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Triangulation Station

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It took me awhile, but I finally conquered my first Triangulation Station, PF1132, HAZEL.

 

Does anyone know why the markers are not referenced to each other? Magnetic heading and distance apart, for example, would help. I have listed this info on my Geo Benchmark report once I mapped the area.

 

Since 1976 when HAZEL was monumented, enough referenced items had changed to almost unrecognizable. One of the markers was even buried with time.

 

I began a few weeks ago by discovering mark #2......found the Master mark this morning and discovered mark #1 this afternoon. Written references to posts, fences, gates and line poles were all obsolete.

 

I am just curious if anyone knows why the markers aren't referenced to each other.

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You mean like this from the original datasheet?

 

PF1132
PF1132
PF1132|---------------------------------------------------------------------|
PF1132| PID    Reference Object                     Distance      Geod. Az  |
PF1132|                                                           dddmmss.s |
PF1132| PF1131 HAZEL AZ MK                         APPROX. 1.3 KM 1770305.4 |
PF1132|        HAZEL RM 2                           21.029 METERS 22826     |
PF1132|        HAZEL RM 1                           11.680 METERS 35856     |
PF1132|---------------------------------------------------------------------|
PF1132

 

This tells you precise distance and direction from the main station. Keep in mind the direction is to true north, not magnetic.

Edited by GeckoGeek

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Thanks GeckoGeek........your point is well taken. However, none of us out here are travelling around with Meter sticks and True North compensating compasses capable of two decimal places to the right.

 

I am simply trying to figure out why the surveyors would not use instruments available to them and everyone else.

 

......or am I just being stupid and naive......?

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I am simply trying to figure out why the surveyors would not use instruments available to them and everyone else.

 

......or am I just being stupid and naive......?

:D Take your choice. Just kidding.

 

Magnetic north does not stay in the same place. Over a long period of time, an error would accumulate. Other influences on magnetic north as well. Perhaps a power line might get installed nearby. A building could be erected. All kinds of different factors. But TRUE north will always be there. When we surveyed South Dakota in 1950-51, we used magnetic to set up the instruments during the day but would go out during the night each month and shoot Polaris to make any corrections. (Yes, that is me in the picture to the left.) Can you imagine what the error would have been for the Chunnel between England and France if they had relied only on magnetic?

 

As for metric, the rest of the world is changing to meter which really makes much more sense. I have been pressing for metric for forty years. Much easier to work with the base 10 rather than 12 inches, three feet, 16-1/2 feet, 5280 feet, rods, miles, acres, bushels, ounces, pounds, tons, 32 degrees, 212 degrees, etc. Why not multiply by 10 each time?

 

Have you ever heard of a measured rod? Know how long it is? Used to be very popular in surveying.

 

BTW, RM2 is about 69 feet, RM1 about 38 feet and AZM about 0.8 mile or 4265 feet. And your GPS will give TRUE bearings. Forget the magnetic compass.

 

(Had to edit this for some typos!)

Edited by Colorado Papa

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With the inception of survey-grade GPS into surveying, these triangulation stations are not maintained with the same savvy they once were. After all, if you need a basis of bearing there is no need to calibrate a brass transit or theodolite and use triangulation stations, when you can set up a couple Pro Mark 2's or HyperLites and let them cook for 20 minutes while you get something to drink.

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Hey DBC,

I was wondering why triangulation stations had three disks (No, not because I don't know what a triangle is!). You are saying they are primarily to calibrate prior to surveying?

And as much as I love GPS, dadgum it all for making benchmarks less needed!

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Why 3? Well not all have 3, some have 4 some have 1, often there is not azimuth mark due to obstructions. (many like that here).

 

A typical station has 2 station marks, one on the surface and underground mark below it, 2 reference marks (min), an azimuth mark (if suitable location is available) and any number of intersection stations (local landmarks). Often there would be a USGS mark in the same location and they would use that as one of the reference mark.

 

The RM's and the Azimuth mark have several reasons for existence. First of all, consider the time when this work was done. To establish a position required a lot of work, they wanted to be able to re-construct the station location if it were lost and the verify its position. Thus the RM's. The azimuth mark was set primarily for local survey use. A surveyor could set on the station mark, observe the azimuth and he had a bearing for his survey. He could use the RM to check to see if the station checked with the RM's. That was part of the thinking behind the work. They wanted to leave something that could be used in the future. But here we are many years later and GPS is the thing. What took a lot of time in 1950's can be done in hours today.

