evenfall

Hi Patty, I think I will pose this question to you and your experience in Radio Station Engineering, In the event of a ahem, Major impedance mismatch, like say.... A small plane crashing into the station tower, I imagine in a split second the usual impedance goes from it's usual 50 to a blitz between zero infinite amount of ohms in the form of a resistive load seen by the amp as first the amperage and then the voltage climbs with it until the grids in the tubes melt away, unless there is a fusible link or a breaker protecting the tubes... Or the power supply didn't crowbar first... Grid damage seems like voltage would spike on the cathode... And who knows if the protections can react to a tail chase condition on the grid in the tube If not, Eimac is going to make a lot of money... I imagine there could be arc over in a lot of places... That would be one wicked welder. A 4CX25000 doorstop... Afterwards... Of course Tower damage is a given, and KFI is an old station with back up facilities, so to get the main transmitter back after the tower is replaced, how much other damage would you suppose will need to be mitigated? Are the matching network and hardline toast as well? I suspect this is a very, very spendy station engineer's nightmare! I think it took out more than a geodetic landmark. Going back together do you think they will stick with similar specs or attempt new designs, different antenna types, requiring a complete start over, or is standard practice to put it back to as close to as was condition in an updated way, so as to see a new tower of similar height and dimensions that could be mistaken as the original tower? Can you shed any light or save any possible wisdom Patty? Rob

Bilbo, I climbed to the top of the Bunker Hill Monument in early April 2001 on a trip to Boston... Boy was THAT a long spiral like stairway... Half way up a hoard of teens entered the monument on a mad dash to the top... I thought I was in pretty good shape with all the time I spend in the field... So I kicked it in and, and... 3 of them beat me to the top... (at the top I felt like I was going to die as I looked out over the bay... Looking down through the hole in the floor that is the center of the monument for an easy way down... Ugh) I remember looking at those stations on the ground as well. It is amazing to consider what once happened on that 2 block stretch of Boston, as it is entirely surrounded by houses now. If you are near Bunker Hill, Or N. Boston for that matter, Go see the USS Constitution, Old Ironsides, It is just down the hill moored in the bay at the old ship yards and is a real treasure. Well worth a tour. Happy Holidays, Rob

DaveD, Since optical leveling is path dependent, do or rather did these junction points undergo a least squares adjustment so the numbers from each path will average? My experience has been that my field measurements to a similar place via different paths will not exactly match. I was wondering if these junctions are treated differently, By NGS, for geodetically published data than other stations, so as to have an accurate value no matter which established path leads to them? Thanks in advance, Rob

HWyatt, In reply to your thoughts: "Knowing what you all know, and it is formdable, and knowing how little some of the rest of us know, I wish there was an easy to find faq for BenchMark! and survey mark finding including the rule of not distrubing things." Well, please don't feel bad. We learned it the same way anything is learned, one day at a time and what we don't know still seems formidable to us as well. Technology has us all racing to keep up! I think, Looking back, many of us learned from the old school folks who were not quite as kind, patient or forthcoming with the ways of all the Ropes we had to learn... Under their watchful eyes they allowed us to make mistakes so they could show us our lessons. Call it a method of initiation or a rite of passage... :-D We like that you are interested. We are interested too! If you find the easy way, please share! All the Surveyors of the world will honor you! Happy Holidays! Rob

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. Wolves, 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, Rob

GeoSar, I wrote a post about this while back that goes into what you did find and why you can't log it here. Like Mike said, there is a whole lot of survey markers out there and only some are game pieces here at geocaching.com You can have a look at that post, Here. Good Luck! Rob

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. FM 3-25.26 MAP READING AND LAND NAVIGATION http://cartome.org/fm3-25.26-ch1-ch6.htm 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. Enjoy! Rob

Wolves shepherd, Here is a link that may have something... http://www.colorado.edu/geography/gcraft/n...s/coordsys.html 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! Rob

orome, I don't use the programs you refer to, so my suggestion may be just something that makes work for you. I have been just using the standard waypoint icon in my GPS, though I have emailed Garmin and asked them to consider developing a survey mark icon. In fact I need to email them again, as I have not seen the new icon , so maybe we should all email them and bug them for a survey marker Icon in droves so they will get it done. The Magellan users should do the same. When I use the waypoint icon, I can name the waypoint. I usually use the NGS PID for the station. AA1234, ZZ5678... This way it corresponds with the data on Geocaching or NGS, and fits well in the space provided by the GPS. Hopefully someone here knows the programs you are using well and can help you alter a setting, but that scheme works well for me. Rob

