Prospect Park 1887 "square Stone Post"

[+KC0GRN]

Hey all,

 

I've been getting more into looking for benchmarks recently (going to try for some milestones in benchmark finds). I found this listing near my work coordinates (as luck would have it, back in June they had the tower open for a day to climb up to teh observation deck, so I got the nearby brass disk benchmark mounted in the observation deck floor.

 

This one however is being more ellusive. Here's the link to the benchmark page

 

http://www.geocaching.com/mark/details.aspx?PID=PP2586

 

I looked it up on the more updated NGS database and see that in 2001 the US Power Squadron said the mark wasn't found.

 

Still, I went up and looked anyway. When the mark was placed in 1887, the nearby watertower obviously wasn't built (that was in 1914). However, I did find an unusual square in the paved surface that surrounds the water tower. The center looks like it might have been cemented, but there are no other similar squares nearby to suggest it used to be a foundation for a park bench or anything. Obviously I couldn't read the letters "USGS" on top of it, but the 1887 note said it was mounted flush with the ground. The square was about 8"x8", just a bit longer than my gps.

 

I took pictures, and will post them on the benchmark page this evening. Does anyone know what these square stone posts look like, or an idea of how large they are?

 

And thanks for helping a newbie out.

[+Black Dog Trackers]

I can't describe the stone post, but I do have some other observations.

 

PP2586 is an ADJUSTED mark, so your GPS receiver should take you to within 10 feet or so of its position. If what you found is far from where your GPS says, then it isn't the monument.

 

I find it odd that the mark is coded DD; survey disk, when the description says it's a square stone post with the letters USGS on top.

 

The mounting was done by the Missouri River Commission. Their monuments are often (always? sometimes?) an early type of disk. PT0130 is an example.

 

The description says the stone post is on the highest point. If the area had nothing there at the time, they would've probably put it on the exact highest point. If the lighthouse occupies that point now, then the stone post is probably gone.

[+PFF]

Good work! What you found is typical of markers that were established throughout the United States at the end of the 19th Century. Most of the time, they were near the County Courthouse, but they also appeared at other locations when the courthouse was not at a suitable elevation, or where there was not enough room.

 

These often were done in pairs, on an exact North-South line. It was typical for the post to project several inches--or even a foot or two. However, I've seen numerous instances where they were mounted flush with the ground, and even intentionally set in a street. Here's one in North Carolina:

 

 

Mocksville South Meridian (FA2608)

 

There's a companion mark across the village square, to the north. See Mocksville North Meridian for a photo. Then check out FA2610 for full recovery details and multiple photos. It is a triangulation station, for which the granite posts serve as reference marks.

 

One of the professional surveyors contributed to a recent thread in this forum which explained these marks in great detail. Meanwhile, pat your self on the back for recovering a piece of history!

 

-PFF-

[+KC0GRN]

Thanks for the help. I've updated the benchmark page with the photographs I took.

 

The water tower does occupy the top of the knoll, but as you can see there is a large path of pavement at the top as well.

 

My GPS did almost zero out over the square at the posted coordinates for the mark, is that a positive indication? I'm sure in the years gone by the area has been repaved and blacktopped a few times, it's been almost 100 years since the tower was built.

 

Anyways I'll let the experts here decide if I'm okay to log this mark as being found or not Either way it's been interesting research.

[+Black Dog Trackers]

KC0GRN -

 

This is looking good. The pictures are good too.

 

Perhaps the flour trick would work; putting some flour on the stone and then carefully blowing or brushing most of it off to see if any lettering appears.

 

The GPSr zeroing out at the stone is a very good indication.

 

The main indication would be to find out whether or not the stone is deep. That would require pounding a probe in from the side through the asphalt, but that's probably going a bit too far for a hobby finding.

 

Probably the best thing is to try to find someone 'in the know' and ask them what the square is. I bet someone knows exactly what it is.

 

I vote Found-it!

[alohadavid]

There are some stone markers like the on my street in Boston. They have an indent in the center, but no other markings, set flush (well mostly flush, the street is on a hill, and the markers are level) in the sidewalk. I figured that they were used by city surveyors but they aren't in the database.

 

Then one day I drove past a surveyor using one of the markers.

[+bicknell]

Are you sure there isn't a layer of asphalt on top of it?

[evenfall]

I can't describe the stone post, but I do have some other observations.

