tosborn

...

A radial search on the NGS datasheet database shows no NGS marks within 1 mile of those coordinates. Therefore, it won't be in the geocaching benchmark database either. You should read the "2) We found a disk not listed on GC.com, now what?" section of the pinned "Me First" thread.

It might be a mark near Paonia Dam (lat 38 56 30, long 107 21 07). The elevation is approximately correct and it is a BOR dam (http://www.usbr.gov/dataweb/dams/co01691.htm) located in Colorado. The stamping toward the bottom looks to me like "USGS 6445.20". The "USGS" is in an unusual font for a stamping. The upper stamping I believe is just "64". What appears to be a "5" superscript afterward is just the bottom of the second "E" in "FEET" and a circular scrape that gives the illusion of the bottom of a "5".

Black Dog: I see that Okiebryan has posted your questions on the POB message board....an online surveyor's forum, which should result in some good responses. I won't attempt to answer all the questions that you've posed, but here's my stab at a few: Usually, for an ordinary property boundary survey, the vertical component is not part of the equation. All distances are reported as horizontal distances and thus areas are horizontal areas (Plane Surveying). Consequently, the true square footage of land surface of a parcel on the side of a steep mountain will be somewhat greater than the "surveyed area measurement." However, a property survey can also include a topographic component in which the elevations/contours of the property are also measured. GPS is increasingly being used in boundary surveying. However, in areas with tall buildings or dense tree cover, the total station is still the tool of choice. In the metes and bounds States (Eastern States and Texas), private property was historically described relative to physical monuments (e.g. trees, rocks, streams, roads) and by record monuments (e.g. adjoiners). In the Public Land Survey System (PLSS) States, the Federal Government first delineated the land by marking Township corners, Section corners, and Quarter Section corners. The land was then patented to individuals and described relative to the PLSS decription (e.g. the SW quarter of Section 15, Township 16N, Range 30W of the 5th Principal Meridian). If by cadastral marks we mean mounments to property corners, a metes and bounds State has as many marks as a PLSS State. If by cadastral marks we mean marks set by the General Land Office/BLM marking a Township or Section corner, then of course those only occur in the PLSS States. As properties in the PLSS States get subdivided again and again, the descriptions become metes and bounds descriptions, but with a Point of Commencement or Beginning usually tied to a PLSS corner (e.g. Beginning at the SW corner of S15, T16N, R30W, thence N37d57'13"E to an iron pin, thence...).

As a cadastral mark, it is significant in terms of delineating land ownership. It is, however, not a geodetic mark in that it has apparently not been occupied for an accurate height determination (vertical control mark/benchmark) nor an accurate horizontal geodetic position (horizontal control mark). Cadastral versus geodetic...two different things, two different purposes.

>>I don't understand. The new crew decided they were better "expert measurers" than the surveyor(s) that preceeded them. Rather than hold the old pin which they determined was 2 inches off, they pounded in their own pin creating the "pin cushion" and the confusion that Okiebryan mentioned above.

For those interested, the beta website for OPUS-DB is http://beta.ngs.noaa.gov/CORS-Proxy/oraOpu...b/view.jsp#view. At the top of the page it says "OPUS marks are not yet fully integrated with the NGS database." So it sounds like maybe at some point OPUS-DB marks might be integrated into the NGS database. For example, currently if you search for the Arkansas horizontal control mark "Knowles" in the regular NGS Datasheets it will come back telling you "SORRY - No Stations Found." If you search for "Knowles" in OPUS-DB you get the following "datasheet" for PID BBBC60: http://beta.ngs.noaa.gov/CORS-Proxy/oraOpu...mp;style=modern Also note that OPUS-DB is not the same thing as OPUS. The former is an alternative NGS database of points submitted by surveyors and other geomatics professionals via streamlined methods while the later is a general service for surveyors for post-processing positions against CORS stations. Very few of the points surveyors process through OPUS are submitted to OPUS-DB.

Did you fully Bluebook the mark, or go the OPUS-DB route? Also is the actual point the unmarked center of the disk?

When going from true to magnetic (as in going from geodetic azimuths on a datasheet to a non-declination-adjustable compass) "EAST IS LEAST, WEST IS BEST." Meaning subtract Easterly declinations and add Westerly declinations. When going from magnetic to true, just do the reverse.