Hi Mike, No, I am not sure anyone gives out those awards to short wave listeners anymore. I just have a Grundig YB400 radio, It came with a long wire but I have never used it. I have it plugged into a set of amplified speakers with subwoofer in my shop, it sounds great, like a big stereo would without taking the space or expense, and I listen to it while I do maintenance on some of my surveying tools or other putzing. There are a number of tools that wear quickly from use in the field and you have to constantly keep after them. This time of year the machete needs a light oiling to guard against wet weather as well as their regular sharpening and cleaning. Tape measures need to be unwound and cleaned to help keep them serviceable from use in wet weather, The dirt and grit can really shorten the life of a tape measure, and surveying tapes are a bit spendy. I own my own and I find this is a daily deal this time of year. Hammer faces can get burrs on them, and you want to file them off so you don't inadvertently cut yourself. In some of the work I do, I occasionally use hand levels to determine an elevation quickly and it is a good idea to keep these calibrated and clean. This time of year they are subject to moisture so that is an issue, I also use nimh batteries in a lot of my tools and instruments and various equipment so I do all the recharging and rotating of the batteries... Just like anything else I suppose, you have to take care of the tools that take care of you. So sometimes while I am at it I have used the seek function to see what the AM band has to offer. Most of the time I have not noticed AM propagation to come in well from too far east. The lions share of what seems to come in well at night here comes in from south and southwest. AM is unpredictable at night and you never know what you might find. Rob

Gold fishy, Here is how to approach these. This is a landmark station, the surveyors usually do not place a brass disc on them, but if they do so, the information will be made note of in the narrative on the Datasheet. Usually these are an intersected point, meaning they trained the survey instrument, usually known as a theodolite back in the day, at a place on a landmark and measured the angles the instrument was pointed in both the horizontal and vertical plane, then they did the trigonometry involved in locating the location of that point based on the information from the places they were when they looked at it from the ground. Once the location is triangulated they could go to a new place on the ground which has not been yet established to help establish it. A sort of leap frogging around by triangulation, if you will, based on the fact that all survey in that day was optically, line of site based. Mathematically you need to know two places to determine the location of a third. Landmarks used as intersected points were up high, and allowed the geodetic surveyor tie in in places that would have otherwise require very tall towers erected to see from place to place. If you could see a tall place from many places on the ground nearby, you could speed the process of locating the where of all the places you are surveying are. Keeping in mind that they are trying to establish the latitude and longitude of these locations. These stations were usually considered third order survey accuracy, some were at one time considered of second order value but the decision was made at some point to downgrade landmarks to third order. It was an ease of use situation, it located things on the ground to third order accuracy, so as to establish a survey network and precisely locate areas, and do so more cheaply than the longer and more involved surveys with more triangulation's per higher order, and tall towers to accommodate the need for higher accuracy. So let's look at your church steeple; 'DESCRIBED BY COAST AND GEODETIC SURVEY 1944 (FN) They originally did this in 1944, the person who wrote the description, the chief of the survey party's initials are FN MF1312'STATION IS LOCATED IN THE NE ANGLE OF THE INTERSECTION OF MF1312'SOUTH ELLSWORTH STREET AND EAST BENTON AVENUE IN THE CITY MF1312'OF NAPERVILLE. Go to this city and stand in this intersection. Look northeast. this should be a church named NAPERVILLE SS PETER PAUL CH, if not, you may not have the original church. Is it still belonging to the same congregation? is it still a church? THE CHURCH AND SPIRE ARE OF RED BRICK CONSTRUCTION. Are they? Confirm this. If not, this may not be your church. Go inside and see if the Church leaders know about the buildings history. MF1312'THE SPIRE HAS A GRAY SLATE ROOF WITH OPEN BELFRY AND A CLOCK FACE MF1312'ON FOUR SIDES. The roof may have been replaced since then but are the four clocks still there? If not, Go in and ask what is going on. THE OVERALL HEIGHT IS 215 FEET A story of a building is oh about 10-12 feet high so does this look to be about 20 stories high? AND THE MF1312'CONSTRUCTION WAS COMPLETED IN 1925. Can the owners of the church confirm the buildings age for you or has the visual already confirmed this without asking? MF1312' MF1312'THE BASE OF A CROSS LOCATED AT THE PEAK OF THE SPIRE WAS MF1312'THE POINT SIGHTED. This is the spot that the surveyors trained their instrument on when they used this spire for triangulating other places, and this place as well. There was no mention in the description of a disc mounted on the spire, and the Datasheet states: MF1312_MARKER: 90 = CHURCH SPIRE so there isn't a station disc. Does this spire still have a cross? Some do not, if not, this may not be the original spire. Remember, the original one did. You can also use this information: NAD 83(1997)- 41 46 30.59710(N) 088 08 41.63694(W) ADJUSTED Take that latitude and longitude that the surveyors in 1944 determined, load that in your GPS using the settings for degrees minutes and seconds mode, NAD 83 Datum, ( and yes the correct datum does very much matter ) Make that a waypoint then run a "go to" to that waypoint on the GPS to confirm that the GPS points at the spire. The accuracy on your GPS is not as accurate as third order triangulation is so your GPS should point right at it for the most part. The GPS is good for 5-10 feet accuracy and third order Triangulation is good to less than six inches accuracy. If it does not point at the station, er ah, spire, as you circle the building, pointing at the spire exactly, this may not be the original spire or spire location. I have found remodeled churches with relocated spires, an that is a not found. It has to be the original item in the correct location. In many many cases, there is no need to big deal this as you will see at a glance whether you have or do not have what you are looking for, even if you are in the right place. That's right! It isn't you, it is the landmark! :-) The big point is that on the geodetic survey marker, the find is not as much the object itself as it is the accuracy attached to the object in ensemble. You will read about this in the attached letter from Burt Smith of NGS just above this post in his correspondence with Mark Johannes, a surveyor and geocacher. The station accuracy is important. If the station is disrupted and moves, all the calculations are off. On Landmarks, this is not something the NGS can control so they generally just consider the station lost or destroyed but on their own monumentations, they can generally re-survey and correct the data if need be, happy that the station is still in the ground. Ok, Enough on the NGS aspect. Here is the geocaching lowdown. There is no rule that requires you show proof for the benchmark find, whereas a cache log signing is really necessary in geocaches or the cache owner can remove your credit for the find. However most people feel that if they have a digital cam, Why not prove it, so this Photo for proof has become accepted practice. The Geocaching scoring schema seems to only give credit for the benchmark find. It is a shame that they give no credit for the Not Found as they are equally hard to, ahem, not find, Mostly. :-) Most folks seem to go with the all statistics route. They keep track of it all and there are many ways of going about it. The three benchmark hunters I have learned the most from, in how they go about this keeping of unofficial score, and it seems like a good fair, and accurate scheme to use for this are 2oldfarts, Black Dog Trackers, and Seventhings. All three of these people, and it is a Husband and Wife team on the 2oldfarts part, have all written some great posts about how they work the bench mark scoring they follow, so I will leave it to them to direct you to the posts they have made in the past so you can brush up on that if you like. The benchmark finds are a separate total from the cache finds. Several of us who are regulars here in the Benchmark Hunting are proud owners of the 0 caches found total. Seventhings is the over 1000 benchmarks 0 caches found leader. There are many who are doing well in both arenas as well. Good Luck and Happy Hunting Holidays! Rob

