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Traverse station ?

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Found a mark today that is supposed to be a Triangulation Station according to the geocaching page. However, it's marked Traverse Station, is this the same thing ? Somewhat marred, but still visible.

 

CG0338

 

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Traverse and triangulation are not the same thing, but the USC&GS carried out both kinds of survey and on several (or many?) occasions used traverse disks at points which the data sheets call triangulation stations. We don't know why a traverse disk would be used at a tri-station, but yours is an instance. If you read the prose description at the end of the data sheet as found on the NGS site, you find it plainly stated that the station is a traverse disk, but up in the marker type area it's labeled DS = Triangulation Station Disk.

 

VERY briefly and oversimply, a triangulation is a network of connected triangles laid out trigonometrically between baselines measured to almost unbelievable tolerances of accuracy. A traverse is a sequence of lines not interconnected, established by measuring angles at end points and linear-measuring to the next end point. A traverse could be open, going zigging and zagging along from here to there, or it could be closed into a large polygon so that additional checks could be brought to bear on the angles and distances. The CGS had standards of accuracy for both kinds of survey, and determined that traverse was sometimes preferable in areas where it was very hard to locate points that were far enough apart to be useful, yet still intervisible. Flat and timbered country, for example.

 

Not like southern Arizona, where we would imagine the station was in fact triangulated, as the data sheet indicates that it was.

 

We hope we're in deep enough to encourage expert comment, and not so deep as to scare it away.

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I was out benchmarking east of Yuma last month and recovered a string of traverse stations, all set in 1960. Upon further investigation, it looks like the line follows what was US Highway 80 (now I 8) from Yuma east most of the way to Gila Bend. Looking at the marks near CG0338, it looks like a similar traverse line was run along I 10 in that area at about the same time.

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Found a mark today that is supposed to be a Triangulation Station according to the geocaching page. However, it's marked Traverse Station, is this the same thing ? Somewhat marred, but still visible.

 

CG0338

 

 

Apparently there was a typo/incorrect data entry.

 

It's listed as a triangulation disk, but the description clearly states it's a traverse disk.

 

I have seen similar situations with azimuth disks used as reference marks, presumably because the survey party ran out of the correct disks. I don't think that is the case here, though.

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I would clarify and say that traverse lines ARE definitely connected, as much so as stations in triangulation. However positions are computed by directions and measured distances. The directions being determined from the angles turned AND the distances measured between the stations by EDM or Electronic Distance Measuring equipment.

 

Triangulation you could think of as a way to determine the distances between stations by geometry given only occasionally measured lines. But once EDM technology became available in about that 1960 timeframe distances could be measured directly either with light or microwaves. So now the geometry is a series of points connected more linearly by measured distances. I would expect a C&GS traverse to almost always go from one previously established high order station and close into another. Early EDM's used both light and microwaves and you can probably find pictures of various kinds on the NGS site.

 

Once distance meters became more prevalent, traverse became the preferred and/or economical way to position control points. The first affordable EDMi's came onto the market about 1980. Before that they were more specialized and expensive gadgets to do it. From then on until GPS technology came along in the late 1980's, traverse was how most surveying as well as control surveys were done.

 

One of the last pre-GPS NGS control improvement exercises was the transcontinental traverse which was intented to be very high precision and was included in NAD83. This station is probably not one of those based on the date

 

It is possible that a triangulation station (that is to be completely correct, a station whose position was actually determined by triangulation) may have been monumented with a traverse disk. But by 1960 it is also possible that the station WAS part of a traverse and I suspect that is the case here. Traverse would fit within the definition of 'classic geodetic methods', as opposed to satellite methods.

 

- jlw

 

... A traverse is a sequence of lines not interconnected, established by measuring angles at end points and linear-measuring to the next end point. A traverse could be open, going zigging and zagging along from here to there, or it could be closed into a large polygon so that additional checks could be brought to bear on the angles and distances.

Edited by jwahl

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Thanks for the replies everyone. Yes, I did read in the description that it was a standard Traverse disc, which is why I was confused whether they were the same thing.

 

So, it was probably meant as a Traverse station but was incorrectly entered as a Triangulation station? As noted, there are other nearby traverse stations along I-10. To follow on southpawaz's post, this stretch of I-10 used to be US Hwy 80 also. Perhaps they were setting a traverse line along Hwy 80 in advance of creating the Interstate Highways ? hmm, more research needed...

 

thanks again

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We had a Laser EDM back in the late 70's. K&E Laser Ranger III or IV, can't recall which. I believe it was equipment we acquired from NGS after they did a tower survey in SE lower Michigan CIRCA 1977ish. We measured over 25 miles with in from 25 ft towers and we used it to measure highway c/l traverses. Motorist would always stop and ask about the bright red light. It was sight to see, pulsing red light. It was a pita to aim at long distances.