Coach88: I've written a small utility to do conversions to and from New Brunswick Stereographic double (NAD83) and Lat/Long (NAD83). It implements the equations in the document I linked above. If you are interested you can download it from this LINK. Run the program and it will install the small utility. You will also need Microsoft .NET Framework version 2.0 or later installed on your Windows machine. Note that data entry requires that you use periods for decimal points rather than commas. I have tested the program on a number of conversions and everything appears to be working correctly, but use at your own risk. When converting from Lat/Long to Northing/Easting you can enter lat/long in any number of formats. For example decimal degrees (e.g. 46 or 46.1 or 46.12343), or degrees and decimal minutes (e.g. 46 38 or 46 38.1), or degrees, minutes and decimal seconds (e.g. 46 38 12 or 46 38 12.4 or 46 38 12.4352322).

Double Stereographic is better know as Oblique Stereographic. The formulas for Oblique Stereographic can be found in the following publication beginning on page 46. An example computation is shown on page 48. It's not something one would want to attempt with a handheld calculator. http://www.epsg.org/guides/docs/G7-2.pdf

...

On doing your own conversions.............. There is a free application called FWTools (http://fwtools.maptools.org/). If you download and install it, it contains a command-line utility called CS2CS which can be used to perform transformations between source and destination cartographic coordinate systems. Basically you would double click the FWTools Shell icon that is placed on your desktop, then type-in or cut and paste the following command as one line: cs2cs +proj=sterea +lat_0=46.5 +lon_0=-66.5 +x_0=2500000 +y_0=7500000 +k_0=.999912 +datum=NAD83 +to +proj=latlong then hit enter. At that point you can enter an Easting and a Northing, in that order, all on one line separated by a space such as: 2643590.696 7475159.228 then hit enter. The converted longitude and latitude will then be displayed on the next line such as: 64d38'14.29"W 46d15'40.701"N 0.000 The third number 0.000 I think represents ellipsoid height, which we didn't enter anything for so naturally it is 0. You can then enter additional Eastings and Northings in the same way.

I think you got your Northings and Eastings reversed in your last response. Here are the converted coordinates: There are equations to convert the NAD83(CSRS) / New Brunswick Stereo coordinates back to Lat/Long, but I don't have a ready source and such equations are often pretty hairy. Manifold GIS is Geographic Information System software. Their website is: http://www.manifold.net.

The Northings and Eastings you have are not expressed in UTM (it would be zone 20 if they were). What you have are Northings and Eastings expressed in New Brunswick Stereographic Double projection, NAD83(CSRS), meters. You can read more about it at http://www.snb.ca/e/6000/6904e.asp. On that page they list a utility called NBGeocalc that can be used to covert to and from New Brunswick Stereographic Double projection. It appears that it costs $100....wow! I entered the Lat/Long coordinates you provided in Manifold GIS and then changed projection to New Brunswick Stereographic Double projection and got a Northing and Easting very close to the ones you listed in your initial post. If you have a limited number of Northings and Eastings, post them here and I'll convert them to Lat/Long for you. For example, Easting 2643439.145, Northing 7475081.373 from your initial post converts to Latitude 46°15.63813 N, Longitude 64°38.35750 W.

Don't you have to observe on two consecutive days 4 hours apart?

Looks like Deb declared it destroyed back on 8/7/2008. EE0028 HISTORY - Date Condition Report By EE0028 HISTORY - 1934 MONUMENTED CGS EE0028 HISTORY - 20080807 DESTROYED NGS EE0028 EE0028 STATION DESCRIPTION EE0028 EE0028'DESCRIBED BY COAST AND GEODETIC SURVEY 1934 EE0028'IN ELLIJAY. EE0028'TWO FEET OUTSIDE OF SIDEWALK, ONE FEET INSIDE OF STREET CURB, AND EE0028'SIX FEET EAST OF S.W. CORNER OF GILMER COUNTY COURTHOUSE. EE0028'EAST CHATTANOOGA, TENN. AND ELLIJAY, GEORGIA LINE EE0028 EE0028 STATION RECOVERY (2008) EE0028 EE0028'RECOVERY NOTE BY NATIONAL GEODETIC SURVEY 2008 (DB) EE0028'THIS REPORT WAS SUBMITTED BY MIKE MORREY.

