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More Recently Set Marks


mloser
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I spent about 6 hours hunting today and ended up with 2 finds out of 12, my worst yet. What prompted this post however was the horrid description of AB6517, which was set in 1993.

THE STATION IS IN THE SOUTH QUADRANT OF THE INTERSECTION, 19.3 FT (5.9 M) NORTHEAST OF PP AND L POLE 4668-S35285, 51 FT (15.5 M) WEST OF PP AND L POLE 44685-S35277, 53.6 FT (16.3 M) SOUTHWEST OF A 28 INCH TREE ACROSS TEXTER MOUNTAIN ROAD, AND 58.2 FT (17.7 M) SOUTH OF PP AND L POLE 44675-S35291 IN THE NORTH QUADRANT OF THE INTERSECTION. THE STATION MARK IS A BRASS DISK IN TOP OF A 6 INCH HEXAGONAL PRECAST CONCRETE POST SET FLUSH WITH GROUND AND STAMPED LC- 93-148.

Not ONE of the poles had the number as described! NOT ONE! Most were close, but of course that doesn't quite count, does it? In the end, I think the mark was under new macadam, but this sparked a memory of another frustrating hunt, for AB6475, where none of the measurements tied at all. I spent an hour poking in a soccer field (one I had visited for my daughter's soccer many times--I was hoping I would find that mark!), but despite repeated measurements I struck out.

I remembered both marks being set in 1993 so I looked at the descriptions. Sure enough, both are the same agency, ADR Geodetic Services, and both were described by "AK". I see a pattern here. Both seem to have been set in locations destined to be disturbed too. What a shame that I can usually find the older marks in my area but these new ones, which would seem to be easy home runs, are dismal, frustrating failures!

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Frustrating, I'm sure. On AB6475, note that the street runs NE-SW, and not directly east-west. Therefore, south of the manhole will be taking you on an angle across the street.

 

c43c5597-3088-47a7-990f-2c5b5f11981a.jpg

 

According to the coordinates, the station should be on the south side of the road, almost centered between the two intersections. The houses mentioned in the description are visible from the air.

 

Best regards

-Paul-

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DESCRIBED BY COAST AND GEODETIC SURVEY 1942 2.1 MI S FROM GILEAD. ABOUT 2.1 MILES SOUTH ALONG THE EVANS NOTCH ROAD FROM THE JUNCTION OF U.S. HIGHWAY 2 AT GILEAD, OXFORD COUNTY, ABOUT 0.25 MILE SOUTH OF LITTLE LARY BROOK, ABOUT 100 FEET NORTHEAST OF A CURVE, 16.5 FEET SOUTHEAST OF THE CENTER LINE OF THE ROAD, IN THE TOP OF A ROCK LEDGE, AND ABOUT 3 FEET HIGHER THAN THE ROAD. A STANDARD DISK, STAMPED H 92 1942.

 

Some of the older ones aren't much better. This was a DNF for me yesterday. Monumented in 1942 ( PF0216 ) It is almost impossible to locate this position without the help of a 'crew'.

 

ABOUT 2.1 miles......ABOUT 0.25 miles....ABOUT 100 feet......ABOUT 3 feet......

 

The co-ordinates take you almost 100 feet east of the road and almost 300 feet away from any ledge rocks.

 

This is in the midst of a wilderness....but still......no WITNESS POST, no blazed trees. Looking 16.5 feet off the center of the road (the only firm measurement) could take you quite awhile given the forested area and years of accumulated natural debris that settles over everything.

Edited by Spoo
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I spent about 6 hours hunting today and ended up with 2 finds out of 12, my worst yet.

 

I thought Friday afternoon was going to be one of those days for me. I finished up my real estate activities at 2:45 and decided to loop through the country on back roads and spot a few benchmarks.

 

My first stop was EZ1112 where the plotted position was on a cut for a ditch. (See photo.) Based upon the one reference point--a pole with ref tag--it appears that the intersection has been realigned and the station appears to have been lost.

 

On to Number Two. Opps! It should be a 1930's concrete bridge, but it has been replaced. Will return later to see if the original headwall remains. So far, the score was Progress, 2, Paul Zero.

 

Things looked up when the next bridge was intact. EZ1115 was found as described, minus the reference tags. I made notes to expand the description and then moved on to EZ1378. I had determined during the summer that the description contained a typo, but I was unwilling to enter the tall weeds during tic season. The metal detector quickly picked up the disk beneath the vegetation.