Klemmer & TeddyBearMama, Hey thanks for the heads up on the frequency, and I corrected the hertz bit. Maybe a little off topic but please forgive, I had to go look at my shortwave radio as I thought I had a preset for KFI... I had 810 khz... I thought it was KFI, but it was actually KGO. I used to listen to it a few years back in the late night when it would come in here in Seattle... My Bad... You never know what you may hear on any given night on AM, It all comes and goes when you are trying to DX AM stations... Rob

Aww C'mon Artman, Overall I would say that the article was pretty good coming from a journalist... No offense to journalists either. This is a tough subject to tackle even for a surveyor. I would say John Kelly did pretty well. He even quoted DaveD... That is pretty good I'd say. And as for the part about stainless steel rebar being driven as far as 200 feet in the ground, that is true, and plausable. Today's geodetic survey marker is a brass disc attached to sections of rebar which are driven into the ground until they reach what is called refusal. Refusal is when the bar stops going into the ground. If you attach lengths of these rebar together and keep driving until it stops going into the ground any further, which means how ever far that is... 200 feet is a long way but it isn't impossible. These are a different kind of station than the old concrete monuments that many are used to seeing, But it is a very very stable station by comparison. There are a lot of factors that can cause the stability that we would like to have in survey marks to be found lacking... One of the ways these rods driven to refusal do is to go well below the surface so at to avoid the factors that affect the surface. At the surface, these survey markers sort of borrow from an old trick that the pile driver crews have used for years. A sleeve is placed over the rod which is greased so that surface movement from things such as frost heave and such will not affect the stability of the station. Unfortunately the old concrete markers could be pumped and heaved right out of stability by frost. This design helps solve that. The things we have learned from more stability and higher accuracy as well as GPS and real time monitoring is that the earth moves a lot more than we thought. And it moves more in the western US than the east. Earthquakes, Tectonic plate movement, other forms of geological instability and so on. Welcome to the Pacific Rim. The accuracy tells us a lot! I imagine John Kelly knows his readers are adapted to about a 3 minute read per story. Overall he covered it pretty well. Really Artman, Think about it... Some people do think it is geeky and pretty boring, ( I have been so counseled, yes I have, ) I'd say the three minute taste was about right! :-) Happy Holidays! Rob P.S. For more boring geeky stuff about survey markers, yes, I did say about survey markers click Here. Of course your IP will be logged and soon we will expose your interests to the world! Bwahahaha, Bwhahahahahahaha!!!!

