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Coordinate System Question

wolves shepherd

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Found (I think) a neat marker that I can use for the virtual cache Not the Benchmark. However, I'm try to decipher the coordinates marked on it.


At N 34 00.9748 W 080 54.8994 there is a military marker that, I

believe, was used during WWII for training artillery crew members at

Fort Jackson SC. It was erected in 1940 according to the inscription

and it gives the following as coordinates on the marker 8.567 13.062


Does anyone have any idea what system the coordinates on the marker

are? My coordinates at the top were taken with my GPS so there is some

wiggle room.


Any help would be greatly appreciated, I've done some looking on the

net but have found nothing to give me that "aha!" moment. I can't get them to make sense with MGRS (Which may not have even been in use durning WWII?)


(I can postl a pic of the inscription if it would be helpful)

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Wolves shepherd,


Here is a link that may have something...




If it is not UTM or MGRS then Hmmmmm.


I did find this tidbit while looking around...


UTM Grid Developed


The Universal Transverse Mercator (UTM) grid, a world wide plane coordinate system was developed in the 1940's by the Corps of Engineers, U.S. Army, following the recommendations of Oscar S. Adams of the C&GS Geodesy Division. The grid consists of bands, 6 of longitude wide, and a maximum scale reduction of 1:2,500. Original tables (for the Clarke spheroid of 1866) were computed by a Civil Works project, in NYC, sponsored by the U.S. Lake Survey (USLS) during the early 40's. The USLS unit evolved into the Geodetic Division of the Army Map Service (AMS) about 1943. Later, tables were computed for other ellipsoids then in use. Floyd W. Hough, David Mills, Homer Fuller and Frank L. Culley were directly associated with the grid's development.


I also looked at Artillery Aiming and Gunnery at Google but I am running low on time to go through it all...


Good Luck!



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Post a picture please. With the small numbers give, i.e. numbers less than 20 it is hard to tell. Most mapping projections deal in large numbers. Even local surveys use 1000,1000 or 10,000 10,000 for starting coordinates. So it is probably something else.


- jlw


Examination of Terraserver imagery it looks to me like this point is west of some kind of large antenna array and nearly in line with one axis of the array. However that may be a co-incidence. It may be some kind of referenc mark offset or angular related to that array.

Edited by jwahl
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Further Diggings...


Seems there is a new and Old version to MGRS.


https://www.navigator.navy.mil/ navigator/map_reading_201.doc


This is a well written Navy .doc paper which is a download. Be prepared to download a Word Doc File. It has some great info about MGRS and it evolutional development. It seems there has been changes to the numbering system over time.


I am not sure this is going in the right direction here or not but thought I would pass it along.


I also came across this link to a US Army Map reading Manual.





It seems to have a lot of information concerning coordinate systems that have been recognized by the US military. Perhaps it will serve as a resource here as well.


Both seem worth adding to the personal archives.





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Well, I looked throught the material you all posted and it's good stuff. :angry:


Unfortunately, I don't think we've answered the mystery yet of being able to explain the alleged coordinates on St. Barbara 2. :lol: (As long as we're all learning here, St. Barbara is the patron saint of artillery. I don't know why.)


Maybe I can get over to the museum on post and find some answers/hints/clues.

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Artillery opens up a lot of options. My first guess is that the coordinate by be in kilometers or thousands of yards. So say you set up artillary on this point and have been given another particular point to shoot you have to compute some things.


1) know where you are (thus the coordinate here)


2) which direction the coordinate system is oriented.


Thus the list that follows is probably a list of the azimuths to those objects in mils. There are 6400 mils in a circle. I have no training in artillery, but I have heard that mils are used for that purpose and they may have a correlation to actual units of distance at a certain distance. That is if I miss by 50 yards left and the target is 2000 yards away, I have to adjust 25 mils. But this is just a guess.


Anyway the first test would be to see if they fit anything left on the ground.


I suspect the coordinate system is based on a local 'practice battlefield' map.


You would have to get someone with WWII era artillery to help out.


Anyway once they know where they are and which way to orient, they can then work out which way to rotate the gun and what elevation to fire to hit a specific target coordinate.


Now the Azimuth test


1) Water Tank on Hill 5503.9 ?? I think


This would put it at map azimuth 309d35' or if their map is oriented to true north (we don't know, maybe it is magnetic north in 1940...) would be N. 50d 24' W. There is a tank on a hill to the NW.