Edited by Z15

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During the 1960’s, the USC&GS conducted surveys along Interstate highway routes using the traverse method of surveying. Some of these projects were conducted in cooperation with state agencies. For a photo of an unusual disk with the factory stamping “COMMONWEALTH OF KENTUCKY, U.S. C OAST & GEODETIC SURVEY, GEODETIC MARKER…” see: http://www.flickr.com/photos/12262796@N06/3328281831/. This disk has I-275 and 1966 stamped on it. I would guess that the disk in question was placed during a traverse survey along the road mentioned and the entry “Triangulation Station” was in error.

 

The traverse method is not as accurate as triangulation (less checks) but it is good for surveying along a fairly straight, clear path, like along a railroad or Interstate highway. The USC&GS/NGS traverse specifications limited the amount of “zig-zag” in a traverse, see: http://www.ngs.noaa.gov/FGCS/tech_pub/1984...etworks.htm#3.3,

Section 3.3 Traverse.

 

For the “Manual of First-Order Traverse” see: http://docs.lib.noaa.gov/rescue/cgs_specpu...35no1371927.pdf. For the “Manual of Second and Third Order Triangulation and Traverse” see: http://docs.lib.noaa.gov/rescue/cgs_specpu...35no1451929.pdf, esp. page 147.

 

For a write-up I did explaining different surveying methods (including traverse and triangulation) for the USC&GS 200th Anniversary see: http://celebrating200years.noaa.gov/founda...e2_spatial.html

 

GeorgeL

NGS

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Last year I recovered a Traverse station (as opposed to a vertical one? Can a station appear directly over or under another one? :)) And I thought - at the time - that the other station they linked to was the water tower. By stading over the mark, I could barely see the water tank on the horzon. It was a neat view. :anicute:

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GL1424 would be one that the USGS measured when electronic distance measurement was relatively new. They did a lot of these angle and distance traverses to fill in control for the topo maps. The tie to the water tower was for additional checking and not the primary way of locating the position. The angle given in the notes doesn't always match the value NGS computes in the box score.

 

ET is Electronic Traverse, 2 is the number in the series, and JS was probably the party chief or else a traverse ID.

 

They would have had a series of mostly temporary points (stakes?) a fraction of a mile to a few miles apart with a permanent mark now and then. ET 1 JS is almost 75 miles away as GK0823 and ET 3 JS is almost 80 miles away as GK0827. I know of another series where the permanent marks are only a few miles apart.

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After reading these posts I was wondering how you could find out the control net that a station is part of (hope I phrased that correctly). I ran across this at the end of the geodetic controls network standards document posted above - "The National Geodetic Control Networks are cartographically depicted on approximately 850 different control diagrams".

 

Does the NGIB still exist as an entity? same name? Can you get these diagrams?

 

thnx

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GL1424 would be one that the USGS measured when electronic distance measurement was relatively new. They did a lot of these angle and distance traverses to fill in control for the topo maps. The tie to the water tower was for additional checking and not the primary way of locating the position. The angle given in the notes doesn't always match the value NGS computes in the box score.

 

ET is Electronic Traverse, 2 is the number in the series, and JS was probably the party chief or else a traverse ID.

 

They would have had a series of mostly temporary points (stakes?) a fraction of a mile to a few miles apart with a permanent mark now and then. ET 1 JS is almost 75 miles away as GK0823 and ET 3 JS is almost 80 miles away as GK0827. I know of another series where the permanent marks are only a few miles apart.

 

Bill - Thanks for that! I did wonder at the stamping configuration on that one when I was out there. How long would that have gone on this 'line'? Near my home here, I have EE1738, ET 16 AAS and I doubt that I can link mine out there. :)

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ONE MARK OVER ANOTHER – I can think of two cases where this happens. The one mentioned is quite rare, that of a mark under a tank. This may have been done, as mentioned above, to check a traverse, or the tank could have been originally positioned by a traverse (even though the normal case was to position elevated structures using the “intersection” survey method).

 

The second case is much more common and was standard procedure for USC&GS and NGS for many years. This case was at triangulation marks where both an underground mark and a surface mark were set. The surface mark was very carefully set directly over the underground mark using a “plumbing bench”. For a diagram, see: http://www.flickr.com/photos/12262796@N06/2181541314/. Note, during the time period when Azimuth Marks were positioned using electronic distance measuring instruments, underground marks were set at some Azimuth Marks.

 

CONTROL NETWORKS – For survey marks in fairly close proximity, the easiest way to be fairly certain about which were surveyed in the same project is just to look at the year the marks were set. If the years are the same (or maybe even one year different) and the marks are in the same area, then they were probably surveyed together.