 

I was tied 2-2 with Progress until I hit the next two--another realigned intersection, and a modernized railroad signal which had been moved farther off the highway. I picked up a water tank at a power plant, but then encountered another #$&@ railroad signal which had moved. Next came a bridge which was relocated. I did not search the old roadbed for the old bridge's retaining wall.

 

Next, I lost the railroad. No kidding! They took up the tracks and the woods had taken over. I was scratching my head until I followed my nose and found an abandoned trestle over US-1. It was now 5:05PM and I was a mile from an elementary school with a disk in the steps to the boiler room. With the kids gone for the day, I wandered onto the grounds and recovered the station.

 

There was time for one more search before supper, and a data sheet mentioned an abandoned chuch by a cemetery about three miles from my present location. Being a history buff, I took off. This time, I lost the road. I'm serious! I passed a sign that said, "ROAD ENDS IN WATER", and found myself at a boat launch facility. The road has been submerged by a Corps of Engineers lake. Was the old church under water, also?

 

I punched the coordinates into my iQue3600 and it came back with a route. I followed it and recovered EZ1311 in the cemetery. It took a while, but I also found the steps and foundation of the church. (The rest has been dismantled.) It now was 6PM and the sun was going down. I called my wife and told her I'd be home in 30 minutes. Elaspsed time for this exercise was three hours, and the total distance, including the return home, was 60 miles. It was a great afternoon!

 

-Paul-

Edited by PFF
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mloser,

 

It is common for poles to be replaced for whatever reason. If there was a road widening, then there would likely be new poles and the new poles will have new numbers. This is common Power Co Practice, NOT a bad practice of the setter of the Monument. Nothing is forever, and we have no right to expect that, and nor does the NGS, when we leave the shop in my profession we go to the field to see what is there. No expectations. I would go see if that tree is still there and go from there. Oh, and for those who do not know what Macadam is, It is a very old fashioned word for Asphalt Pavement. The asphalt industry stopped using the term over 50 years ago.

 

Spoo, One trick to all this is go to the NGS site and pull the real data sheet and see what you are really looking for. if it is a Bench Mark. I mean in the strict term, a Bench Mark, an Elevation Station. If it is as such the coordinates will be often scaled and you cannot expect to find it near the printed coordinates. It it is a Triangulation Station, the coordinates should be closer a few inches, which is closer than a consumer GPS can do.

 

The real deal is the real Datasheet. I would not fool with the GC.com description. Just use them to find marks that are in their database, then go get the real info. There is so much more to know if you use the latest NGS Data. Knowing if a mark is horizontally scaled is going to make a difference on finding a hard one.

 

Rob

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PFF, south of the manhole is indeed an angle across the street, but as I mentioned in my (lack of?) recovery, if the mark was to be SOUTH of the manhole it could not be SOUTHWEST of the power pole, since the power pole was between the manhole and the mark location. (I never considered the street's direction in my measurements but just went off compass direction anyway). Something is definitely amiss in that description, and since the station is not showing at ground level it was impossible to find. Sooner or later I will take a metal detector to the site and go over it carefully, then redescribe the mark.

 

Evenfall, the only tree that fit that description was across the street, and although I suspected it was the one in question, deep brush and large piles of dirt prevented me from measuring from it, especially since I was alone. As for renumbering the poles, I have witnessed so little of that in this area that I simply don't believe all the poles were mystically renumbered to be "close" to their old numbers but not exact (poles are often renumbered but one can usually find the old numbers on the poles). I DID measure from the three most likely poles, ignoring their numbers, and came up with the location I first got when I measured from the closest (and newest looking) pole, which had the number that matched most closely (I think a digit was simply left out of the first part of that pole's description). That location put the mark under the asphalt (was that better? I am not sure where I started calling it macadam.. maybe that is a local idiosyncracy). What made the descriptions of the poles frustrating is that the numbers were all CLOSE, as if Mr AK wrote them all down, then scrambled them to make a puzzle of the hunt before finishing the description.

 

And I DID screw up by not reading the datasheet--the position is adjusted, which could have let me trust my GPSr much more closely instead of being just a starting point. It will be a while before I return to that location however.

Edited by mloser
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evenfall:

 

Trust me, I do use the NGS pages and I do know the difference between SCALED and ADJUSTED. This was one of three DNF's that day. Two of them no longer matched the terrain and description. (One was referenced from a dam, trust me again, I know what a dam looks like. lol) It is possible that the road actually changed in the 60 years since monumenting or in the 30 years since NGS last documented.

 

My point was simply that even being NOT in a city, things change. And to reference points at hundreds of feet away (while saying, ABOUT) makes for terrible descriptions.