One could go on, but a lot of this stuff is going to be based on the way it was in 1940 and not now.


- jlw

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Jerry and all,


This may be one of those... What say if the truth were to be known, the US Army, more likely the US Army Corps of Engineers know what the data for that station is all about and can perhaps decipher it? I once knew a guy who was in artillery and he had told me how it worked with howitzers once, but it was years ago and he is no longer with us, so oh well... It all goes back to the truism about Survey markers... It is the data ascribed to them which is important.




My thoughts are when you write, if you should choose to do so, use the conventional method of Degrees Minutes and Seconds, and based on the age of the station, set your GPS to NAD 27 Datum and use that coordinate for them. This will aid them in looking up the data faster and more accurately. If you like you could supply the data in both NAD 27 and NAD 83. The Corps of engineers commonly use the North American Datum for their Civil work inside the Continental US, Rather than WGS 84. They are pretty receptive to requests about their survey markers and should be happy to help if you reach the right people. You may want to see if there is a local district office and pick their brains as to whom in fact is the right person to address the question to. That will also speed you up a lot.


Good Luck,



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Cartesian (x,y) System


The Cartesian (x,y) system is a grid which is divided into quadrants by perpendicular (at right angles) horizontal and vertical lines labelled 'x' and 'y'. Point locations, called coordinates, are located on the grid by giving first the horizontal, or 'x', coordinate, and then the vertical, or 'y', coordinate.


In 1940 they were probably using the Compass in training and the field.

Yes the Mils and clicks.

My 1942 Military Lensatic Metric compass has all the stuff on it for mapping.


I would try to find the 0 point,for the training or P.O.B.

I am sure there are still Old Military maps around in collections in the library,or museums,ect.


If not if you have the time use WGS 84 True Grid and mark all the points you can find.(also using the compass) make good field notes of bearings and distances from one point to another.

Back engineer the findings and it will yield the data you seek.

You will also(for magnetic) figure the magnetic slippage since 1940's.

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The Mils to Tank Hill work out. I had one waypoint I took between the current tanks which gave me a bearing of 304.84º I then projected one using www.lostoutdoors.com to the approximate location of the old tanks (some of the foundations are still on the ground) and got 310.87º. So somewhere in there would fall the 309.59º that the mils given on the monument refer to. Tank hill is the only point I know where it is for sure 64 years later.


I'm now working trying to find the 0,0 point for the coordinates using different units for the coordinates.

Edited by wolves shepherd
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From the Plaque coordinates here:



To this Traingulation Station Jackson:










0.474 mi.


There are several more in the area here is their links.


PERCIVAL BRIDGE very interesting recoveries.




HM ON 77






Thats just a few that are there.



Oh, I ain't figured it out yet but have been trying to figure the 0 point too.

One guess so far is if you do the reading backwards that is;


south 13.062 km then west 8.567 km.

I get

33 53.91561

81 00.45670




Further study on one 3441.6(197.?? *)

puts you here.




The water tank at 1690.5 (95*) appox.,still looking.

Umbrella tree 1288.4 (72*) approx. ??

I projected the azimuths on my programs and still haven't found anything.

Fun looking though.

Edited by GEO*Trailblazer 1
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Interesting. Your second plot puts you on Pickney Elementary school on post. (obviously) a fairly new structure.


GT, yes, the tool is nice. I've got one, somewhere.


I think the big mystery is what unit the coordinate numbers are in. If we could get a lock on that.......


Still thinking. Not much open over the holiday. Maybe next week and can find some folks to talk to.

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I think the big mystery is what unit the coordinate numbers are in. If we could get a lock on that.......


Hey, guys! Looks like someone mounted the large marker upside down. I rotated it 180 degrees with my computer software. The "jumble" of random figures suddenly jumped into focus. It reads:




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While doing a search on measurement systems of 1940 I ran across this:



This probably has no meaning,but the base line measurement seemed to come close to 8.




In this CW system, ambiguous LOP's occur since there is no means to identify particular points of constant phase difference which reoccur throughout the coverage area. The area between lines of zero phase difference were called lanes. Single frequency receivers use the 10.2 kHz signals whose lane width is about eight nautical miles on the baseline between stations.


FROM Here:


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This Site sheds a glimmer of light, indicating that it might be an arbitrary grid, as it sounds like that was what the US employed, along with the British in artillery operation for WWII.