Even if an antenna is reconstructed at this location, the station is destroyed. It has to qualify as the original object. Your submission of news paper articles and news photos should suffice. Welcome to the changing world. Nothing is forever. The intersected point was likely the top, or the light on the top. Surprisingly, and of note, KFI is an AM radio station. AM radio station antennas are peculiar little buggers as many Ham Operators will attest. FM, TV and other types of towers are tall and just simply act as a platform to bolt the antenna to. No particular requirements to the tower design beyond being tall enough to convey the signal appropriately, and strong enough to bear the load in high wind. AM Radio towers are the antenna itself and a very involved, precise design which works only for the designed frequency. Radio Frequency at 850 Khz is a component of how long or in this case tall, that the antenna has to be. However at these very low frequencies the antenna even at a quarter wave length of the frequency wavelength is often impossibly tall for an antenna. What is done to compensate for this is the use of a custom high output power handling antenna matching network, built to specifically work to a specific length of antenna. What this does is allow you to physically shorten the length or height of the antenna, while electrically leaving the tuning in the transmitter with an antenna which seems to it to be the correct length for the tuning, hence the meaning "Match". In addition, there is likely a lot of enhancements done to the ground around that antenna so as to improve it's performance. It is called a ground plane. I am not sure what kind of total antenna system KFI uses but this is likely a quarter wave ground plane system and may be part of what is called a phased array. it is a common type of antenna for use at these radio frequencies. Going forth I would watch to see if a new antenna of similar height and construction is erected in this same location. The reasons why are many, and it is a lot of work, but part of it is that they are FCC licensed, and exhaustively tested for the location, they have a lot of very expensive equipment made to work only as a designed system at this location, New locations are near impossible for AM Stations to find as Hilltops are not where AM antennas work well, They actually work best in low lying areas as they bounce signals off the ionosphere during the day at that frequency, more so than working line of sight. They also often have the capability of making their signals directional at night with the use of a phased array, a second antenna used at the same time, to avoid interfering with other AM stations on the same frequency at night. This combination of ionospheric reflective conditions and antenna directionality are why we can hear distant AM radio stations at night. AM stations are not usually seen as good neighbors to nearby residences as you may hear their station on every appliance in your house if you have grounding problems etc... Being left where they are already established is where they seem to work best. Most all the bugs are worked out. I do wonder what it must have been like in the transmitter shack when the tubes running 50-100,000 watts to that antenna experienced an impedance mismatch by aircraft. Z-z-z-z-z ZAP! I bet it cooked a lot of french fries! I would not be surprised at all if a new and very similar antenna goes up at that site. It won't be the original, and no, it will not be the one in the NGS Database. Asking NGS to have it destroyed is a good call. Edited to Kilomegahertzesessszz... :-) Rob