 

PP2586 is an ADJUSTED mark, so your GPS receiver should take you to within 10 feet or so of its position.

 

The mounting was done by the Missouri River Commission. Their monuments are often (always? sometimes?) an early type of disk.

 

Black Dog,

 

All Horizontal Survey Stations are Usually Adjusted. It is prerequisite to be included as having quality enough to be included in the NGS Database. Vertical Control is also most often found to be "Adjusted". Some Vertical Control can be found to be "Posted" as well.

 

So you have Horizontal Control Stations, and Vertical Control Stations... All most usually "Adjusted".

 

Which Kind are you referring to? the Term "Adjusted" is simply too Vague. What were you trying to say? PP0994 is in the same vicinity, 0.3 miles away, and it is "Adjusted" too

 

Wouldn't it be more clear to say it is either Horizontally Adjusted or Vertically Adjusted since "Adjusted" has only to do with the quality of the survey data?

 

The entire body Of the Missouri River Commission's work was done in the late 1800's before the advent of brass discs. From approximately 1884, and ended in 1902. http://aa179.cr.usgs.gov/1894maps/ So Ahhhhh... It would be safer to say that there were probably zero brass discs Monumented by the Commission. They Did have their own Pipe Cap Monument though. Pipe Caps were not an early type of a Disc Monument, They were Pipe Caps. Totally different animals.

 

Rob

[2oldfarts (the rockhounders)]

All survey marks are adjusted and if you look on the datasheet it will tell you if it is adjusted Horizonally or Vertically. Since the opening poster provided a link to the datasheet, that resolves which adjusted it is.

 

If it is a vertical setting then the adjustment is for elevation ONLY! If it is a horizontal setting then the adjustment is for lat/long ONLY...

 

Boy do things get complicated sometimes.....

 

John

[+Black Dog Trackers]

2oldfarts (the rockhounders) -

 

Since the opening poster provided a link to the datasheet, that resolves which adjusted it is.

 

Yep!

[+KC0GRN]

Thanks for everyone's expertise on this mark. I've decided to log it found, as it appears to be in the correct location, the only mystery remaining is the lettering on the top, has the mark been paved or cemented? Or has it worn down over the years of heavy traffic?

 

More investigation could reveal clues, history of the construction of the water tower, probing the area more. I'm not prepared for either endeavor though, but I do know someone that's into the local history, I'll check with them. And due to the nature of the neighborhood this mark (and water tower) is in, I'm not going to disturb anything to check the mark out more, leave that to the professionals.

 

On a side note, since the NGS database shows the US Power Squadron logging a "Mark Not Found" in 2001, is there any use or reason to inform the NGS of this?

[+jwahl]

This comment is not so much in regard to this particular mark, but something I thought I would point out.

 

There are some of these type questions where considerable more weight for or against a particular piece of evidence could be obtained with a precise GPS position both vertically and horizontally. Thus if you can get a local surveyor interested in the hunt, you might be able to get them to position the point using survey grade GPS. Or level from other nearby marks in the case of a vertical only BM.

 

For example if the mark has adjusted NAD83 coordinates on it, I would expect it to be well within a foot (and usually much less) of that coordinate as recovered by GPS from other nearby monuments of the network.

 

Even on a benchmark, the elevation itself is a valuable tool to aid in recovery or help eliminate possible recoveries or help in determining if it is lost. This again assumes an accurate surveyed in elevation, not one from a typical GPSR

 

If you find the location ground level is 10 feet lower than where you are looking then it is probably not the right place or the ground has been greatly excavated. If you are certain of the horizontal location, it can tell you how deep the BM might be buried today, etc..

 

There is an old mark listed near me that I would not dream of excavating until I had a good surveyed position in the immediate area so that I can know where exactly to dig, and how deep to look, or if it has likely been destroyed since it cannot be 6 feet above the current ground.

 

Just some thoughts.

 

-jerry

Edited August 11, 2005 by jwahl

[holograph]

On a side note, since the NGS database shows the US Power Squadron logging a "Mark Not Found" in 2001, is there any use or reason to inform the NGS of this?

My own opinion is that a square patch in some asphalt paving isn't enough evidence to submit a "found" report to the NGS. If you submitted anything, it might be a "not found" with a note that the area is paved but there is a patch at the approximate former location of the granite post.

 

That patch may be due to the fact that the post had been preseved at some point, and then someone removed it and patched the asphalt where it had been. Without actually finding the post, I don't think you should submit a "found" recovery reoprt.

