you may be able to find one or both of the reference marks.

 

Like GH55 said, finding the azimuth mark is often a crap shoot, and you can only follow the "to reach" in the description and hope you find enough reference points to locate it.

 

Good luck.

[ggmorton]

I have also noticed that most of the reference marks have an arrow on them pointing towards the main station. At least the ones I have seen do.

[mloser]

Yes, they do, but that arrow is only as accurate as the person setting it. I don't think they used heroic measures to line them up. They just sighted along the arrow as they pressed it into the concrete. I have seen some pointing quite a bit off. I wouldn't blindly follow the arrow unless that was all I had to go on, and since the box score gives you more accuracy (or is it precision?) than you can handle you are better off using it.

[+Black Dog Trackers]

ggmorton -

 

The area of KX2093 has a -9 degree declination (on the geocaching datasheet for KX2093, click on Topozpone and look at the M value in the bottom right corner of the map). The box score is in terms of True North, but your compass uses Magnetic North instead. For longer distances such as the distance to the azimuth mark, you might need to convert the box score's azimuth to magnetic degrees if you want to accurately follow the box score's direction to it.

 

For an explanation on how to do the conversion, read holograph's wiki site here. In that site, click on "Benchmark Hunting", then on "Finding the main station from reference marks and vice versa".

[Cavalier53]

Thanks for the help. This site is obviously great because of the people that use it. What a wealth of information! I'll find this one soon.

[+PFF]

It appears that the station is in the southwest quadrant of the intersection of Community Park Road and Arbour Lane. The area probably has changed considerably. However, the station has ADJUSTED coordinates, and your GPS receiver should get you within a few feet of the published location.

 

Good luck, and let the group know how the next search turns out!

 

-Paul-

[ArtMan]

You might also try entering the coordinates into Google Maps or Google Earth, which will give you an aerial view. Depending on the resolution available, it could be very helpful. -ArtMan-