Muirwoody, What happens to muggled benchmarks is that they are flown under high, well, relatively high security, depending on who you are asking these days, to Guantanimo Bay, Cuba where they are driven in un-armored humvees to otherwise undisclosed locations for intelligence gathering reasons and other um... Procedures... which result in ahhhh... Well, We have never heard from any of them again! Mostly... But you never heard that from me. Actually, There is a procedure for doing what you ask, and not a silly question at all. It is an elective thing you could volunteer to do but it does take someone who has seen this Survey Marker with their own eyes. Just because some of these survey markers are old, they are not forgotten. The Procedures are outlined pretty well throughout this forum, however the most specific information is on the Pinned Topic at the top of this forum listing, which says ask Questions to NGS... In Executive Summary style, as opposed to reading tons of forum thread, Go look at the Bench Mark Station with your own eyes and remember what you see. Then if you like, point your web browser at this page: http://www.ngs.noaa.gov/FORMS_PROCESSING-c...y_entry_www.prl From the top of this form you will want to ENTER PID: KA0269, Click the Not recovered, not found Button, Click the agency code button for "Other" and then further down the paragraph you will want to type in the code: GEOCAC which is the agency code for geocachers, Enter your initials if you like, or not if you would rather not, Enter the date you looked at or last visited the missing Station, which is the date of recovery, enter your name and email address, which will remain private and you will not be bothered unless there are further questions which rarely ever happens, Then the bottom box on the form allows you to enter a narrative summary of your station recovery. In this case you can leave that blank if you like, but you could submit the following succinct recovery. "STATION APPEARS TO HAVE BEEN VANDALIZED, AS THE STATION DISC HAS BEEN REMOVED FROM ITS MOUNTING. THIS STATION IS LOST." You could even copy and paste what I have written between the quotes if you like. If you want to write your own recovery, that is fine also, and there are a lot of clues as to how to properly do this found in other station recoveries. It is a form of technical writing all it's own. And that is it. Click on the Submit button and you are done. You will have improved the data for that station, and all the users of the NGS Database which is the National Spatial Reference System. All Surveyors and Agencies which use the data will know that the station has been removed from it's setting for the future. The old data will remain in the database forever, and so will your recovery. Of note, the reason I am advising you to file this as a not found as opposed to a poor/disturbed, if you choose to do so is considered debatable by some, but in this case, here is my surveyor's perspective. This station is a Bench Mark. Which is to say it is a station for marking an accurately determined elevation. The method for measuring the elevation is such that an instrument is physically set upon the top of the disc to measure the elevation at the disc itself. This is accurate in the case of this particular station to the Hundredth of a foot, at 732.87 Ft. (roughly 782 feet 10 and 5/16ths inches) NAVD 88 Datum. (for reference, there are 8.3 hundredths of a foot to one inch.) Some stations have accuracy higher than this and this is very important to the overall scheme of geodesy. The thickness of the station disc is missing now and will cause the station to have a different elevation. This is not good enough for Geodetic control because like I said, you have to physically rest upon this station marker in order to measure it directly and accurately on site. In the case of horizontal control survey, which you may encounter as a "Triangulation Station", I would consider a station with damage similar to this as poor/disturbed because that type of survey marker is used to horizontally position. We can determine what kinds of survey data are ascribed to any particular marker by reading it's datasheet. The Datasheet is the best source for information and there can be stations with more than one kind of data ascribed to them. The position can be done optically, as in centered over the station marker, rather than using it's structure as part of the vital measurement for the data, as in being in physical contact with it as a means of accurately measuring it's value. This is not to say that surveyors do not come in physical contact with horizontal survey markers when we use them, it means that there are methods of performing this type of survey without physically contacting the marker. Even with the station disc missing, the triangulation station could still be used for horizontal work. We do not need physical contact with the station to accomplish all types of horizontal measurement at high accuracy. This particular station which you have found is strictly for vertical control and so due to the methods involved for using it, it is destroyed. It has only relative accuracy now and will no longer meet geodetic criteria for vertical control. In the final analysis, the reason we can know any position or elevation with this degree of accuracy is because we do adhere to the methods that will perpetuate this kind of accuracy. If we begin to get sloppy, the sloppiness will affect the entire system and we cannot continue to be sure of anything. In a lot of applications, more than we may think, knowing to the hundredth of a foot is important. (for instance roads are often built to have crowns with a 2% grade. That equals 2 hundredths of a foot vertical change over 1 foot of horizontal distance. This is a measurable design to a pre-determined elevation on any straight stretch of most any road, provided we are not located somewhere inside a horizontal curve. (however we need to know those curve elevations too)) Does one station become the fly in the ointment? Simply Put, No, but this particular one was the keeper of elevation at that location, and error is inherent in any measuring system. It grows unless we work constantly to help keep it accurate. If you like, this section of the forum is filled with a lot of informative stories about these stations and how to hunt them, and it goes back well beyond what is displayed on the main page. You don't have to know what a surveyor knows in order to have fun or become a benchmark person, and there are plenty of people here in this forum who like helping to answer questions. Many of the most accomplished hunters are not surveyors. I would highly encourage anyone to read up on this. To be honest, Benchmark hunting is a very pure treasure hunt, all you should really need is the description to find these stations, as that is all we had before there was GPS. Some times you win and sometimes you lose, and you don't have to take or leave anything as they are more about the hunt than the treasure, and you may learn some local history along the way, but either way they can all be some very challenging fun! It can take getting the hang of it, but that is part of the fun. Happy Holidays! Rob

