Missing Rm - Pid# Ew7694

[+California Bear]

I discovered something odd about the RMs when I found EW7694.

 

The location description for RM 1 and RM 2 are identical:

REFERENCE MARK 1, A STANDARD CDH DISK STAMPED HORSESHOE R.M. 1 1972, IS SET IN THE TOP OF A 15-INCH CONCRETE MONUMENT WHICH PROJECTS 3 INCHES ABOVE THE GROUND SURFACE. IT IS 6 FEET SOUTH OF THE NORTH SLOPE OF THE HILL AND 40 FEET EAST OF THE TOP OF THE HILL.

 

REFERENCE MARK 2, A STANDARD CDH DISK STAMPED HORSESHOE R.M. 2 1972, IS SET IN THE TOP OF A 14-INCH CONCRETE MONUMENT WHICH PROJECTS 3 INCHES ABOVE THE GROUND SURFACE. IT IS 6 FEET SOUTH OF THE NORTH SLOPE OF THE HILL AND 40 FEET EAST OF THE TOP OF THE HILL.

 

I found RM 2 but couldn't find RM 1. Anyone have any ideas (other than that the initial surveyor made a mistake) as to why RM 1 and 2 would have the same location description?

[mloser]

EW7694|---------------------------------------------------------------------|

EW7694| PID    Reference Object                    Distance      Geod. Az  |

EW7694|                                                          dddmmss.s |

EW7694|        HORSESHOE RM 1                        6.845 METERS 01633    |

EW7694| EW7684 HELIPORT                            APPROX. 5.0 KM 0515546.2 |

EW7694|        HORSESHOE RM 2                        6.060 METERS 09325    |

EW7694|---------------------------------------------------------------------|

 

This section of the original description is the key to the reference marks, and shows RM1 is 6.845 meters away at a heading of 16.33 degrees.

 

I usually start with the description of the reference marks, as it often references things I can measure from, I often resort to the above section that states exactly what angle and what distance. If there are no obstructions you can stake your tape at the station and swing an arc with it at the prescribed distance to make sure your cover all possibilities.

 

There was a long thread on triangulation stations a while ago at: Triangulation Stations which might prove very helpful.

 

Matt

 

[Edited to add thread about triangulation stations]

Edited July 26, 2004 by mloser

[mloser]

California,

If you find RM1, you might want to measure it and redescribe it and submit the recovery to NGS.

Edited July 26, 2004 by mloser

[+California Bear]

That'll teach me not to include the box score on my printouts!

[mloser]

Tonight my son and I needed all the help we could get looking for a station and two reference marks. Not a single item in the description was available to measure from. The property owner and neighbor came out and showed us where they thought the station was, and sure enough, it was under 2 inches of dirt. We used the information about reference mark distance and angle was absolutely necessary to find the two reference marks as they were also under dirt and grass. Luckily the owner thought nothing of digging two holes in his yard to help us.

We measured from existing trees and will redescribe the marks to NGS later tonight.

 

This is the kind of hunt, and find, that make benchmarking worth it. Of course, we were lucky the owner had no qualms about digging up his yard.