 

BTW, in this neck of the woods, I have found that new Tele-line poles still bear the same number when replaced. Alas, they often change position or even sides of the road !

Edited by Spoo
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Power Companies are Strange when it comes to procedures, that is for sure. Sometimes they will never renumber, sometimes they will replace a pole and renumber or not. You just never know. What I want to say from the field, and it is a common thread from most of us who work in the field here is that just when you think there is a hard and fast rule you can sort of trust, something will come along to shatter that rule.

 

Spoo, You are correct in your neck of the woods, and practices vary in all necks of the woods, Some utilities cannot make up their minds as to what the practices are. I have about four different utilities in this area who's practices are all over the map. I know you are a seasoned hunter but for the sake of those who are not, I think you will agree we read about two posts a week about PID's that are said to be way off coordinates and when I look, I find they are a Scaled Bench Mark station and that is why the coordinates are way off. For the benefits of the many who read and never post here, I thought I would bring that up for their benefit. This is how we can know more that just what is first presented on the GC website.

 

mloser, I was not correcting you, you can legitimately call it macadam, but many people, in a national sense will not know what you are referring to. It is not better to call it asphalt, just more widely known by everyone. It was at one time in the early days referred to as macadam. That usage has fallen out of use even in the asphalt paving industry. I just pointed it out as many people would not have realized they are the same thing. More people read this forum than we think :-)

 

Triangulation Stations can be off. It happens, but not as routinely off horizontally as Bench marks are. I have a third class Triangulation station I am hunting that is a real poser. I know where it should be based on the description, and my telephone poles have moved. Instead of a tree I have a Man Hole cover as a reference point that has been paved over. But I can see where it is. My Station is in a one time parking strip along side a street that is now covered with a 13 foot high dense blackberry bush. I hacked in and did not find. There is no reason it should not be there despite the changes. I am on the right street, right intersection, right location...

 

On the interesting side of things this Station has a weirdness. my intersecting streets have an east-west street, and a southeast-northwest street. Based on the description the Station _should_ be West Northwest of the sewer man hole in the named intersection at a stated distance. Did not find, and so far as the reference marks are DNF too. I can live with that, but the Station Coordinates should be good. Most typo errors on a triangulation Station will run you either North, South, East, or West of the correct location. A mistake is either in the Latitude or the Longitude, rarely both and if both it would be wildly off. In this case the Station Coordinates lead to a place there is no intersection at all, not within anywhere near the stated lengths in the description, and this is along the southeast- northwest running street 500+ yards southeast of the described location. Oh and the distance from the centerline of road is the same for the described location. This would require a fluke or something to properly parallel the street in the manner this has, but I have not yet hacked into the brush. This means the Lat and Long were both off but still follow the angle of the Street? Too weird. To add, the changes in the area, and growth of trees and foliage around this Station in either of It's possible location would require a Bilby Tower of 75+ feet to do much with it optically.

 

I think the Station Descriptions that I find most troublesome are from any era, the ones where there are 2 reference marks set, like in curbs where they are easy to find, but they use everything under the sun to describe the Station location, and do not use the RM's. If they would add that the Station is 54 feet NW of RM 1 and 37 feet NE of RM 2 then you could find it in a second with 2 tape measures. But that part is often omitted. However, if I go (about) 229 paces to the left of the centerline of a sidewalk that is in line with a jog in a road and near a tree whose diameter is about 22 inches in circumference... :-) I too, feel your pain.

 

Rob

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If they would add that the Station is 54 feet NW of RM 1 and 37 feet NE of RM 2 then you could find it in a second with 2 tape measures. But that part is often omitted. However, if I go (about) 229 paces to the left of the centerline of a sidewalk that is in line with a jog in a road and near a tree whose diameter is about 22 inches in circumference... :-)

 

Rob:

 

You omitted that on the date the mark was set, it had rained and there was a puddle 25.5 feet SW. And how about that dog lying in the street.....can't we use him, too? He's there nearly every day! [grin]

 

My personal thanks to everyone for the excellent information regarding scaling of position. I also want to endorse reading the original data sheets (from the NGS site!). If there have been updates to the PID anytime in the past three years, you will see them at NGS, but not on GEOCAC.

 

Being new, I seldom have the opportunity to contribute technical information, so let me jump up from my school desk, waving my hand and yelling, "I know!" when it comes to the road surface mentioned in old reports.