I want to add to what Jerry said towards the end of his excellent post, one small addendum. I sensed that you asked if there were benchmarks on all section corners. The answer is no, there isn't, although it does happen in some cases. To be most clear here, just for the essence of survey nomenclature, there are many kinds of survey marker. If you are playing Benchmark hunting here at geocaching, you are using the survey markers which are the National Spatial Reference System maintained by the National Geodetic Survey. These stations are used for locating horizontal positions and vertical elevations, monumented for the study of and working references for Geodesy. In geodetic survey terminology, the word benchmark is actually meant as two words; Bench Mark, and it means a location of Known Elevation. Only Elevation. Every other kind of survey marker which has no vertical data ascribed to it is not a Bench Mark. Geodetic Survey Markers are generally not concerned with property line survey. Sometimes the two kinds of survey meet, and it should be noted that Property Line Survey though different, is interested in the study of geodesy and how it affects PLSS. The Ideas of one are applied to the other in the thinking of the Survey industry, after all, these square miles have to fit the actual shape of the earth somehow. As Jerry mentioned, when you are working with the Township and range system then that is PLSS, Property Line Survey System Maintained by the BLM. The stations set in this arena were not often as stable as the station that the geodetic surveyors set. In fact many are quite fragile. Jerry mentioned in his post that some survey markers in the PLSS system can be mounds or depressions... things you may not realize are survey markers... I just wanted to draw attention to the fact that when you are on BLM land out in the middle of nearly no where looking for a survey marker, for a section corner as a for instance, the very rock pile that you dug up looking for a man made station under it may very well have been the station itself. That is to say, the pile of rocks was a man made survey station just as you found them. The old surveyors used what they had, they used the things of that day that they hoped would be lasting, and sometimes a pile of rocks to make a mound was what they used. Sometimes it is good to know what to dig for or not to dig at all. So just as a side note, having the BLM Data, if you can obtain it will be good to have before you search, because that fragile pile of rocks is sometimes what you are looking for. You just never know without the data in your hand. Print out a copy of that diagram which Mike was nice enough to include here. It will give you a good idea of the distances involved in PLSS, even though the realities do not always perfectly fit the diagram. Just remember that most of those section corners have nothing to do with the game here at geocaching. You may find some will, but for the most part the stations for benchmark hunting are different all together, and they are the only stations that can be logged for credit here on geocaching.com. Happy Holidays! Rob

Mike, Zygote is right, as a Surveyor, we cannot second guess. Generally the USGS will set a station with the markings on it which are a dead give away. That will do a good portion of the figuring for us. This is a pipe cap with a hand stamping. Hard telling what it says because it seems to have a letter which to me, based on the photo, is difficult to be sure of. No agency with what I can read comes to mind, but maybe it is not clicking in my mind... Interestingly, I have seen the USGS have a location on their maps for which they have positioning and leveling but they monumented no station. I have heard lore about how on maps a certain method is used by the USGS to portray such a station but I have busted that myth too. As for the pipe cap, well in my area, USE, and USACE were common users of pipe caps for survey markers, but I have never come across the USGS use of one. There is a first for everything and anything, and it certainly is not uncommon to adopt someone else's monumentation for use by another if it seems permanent enough for the purpose. I would contact the USGS and see if they have any data for this station coordinates and elevation and see if the data contains a monument type. If it is a pipe cap then you have found your station. Without knowing the station type, and more data about this station as Zygote said, you are kind of made to wonder. What would be most important to us at this point would be to know what type of station marker was used at this location. In the surveyor's world, we need a higher level of certainty than that, but you may be happy with what you found. Merry Christmas Mike, Rob

Bill, You sound like you are on the right track, but I have a few thoughts... You are an engineer so I assume you are familiar with the basis for differential leveling. As you know, leveling isn't about turning angles, so in effect, a "level line" of Bench Marks can follow a meandering line even go around corners and skip over a block or two here and there. They basically just put them in places that seemed stable and would provide longevity. They were never really triangulated so it is a best guess and a good hard reading of the description to find them. For leveling, the vertical circle has to be right. At the stadia, you have to be able to turn 360 degrees bubble level. If this varies at all you, cannot perform leveling. Hopefully you will be able to repair this so as to be sure that at zero, you are bubble level at the stadia. After being bent, it may not be level at zero, nor can you count on it being the same twice. With precision instruments, damage like that almost never comes back and replacement parts do not exist. You could rent a rotating construction laser, used for leveling, and set yourself up a permanent calibrating range in your yard for the transit, but renting a laser even for one day is not always cheap. The other trick to this process is getting a custom stand set up so you have the transit stadia match the exact height of the laser eye. The H.I has to be exactly the same. All this will do is calibrate you for level however. You may never know where you are on a bent vernier if you get off. If all you ever plan to do with this transit is leveling which is all it may every be able to do based on the damages, you could lock it level, and calibrate it so that it optically will shoot your leveled range, and going forth the vertical and horizontal circles will not be all that important. As you are aware, this leveling will take two people to perform, and you will likely need to have a leveling rod which reads in tenths of a foot or meters, if you would prefer not to convert in the field. I would recommend a plastic telescopic leveling rod over the metal or wooden ones. The safety factor from electrocution by overhead power lines is a factor. Leveling is a leap frogging process, one that will have you moving the transit after nearly every shot and you will have to mark the location of the last shot you took and keep it's elevation so you can re shoot the Back Sight from that for each move. For those who may be interested in some of the details I am skipping over here, the gist of it is Here. As for the field tests to check for eccentric wear, you would almost have to set up a tripod and establish a series of hubs around it. Shoot them with a calibrated instrument and someone steady with a prism pole. Record your findings after double checking, and be sure to vary, and record the height of the prism pole at each shot. Then take the known good instrument off the tripod without disturbing the tripod and mount up your transit. Turn your angles again, both vertical and horizontal and compare the data. It will be important as both kinds of angles will need measured at once. For triangulation, you will need to make use of the vertical and horizontal circles. Of course, Trigonometry will require you to shoot an azimuth to establish the first angles. You will need to establish a base line to triangulate from, so as to have two known points to establish the third. There will be a lot of trigonometry involved. You are going to be line of sight dependent. and this is a limiting factor, Literally. Geodetic Triangulation was based long lines of sight, and often required tall towers, then to add, the optical power of the theodolite was a big factor in how far you could see. Further complicating this is that the transit also does not have the accuracy on the verniers as would a theodolite let alone the optical power. The best you may be able to achieve is an open, or closed traverse between stations. Lines of sight are the hardest thing, then doing all the trig... Today's professional instruments do a lot for us but it still is a stretch sometimes. We have to use a lot of tricks. At the consumer grade level, GPSr will get you within 5-10 feet of any triangulation. With leveling being scaled you are still having to live with the narrative description and a tape measure for location. For quick and easy short range leveling, you may get by with a Hand level and a lufkin folding ruler. They make those in engineering scale tenths and hundredths, as well as metric too. Beyond this, a call to a local surveyor may steer you towards a shop who may be able to repair it enough for leveling, especially if the repairer is an old timer... Some of them were miracle workers. I fear the worst may have befallen this instrument Bill, but I will hope for the best. Good luck! Rob