Paul: It was good of you to write up a practical guide to declination. Here are a few expansions/corrections: 1) the difference between geodetic North (which is usually what folks mean when they refer to "True North") and astronomic North is know as the Laplace correction. The formula is : Astronomic Azimuth + Laplace Correction = Geodetic Azimuth. The Laplace correction is found on NGS datasheets for adjusted marks and is calculated using the DEFLEC99 program of the NGS Geodetic Tool Kit. As you say, the Laplace correction is typically only a few arc seconds in magnitude. 2) accounting for declination in one's head can be a confusing exercise. When you have a true azimuth and you want a magnetic azimuth you have to do one thing (subtract or add the declination) depending on whether your declination is East or West. And then when you want to go from a magnetic azimuth to a true azimuth, you have to do the opposite mathematical operation. It very easy to get confused and make a mistake. That's why having a compass with the capability to set declination is so desirable. 3) In describing the declination adjustment feature on some compasses you state that "To adjust for West declination, which is negative, the graduated circle is turned counter-clockwise." Be aware that different compass manufacturers have different ways of setting declination. Some have a scale that reads from the top of the compass, others have a scale that reads from the bottom of the compass. So, clockwise...counter-clockwise.....it just depends on the way the compass is constructed and which side you are looking at. 4) Unfortunately, your examples for Boston and San Francisco of how to convert between magnetic and true azimuths are exactly opposite of what they should be. Lets take an example. Let's pretend that you are in San Francisco standing on top of a triangulation station. You sight your compass (not adjusted for declination) at a reference mark and amazingly the azimuth you read from the compass is exactly 0.00 degrees. Of course you know this is a magnetic azimuth, so the reference mark is a point on a line between the triangulation station and magnetic North. What you need is a true azimuth. You know that the local declination is 14.5 degrees East, meaning that a magnetized needle will point 14.5 degrees East of True North. So, the True azimuth between the triangulation station and the reference mark must be 14.5 degrees. You've ADDED the declination to the magnetic azimuth in order to get the true azimuth. In your writeup, you have us SUBTRACTING the declination. Likewise, let's say we are in Boston. Again we sight from a triangulation station to a reference mark with a compass unadjusted for declination. Again we get a magnetic azimuth of 0.00 (a.k.a. 360) degrees. In Boston we know that a magnetized needle will point 15 degrees West of True North. So the True Azimuth from the triangulation station to the reference mark must be 345 degrees. In this case we've SUBTRACTED the declination from the magnetic azimuth to get the true azimuth. In your writup you have us ADDING the declination. Here are the rules: 4a) When going from True azimuths to Magnetic azimuths subtract east declinations, but add west declinations. (In Boy Scouts we learned the following rhyme to aide us in going from azimuths taken from a topo map (true azimuths) to correctly setting our non-declination adjusted compasses correctly (magnetic azimuths) ...EAST IS LEAST, WEST IS BEST. Meaning subtract east declinations and add west declinations to go from true to magnetic. 4b) When going from Magnetic azimuths to True azimuths, do the opposite of the above rule. In other words, add East declinations but subtract West declinations. The foregoing assumes that ones treats both East and West declinations as positive numbers. At one point in your writeup you did bring up the idea that West declinations can be considered negative and East declinations positive. But then you didn't seem to follow through with that distinction in your examples. However, if one consistently treats West declinations as negative numbers and East declinations as positive numbers, the following formulas can be used. In the end, it works out identical to the above two rules. True azumith = Magnetic azimuth + magnetic declination (where West Declinations are negative), and Magnetic azimuth = True azimuth - magnetic declination (where West Declinations are negative) 5) In addition to spatial and long run secular changes in declination, there is also daily variation and irregular variation. Daily variation in the US averages 8 arc minutes. It is furthest East at around 8 in the morning and furthest West at around 1:30 in the afternoon. In terms of irregular variation, it can be as much as 1 degree resulting from electrical storms and magnetic disturbances. Then there are local sources of attraction such as iron-bearing rocks, etc which can cause deflection in a magnetic needle. Also, things worn by the individual can cause the needle to deflect. There is the story about the surveyor from the 1800's who's bearings were consistently different from what current-day surveyors would find when they retraced his lines. One day, the mystery was solved when a photo of the old surveyor surfaced. It showed him standing next to his waist-high compass with a large pistol strapped to his hip. Now you know the rest of the story.

Jerry: Thanks for that. I've heard you speak about the "Arkansas Windage" before, but I don't think I heard a possible explanation for why it may have occurred. It's interesting that this phenomenon is unique to this part of PLSSia. I've read through the 1815 field notes of Prospect Robbins and Joseph Brown and I don't find any mention of how they set the "variation of the needle" nor do they even mention periodically checking the length of their chains. Some 15 years later in 1830, Deputy Surveyor Nicholas Rightor who did a lot of work in Arkansas establishing townships and sections does mention such things. Apparently in retracing portions of the 5th P.M. he determines that his compass must be set to a variation of 8 degrees to 8 degrees 10 minutes East to coincide with the 5th P.M., and as you say, he perpetuates that direction. One thing that I am unsure of it why doesn't the Arkansas Windage eventually get filtered-out at some Guide Meridian East or West of the 5th P.M.? In checking historic declinations from the National Geophysical Data Center website, it indicates that the declination at the 5th P.M. initial point was 8d 22' E in 1815 and 8d 36' E in 1830. In St. Louis, the NGDC indicates the declination was 8d 10' in 1820 and 8d 14' in 1830. Based on that it doesn't appear that the declination difference between St. Louis and SE Arkansas would account for the "Arkansas Windage." Of course, the NGDC declination numbers are modeled and are apparently only accurate to about 30 arc minutes. Do you know of any other information that would give a clue as to what Robbins and Brown actually did other than their terse field notes? Are there other theories that would account for the Arkansas Windage? Tim Osborn