 

In the early 1800's, John L. McAdam, a British engineer, developed the concept of constructing a road by compacting a layer of small stones into a solid mass, using a binder such as cement or asphalt. A special feature of his design was incorporating a convex shape to create a well-drained roadway.

 

Obviously, he was ahead of his time. In 1836, very few vehicles hydroplaned. [chuckle]. But it made travel more pleasant. On early roads, the "crown" was quite pronounced. The technique (and the misspelled name) stuck around for the next 100 years. Modern engineers utilize different methods to control storm water runoff. Not only must enviornmental factors be considered, but it would be difficult to produce a "crown" using today's equipment.

 

-Paul-

Edited by PFF
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you want a crummy description?

 

DESCRIBED BY COAST AND GEODETIC SURVEY 1889 (ATM) ON THE SOUTHWEST CORNER OF THE SQUARE OR CENTRAL PART OF THE CINCINNATI OBSERVATORY ON MOUNT LOOKOUT. THE STATION IS JUST SOUTHWEST OF THE DOME AND IS MARKED BY A COPPER TACK SURROUNDED BY THREE OTHER TACKS IN THE FORM OF A TRIANGLE.

 

from JZ3140

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I wouldn't say that is particularly bad. It would have been better to indicate horizontal distance and height relative to something. But it sounds like it must be in the roof or othewise on the structure that the dome is on. How much area is there to search?

 

Notice that the location is ADJUSTED, so you should be able to get within a few feet using your GPS. I'm betting that, if the building is still there, you will find a newer roof at those coordinates hiding the spot where the tack might or might not still be resting.

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For the people who may wonder, or be interested what an adjusted coordinate location is, or means, here is an attempt to explain. It is a rather big picture to draw and there are probably a few good ways to draw it but here goes...

 

The NGS has programs which have the ability of taking a coordinate location from a given datum and converting it to a coordinate location of a different given datum. It could be considered as simple as converting NAD 27 to NAD 83, or NGVD 29 to NAVD 88, and it sort of is, but it is also more involved than that.

 

This means I can start with a first order horizontal control station (triangulation) which was originally surveyed into the NAD 27 datum, meaning I should be reasonably safe to say that I am less than 3 centimeters of the actual latitude and longitude of a place on earth. I can then adjust it to the NAD 83 Datum which means physically the monument is still in the same place but the datum causes the station coordinate to change to match the the way that location is accurately located in the different datum. There will most usually be a shift of some sort. The important thing to note is that you are still accurate to the 3 centimeters even after the shift because we are adjusting a first order station. The same level of accuracy is maintained when the "adjusted" type of conversion is used.

 

Briefly, a datum is a mathematical baseline reference which expresses something. in this case the something is called a geoid. A geoid is the hypothetical surface of the earth that coincides everywhere with mean sea level. (if you could imagine two earths, with one being as it is, mountains and sea, but with no water in the sea. Then an earth that was the same size, and identical as to the overall shape of the orb, but it was entirely "mean sea level" size, with no mountains or under sea valleys. Simply combine the two, slide the two together all at once with both sets of feature displayed. That would be the frame of reference used to express Latitude Longitude and elevations both above and below sea level. all at once.) Now to add to that, we have more than just one model of "the geoid" It is interesting to note that the gravitational pull of the earth is not uniform in all places and so this means the earth is not a perfect sphere. it is really more of a sort of lumpy orb. We keep re evaluating it and determining that we can define it better. We attempt to describe the shape of our lumpy orb. Then we use a datum which we use to describe that geoid. That means we use a coordinate system to define where points and places on the lumpy orb really are. We are also finding ways of mathematically improving the ways accurizing the datum, by constantly measuring and getting more and more accurate instruments to measure it.

 

When we compare the orb changes in terms of defining the Geoid and then take our way of measuring that with the latest Horizontal and vertical Datums we are actually closer to where we really are than we have ever been.

 

When you see the word "ADJUSTED" on the datasheet, in tech speak, yet as simply as I can state it, it means a program took the old coordinates in NAD 27, converted it to NAD 83, then a least-squares adjustment is performed, which means all of the unknown parameters in the mathematical equation (read Calculus) are simultaneously adjusted to minimize the sum of

the squares of the residuals in all of the measured quantities (weighted inversely proportionally to their variances if the measurements are not equally accurate), with suitable constraints among the parameters to force any theoretically required relationships to be exactly true.

 

And since I am a Surveyor and not a Geodesist, that is the best I can do on it. It is not math for the meek, and not math I do. It was converted in a highly accurized way.

