# jwahl

274

1. ## Need Surveyor Help, Please!

One quick thing to use is a 60p nail or a thing called a barn spike which is similar. Both are like long nails about 6" long and make good temporaty points and can be driven into the ground with a hammer or hatchet if it is not really concrete hard. There are a dozen ways to construct a search area from RM1. For example you could set a site pole on RM1 and go over the the vicinity of your station and line up a point right on the extension of the line from the RM to the edge of the building. Now you can measure that line the given distance for the RM1 to station. Then take a careful compass bearing from RM1 to that line which will be coincident with the corner of the building (addition). Now you have your bearing, and can subtract what it is supposed to be to the station per the box score and get an angular difference. Say it is 3.5 degrees. Many simple scientific calculators contain trig functions, so you can now take the sine or tangent of that angle and multiply by the distance and that will give you an offset to go estimating perpendicular to your line. For 3.5 degrees and distance to RM of 98.48 ft, that would give you 6.01 feet offset. That is not perfect because you measured out the full distance on your trial line , but if the angle is small it will not make much difference and the angle or your estimate of perpendicular is not going to be that precise anyway. If necessary it can be precisely computed the small distance back towards RM1 set off. But I think it would get you within a foot depending mostly on the accuracy of your compass bearing with respect to the plot basis of bearing. - jlw PS if you believe that the main part of the building is as reported in the 1953 recovery note you can also measure off 36.7 feet from there and correlate the distances.
2. ## WAAHILA (TU1201)

Well my interpretation is that the disk is on that small concrete platform that even shows a 1969 date, and then someone placed a new or reused the old tapered concrete thing over it. It looks sort of 'portable' and can probably be tipped aside, particularly if it had a long pipe in it.
3. ## Need Surveyor Help, Please!

You can hope for that, but since the diagram appears to have been created for diminsioning the easements, and shows no ties to the buildings, there is no guarantee that their location is anything but schematic. You have to try anything you can though. It is true that it would not be uncommon for someone to grab an existing plan and reuse it for the current purpose. Can't it be related to the tower as a check? On the other hand the exterior appears to have been fenced, and maybe there is some evidence of that which can be recovered. Particularly at the SE'ly corner. And that exterior is tied by bearing and distance directly to the station #136, although the basis of bearing is not specifically shown. - jlw
4. ## Triangulation in Hawaii

The report of the general survey of Hawaii referenced in SP156 is available on Google Books, and at least one of the beautiful maps is available on the David Rumsey map collection on line. Those mainly deal with cadastral surveys, but the first endeavor was to build up good maps and locations based on sound triangulation system. Much history is contained therein. I can provide links to those later if anyone is curious. - jlw
5. ## Adjustment of locations (tri-stations) over the years

I'll add a few more thoughts and then shut up. First the number of digits that coordinates are reported to does not reflect the accuracy of the position. It didn't in 1916, and it doesn't today. That is just the way they have always done things. We do know that they truncated scaled coordinates though as opposed to adjusted coordinates. But do not believe that because the data sheets report the position to .00001 seconds that the position is actually to a millimeter. The station WATATICK was reported as third order, and even though it may have been observed from first order stations, the reason it is classified as third order is that for those triangles the observations were only done to third order standards and only third order results can be expected. There are statements in the preliminary pages to the publication which indicate that the distances given in the table with the positions (which are of course derived from the solutions of the triangles) are reported to 2 more decimals than might be justified by the solution. For WATATICK all the distances are reported to the decimeter, so I think it is safe to say they did not expect the sides to have been solved to better than 1 or 2 meters. Third order is often specified as 1:5000 or 1:10000 depending on the class. Work of that kind can often exceed those minimums, but it would not be unreasonable on that specification to expect a meter or two of error. A lot of this is discussed in various forms in the Massachusetts triangulation publication itself. There could, of course, be blunders in the data capture that show up in the NAD83 adjustment, or some other reason that can only be evaluated if you know specifically what observations were adjusted and the errors found in the network leading to the position. - jlw

7. ## Adjustment of locations (tri-stations) over the years

PS to my last post. The early instructions you quote on using nearby stations to find an obscured on is still valid. But you must keep in mind that those stations all have error in them. So the one station would have gotten you within about a meter in a search for the other, good enough to probably recover the other station. That was of course written before the day of hand held GPS that can get you nearly that accuracy in the first place. The nearest data point is always the most likely to get you into the right area, but it is not perfect in the same way your GPS handheld is not perfect. - jlw

10. ## Off topic - surveyor in fiction

I would be willing to advise on technical details. Surveying is almost all detective work by nature, finding the records, snooping out what is on the ground, and a mathematical treasure hunt... Gee not that unlike benchmarking. - jlw
11. ## How Do I Log a "Picked Clean" Drill Hole?