 

The patch is not sufficient for survey purposes (and suitability for survey control is the only thing that matters in an NGS recovery report), so anyone who attempts to use the station will have to dig under the asphalt to see if the post is there or not. Your "not found" report would help them decide if visiting the station would be worth their while.

[+PFF]

I endorse Holograph's remarks about reporting this particular mark to NGS. But here's something you CAN do, if you wish:

 

Submit recovery reports on the nearby stations (which are not in doubt). In one of them (preferably a disk and not the ball on the water tank), add some comments to the effect that nearby station xxxxxx (PP2586) was searched for. An 8x8 inch square object was found at the described location, but no positive identification marks were visible.

 

I've seen many NGS entries from the "pro's" which took this approach. In addition to my Mocksville entries earlier in the thread, you can look at ELIZABETHTON and ELIZABETHTON 2 in Bladen County, North Carolina. Note how they tie in the old granite marker to the description of the modern mark.

 

This cross-reference approach also is common along the NC-VA border, where 36 granite posts were erected at intervals. Often they do not have a PID, and NCGS and I find them through casual mention in the descriptions of nearby marks.

 

(Writers of the PBS series, History Dectives, are you getting this? For the right price, I'm available for a guest appearance!)

 

-Paul-

[+Black Dog Trackers]

Agreeing with holograph, I would also advise not reporting a found on this mark to the NGS. Reporting a found on this hobbyist site is one thing, but reporting to the National Geodetic Survey is a much more serious undertaking. If I had been to the site, I would probably report a found to this site with plenty of qualifiers (as you have done), and not report anything to the NGS on this PID. The evidence is too inconclusive for the NGS, I think.

 

Even though your GPS receiver 'zeroed out' at the square, as jwahl points out, our GPS receivers are nowhere near as accurate as professional GPS receivers. Basically we're using an instrument that can only say that it is within 8-15 feet of the given coordinates.

[+KC0GRN]

Again thanks to everyone for the suggestions. Since I'm still new at benchmark hunting I've got a few things to learn. At least I know enough to ask questions before acting, especially as far as the NGS goes.

 

I have found that looking for the older benchmarks can be rewarding, even if not in any official way. Next up I'm planning to visit the Highland Park Water Tower, another historic one with an observation deck. This one looks to have a few more benchmarks on and around it. Here's the search from the tower coordinates.

 

http://www.geocaching.com/mark/nearest.asp...&lon=-93.166583

 

Since the tower is only open a couple times a year, I'm hoping to find all the marks in a single visit. Most of them as you'll see haven't been found yet (at least by geocachers/benchmark hunters)

[+Black Dog Trackers]

KC0GRN -

 

It looks to me like there's a slight weirdness in the database and that PP2595 and PP2569 are actually 2 PIDs for the same disk. This isn't the first time we've seen this sort of thing.

 

PP2590 is supposed to be under the signal tower but has different horizontal coordinates (all 3 of these have ADJUSTED coordinates). Rather mysterious.

[+KC0GRN]

Thanks Black Dog Trackers, I was noticing that myself. Looks like the only difference is the posted Altitude?

 

I checked the NGS database and PP2595 isn't showing up. It's listed when you search for it, but when you call up the datasheet it generates an error saying it's not there.

 

1004 feet looks to be the altitude of the ground, considering PP2590 was monumented in 1888 (Hmm another old mark near a water tower, am I headed for trouble again?) and is near the ground. PP2595 shares the same altitude, I wonder if there's a mark monumented on the floor inside the tower? I'll have to check.

 

I've also lucked out, the tower is open this weekend!!!! I'll hit it up on Sunday, get photos and all.

[+Black Dog Trackers]

You're right; I didn't notice the altitude of PP2569. Probably the altitude shown for PP2595 was an error. I get the PP2595 from the NGS with a recovery note by MNDT in 2001 saying it's destroyed. I'm wondering if it's really destroyed or the same disk as PP2569.

 

PP2590 is (was?) on (in?) some 4-foot tall structure. Hard to miss. The description is a bit confusing - is the mark in a hole or not?

 

Very mysterious.

 

It would be good if you can find out when the structure was built. It may be newer than PP2590.

[+PFF]

To get to the data sheet for PP2595, call for it on the NGS site by PID. Before clicking SUBMIT, look for a check box which will include destroyed marks.