Based on your comments above, this is probably out of your price range but my recommendation would be the Suunto KB-14 Azimuth Model compass with declination adjustment. These are accurate direct-sighting compasses you put up to your eye, so there is no fussing with mirrors and getting arrows and needles more-or-less lined up. Also, unlike the compasses you've mentioned which only have markings every 2 degrees, the KB-14 azimuth model has markings every 0.5 degrees. The KB-14 offers ease of use and accuracy, but at a little over twice the cost of the models you've mentioned. As to your question about "fixed declination scales versus adjustable declination," I not sure I know what you are referring to when you say "fixed declination scale." All the compasses I have, such as the Silva Ranger, etc have a declination scale which you set to your local declination. So, they all are "adjustable," but once you set it, it is fixed until you decide to set it to another value.

pgrig: In your last report you state that "Bearings were measured with a Brunton pocket transit adjusted for 15d W declination and aligned on the top of the laser device." You also say "I was surprised at the variance of the bearings" compared to what you got previously. I'm taking that to mean that you set the pocket transit on top of the laser device to take your bearings. That raises the question of whether the magnetic needle in the pocket transit was affected by 1) the 1/4" x 20 mounting screw (most likely a steel screw) of the tripod going into the bottom of the laser measurer, and/or 2) any ferrous metal that might be contained within the body of the laser measurer. Did you check to see if the needle of the pocket transit was affected by such local attraction? The reason I ask is that I have a Leica Disto A8 laser measurer and it definitely will deflect the needle of a compass held in close proximity. I've also observed that my Suunto KB-14 compass is deflected by the mounting screws of photographic tripods and monopods. Just wondering.

It's true that the 5th Principal Meridian does not run due exactly North-South (astronomic, geodetic, true, whatever). Based on what I've observed from USGS 7.5 minute topo maps, the section of the 5th Principal Meridian that runs from the mouth of the Arkansas River to the Initial Point (established by Prospect Robbins and Joseph Brown in 1815) has an azimuth of about 1 degree (1 degree East of "True" North.) However, I don't think this divergence has anything to do with the precession of the Earth. It's my understanding that surveyors in the early 1800's were well aware that polaris appears to rotate around celestial North. That's why they would normally make their star observations at Eastern or Western elongation, when Polaris' East-West motion was minimal and when the azimuth of Polaris could be accurately determined. So in theory, finding "true" North (actually determining magnetic declination) wasn't a problem. I think the problem was in accurately placing the line on the ground using the tools of the day (compass and chain) through heavily forested low-land hardwood swamps.

An azimuth is an angle measured from a meridian (usually North) going clockwise from zero to 360 degrees through a full circle. A bearing is an angle measured within a given quadrant (e.g. NE, NW, SE, SW). In the NE and NW quadrants the angle is measured from North toward East or West. In the SE and SW quadrants the angle is measured from South toward East or West. A bearing will never exceed 90 degrees. Bearings are typically used in property descriptions. It's easy to express a back-bearing....you just reverse the quadrant. For example the back bearing of N35E is S35W.

See the article by Jerry Penry in American Surveyor: http://www.amerisurv.com/content/view/4318/136/

fourteenthstreet: You need to tell us what you mean by "exact latitude and longitude." Exact to the nearest .04', exact to the nearest foot, nearest meter? Assuming you can't find published horizontal coordinates for the point in question, you could do any of the following: If you precision requirements are only to the nearest 10 feet, you could obtain acceptable Lat-Long coordinates by standing on the point with a handheld consumer GPS receiver with WAAS capability, assuming the sky is not blocked by trees or nearby buildings. Using the averaging capability of the GPS receiver will improved the results. If your precision requirements are sub-meter you could probably borrow a mapping-grade GPS receiver and occupy the point as above. If you require greater precision than sub-meter you are getting into the province of the surveyor who could occupy the point with survey-grade GPS equipment or traverse to the point from known horizontal control using a total station.