 

btw-In our traverse surveys at the DOT we often started and ended our surveys on triangulation stations. We were obligated to tie our major work to the State Plane Coordinate System which prior to GPS, the only way you could do this was to use these marks. Eventually in the late 90's all our crews were outfitted with GPS and this made our work much easier and cost efficient. Prior to this is was always thought to be cheaper to have more people to do the work but with the his cost of employing people is was realized ti was cheaper in the long run to invest in state of the are equipment and less in employee's.

Edited by elcamino

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Mike

While it seems GPS is replacing benchmarks, there must still be a lot of use of them, as I come across them with flag markers, spray paint, etc. How are they used today? What is a typical, if there is one, use of a benchmark for a surveying project?

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No, GPS is not replacing Bench Marks per say. Its replacing triangulation.

 

Bench Mark is a term in the survey profession that relates to vertical points (elevation). They are still refining the GPS derived elevations. Also, due to the cost of GPS equipment it is not always feasible to use GPS for every survey.

 

The term Bench Mark is used on this site to refer to all survey marks.

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So despite what our resident engineer says, GPS won't be replacing benchmarks very soon, and the work I am doing is not to waste?

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"Engineer is someone who leans more and more about less and less until he knows everything about nothing"

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Good control is just as important today as it was years ago. Sanitary sewer grades are usually built on a relatively flat grade. Good control helps to insure that it flows down hill. Just one of many modern applications.

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I am simply trying to figure out why the surveyors would not use instruments available to them and everyone else.

Actually, they did use what was available to them and all other surveyors. I don't think in their wildest dreams they'd ever think the general public would have any interest in this.

 

The numbers are as accurate as they are because it fits their needs. It's not hard to approximate the number for our use. Just multiple meters by 3 to get a rough measurement in feet, and simply round off the heading and add/subtract the local declination. At least that will get you in the right area for searching rather then going nuts trying to figure out where it might be.

 

Depending on your GPS, you may even be able to project that point and let your GPS guide you to the spot.

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"Engineer is someone who leans more and more about less and less until he knows everything about nothing"

 

That reminded me of this.

 

The Quest of the searh for the Knowlege of Everything

 

So back to the Triangulation of the three point problem and closing within 6 seconds,600 feet.

That would amount in the Least Squares Model to be about 2 seconds or 200 feet in each corner of the Triangle or Geoid Model.

 

Hm is that correct?

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Good control is just as important today as it was years ago. Sanitary sewer grades are usually built on a relatively flat grade. Good control helps to insure that it flows down hill. Just one of many modern applications.

I have a friend that is an Environmental Engineer specializing in municipal sewage systems. he says there are only two things you need to know to be a Sewage Engineer:

 

1) Water runs downhill.

 

2) Not everything in a sewage system is water.

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As for metric, the rest of the world is changing to meter which really makes much more sense. I have been pressing for metric for forty years.

Got to this thread late but got a warm fuzzy feeling when I read this part of the post. I thought I was still the only one pressing for metrics. My commitment to metrics grew out of electronics experience - but metrics is metrics and the sooner we ALL convert to that system the sooner we'll improve our mathematical accuracies.

With the obvious exception of hexadecimal (which is another story)

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As for metric, the rest of the world is changing to meter which really makes much more sense.  I have been pressing for metric for forty years.

Got to this thread late but got a warm fuzzy feeling when I read this part of the post. I thought I was still the only one pressing for metrics. My commitment to metrics grew out of electronics experience - but metrics is metrics and the sooner we ALL convert to that system the sooner we'll improve our mathematical accuracies.

With the obvious exception of hexadecimal (which is another story)

I do not think Aristotle, Plato and Ptolemy used metrics and we still derive our mathmatical functions from the things that they discovered in math especially Aristotle.

 

The distance between two points remains the same no matter the system used to measure it,in my opinion.

$.02

 

TRIGONOMETRY----TRIANGULATION

Edited by GEO*Trailblazer 1

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I do not think Aristotle, Plato and Ptolemy used metrics and we still derive our mathmatical functions from the things that they discovered in math especially Aristotle.