 

When you retrieve the data sheet, you will notice at the very bottom of the page that there is a code of "X" in the lower right corner. Looking at the chart above, you will see that X indicates the surface mark was destroyed.

 

Often, you will not get the data sheet--only the chart and the one-line of info at the very bottom. In the case of PP2595, you're in luck. The data sheet is displayed. Looking at the HISTORY, we see:

 

PP2595  HISTORY    - Date    Condition        Report By

PP2595  HISTORY    - 1931    MONUMENTED      NGS

PP2595  HISTORY    - 19880601 GOOD            MNDT

PP2595  HISTORY    - 20010711 DESTROYED        NGS

PP2595

PP2595                          STATION DESCRIPTION

PP2595

PP2595'DESCRIBED BY MN DEPT OF TRANSP 1988 (DKH)

PP2595'RECOVERED BY MNDT 1988 THE STATION WAS RECOVERED IN GOOD CONDITION AS

PP2595'DESCRIBED IN 1974.

PP2595

PP2595                          STATION RECOVERY (2001)

PP2595

PP2595'RECOVERY NOTE BY NATIONAL GEODETIC SURVEY 2001 (DB)

PP2595'MNDT HAS VERIFIED THAT THIS STATION IS DESTROYED.

 

-Paul-

[+PFF]

When you're on the observation deck, don't forget to look for the chisled mark five feet from the disk. See the published description for details.

[+PFF]

And here's another underground mark you should check out while nearby. Looks like that was the standard means of mounting in 1888.

 

-Paul-

[+Black Dog Trackers]

Internet evidence is that the tower was built in 1927.

[evenfall]

2oldfarts (the rockhounders) -

 

Since the opening poster provided a link to the datasheet, that resolves which adjusted it is.

 

Yep!

I support being succinct. Clear in your communications. Even doing homework about Pipe Caps and Brass Discs is a good idea. Be as accurate as possible from the get go. You know, like using NAD 83. This way your answers are more helpful. Not misleading or confusing.

 

It is not about what you "think" you know, or acting like Trolls, it is about helping the person asking, and those who may read the whole thing in hopes of learning something. It is important.

 

I would not turn angles with this station without surveying it in. It is severely view blocked for optical work, and since it's original markings are not viewable, it would be hard to determine the proper spot on it for an instrument set up. Subsequent construction of the water tower may have even disturbed it. Without surveying it in, there is no way to know. I would not trust the Second order quality in my professional opinion.

 

Rob

Edited August 12, 2005 by evenfall

[evenfall]

All survey marks are adjusted

 

Boy do things get complicated sometimes.....

 

John

Unfortunately Not all Stations are Adjusted, so what you are saying is not correct. I said most are usually Adjusted... In your attempt to correct me, you are now in error.

 

Case in point, the station 0.3 miles from the Station this thread is about, is NOT Adjusted.

 

PP1414 DESIGNATION - 827

PP1414 PID - PP1414

PP1414 STATE/COUNTY- MN/HENNEPIN

PP1414 USGS QUAD - ST PAUL WEST (1993)

PP1414

PP1414 *CURRENT SURVEY CONTROL

PP1414 ___________________________________________________________________

PP1414* NAD 83(1986)- 44 58 05. (N) 093 12 26. (W) SCALED

PP1414* NAVD 88 - 277.234 (meters) 909.56 (feet) POSTED

PP1414 ___________________________________________________________________

PP1414 GEOID HEIGHT- -27.16 (meters) GEOID99

PP1414 DYNAMIC HT - 277.230 (meters) 909.55 (feet) COMP

PP1414 MODELED GRAV- 980,581.8 (mgal) NAVD 88

PP1414

PP1414 VERT ORDER - * POSTED, Code E , SEE BELOW

PP1414

PP1414.The horizontal coordinates were scaled from a topographic map and have

PP1414.an estimated accuracy of +/- 6 seconds.

PP1414

PP1414.The orthometric height was determined by differential leveling

PP1414.and adjusted by the National Geodetic Survey in 1992.

PP1414.* This is a POSTED BENCH MARK height. Code E indicates a distribution

PP1414.rate of 4.1 thru 8.0 mm/km.

PP1414

PP1414.The geoid height was determined by GEOID99.

PP1414

PP1414.The dynamic height is computed by dividing the NAVD 88

PP1414.geopotential number by the normal gravity value computed on the

PP1414.Geodetic Reference System of 1980 (GRS 80) ellipsoid at 45

PP1414.degrees latitude (g = 980.6199 gals.).