 

The best way is to go to the NGS page: http://www.ngs.noaa.gov/cgi-bin/ds_proj.prl which explains how to get datasheets by Project ID (and how to get Project ID’s).

 

CONTROL DIAGRAMS – At the completion of each survey project, the USC&GS/NGS survey party would create a control diagram showing the new marks set and positioned, and the old marks tied to. In addition, NGS used to maintain and update survey control diagrams, one set for horizontal control and one set for vertical control. There were three series of these, one showed the control for an entire state, the second was based on USGS 1:100,000 scale quad maps, and the third was based on NOAA nautical charts. These have not been updated for many years and are not longer available. For a look at one of the NGS state horizontal control diagrams, see: http://www.flickr.com/photos/12262796@N06/2308454062/.

 

GeorgeL

NGS

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Tell us more about the plumbing process. Did you have to use a periscope to see that the plumb bob was over the mark in the bottom of the hole? Mason's cord or thin wire on the plumb bob? Did the crew pour the concrete while working around the plumbing bench or was the cross-beam taken out and put back?

 

What accuracy would typically be expected in aligning the two marks? I would have trouble holding a couple mm but I expect the pros were a lot better than that.

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Bill93, No, no submarines are involved. The plumbing bench was simple yet quite accurate. The hole was dug about 4 ½ feet deep including a small hole at the bottom for the underground mark. A plumbing bench was constructed such that the edge of the cross board would be directly over the center of the underground disk. The nail through the top, cross piece was only partially nailed into one of the two uprights (to allow it to swing out of the way). A plumb bob was hung over the edge of the cross board and centered on the hole and the disk was set. With the plumb bob centered on the disk, a small pencil mark was made on the edge of the cross board where the string went over the edge. Then the cross board was swung out of the way (as shown by the dotted lines in the lower diagram referenced earlier). Then the underground mark was covered by a board and several inches of sand or dirt to isolate it from the surface mark. Then the concrete for the main, surface mark was poured. Then the cross board was swung back into place, making sure that the partially driven nail went back into the same hole as before, and the plumb bob was hung over the pencil mark. The surface disk was then set in the concrete directly below the point of the plumb bob. The instructions for this are in USC&GS Special Publication No. 247, page 90, Section 10 at: http://docs.lib.noaa.gov/rescue/cgs_specpu...o247rev1959.pdf, and the diagram I reference earlier and copied to FLICKR some time ago is on page 92. I, of course, skipped many steps about setting the mark which are detailed in the referenced pages. Both disks were the same type of disk TRIANGULATION STATION (under USC&GS) or HORIZONTAL CONTROL MARK (under NGS) and both were stamped with the same name and date. I don’t know how accurate the average marks were in relation to each other but quite good.

 

In an earlier post, BILLWALLACE asked about the acronym NGIB. I’m not sure what that stands for, could it have been NGSIDB? NGSIDB stands for the National Geodetic Survey Integrated Data Base – it’s the huge NGS database from which the survey mark datasheets are created.

 

GeorgeL

NGS

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"The National Geodetic Control Networks are cartographically depicted on approximately 850 different control diagrams".

 

 

I have black and white photo copies of 1:250,000 Geodetic Control Diagram maps for about 1/3 of Montana that were jointly published by the Department of Commerce Coast & Geodetic Service and the Department of Interior Geological Survey in the late sixties.

 

They sure show the big picture for triangulation stations and indicate which roads or railroads will have vertical control along them.

 

Mike

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NGS Suveyor - Sorry about the odd acronym. it came from the 1984 "Specifications for Geodetic Control Networks" document that you posted a link to earlier... National Geodetic Information Branch (NGIB)

 

Thanks for the tip about the project ID's

 

I imagine, that one consequence of the National Spatial Reference System is the inclusion of all the control points into one huge net - that would be a busy diagram.

 

I have black and white photo copies of 1:250,000 Geodetic Control Diagram maps for about 1/3 of Montana that were jointly published by the Department of Commerce Coast & Geodetic Service and the Department of Interior Geological Survey in the late sixties.
Hmmm.. exactly what I'd like to get my hands on - for California, I bet there are still some lying around in a closet somewhere.

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I remember the entire country was covered with control diagrams on a 1:250,000 base map blued out. They showed C&GS control in black and USGS in red and other agency control in a gold yellow.

 

Before the days of internet or even computers, they were extremely useful for planning control projects and I would always acquire one for each project and then order the actual data sheets which were often published by quads from those sheets to cover the areas needed.

 

I am pretty sure they quit publishing those many years ago, but I don't know when, but they may not have been carried forward into NAD83 at all and that is the timeframe of their demise.