I think the answer could be found in either FM 6-20 or FM 6-40 from that era. However, I have not been able to find and on-line versions as of yet.


Right now my hope is pinned on either finding the above manuals or a period map from Fort Jackson to explain the coordinates definitively.

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It may be a coincidence, but the station is very close (probably within the GPSr error) of being 8,567 yards east and 13,062 yards north of N33°53'30"  W81°00'00" NAD27, when measured on a map using the UTM projection.  That is, if my calculations and conversions are correct. <_<



33 59'58.27476"

80 54' 55.32166"



34 01' 14.08905"

80 55' 16.47034"



34 00' 58.48800"

80 54' 53.96400"


34 00' 58.5"

80 54' 54.O"



WEST --8.567 KM (8567 METERS)

SOUTH --13.062 KM (13602 METERS)

33 54' 09.89142"

81 00' 49.92504"



WEST --8.567 KM (8567 METERS)

SOUTH --13.062 KM (13602 METERS)

33 53' 54.93660"

80 00' 27.4020"


33 54' 00"

81 00' 30"





80 55'.00"







Edited by GEO*Trailblazer 1
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Meters, federal gov always used meters.


Been in the survey field since 1972 and never saw yards used for anything but football and hunting.


Like a story in the local paper lastg deer season about this guy who bagged a big buck, he said he shot him at 1000 yards, 1 shot. Say What? 3000 feet, me think he does not know his yard from his feet.

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What you found is a aiming circle used for artillery here is a excerpt from a artillery course handbook .

Loading FA 3074 Hasty Survey..please wait

Page 8 of 174 EXIT TOC To go to the lesson you want, click on that button below. If you would like, you may use the navigation buttons at the top right of the page.

Table of Contents



The azimuth of a line may be defined as the horizontal clockwise angle measured from a base direction. There are three base directions--grid north, true north, and magnetic north. The direction used by the field artillery is grid direction based on the universal transverse mercator (UTM) grid system. True direction is based on the north pole. The difference between a true azimuth and a grid azimuth is grid convergence. Magnetic direction is based on the location of the magnetic field of the earth. The difference between a grid azimuth and a magnetic azimuth can be expressed either as the G-M angle or as the declination constant. In the event that the orienting line (OL) has not been established by battalion surveyors, battery personnel can still determine accurate directional control by employing the simplified technique called simultaneous observation.

Page 16 of 174 TOC EXIT 1. SIMULTANEOUS OBSERVATION: Simultaneous Observation is the process of two separate observation stations, observing the same celestial body at the same time. Simultaneous observation (SIMO) of a celestial body provides a rapid method of transferring direction over great distances without time-consuming computations. This method is ideally suited to the needs of the artillery, since many units can be placed on common directional control in minutes. The principle behind simultaneous observation is that any celestial body is so far away that, for practical purposes, the lines of sight to it at any instant from two or more points on the surface of the earth are parallel (Figure 1, next page). A point having known directional control (grid azimuth to an azimuth mark [Figure 1-2, next page]) can be occupied by battalion surveyors with a T-16 theodolite or by personnel from the firing unit with an aiming circle. An azimuth to a known point is all that is required to start a simultaneous observation. This known point becomes the master station (Figure 1-2) for the simultaneous observation. Each firing battery needing directional control becomes a flank station (Figure 1-2). At the flank station, the aiming circle is set up to observe a prearranged celestial object and becomes the orienting station for the battery.


Figure 1-3. Theodolite over orienting station.


Figure 1-4. Horizontal circle setting.

(2) The theodolite operator then sets the known azimuth to the azimuth mark on the scales of the horizontal circle. (Example: 1429.4 mils [Figure 1-4] ).

(3) Next, the theodolite operator sights on the azimuth mark (Figure 1-5 next page) and unlocks the scales, then sights on a predetermined celestial body (sun or star).

Figure 1-5. Sight on azimuth mark.


(4) He then alerts the flank stations by announcing, "THIS IS HOTEL 38"--"START TRACKING OUT."

(5) The theodolite operator tracks the celestial body and reports--"THIS IS HOTEL 38, TRACKING, TRACKING, TRACKING, TIP, OUT."

Figure 1-6. Tracking.

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I posted something like this last,or did I just think I did??

I did,did I?