PP1414

PP1414.The modeled gravity was interpolated from observed gravity values.

PP1414

PP1414; North East Units Estimated Accuracy

PP1414;SPC MN S - 318,980. 862,540. MT (+/- 180 meters Scaled)

PP1414

PP1414 SUPERSEDED SURVEY CONTROL

PP1414

PP1414 NGVD 29 - 277.182 (m) 909.39 (f) ADJ UNCH 2 0

PP1414

PP1414.Superseded values are not recommended for survey control.

PP1414.NGS no longer adjusts projects to the NAD 27 or NGVD 29 datums.

PP1414.See file dsdata.txt to determine how the superseded data were derived.

PP1414

PP1414_MARKER: DD = SURVEY DISK

PP1414_SETTING: 0 = UNSPECIFIED SETTING

PP1414_STAMPING: 827

PP1414_STABILITY: D = MARK OF QUESTIONABLE OR UNKNOWN STABILITY

PP1414

PP1414 HISTORY - Date Condition Recov. By

PP1414 HISTORY - UNK MONUMENTED

PP1414 HISTORY - 1966 GOOD MNDT

PP1414 HISTORY - 1987 GOOD USPSQD

PP1414

PP1414 STATION DESCRIPTION

PP1414

PP1414''DESCRIBED BY MN DEPT OF TRANSP 1966

PP1414''IN MINNEAPOLIS.

PP1414''MARK IS LOCATED AT THE HENNEPIN - RAMSEY COUNTY LINE BETWEEN ST. PAUL

PP1414''AND MINNEAPOLIS NEAR THE KSTP RADIO STATION, IN THE CENTERLINE OF

PP1414''EMERALD STREET, IN LINE WITH THE SOUTH CURB OF UNIVERSITY AVENUE,

PP1414''FLUSH WITH THE PAVEMENT.

PP1414

PP1414 STATION RECOVERY (1987)

PP1414

PP1414''RECOVERY NOTE BY US POWER SQUADRON 1987 (CAF)

PP1414''RECOVERED IN GOOD CONDITION.

 

Yup, Things sure can be complicated, sometimes. That is why it is important to be careful, Succinct, and Thorough in our attempts to give others accurate advice.

 

Rob

[2oldfarts (the rockhounders)]

[evenfall]

Since the opening poster provided a link to the datasheet, that resolves which adjusted it is.

 

No, not really.

 

Blackdog said: "PP2586 is an ADJUSTED mark, so your GPS receiver should take you to within 10 feet or so of its position. If what you found is far from where your GPS says, then it isn't the monument."

 

He made no note of the type of survey. Those who do not research the links will be mislead, and they will not likely learn the fine points from the word Adjusted anyway. It is a common word on Datasheets. So BlackDog can smile if he likes, but he was still misleading in his statement. Just like he was about Missouri River Commission Survey Markers.

 

Most Horizontal Survey is Adjusted. If it isn't, Horizontal Survey won't usually qualify for inclusion in the Active Database. So is most vertical ... Mostly. But that does not address anything beyond performing a least squares equation on the position to accurize it in a network.

 

There is no point to saying adjusted, it is a usual given. "Adjusted" tells the user very little and if the habit is developed to not read beyond that word, then most of the information is lost. There is more to be learned from looking at a datasheet, determining the Type of survey data ascribed to the station by looking for the quality of the survey. The "Order" is where the action is. Listed next to the Horizontal Position or the Elevation.

 

Hopefully this will help "Adjust" everyone's understanding of this subject matter.

 

Rob

Edited August 12, 2005 by evenfall

[evenfall]

By The way, I am not trying to be a Hater with you Guys, But I Have hinted plenty about being accurate in the Past. I have decided that being more direct with you will be more effective.

 

It really is important to speak clearly about these things, even in a Game, so that everyone learns and becomes better players. Knowing something which isn't correct isn't helpful, Not really. The truth about survey markers is still the truth whether you are playing a game or you are surveying with them.

 

We have plenty of time to help others in their understanding here, so lets make sure we give them our best.

 

Rob

[evenfall]

And Now a Little edification for all:

 

DATA ITEM: Current Survey Control

DISPLAYED: Always, but the HEIGHT may be blank if the station

is a horizontal control station only.