They all used the system that was available at the time, but I doubt they used fractions. It was all in decimals, exactly what SI (metric) is based upon. The US was the first to use the decimal system for money. Originally it was the pound, pence and shilling. The stock market recently converted to decimal.

The distance between two points remains the same no matter the system used to measure it,in my opinion.
Which is easier to do?

A room measures 15 ft. 3-3/4 in. by 21 ft. 7-1/2 in. (4.667 m by 6.591 m).

Questions:

What is its floor area in square yards?

What is its floor area in square meters?

 

No conversions.

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Well we agree there should be a STANDARDof measurement.

 

As the Law states for our purpose of Surveying the Intergers should remain the same and not have other types of mathmatics placed over them and try to correct it.(make it more precise).

 

6 mile squares,mathmatically works out the best,as Thomas Jefferson so stated, he also had the most famous mathmatecians work out.

 

Oh well we could talk numbers all day thanks for your input.

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I thought I was still the only one pressing for metrics.

Since I have at least one other compatriot, can't drop it, yet. ;)

Here's another one. How many gallons in an acre-foot?

Clue:

1 U.S. gallon = 231 cubic inches = 128 U.S. fluid ounces = 256 tablespoons = 768 teaspoons = 16 cups = 8 U.S. fluid pints = 4 U.S. fluid quarts = 1/31.5 U.S. federal barrel = 1/42 oil barrel = 1/55 drum

 

1 acre = 43 560.17 square feet (approximately) = 1/640 square mile (approximately) = 4840.01 square yards (approximately) = 160 square rods = 10 square chains = 1/10 square furlong = 100 000 square links

 

;) Sheez, too many ways to measure something with the English system.

 

Comeon, gang, let's support METRIC!

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I have nothing but kind things to say about the metric system, except...

...nyone know where I can get a 30m tape? I have my 100 footer but I don't think Lowes carries the metric version. Anyone wanna send me one from the UK?

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Here's another one. How many gallons in an acre-foot?

Clue:

1 U.S. gallon = 231 cubic inches = 128 U.S. fluid ounces = 256 tablespoons = 768 teaspoons = 16 cups = 8 U.S. fluid pints = 4 U.S. fluid quarts = 1/31.5 U.S. federal barrel = 1/42 oil barrel = 1/55 drum

 

1 acre = 43 560.17 square feet (approximately) = 1/640 square mile (approximately) = 4840.01 square yards (approximately) = 160 square rods = 10 square chains = 1/10 square furlong = 100 000 square links

Point taken. It's a good one.

 

But I got intriged by the problem that was presented. I want to see if I got it right:

 

an acre-foot = 43,560.17 sq ft * 1 ft = 43,560.17 cubic ft

1 cubic foot = 12 * 12 * 12 = 1,728 cubic inches

1 US gal = 231 cubic inches = 231/1,728 = 0.13368 cubic ft

43,560.17 / 0.13368 = 325,852.7 gallons per acre-foot

 

Is this correct? Do I at least get partial credit for showing my work? ;)

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I'm all for metric, however, non-metric does have its place.....

 

Interestingly, time isn't metrically mesured. For computers, time is measured in seconds, even if the period is several years' worth, but there's no metric larger unit, like a unit name for 10 or 100 or 1000 seconds. For humans, time is non-metric - you have seconds, minutes, hours, days. Bases like 24 and 60 have lots more factors than base 10. People like to be able to divide time into pieces easily.

 

I have noticed by experience that measuring a bunch of distances with a metric tape (meters, centimeters, millimeters) is a lot more error-prone than a tape in feet, inches, and fractional inches. The difference is rather subtle, but try it sometime and you'll see what I mean.

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THOMAS JEFFERSON 1790

 

I guess it all depends on the system you were taught in.

I have a good example posted a year ago that no one has answered.

 

Maybe this is a good place to bring it up again.

 

Here is the question most simply put.

What is the Value Longitude-Latitude of

SW Township Corner.Township 22N Range 27W of the 5th Principal Meridian?

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But I got intriged by the problem that was presented.  I want to see if I got it right:

 

an acre-foot = 43,560.17 sq ft * 1 ft = 43,560.17 cubic ft

1 cubic foot = 12 * 12 * 12 = 1,728 cubic inches

1 US gal = 231 cubic inches = 231/1,728 = 0.13368 cubic ft

43,560.17 / 0.13368 = 325,852.7 gallons per acre-foot

 

Is this correct?  Do I at least get partial credit for showing my work?  ;)

Close enough to pass the test.