I see in your pictures a rather clear outline of cement or something that would indicate to me that a disk was probably there. I have not reviewed the NGS criteria for 'destroyed', but for horizontal control point purposes, as a surveyor I would probably consider using it subject to later problems which would indicate it isn't right. The statement that I see "As a person on Geocaching.com pointed out, even though the disk has clearly been removed, and although their are no local reference marks, a new disk could be set by surveying off distant known points to the (E) and (S)[the view is now obstructed completely between about 270d and 60d, and intermittently by new growth of pine trees in the remaining visible arc]. " In my opinion no one but NGS should engage in remonumenting, or re-establishing a lost control point that was originally established by them. It is difficult enough to determine an obscured point without a lot of additional work done by others. The best thing that a benchmarker can do to perpetuate these marks is good documentation, as you have done, of what you found and where it is, so that others can follow, find, and evaluate. - jlw
12. ## Bagged My First Chiseled Square!

I see it fine. You get used to looking for faint marks when looking for marked stones in PLSS surveying. The data sheet describes it pretty well. Is it close to the 15 feet from the gatepost? Hard to tell from your picture. - jlw
13. ## Can you recommend a magnetic compass for Benchmarking?

If we want to get into instruments that are no longer in production.... or ones that are but are of a higher class... For those who are more serious about using a compass for surveying there are what we would sometimes refer to as logging compass' or surveying compasses. Another term is "staff compass" which describes the normal use with a jacob staff. K&E was one significant maker and 4-4.5 in. needle models come up frequently on ebay and go for from \$100-\$200. Then you need to be aware of how to mount it. Some have tripod mounts and most logging type compasses come with an attachment for what is called a jacob staff. Those are hard to find also, but can still be obtained. Their principal purpose was to allow retracement of PLSS lines in the woods and some reasonably accurate line marking. Warren-Knight produced one of the last high quality compasses of this type, referred to as the "Sipe-Sumner" compass, it is very high quality with a 6-7 inch needle. Sipe was LS #1 in West Virginia and wrote an excellent book which is still readily available on compass surveying. A number of tests he discusses in the book illustrate the high degree of accuracy possible for running lines with such instruments. Some of his tests are with a compass with a 4" needle which is probably a K&E. A 19th century survey compass is even more refined and typically a 5-6 inch needle and sight vanes 15 in. apart. The slit/wire sites on the Sipe Sumner and K&E compasses are pretty good also without requiring the same size for the instrument. - jlw
14. ## "Geodetic Azimuth" and RMs (Again)

I have to admit that I have never verified whether that theory worked out or not. It was just a theory that I have heard to try to explain a 'why'. If the St. Louis difference does not work then perhaps someone decided to use a specific declination from some prior surveys. I will do more investigation and see if I come up with anything. If the standards and guide meridians all used the same incorrect declination or assumptions then it would never be corrected. It seems like once they got up to southern Missouri someone decided to straighten it out. - jerry
15. ## "Geodetic Azimuth" and RMs (Again)

The original GLO surveyors operated under instructions from a particular Surveyor General. In that era the instrument used was the well known survey compass which had a vernier for setting off the declination. Many early instructions provided relatively easy ways to obtain true north at any place from polaris at upper or lower culmination by means of 'pointer stars' in adjacent constellations. However one theory is that in regards to the 5th PM, it may be that the surveyors set their instruments based on an established meridian or true north line at the surveyor general's office in St. Louis and then proceded down the river and commenced their surveys. The fact that the magnetic declination varies with time and place was known in that time frame, but perhaps not known to everyone. In any case there is a difference between the proper declination at St. Louis and down in SE Arkansas that one theory has it, they did not correct for and this accounts for what we refer to as the "Arkansas Windage". Apparently other subsequent deputy surveyors used existing lines to set their compasses and perpetuated the basis of bearing which was off. There is no where else in the PLSS, (except all the oddities in Ohio), where this occurred and most of the PLSS is on the average at least fairly well oriented to true north. - jlw
16. ## Is this a type of Benchmark?(photo included)

Being that large in diameter it is probably the lid of a monument box. Inside would probably be a monument set to mark the centerlines of the roads for the subdivision. Different jurisdictions have specific monumentation requirements for things like that. If you went to the County Courthouse and try to see or get a copy of the subdivision plat, it will probably show it as a monumented point. That area has google street level photos, but I can't see the thing very clearly using that. - jerry wahl
17. ## Can you recommend a magnetic compass for Benchmarking?