COMMENTS : Current Survey Control is identified by a '*' in cc8

and comes under the heading "*CURRENT SURVEY CONTROL"

 

The horizontal datum in use is the North American Datum of 1983

(NAD 83). This datum also defines ellipsoid vertical height.

The orthometric vertical datum in use is the North American

Vertical Datum of 1988 (NAVD 88).

 

NGS no longer adjusts projects to the NAD 27 or NGVD 29 datums.

Care should be taken not to "mix" current datum(s) with

past datum(s) within a project.

 

NAD83 (1986) indicates positions on the NAD83 datum for the

North American Adjustment, completed in 1986.

NAD83 (nnnn) indicates positions on the NAD83 datum for the

North American Adjustment, but readjusted to a State High

Accuracy Reference Network (HARN) on the date shown in (nnnn).

NAD83 (CORS) indicates positions which are part of the CORS

network.

 

There are various Horizontal Control sources, as specified below:

 

ADJUSTED = Least squares adjustment.

(Rounded to 5 decimal places.)

 

HD_HELD1 = Differentially corrected hand held GPS observations.

(Rounded to 2 decimal places.)

 

HD_HELD2 = Autonomous hand held GPS observations.

(Rounded to 1 decimal places.)

 

SCALED = Scaled from a topographic map.

(Rounded to 0 decimal places.)

 

NAVD 88 orthometric heights are displayed where available.

If there was a height for the station on the National Geodetic

Vertical Datum of 1929 (NGVD 29), then that height will be

displayed under SUPERSEDED SURVEY CONTROL.

 

There are various Vertical Control sources, as specified below:

 

ADJUSTED = Direct Digital Output from Least Squares Adjustment

of Precise Leveling.

(Rounded to 3 decimal places.)

 

ADJ UNCH = Manually Entered (and NOT verified) Output of

Least Squares Adjustment of Precise Leveling.

(Rounded to 3 decimal places.)

 

POSTED = Pre-1991 Precise Leveling Adjusted to

the NAVD 88 Network After Completion of

the NAVD 88 General Adjustment of 1991.

(Rounded to 3 decimal places.)

 

READJUST = Precise Leveling Readjusted as Required

by Crustal Motion or Other Cause.

(Rounded to 2 decimal places.)

 

N HEIGHT = Computed from Precise Leveling Connected

at Only One Published Bench Mark.

(Rounded to 2 decimal places.)

 

RESET = Reset Computation of Precise Leveling.

(Rounded to 2 decimal places.)

 

COMPUTED = Computed from Precise Leveling Using

Non-rigorous Adjustment Technique.

(Rounded to 2 decimal places.)

 

LEVELING = Precise Leveling Performed by Horizontal

Field Party.

(Rounded to 2 decimal places.)

 

H LEVEL = Level between control points not connected

to bench mark.

(Rounded to 1 decimal places.)

 

GPS OBS = Computed from GPS Observations.

(Rounded to 1 decimal places.)

 

VERT ANG = Computed from Vertical Angle Observations.

(Rounded to 1 decimal place;

If No Check, to 0 decimal places.)

 

SCALED = Scaled from a Topographic Map.

(Rounded to 0 decimal places.)

 

U HEIGHT = Unvalidated height from precise leveling

connected at only one NSRS point.

(Rounded to 2 decimal places.)

 

VERTCON = The NAVD 88 height was computed by applying the

VERTCON shift value to the NGVD 29 height.

(Rounded to 0 decimal places.)

 

NOTE: NAVD 88 and NGVD 29 heights in meters are

converted to U.S. Survey Feet by using the

conversion factor:

U.S. Survey Feet = (39.37 / 12.00) x meters

Height in feet is rounded to 1 less decimal

place than the corresponding height in meters.

[+Black Dog Trackers]

[evenfall]

Hey, Not Bad for a Troll there BD! I'm glad you have master the Icon clicking gig! Let's all crow for you! You Go! Show us what you got! Troll. Maybe someday you'll either burn out, or "Get It".

 

Rob

Edited August 12, 2005 by evenfall

[2oldfarts (the rockhounders)]

And Now a Little edification for all:

 

DATA ITEM: Current Survey Control

DISPLAYED: Always, but the HEIGHT may be blank if the station

is a horizontal control station only.

COMMENTS : Current Survey Control is identified by a '*' in cc8

and comes under the heading "*CURRENT SURVEY CONTROL"

 

The horizontal datum in use is the North American Datum of 1983

(NAD 83). This datum also defines ellipsoid vertical height.

