Help in finding reference marks - maps and diagrams

[Papa-Bear-NYC]

Like many benchmarkers on this forum, when I go after a triangulation station, I like to find all the reference marks too. Ironically, although the reference marks were put there to help you find the main station, I most often find the station mark first, and then go searching for the RMs. Perhaps that's because the location of the station mark is more well known, and we often put it into a GPS. We would seldom go to the trouble of computing the location of RMs and loading them into a GPS.

 

But recent improvements in technology has given us more help. I now often calculate RM locations using the forward program and the box score. There are several recent routines that automate this process: the one that comes to mind is the new version of BM2GPX by foxtrot-xray. See threads:

http://forums.Groundspeak.com/GC/index.php...171790&st=0

http://gsak.net/board/index.php?showtopic=6043&st=0

With this it's much easier to put these locations into GSAK or feed them to Google Maps, Google Earth etc.

 

Like several folks here, I use Google Maps to plan my searches. I use custom maps that I build myself using the API. I made good use of this in my recent trip searching for tri stations in Massachusetts which was the subject of another thread.

 

The first thing I do is put the station and RMs on the map and try to get a good satellite view. If the imagery is good and the RMs are far enough away to avoid a jumble, I can get a good picture which will show me where to look. Here's one for station LW4436 - "Manomet": Manomet satellite map. You can see where the path comes in and where the clearing is. This is where this technology is really helpful. Printing a copy of this along with the datasheets puts you in a good position to find them all.

 

But look at this one for MZ1808 - "Mount Tom": Mount Tom satellite map. The photo quality is poor, and the marks are all jumbled together, even at maximum zoom.

 

To solve this I had an inspiration: why not have a "blank" map and allow the zoom level to go much higher? Voilla! Now the map becomes a diagram. Bring up the Mount Tom image again and do this:

1) Use the map type selector in the upper right corner and click on "Blank".

2) Zoom in several levels till you get a nice diagram to print out.

 

ddnutzy and I used these diagrams to great advantage on our Massachusetts searches. We would just put the diagram on a clipboard, put it on top of the station and orient it to one of the marks. Then it points to all the other RMs. With this diagram and a tape, we could get all the RMs in minutes, which would otherwise take much longer. I can alternatively put the distances on the diagram, although the more you put there the more it tends to get cluttered. KISS.

 

Here's a good example for MY3792 - "Wachusett 2 Reset": Wachusett Diagram. (That yellow line going off to the southwest is for the Azimuth Mark - which without an accurate distance, we never did find!)

 

I firmly believe using the tools available to us (GPS, metal detectors, Computer generated maps, etc.) we can find marks that in former times were considered unfindable.

 

So go find 'em!

 

Edit: Foxtrot xray's program is BM2GPX, not GM2GPX, sorry. Fixed now.

Edited May 1, 2008 by Papa-Bear-NYC

[+Ernmark]

Nice !

I try to plot out the RM's & AZ also...but I must admit doing it "old shool" by plotting it out on paper.

 

I'll have to give this hi-tech method a try (being a computer person by trade & all) !

[+shorbird]

Reading over an old description, I have come across the following instructions for the location of a reference stone:

 

BEARING NORTH 34 DEG. 02 MIN. WEST, DISTANT 284.9 FEET.

 

Not being familiar with this type of direction, I would like to know how this instruction translates into the exact direction you need to go.

[+GEO*Trailblazer 1]

That is called Quadrant Reading.

 

All 4 Quadrants being 90 degrees.

 

WIKI QUADRANT

 

The 4 quadrants are broken into 4 parts.

NE,SE,SW,and NW 90.

 

So you would begin your reading in the North West Quadrant

BEARING NORTH 34 DEG. 02 MIN

Ending on the WEST.

 

North being 0 and then click off west (counterclockwise) 34 degrees and 02 minutes.

 

If you take 34 degrees .02' from 360 you can get it that way too.

About 326 degrees. + or - .02'

 

326 + 34 = 360

Edited May 27, 2008 by GEO*Trailblazer 1

[mloser]

Old school! That means that the bearing is North, then head 34 degrees 02 minutes west. You can do this on site with a compass (it is how I have done it the couple of times I have run across it) or calculate it by subtracting 34 degrees from 360--your mark is at 326. I am not sure if that is magnetic or true north but suspect true north. Of course, since it is 300 feet away... Whoo--good luck on that one. All of my bearing reference marks were close and were reference holes in nearby rocks so finding them wasn't too difficult.

[+Kewaneh & Shark]

Old school! ...

Old School??? Maybe, but quadrant bearings are what surveyors currently use every day, particularly when writing metes & bounds property descriptions. Azimuth bearings, are rarely used, if ever, for that purpose. In fact, I've only seen one in the past 18+ years, and it was a "special circumstance" description. Azimuth bearings are used in geodetic work and navigation. Quadrant bearings may be "old", but they're tried & true, and, in some cases, more functional than azimuth bearings.

 

- Kewaneh