We almost come up with the same answer although the approach was different.

12x12x12=1728 cu in/cu ft

1728/231=7.48052 gal/cu ft

5280x5280x7.48052/640=325,851.43 gal/acre-ft.

 

;) Have a good walk this Sunday for MS. ;)

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I'm all for metric, however, non-metric does have its place.....

 

Interestingly, time isn't metrically mesured.  For humans, time is non-metric - you have seconds, minutes, hours, days.

Correct me if I'm wrong; with the exception of KM/HR, all other metric items are related to the second. That breaks down to milliseconds and nanoseconds. The meter itself is a relative thing just like the second only good for us earthlings. The advantage is that it is a decimal system. It's much easier to move the decimal than to have the hodge-podge of the English system.

 

History of the definition of a meter:

Year Definition

1793 1 / 10 000 000 of the distance from the pole to the equator.

1795 Provisional meter bar constructed in brass.

1799 Definitive prototype meter bars constructed in platinum.

1889 International prototype meter bar in platinum-iridium, cross-section X.

1906 1 000 000 / 0.643 846 96 wavelengths in air of the red line of the cadmium spectrum.

1960 1 650 763.73 wavelengths in vacuum of the radiation corresponding to the transition between levels 2p10 and 5d5 of the krypton-86 atom.

1983 Length traveled by light in vacuum during 1 / 299 792 458 of a second.

 

I wonder what Frenchman in 1793 walked all the way from the North Pole to the Equator to measure the distance? ;)

Edited by Colorado Papa

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Here's another one. How many gallons in an acre-foot?

Got to thinking about it. Since we determined about 325,852 gallons in an acre-foot, I wondered how that would equate to oil production.

 

325852 gallons divided by 42 gallons per barrel = approx 7758 barrels per acre-foot.

 

If someone knows the number barrels produced each day world-wide, we can equate that to acre-feet of oil then compare it to someone's water supply reservoir. Two million barrels would be about 260 acre-feet. I think I'll go out and find a benchmark... ;)

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THOMAS JEFFERSON 1790

 

I guess it all depends on the system you were taught in.

I have a good example posted a year ago that no one has answered.

 

Maybe this is a good place to bring it up again.

 

Here is the question most simply put.

What is the Value Longitude-Latitude of

SW Township Corner.Township 22N Range 27W of the 5th Principal Meridian?

That should be the South East corner

not SW.

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Hey spoo, I wouldn't worry about whether the direction is true north or magnetic north. At a distance of 20 - 30 meters the difference of a couple of degrees between the two doesn't amount to very much. You will be able to find the disk regardless of which one you use.

 

When the pyramids were built true north was aligned with Sirius (the dog star) now it is aligned with Polaris, so don't trust true north! :lol:<_<

 

Just something to think about.

 

John

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Hey spoo, I wouldn't worry about whether the direction is true north or magnetic north. At a distance of 20 - 30 meters the difference of a couple of degrees between the two doesn't amount to very much. You will be able to find the disk regardless of which one you use.

 

When the pyramids were built true north was aligned with Sirius (the dog star) now it is aligned with Polaris, so don't trust true north! :lol:<_<

 

Just something to think about.

 

John

2oldfarts:

 

I might have agreed with you until last week. I had three able bodied assistants that helped me climb Bill Merrill Mountain in Hiram, Maine. On the top was a Triangulation Station that had RM's nearly 100 feet from the Main Disc. After trial and error, we found that my compass (or my eye) had an error of 1.7 degrees resulting in a 3.2 foot error over the distance.

 

Once we figured that out on RM 2, we were able to find where RM 1 was supposed to be...............3 inches under the humus and missing. That 1.7 degrees may seem slight but over 100 feet by yourself it would mean a world of work. I thank my lucky stars that I had help that day.

 

You can read about that adventure and see the pix here:

 

http://www.geocaching.com/mark/details.aspx?PID=OC2760

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Colorado Papa  Posted on Jun 3 2004, 01:46 PM   
(Black Dog Trackers @ Jun 3 2004, 12:04 PM)

I'm all for metric, however, non-metric does have its place.....