Surveyors have used the Silva Ranger for many years as a favorite sighting compass, but recently the design has changed and they seem to be more cheaply constructed and we have even gotten shipments of defective ones. The kind that actually has two mirrors in the top lid, the mirrors are poorly fixed with simple double sided tape. The design change provided a sighting slit through the lid, but as a result you have a non planar dual cheap mirror that can fall apart. They may have fixed this defect, but be aware. Originally it was a single piece mirror with a line inscribed on the middle of it. There are a number of places on line that sell the Silva Ranger at \$39.95 or so. But then you can't see what you are buying, or many online sites do not picture the product they actually currently have in stock to send you. Silva is now marketed or owned by an outfit called Tech^4o. http://www.tech4o.com For a simple compass, the Brunton 9020G Classic Compass is one of the few I have seen that does have a mechanism for setting off the local declination, but there is no sighting mechanism. It is, however, very inexpensive. Also be aware that there are quadrant compass' and azimuth compass scales. Since your box score is in azimuth, that type may be preferred, but if you do anything with bearings then a quadrant scale is preferred. - jlw
18. ## Going for my Supreme Court!

Typically on boundary surveys, or PLSS, an occasional monument is tied in or used by USGS or NGS/CGS for control and it gets published. This is not usually the case. Some state lines have been completely integrated into the control network, probably based on a specific state funded project. Anyway the point is that specific to your boundary, the little squares you see are most of the mile markers and intermediate markers set in the state line survey and each one should have had a similar monument set. On the Colorado NM boundary both mile posts, and points on ridges and occasionally other points of interest were monumented. That line was surveyed relatively recently, so they are all nice pipe and brass capped monuments. Many state lines still have stones, or are very old and only fragmentary evidence of the monuments remains. - jerry

20. ## Tree ID? Merci...

One thing to note is that your distance measuring device may be measuring the direct distance between it and your target, but that is what is called 'slope distance' and the data reported on the data sheet will be horizontal distance. The distance must be reduced to horizontal by some accurate means of measuring the angle from the horizontal (or level) line between the points. Some of these gadgets may do that if they contain some sort of vertical sensor. Perhaps it has a level bubble. - jlw
21. ## GPSr Accuracy: Understanding Variance?

I generally use a rough approximation mentioned above. 1 second is 'about' 100 feet and 0.01 sec. is 'about' 1 foot. But also remember that the typical recreational grade GPS receiver even with WAAS may only be good to 5-10 feet under ideal conditions. If there is much in the way of structures or tree canopy, this degrades considerably. Averages help a little. You can do a test yourself by taking a number of positions at a given point at different times and even on different days, and see how much they vary. I find the most accurate way to navigate to a known point is to use the direction indications from a few points nearby (50 feet of so) and intersect them. Or if you are on the move and in the clear the so called compass screen.
22. ## How do I find this Benchmark?

No they are simply as described in the previous posts, nothing to do with a 'human witness' except of course humans set the mark, the RM's the witness post and wrote up the data sheet. I guess the posts are more of the 'bearing silent witness' type.
23. ## Coords in Northing and Easting, In Feet--Help!

Note about previous post: UTM north and the local town north will be different. So if you do get a listing of a few points in the town system that you can also get UTM on, then you will need to do a transformation which will be a scale, translation and rotation. There are a lot of programs around to do that, or it can be done by hand. Then you can take any number of town coordinates and convert them into UTM. Did the 1899 map show town coordinates? If so you should be able to use it to compute a conversion. Coordinates like that are very very common as surveyors set up a simple rectangular grid all the time to do their work and computations. It has primarily only been in the last 15 years with GPS that more surveyors are using State Plane coordinate systems with greater regularity. So what you need is at least 2 points for which you have coordinates in the local system, and you also have geodetic or UTM coordinates. Then a fairly good transformation can be computed. If the map makes it clear what the orientation of the system is relative to true north, then only one point might be able to be used. We have a similar system in the D.C. area called WSSC coordinates and is based upon 0,0 being the center of the U.S. Capitol Dome. True north is Grid North at the origin. It has been used for a lot of mapping and infrastructure surveys even out into surrounding counties. - jlw
24. ## "Stumps Marked with Nails"

NGS.. Is that the same thing as the oft described 'earthenware cone'? If not I would love to see a picture of one as I may be involved in trying to recover one. - jlw