I would look around the areas where it is cleared or white in the photo,you can see several diffrent places where it looks like fodder fire :unsure: has cleared the areas.

And if you look a little further SW from the 197* (school)you see another cloverleaf circle.Maybe another firing circle for another gun.


I am shure you will find an encirclement of implements as given by the Mils.

I was there once (didn't look as close as I shoulda)and even had a tat or two done in Columbia,then I went to Ft. Benning,then to Well some thing happened between there an Ft. Bragg.

Anyway I am Honarably still here.


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It may be a coincidence, but the station is very close (probably within the GPSr error) of being 8,567 yards east and 13,062 yards north of N33°53'30"  W81°00'00" NAD27, when measured on a map using the UTM projection.  That is, if my calculations and conversions are correct. :rolleyes:



33 59'58.27476"

80 54' 55.32166"


I just got back from the holiday, and I see my original message's N 33°53'30" was a typo, it should have been N 33°54'30".


Assuming a grid origin of N 33°54'30.0" W 81°00'00.0" in the NAD27 datum, I arrived within 8 meters of the GPS reading if the plaque's coordinates were in thousands of yards on a map grid. Granted, this would be an oddball coordinate system, but it is also an odd coincidence.


Here's my calculation if anyone wants to check the result:


Converting the proposed grid origin of N 33°54'30.0" W 81°00'00.0" NAD27 to NAD83 using NADCON, I get N 33°54'30.56" W80°59'59.33" NAD83 for the location of the proposed grid origin.


Doing a UTM projection in the NAD83 datum, I get UTM coordinates of the proposed grid origin of N 3752009 E 500017 zone 17 in the NAD83 datum, to the nearest meter.


Adding 8,567 yards (7,834 meters) and 13,062 yards (11,944 meters) to the proposed grid origin obtains UTM coordinates for the plaque at N 3763953 E 507851 in the NAD83 datum, to the nearest meter.


Converting the GPS reading of N34°00.9748' W80°54.8994'to UTM yields N 3763960 E 507848 in the NAD83 datum to the nearest meter, which is within 8 meters of the calculated position, or about the error I might expect of a handheld GPS.


I used the UTM projection merely as a matter of convenience because the conversion software is widely available. Over those distances, most reasonable map projections would give essentially the same results. The Army probably was using a different projection for their map grid at that time.

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More research turned up this. The Progressive Military Grid system in use at the time would have had a zone edge at 81° longitide, and would have had coordinates in yards:


"In 1918 the U.S. Coast and Geodetic Survey and the Army Corps of Engineers established the progressive military grid system, based on the polyconic projection.  First applied to the conterminous United States, it consisted of seven zones each 9° of longitude wide with 1° of overlap, extending from 28° to 49°10' N latitude, except for extensions to 24° in two zones to include southern Florida and Texas.  Central meridians began at 73°W for zone A and continued every 8° to 121° W for zone G.  Unlike the units in feet for the later State Plane Coordinate System and in meters for the later UTM system, the rectangular coordinates of the progressive military grid were in yards." 


- Snyder, John P., Flattening the Earth: Two Thousand Years of Map Projections, 1993, University of Chicago Press, p. 174


"There were seven zones, A-G, with central meridians every 8° west from long. 73°W (zone A), each zone havng an origin at lat. 40°30' N. on the central meridian with coordinates x=1,000,000 yards, y=2,000,000 yards (Deetz and Adams, 1934, p 87-90)"


- Snyder, John P., Map Projections - A Working Manual, U.S. Geological Survey Professional Paper 1395, p 127


See this army field manual and this one for examples.


Final edit: using the PROJ4 software, I calculated the geographic coordinates of the plaque if its Progressive Military Grid coordinates were 1008567 1213062 yards(NAD27). The NAD83 coordinates came to N 34°00.978 W 80°54.900 , which closely agrees with the GPS reading of N 34°00.9748 W 80°54.8994.


That seems to indicate that the plaque contains grid coordinates relative to a grid square with origin at grid coordinates 1000000 1200000. That grid square origin would be N 33°54'30.593" W 81°00'00.000" NAD27, or N 33°54'31.153" W 80°59'59.329" NAD83

Edited by holograph
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Can't help you with the coord system without more research, but the marker is probably an orienting station.


Simplified explanation.