 

One thing they did that the internet based tools does not do, is show the network connectivity.

 

In those days of manual paper records a company or county or agency could subscribe to control and you would get mailed any updated data sheets when they became available, and it was not uncommon for people to maintain their own files of all the control in their area or state which would usually include the control diagrams as indexes. I don't specifically remember the state control diagrams but they probably existed too as a general index.

 

And for Bill, the office I worked in between 1980 and 1991 the CA BLM Cadastral Survey in Sacramento, we maintained a full set of the MGS control sheets as well as control diagrams for the state. I doubt they still have them as Gov Bureaucrats are big on moves and throwing seemingly obsolete things away.

 

I have found on several occasions ground marks set directly under occupiable towers or intersection stations such as fire lookouts, bellfries, and so forth. They are usually described thus on the control sheets. If anyone wants examples, I can probably remember a few.

 

- jlw

Edited by jwahl

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Sorry, I mis-spoke, the nation-wide coverage of control diagrams was based on the 1:250,000 quad maps – been too long. I still have a few of these and I years ago I also used them for planning.

 

The National Geodetic Information Branch still exists as the “Communications and Outreach Branch” of the “Geodetic Services Division” of NGS, see: http://www.ngs.noaa.gov/INFO/OrgChart/NGSXDivXChart.pdf.

 

Until last year, NGS maintained a large stock of these control diagrams, but as I stated earlier, they had not been updated for many years. Last year they told me they were cleaning out all the old stock. I just walked up and talked to them and they have done this. The good news is that they saved two copies of each diagram and they are presently working on having these scanned.

 

Regarding the NSRS and one huge diagram, the points have always been part of one large network, the control diagrams just showed a portion of it. This has been the plan since F. Hassler became the first Superintendent of the agency, in 1807 called, the “Survey of the Coast” (later “Coast Survey” and then later U.S. Coast & Geodetic Survey”). See the 200th Anniversary article discussing the survey network at: http://celebrating200years.noaa.gov/founda...al/welcome.html.

 

GeorgeL

NGS

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GeorgeL and jlw---

 

About three years ago, we came across the term “Triangulation Diagram 6460” in the data sheet for SY2315, then designated “Tacoma Lincoln High School Flagpole.” We had also encountered it in the data sheet for SY2916, DEF, about 7.6 miles to the northwest near the tip of Point Defiance. What connection would there be between this tantalizing document and the ones you’re discussing?

 

Many thanks.

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Boy, that was a tough question - but, I found the answer. Number 6460 was the number of the nautical chart covering that area. And since nautical charts were used as the background for control diagrams along the coast, your survey mark fell on that chart. What made this difficult is that the numbering scheme for NOAA nautical charts changed many years ago, but I have a chart catalog from 1959 that gave the old number. If you would like to see the current NOAA nautical chart catalog for the West Coast, see: http://www.charts.noaa.gov/Catalogs/pacific_chartside.shtml

 

GeorgeL

NGS

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ET is Electronic Traverse, 2 is the number in the series, and JS was probably the party chief or else a traverse ID.

 

They would have had a series of mostly temporary points (stakes?) a fraction of a mile to a few miles apart with a permanent mark now and then. ET 1 JS is almost 75 miles away as GK0823 and ET 3 JS is almost 80 miles away as GK0827. I know of another series where the permanent marks are only a few miles apart.

 

Cool, thanks for this info. There is a series of them here northeast of Phoenix, also set in 1966 by the USGS (ET1129, ET1161, ET1162, ET1163 and ET1164). I've been curious about what they were all about, as well as why they were flying around in a helicopter to set them.

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Boy, that was a tough question - but, I found the answer. Number 6460 was the number of the nautical chart covering that area. And since nautical charts were used as the background for control diagrams along the coast, your survey mark fell on that chart. What made this difficult is that the numbering scheme for NOAA nautical charts changed many years ago, but I have a chart catalog from 1959 that gave the old number. If you would like to see the current NOAA nautical chart catalog for the West Coast, see: http://www.charts.noaa.gov/Catalogs/pacific_chartside.shtml

 

GeorgeL

NGS

GeorgeL--

 

Thank you, thank you! It is so good to have that settled.

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They would have had a series of mostly temporary points (stakes?) a fraction of a mile to a few miles apart with a permanent mark now and then. ET 1 JS is almost 75 miles away as GK0823 and ET 3 JS is almost 80 miles away as GK0827. I know of another series where the permanent marks are only a few miles apart.

 

I ran into some USGS marks that were like this, many miles apart. I thought it strange until I finally got the USGS data sheets and found the reason. There were existing USC&GS Bench marks along the highway route and USGS used them in the transit Traverse instead of setting new marks.

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