 

I can say however, using tools that the NGS has on their website, that where I am sitting, I am Vertically 3.547 feet higher in elevation than I was when I compare the NGVD 29 Vertical Datum with NAVD 88. I can use a program called VERTCON to "adjust" my elevation to the latest datum and here I am. Depending on the Value of the Bench Mark, NGS could have used a least squares adjustment in the calculation of elevation, as part of a conversion as well This set of figures only applies to my location because of the "Lumpy Orb" factor I spoke of in the Geoid Model. For the horizontal conversion from NAD 27 to NAD 83 I can use the NADCON program for my Latitude and Longitude and find NAD 27 - NAD 83 shift values of N Lat: 0.64777 W Lon -4.46385(secs.) All based on improved geoid models and accurate datum. All this specific shift only applies to my location alone and could begin to vary a bit as little as less than a mile away from my location.

 

The monuments in the field are where they are, but in re defining the geoid and datums, the coordinates change, but not too drastically. The hope is that they collectively become more accurate all the time, even without the virtue of being re-surveyed in years. I mean we are talking feet, and yards worth of accuracy between datums, but not miles. And improvements are performed on the accuracy of the NAD 83 datum all the time. Even at that, the earth is not static and man too is introducing both errors as well as more accurate ways of seeing all of this, all the time.

 

Rob

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Evenfal,

 

That is a really nice description of Geoids and datums. I always find it somewhat amazing that there are actually people out there who know this stuff.

 

One of the things you didn't mention that might be interesting regarding the difference between the 1920s datums Vs. the 1980s datums, is that one of the biggest souces of error in the 20s datums was based on the assumption that tides are uniform. We used to believe that "mean sea level" was pretty much the same all accross the US. We have learned that this is incorrect, and was a source of some of the error in the early verticle datums.

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For station HE0206 designated CV. From the Report of the Superintendent of the Coast and Geodetic Survey for 1899 where CV was first published, "The level net adjustments are based upon the assumption that the mean surfaces of the Gulf and the Atlantic and also of Chesapeake Bay are at one elevation." The original elevation published was 332.1108 m (1089.60 ft)

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Thanks DaveD.

This is where the difference in elevation accures then,the mean sea level is different and the least sqaures adjustments correct for these deviations from the mean.

 

Those minor deviations in sea level is one of the least squares ajustments.

 

Another question.

On the GRID Lines Latt. and Long.

On First Order Stations which Azimuth was used, A True North,or were these Southern Observations?

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Prior to NAD 83 the orientation for all geodetic azimuths in the U.S. was south. NGS changed the orientation to the north when NAD 83 was published in 1986. Note that the diiferences in sea level is not part of the least squares adjustment. The use of least squares applies only to the observations in any survey network. These inlcude height differences from leveling, GPS vectors, directions, distances and azimuth observations in triangulation.

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Casey and Geo,

 

First Casey, you made the point that 1920 era datum were erroneous based on how they handle tidal uniformity. You are correct! But given what we knew at the time, it was a good system, and served a helpful purpose. Tides are not uniform as to height and timing at any two places along our coasts. It is a science in and unto itself as to how the times and height of the actual sea water levels are calculated. There are a lot of sources out there attempting to explain this concept. Factor in weather and there is more room for error. Geodetically speaking today, the term Mean Sea Level is a theoretical surface based on a single monument, it is not a component of the actual tidal waters, nor based on an 18-19 year average of all high and low tides at any one or 26 given locations. Nor is the reference standard for this Mean Sea Level based on how much water is in the ocean. (It could be based on this if you are a researcher studying how much water IS in the ocean!) These things are simply not a stable reference for geodetic purposes but some sources will attempt to define it this way. However NGVD 29, the old 1920's Datum was Sea Level based but averaged and computed based on twenty-one tidal stations in the US and five in Canada. 26 different, simultaneously adjusted stations. Tide was however affected by gravity too, and this system could not easily compensate for this because of the instability in the model. Taken together with older models, which define the Geoid, the Ellipsoid, actually thought to be a spheroid then, and other frames of reference, were based on the observations of the time. We really did the best we could with what we had and comparatively; we did pretty well at that! Mean Sea Level was not the same across the US as a belief, but rather made that way for the sake of mathematical reference.

 

Today we use a different standard for Mean Sea Level yet we refer to it in the old way. You can google this definition and you will find many explanations as to what Mean Sea Level is. To be fair, I would say that many who have attempted to explain what mean sea level is, but most definitions seem to explain it in a way we no longer frame the reference. I have to smile upon them for trying. I sometimes wish we would call it something else today but it is what it is, confusion and all.