robtnort, In the case of 508/24, it is likely to mean the distance from each end of the line. 508 miles to one end, and 24 from the other at that particular location, depending on the direction you are facing. 1/100th of a mile is 52.8 feet. Not a real useful reference for much, though we do commonly use the tenth of a mile, 528 ft... On the 1/1000 scale, 5.28 ft is an attractive height for some people, but we don't generally reference them like that, we are just happy they come in that size! Or, would you believe that it could also mean 21 and 17/24ths? Well, Roughly... :-) Paul, Tack Guard... C'mon... Add the definition to your Glossary... It is what you wipe your feet on to avoid tacky goo on the shoe before walking into momma's house after bench mark huntin'... ((I thought you knew!) Shhh! I won't tell the others...) (Edited to repair decimal points placed prior to being fully coffee'd up!) Rob

Bilbo, One of the things I find interesting is that you have likely asked a question that has quite frankly never been tested, and even if tested would likely only apply most specifically to your make and model of detector. I would like to propose a test. I would take an aluminum pop can, a steel soup can, a chunk of steel say of railroad spike size, and perhaps another a little larger, and if you like, add some other interesting items, including say change or other small items you feel would be commonly found when using a detector. Begin this test in your driveway. Just lay them out and see what the distance above the items is when you begin to detect them. What is the signal strength at say 18 inches, a foot, 6 inches, 3 inches, etc. Use the test of nothing as a reference as a start. This will allow you to calibrate for false positives, and take note of the settings you are using. Will some settings work better than others? Be sure to define your frame of reference. Take a notebook and right down your results. Then maybe you go find the snow, and see how the objects test similarly in the snow, on the surface of the ground. You may already know of a Benchmark you have already found and know it to be on the surface of the ground. Go see if you can find it in the snow. Perhaps in addition to the snow, in a flower bed or in the back yard you bury a series of objects of the various types I outlined, and bury one of each at specific depths so that when you have snow, you have your No-snow baseline tests on file in your notebook, and then when you have snow you test and note the snow depth, as it will be a factor. Say you have 6 inches of snow. How do the readings compare with 6 inches of air space. If there is then you may have a density factor based on the thickness, wetness and packed/unpacked density of the snow, and you may even test it based on the age of snow, had the snow hardened? Iced over on top? Been rained on? I know this seems like a lot of doing to do, but in reality your results will really only answer most peoples metal detector questions in a general way. But you will know what your detector is capable of, very specifically in many many different situations. You may learn that there are variables that allow you to tweek your settings and still have a high level of confidence, and you will find that the advice from the others who posted to this thread will also apply. A fully charged battery is an important factor in consisting testing, and a cold battery will not give you the results a warm one will. Good luck and good hunting, I will be in here where it is warm! :-) Rob