An Artillery survey instrument called an Aiming Circle is set up over & centered on this marker. The AC is aligned with the listed aiming points, and the instrument readings are compared to the listed coord (in mils) to determine the accuracy of the instrument before it is used to survey or 'Lay' artillery pieces.


The mil or milliradian was adopted by the military and is based on the radian. pi times 2000 = 6283. We are kinda slow, so we rounded it up to 6400 to make the math easier. Works out well, since @ 1000 meters, 1 mil = an approx. 1 meter spread. Also handy to use with UTM, which is based on meters & a system you can actually manipulate mathematically. 'Mil' system was in use during WWII & still going strong.

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Holograph and Redleg,


Thanks for the great work. It looks like we have 6400 Miliradians to create a highly accurate aiming circle which can pinpoint to 1 meter at 1000 meters distance, and a rectangular coordinate system that is grid based on NAD 27, the going Datum of that time, measuring the distances involved.


They knew where they were on the grid, and what they wanted to shoot at. They overlay the Mil Circle with themselves as at the center, likely at scale so it could help ranging and dial in at less than one mill increments, then calculated how to set the howitzer angles based on how far they knew the shell would go. From there it looks like fire for effect and have a nice day.


Based on the 8 meters that you got for difference at that location Holograph, using the NADCON program to convert back to NAD 27, the appropriate Datum for that station setting, I am curious if that will tighten up the unaccounted for 8 yards in the Datum shift. Do you see a difference?


Mike was right in that the Feds always used Meters. I have seen the use of meters in survey going back forever, but It is interesting that the CGS and USACE used yards for this system. Did the source explain why yards were chosen, though it is obvious they later discarded that choice? It is obvious we are seeing the growing pains of a system which has evolved.


That pretty much explains how the Army knew where they were on the ground at that Base, in reference to their grid system and how to orient themselves from there.


And Wolves, you are technically correct about the system of metric measurement being a system adopted as a whole after World War two. However the meter itself was determined after a six-year survey ending in 1795, based on a line that ran from the North Pole to the Equator, via Paris which whose total length was determined and then divided by 10,000,000 (ten million) and is a unit which was determined to be 39.37008 inches in length.


The name "metre" was chosen for this unit based on metron, the Greek word for "measure." Geodesists later learned they got this measurement slightly wrong, but they decided to keep it, as it was not very wrong and there had been a very large body of work already based on it. It also became the basis for other metric measurements in the metric system as well, and was the product of a postulation made in the late 1500's which proposed that there ought to be a base 10 system of measurements.


Today, I can walk into a shopping mall and stand before the map in the food court and know where I am... It claims: You am here, and so it goes. But I still have a hard time finding a pair of pants there that does not have that extra meter of material which wants to hang to my knees. I guess we haven't solved all the problems...


Happy Bombing, err, Artillery Shelling!



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Don't forget; these days it's much easier to derive a meter by multiplying 1,650,763.73 times the wave-length of the orange-red light emitted by krypton-86.

Much more convieient than measuring the earth & doing all that messy averaging and math and stuff.


Or if you have a good flashlight you can just measure the distance light travels in a vacuum @ 0°K in 1/299,792,458 of a second.


Either method should work just as well.

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Based on the 8 meters that you got for difference at that location Holograph, using the NADCON program to convert back to NAD 27, the appropriate Datum for that station setting, I am curious if that will tighten up the unaccounted for 8 yards in the Datum shift.  Do you see a difference?

The 8 meter difference wasn't really the result of the datum shift, it was a result of my approximating the unknown map projection with the UTM projection, and guessing (erroneously, it turns out) that the grid Northing origin was at a geographic round number rather than a map grid round number as it appears to be. Of course, that's not proven, I'm still guessing, but the circumstantial evidence seems compelling.


The more precise calculations based on the actual Polyconic projection and Snyder's description of the grid origin brings the difference between the plaque's presumed coordinates and the GPS coordinates to 21 feet, which can be attributed to the typical uncertainty of a handheld GPS location.


As far as why they chose yards, Snyder was silent. He mentioned that the military grid (also known as the "U.S. Domestic Grid" or the U.S.C.G.S. "Grid System for Progressive Maps") was extended as the World Polyconic Grid, and was superceded by UTM in 1947. My guess would be that the 19th century US Army and/or Navy used yards for ranging, and that in turn influenced the 1918 system.


Anyway, it has been an interesting research project. I've always wondered what came before UTM.

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