 

For Geodetic purposes today these Datum are earth centered, and you can carry this over to GPS, mapping, surveying, and all forms of navigation, as they are all based on geodetic references, Mean Sea Level is now based on a fixed reference that does not move, One Tidal Bench Mark, Father’s Point/Rimouski, Quebec, Canada. All Leveling is based from there. But that was just leveling the Topographical heights of North America and is not the whole story.

 

At any given point today, a frame of reference as taken by latitude and longitude will be necessary to calculate the GPS height for that location, as either above or below Mean Sea Level. GPS elevation is a component of several equations compared to the actual ground level (read Real leveled Topo, and referred to as the Orthometric surface) which was exhaustively leveled in the 1980's, the Ellipsoid Height, the Geoid Height, and a least squares adjustment taken to remove errors from the measurements. Mean Sea level is used to reference the elevation but it is not used as a part of the equation.

 

Remember the earth's surface is the topographically leveled (meaning elevation determined though the method called differential leveling) earth we stand on, used as a frame of reference. It is the empirically leveled, monumented Bench Mark Elevation, and if not recently leveled it can be Adjusted. It is also simultaneously, the Orthometric Reference.

 

The Geoid is that lumpy orb I referred to in an earlier post, which is a sort of ellipsoid that approximates the size of the earth, which isn't really a truly ellipsoidal shape because it is deformed by the forces of gravity.

 

The ellipsoid is based from a smooth surface meant to be a model of the approximate overall size and shape of the earth as if the earth had neither gravity nor topographical features when compared to the actual Topographical surface.

 

Geoid Height is a comparison of the geoid with the ellipsoid.

 

Ellipsoid height is a comparison of the Ellipsoid with the topographical surface of the earth, or Orthometric surface.

 

The Orthometric Height is a comparison of the Geoid to the actual Topo.

 

Leveling is the most accurate way of determining elevation and was the basis for determining NAVD 88. It is not performed as a usual method of finding an elevation very often any more. The GPS uses the ellipsoidal reference, along with Latitude and Longitude. The GPS Satellite Constellation basically triangulates the GPS to a place and a height above or below the ellipsoid. This ellipsoidal height is not comparable to Orthometric Height, which is the actual height of the ground. This height has to be compared to a high resolution model of the Geoid, the gravitational model, which has a variable conversion factor based on any given latitude and longitude to convert an ellipsoidal height to an orthometric height. We have the capability to do this to a degree of accuracy that approaches that of leveling. Then we can do a leveling loop much like we can do multiple triangulation's and perform a least squares adjustment on the loop to enhance the accuracy of all our observations.

 

Why do we do it this way? To correct the errors we see between the way we see the earth when we perform differential leveling on the actual surface (Orthometric surface), how a GPS actually sees the earth as based on radio telemetry (Ellipsoidal surface), and how gravimeters see the earth as based on measurements taken that base what we think form the shape of the geoid (Geoid surface). They all three differ a bit, but bringing the ellipsoid and the geoid together with the right models and formulas bring us to a single elevation. Again, for the sake of a uniform mathematical reference.

 

Obviously what we believed back in the day and what we believe now are 2 different things.

 

Geo, I hope the old model of NGVD Sea Level reference helps answer you. Your instance is really pre NGVD 29. I imagine they used a reference benchmark, which was of known height as compared to what was considered reference for that time. In 1899 the world was a smaller place and I imagine, even pre NGVD 29 and NAD 27 that the Tidal levels of the Gulf may have been a local frame of reference for the area at the time, again I imagine it was based on an averaged sea level of more than one place. This was probably averaged beyond the Gulf as well. The difficult thing about your instance is that here is a chiseled elevation that really has no Datum to reference itself against. It is not correct now, and was only correct for the duration the reference it was based on was considered correct. This is why a bench mark is generally not ascribed an elevation in person, at least not any more. We have learned we can improve upon all this, and as we do the number will change. A chiseled or stamped number becomes eternally incorrect with the first update.

 

In closing, trying to explain all this is not really cake, and I may have made errors. I have proofed it but I may have overlooked something. If anyone has anything to add or feels that I may have been in error, please feel free to weigh in!

 

Rob

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ROB,DAVE,EVEN...all,

 

As always thanks again for such thourough explanations.

I guess we could call this Surveying 201.

You guy's have answered more questions in just a few posts than I could ever get out of "anyone",or class!!

 

As a student of this great field the time and consistency pays off.

I am glad someone can put into words the figures and thoughts we have and all have questions to.