 

Interestingly, time isn't metrically mesured.  For humans, time is non-metric - you have seconds, minutes, hours, days.

 

Correct me if I'm wrong; with the exception of KM/HR, all other metric items are related to the second.

 

Well there ya go. Time isn't metric. An hour is 3,600 seconds. If all speeds and accelerations (ratios of distance and time) were 100% metric, then they'd ALL be related to seconds, kiloseconds, megaseconds, microseconds OR they'd ALL be realted to hours, kilohours, microhours, picohours, etc., but not BOTH.

 

Hmmm, how many kilometers in a light-megaseond? How about a work schedule of 28.8 kiloseconds on and 57.6 kiloseconds off? <_<

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Hey spoo, I wouldn't worry about whether the direction is true north or magnetic north. At a distance of 20 - 30 meters the difference of a couple of degrees between the two doesn't amount to very much. You will be able to find the disk regardless of which one you use.

 

When the pyramids were built true north was aligned with Sirius (the dog star) now it is aligned with Polaris, so don't trust true north!  <_<  :P

 

Just something to think about.

 

John

2oldfarts:

 

I might have agreed with you until last week. I had three able bodied assistants that helped me climb Bill Merrill Mountain in Hiram, Maine. On the top was a Triangulation Station that had RM's nearly 100 feet from the Main Disc. After trial and error, we found that my compass (or my eye) had an error of 1.7 degrees resulting in a 3.2 foot error over the distance.

 

Once we figured that out on RM 2, we were able to find where RM 1 was supposed to be...............3 inches under the humus and missing. That 1.7 degrees may seem slight but over 100 feet by yourself it would mean a world of work. I thank my lucky stars that I had help that day.

 

You can read about that adventure and see the pix here:

 

http://www.geocaching.com/mark/details.aspx?PID=OC2760

 

You had to find the exception to the rule!! :P

Maybe you should have carried a metal detector up that little molehill. :o

For the average 'benchmark' a difference of 3 1/2 feet is not enough to worry about. Some people just like to do things the hard way! :lol:

Congrats on the find.

 

John

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Spoo -

 

According to this site, the declination in your benchmark's area is about 16 degrees West.

 

2oldfarts (the rockhounders) -

 

When the pyramids were built, Mizar and Kochab in the big dipper and the little dipper were the closest to rotational-north.

 

Rotational-north is essentially the same as True North. Of course, rotational-north moves around the planet too, but not as fast as the earth's pole precesses (26,000 years for a circuit).

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Black Dog:

 

According to all the maps in my area, my magnetic declination is 17 degrees W, plus or minus a decimal point. That is the number I habitually use.

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Hey spoo, I wouldn't worry about whether the direction is true north or magnetic north. At a distance of 20 - 30 meters the difference of a couple of degrees between the two doesn't amount to very much. You will be able to find the disk regardless of which one you use.

 

When the pyramids were built true north was aligned with Sirius (the dog star) now it is aligned with Polaris, so don't trust true north!  :lol:  :P

 

Just something to think about.

 

John

2oldfarts:

 

I might have agreed with you until last week. I had three able bodied assistants that helped me climb Bill Merrill Mountain in Hiram, Maine. On the top was a Triangulation Station that had RM's nearly 100 feet from the Main Disc. After trial and error, we found that my compass (or my eye) had an error of 1.7 degrees resulting in a 3.2 foot error over the distance.

 

Once we figured that out on RM 2, we were able to find where RM 1 was supposed to be...............3 inches under the humus and missing. That 1.7 degrees may seem slight but over 100 feet by yourself it would mean a world of work. I thank my lucky stars that I had help that day.

 

You can read about that adventure and see the pix here:

 

http://www.geocaching.com/mark/details.aspx?PID=OC2760

 

You had to find the exception to the rule!! :o

Maybe you should have carried a metal detector up that little molehill. <_<

For the average 'benchmark' a difference of 3 1/2 feet is not enough to worry about. Some people just like to do things the hard way! :P

Congrats on the find.

 

John

Hmmmmm........ a metal detector would not have helped me find that hole in the rock and the missing disc.

 

That metal detector WOULD have killed me on the climb up that mole hill !

 

LOL......see you on the trails !

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