The orthometric vertical datum in use is the North American

Vertical Datum of 1988 (NAVD 88).

 

NGS no longer adjusts projects to the NAD 27 or NGVD 29 datums.

Care should be taken not to "mix" current datum(s) with

past datum(s) within a project.

 

NAD83 (1986) indicates positions on the NAD83 datum for the

North American Adjustment, completed in 1986.

NAD83 (nnnn) indicates positions on the NAD83 datum for the

North American Adjustment, but readjusted to a State High

Accuracy Reference Network (HARN) on the date shown in (nnnn).

NAD83 (CORS) indicates positions which are part of the CORS

network.

 

There are various Horizontal Control sources, as specified below:

 

ADJUSTED = Least squares adjustment.

(Rounded to 5 decimal places.)

 

HD_HELD1 = Differentially corrected hand held GPS observations.

(Rounded to 2 decimal places.)

 

HD_HELD2 = Autonomous hand held GPS observations.

(Rounded to 1 decimal places.)

 

SCALED = Scaled from a topographic map.

(Rounded to 0 decimal places.)

 

NAVD 88 orthometric heights are displayed where available.

If there was a height for the station on the National Geodetic

Vertical Datum of 1929 (NGVD 29), then that height will be

displayed under SUPERSEDED SURVEY CONTROL.

 

There are various Vertical Control sources, as specified below:

 

ADJUSTED = Direct Digital Output from Least Squares Adjustment

of Precise Leveling.

(Rounded to 3 decimal places.)

 

ADJ UNCH = Manually Entered (and NOT verified) Output of

Least Squares Adjustment of Precise Leveling.

(Rounded to 3 decimal places.)

 

POSTED = Pre-1991 Precise Leveling Adjusted to

the NAVD 88 Network After Completion of

the NAVD 88 General Adjustment of 1991.

(Rounded to 3 decimal places.)

 

READJUST = Precise Leveling Readjusted as Required

by Crustal Motion or Other Cause.

(Rounded to 2 decimal places.)

 

N HEIGHT = Computed from Precise Leveling Connected

at Only One Published Bench Mark.

(Rounded to 2 decimal places.)

 

RESET = Reset Computation of Precise Leveling.

(Rounded to 2 decimal places.)

 

COMPUTED = Computed from Precise Leveling Using

Non-rigorous Adjustment Technique.

(Rounded to 2 decimal places.)

 

LEVELING = Precise Leveling Performed by Horizontal

Field Party.

(Rounded to 2 decimal places.)

 

H LEVEL = Level between control points not connected

to bench mark.

(Rounded to 1 decimal places.)

 

GPS OBS = Computed from GPS Observations.

(Rounded to 1 decimal places.)

 

VERT ANG = Computed from Vertical Angle Observations.

(Rounded to 1 decimal place;

If No Check, to 0 decimal places.)

 

SCALED = Scaled from a Topographic Map.

(Rounded to 0 decimal places.)

 

U HEIGHT = Unvalidated height from precise leveling

connected at only one NSRS point.

(Rounded to 2 decimal places.)

 

VERTCON = The NAVD 88 height was computed by applying the

VERTCON shift value to the NGVD 29 height.

(Rounded to 0 decimal places.)

 

NOTE: NAVD 88 and NGVD 29 heights in meters are

converted to U.S. Survey Feet by using the

conversion factor:

U.S. Survey Feet = (39.37 / 12.00) x meters

Height in feet is rounded to 1 less decimal

place than the corresponding height in meters.

Rob

 

Doesn't this belong in the NGS forum where all the other precision information about & for the NGS was intended to be discussed. Try starting a new thread in the proper forum for the listing of definitions used by the NGS & surveyors. Those that are highly motivated to learn will be able to find it there.

 

If we are going to discuss NGS matters here, then what was the purpose of starting that forum?

 

John

[mloser]

I think this thread just needs to end, regardless of what has been posted and what the content. It no longer has any relation to the topic and has become a massive flame.

[+KC0GRN]

Egads!

 

Sorry about the flame war, even if I don't really feel I was any part of it. Since I've resolved my questions about this mark, I'll close the topic.

 

I may start a new one on the Highland Park, since I'll be checking it out this Sunday.

 

Thanks again for all the suggestions, it's been very educational.