 

No one knows better than the Student the Greatness of the Teachers.

Thanks for being Teachers along with your Professions.

You all have sacraficed and spent lots of time and money learning these things and are just as courtious to share your learned knowledge.

 

My hats off to you all.

 

Happy.......................................................Geotrails

and you know I will be asking more questions someday..........after I do some figurin.... :o

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I have another observation I need claification on.

 

In the PLSS Plat Dated 13 April,1843,William Sheilds, I have,the Reference that is shown is North and the Descriptions to Variation and Declination are North.

 

The change from then untill present is Aprroximately 7*-8* Degrees upon taking that observation (low grade instrument)as given and going out today and taking an astronomical observation with a compass on Polaris here, it is almost at 0*.This date.

 

The Isogonic chart shows almost the same but I have not the instruments to take very calculated observations.

 

So with all that said is the PLSS North or South.

 

MAYBE THE GOVERNMENT WOULD LET ME BORROW THIS.

1cc063a6-a499-40be-bc21-7653d4b65544.jpg

 

Land line adjustments

Edited by GEO*Trailblazer 1
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Evenfall,

You had me thinking I was crazy in my reference to MACADAM, and I mentioned that I thought it might have been a local carryover to use that word. Now I think I am not so crazy, as I drive by "Malony Macadam" every day to work. Maybe my use of the word is just a local custom. I know I have used it and heard it used all my life here in the Pennslyvania Dutch area of south central PA.

Just had to redeem myself a bit!

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Evenfall,

You had me thinking I was crazy in my reference to MACADAM, and I mentioned that I thought it might have been a local carryover to use that word. Now I think I am not so crazy, as I drive by "Malony Macadam" every day to work. Maybe my use of the word is just a local custom. I know I have used it and heard it used all my life here in the Pennslyvania Dutch area of south central PA.

Just had to redeem myself a bit!

To me it does sound like a local thing. I've lived here in Philadelphia for over 5 years and have never heard it used. It makes sense as there are probably things I might say here that you would have no idea what they meant.

 

Nothing wrong with that and heck, I learned something. Nothing wrong with that!

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mloser,

 

No problem there! You were correct all along. I just wanted to help all the people who read your post, as well as those who will occasionally see the word Macadam in a datasheet know what it means. It is an accurate usage of the word, Just not a common usage anymore, and that is why an asphalt company could use it to make the name of their business seem unique. It could be an old business in your area at that and by carrying the old usage in their business name, the locals know what it means. But for the most part the Term MacAdam or Macadam has fallen out of use. It is all based on the name of a guy who pioneered the process is all. In the UK they refer to it as Bitumen. Here in the Northwest, Macadam is a word much like Geodesy... Say what?

 

Asphalt as it is formulated today is an extremely high viscosity oil which acts like a solid at everyday earth temperatures. It is basically the product that is left over after the refining process has stripped all the other useful products out of crude oil. It is nasty stuff really. They add other additives and viscosity enhancers to it of course and many States and Municipalities have other specifications they like added to the oil so it performs better when used as a pavement surface. The Macadam side of all this is when they mix the oil at high temperatures with crushed rock. It is a science getting the hot oil and crushed rock to mix consistently at the correct ratios and temperatures. There are a few processes used to do this, MacAdam was responsible for the particular method he pioneered. I am sure some derivative of his method is still being used in some way even today.

 

I have worked closely with road building companies down through my career, and I suppose I picked up a lot of trade magazines and looked through them along the way. Construction and Surveying is awash in an ocean of trade magazines. I would have to say that it would not seem like it as we drive down the road, but the asphalt industry is pretty technical. They do a lot of testing and formulating. They are always trying to engineer a better, longer lasting product.

 

Rob

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Geo,

 

PLSS uses North. A compass is not considered adequate for survey work anymore but at one time before we had the science available we do now, compasses were used to help determine a north azimuth in some instances.

 

If you want to calibrate your compass this site is very useful:

http://www.ngdc.noaa.gov/seg/geomag/jsp/Declination.jsp

 

If you just want to touch up your general knowledge on geomagnetism, then try this:

http://www.ngdc.noaa.gov/seg/geomag/geomag.shtml

 

Rob

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EVEN,

Thanks

I was merely giving a general synopsis of things I have observed.

I have found several of the Original PLSS Stones and corners and also some of the Blazed trees.

These are the ones which are faced(Blazed) and with the carved numbers behind them(scar).

I do not disturb them and have been doing this study over 10 years or so now.

ARKANSAS-MISSOURI.

 

I have been trying to piece together the various parts which remain.very little.

And is a part of why I ask so many questions.

 

Here I get the truth other places (well)not everyone is truthful,or knows.

 

Like the article says people have been trying to figure out the Geomagnatism of the Earth for a long time.

And for us to try and go back in time 150 years even and find the evidence and try to calculate all the variables is awesome and time consuming,but to me very very interesting.

 

I know what I have observed,to tell someone else is another story.

 

I can give you this story for thought............

 

NEW MEXICO

I know of a Beautiful place among the Mountians in the Four Corners where a hidden trail leads to a secret place.

 

I will give you directions,Go to Counselors N.M.,take the road north to a Y junction

west to Largo Canyon,you will see a bluff that has been marked on all the maps for years to the South side of the Canyon,proceed to the third Cattle Guard and turn south.

From the PLSS Corner of Beth Truby at PALLUCHE WASH,go to the top of Smouse Mesa.You will find an Indian Ruin.

From this ruin go North of the year 600-1100 A.D. ,1/2 of an Indians day walk.

And you will find the hidden trail.

 

One of the info above is not exactly correct.

The Story is true.There is also a map carved in stone here with astronomic observations of the time 600-1100 A.D..

It is a key to the rest of the story and all the other maps in the area.

This is Due North, 600-1100 A.D. of the SUN DAGGER of Chaco Canyon.

SUN DAGGER

 

I only wrote this for the mere explanation that I can not explain on map,in words,feelings thoughts and experience to you or anyone else the exact thing I saw at that time,nor have you find the stones,marks and tralis I set then,with todays more precise technologies.

I can get you close but

 

Now for you to figure it out would take you years.

 

I will keep working on my Ancient Maps though,it has been one of the most intersting things I have ever done,now I have the Technology to do it correct.

 

SOLTICE PROGRAM more on the Sun Dagger

Edited by GEO*Trailblazer 1
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Evenfall,

I was just amazed that the word was not common.... truthfully, everyone in my area would be familiar with Macadam as a term for asphalt. The company I saw is in a rural area so they probably had the same name for 50 years.

 

Matt

fyi

 

Macadam is a paved surface having compressed layers of broken rocks held together with tar, a brown or black bituminous material, liquid or semi-solid in consistency, in which the predominating constituents are bitumens obtained as condensates in the processing of coal, petroleum, oil-shale, wood, or other organic materials. .

 

Asphalt is a dark brown to black, highly viscous, hydrocarbon produced from the residue left after the distillation of petroleum. Asphalt is used on roofs and highways as a waterproofing agent.

 

Source - Google

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Geo

 

I see that  you started a new Topic to follow-up on your post above. You hinted that there was something beyond the Sun Dagger "It is a key to the rest of the story and all the other maps in the area" and as this is going to make for very interesting reading, I was hoping you would keep us posted on your progress. Thanks

 

mrh

Yes there is a Treasure trove of History still hidden.

I am a little cautious about putting everything on the web yet.

 

There are things there that the BLM and other Gov. agencies have left intact for future generations to see in their natural state,just like the Ancient ones(Anasazi) left them,and later the Pueblo Indians.

There are also other things only I know about as well and hope one day to get it documented properly.

 

I have been thinking of doing Events around some of the mapping when I really get started into it.

 

I now live in Missouri and have to set things up way in advance.

I spent 7 years in the area and never did get all the things done I wanted to.

This is also the place where I got poisened with the mercury.

 

I mainly used the story to try and convey a thought of Observations of Celestial bodies then and now and how we are still learning upon it.

 

What was then is not now..................you have to recalculate observations to the time of the observation.

Which is why others left marks for us to follow,but even they did not know the breadth of the Universe.

 

And that crude instruments can be very precise if used correctly.

There are no paper maps,I did not use a compass or a GPS then only observatons of the ancients,some were hard to figure out,and some I am still figurin.

 

(Hint)But believe this or not in or around 600 A.D. the Ancients were using a form of Triangulation.

 

For now the Maps will remain hidden.

If you dig into the Sun Dagger papers you will find some of the aswers to the riddle.

 

New Mexico Really is the Land of "Enchantment"

So for now from the "SHOW ME" state I will share the"Enchantment" all one day soon.

 

Happy.....................................................................Geotrails

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If you think the newer discriptions are vague and the bearings are off check out the ones that we have to put up with in this area. I found five bm's yesterday and had to drive 143 miles to get them. I didn't get these yesterday but a lot of the discriptions we work off of are similar. MY3675, MZ1593, MZ1509 and MY3840.

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