Hi Mom, One other thing worth noting here is this, just based on my experience, and other peoples milage may vary. The USGS Quad Map Link which Kewaneh recommended is a very good steer as to where to get these maps, and the why of this is very important. Many retail stores, but not all, may bump the price up on these maps, and so that adds cost to you. Once you arrive at their store you may also find that they may not carry the entire State you live in, or areas you want maps for, and there is also the risk of them being out of stock. Beyond all that, I have found that generally, the sales help really doesn't know a lot about those maps aside from ringing up the sale. Been there, Done that. At $6-8 per map you can see how 10 to 15 of these will quickly devour a $100.00, if not the better part of it. Especially when you figure in Taxes and fuel and lunch and all the time you spend driving around looking... Not to mention you will not have the whole state. One workaround you may enjoy is owning the National Geographic USGS Software for the entire state of Tennessee, this way you can print out any map you want and you can Zoom way in or out, while never having to worry about whether a particular map is available. Another aspect of the software experience you may enjoy is that many GPS units will interface with this software and so you can either set up waypoints on the software and send them to your GPS, or you can up load where you made waypoints with your GPS and see them on your map. Plus you can print them with your added info and modifications as well. Now if you like, you could go pick that software up at the REI store in Brentwood TN which is not to far from you but, you could save $20.00 by buying it from them online instead as it is on sale online right now. I'll let you do the choosing, but hey, 20 bucks is 20 bucks! Those are some other options. Good Luck and Merry Christmas! Rob

Hi Geo, I am not sure I understand your connections here. This company, Sybase INC. does not seem to have anything with the NGS Database being down. The John Chen of Sybase may or may not necessarily be the same John Chen of Geoteaming, and Geoteaming is not Geocaching or Groundspeak. I already sorted that out up the thread a bit. However, Team building is an important part of any organization, in fact, TV shows like Monster House and Monster Garage on discovery illustrate this each week. Teamwork is a very big deal in life. Geocaching in groups can be used to help build teamwork skills, and there have been events to do exactly that. It is not uncommon for corporate executives to sit on the boards of different companies while they are CEO of others. So, since this is not the topic regarding the status of the NGS database, nor about benchmark hunting in general, maybe asking Jeremy directly would be a better bet. Perhaps it would be a better topic for a different forum? Thanks Geo, Rob

Hi Ted, I did a quick Google Search of the Chile Line. You can access that narrowed search of about 90 links Here; posted as such because it does not seem to want to hyperlink correctly in the usual way. http://www.google.com/search?hl=en&lr=&saf...ine&btnG=Search within results This site, linked Here, has listed some early maps of Colorado Railroads which may be of use for hunting down this old right of way. If JB's information is telling, then there may be some Bench Marks to hunt up the old ROW, and since they are likely Scaled Horizontally, it may lend clues as to where they are. It is likely these maps have no datum, so a compass and a USGS Quad for the area to compare may help a lot. I used this method to find a lot of old Northwest Logging Railroad Grades back in the 80's Prior to GPS and it worked well. I know you don't have heavy tree canopy to deal with so the GPS may be ok, yet I like a Compass better when I am standing still and dealing with a map. Sometimes you can see the old grade as it slices through a topo. Fun Stuff! Another fun aspect is that railroads were known for casting off, and abandoning artifacts in place, old trestle pilings, and if you find really old railroad ties, many had a Date Nail in them that indicated when the tie was made or placed. Finding them is kinda cool, I have found a few on old abandoned sections of Great Northern and Northern Pacific ROW in these parts, but the practice is long since abandoned and many hunter gatherers have already been there. If you should find any, they will take tools to remove if someone hasn't beat you to it. That article explains the best methods for removing them in tact, so it could be a cool treasure hunt on the side. Another resource which may or may not pan out is a discussion forum which seems to discuss Narrow Gauge railroading, and since we are looking for Survey along an abandoned Narrow Gauge line, they may be able to shed some light on further resources, so maybe give This Link a look. Maybe JB will see all this and reveal more clues as well. Rob

And today's blow-by-blow updates! 12/07/04 9:15am - SUN engineer has not arrived yet. Unix Sys administrator says the engineer is probably still waiting for delivery of the disk. 9:50am - SUN engineer is on DC beltway in heavy traffic. 10:50am - Disk is being replaced. Database is shutdown. Hope to back in 1 hour. 12:01pm - Still working on it. 12:40pm - Disk replaced. Working on database recovery. 1:40pm - Recovery Complete. You may resume updates.

Hi Mike, You mentioned, I should mention that the coords. are WGS84 if that matters. In fact, it does matter, and a lot more than you might think, especially if you want to position yourself accurately, and utilize the accuracy that these survey markers represent. First let's define the Datum. A datum, basically put, is a reference system for measuring, which is based on a specific set of measurements. How this matters is this; The survey markers used by geocaching are owned and placed by National Geodetic Survey. They created and maintain the Data for these markers and these markers represent the NSRS, the National Spatial Reference System. The NSRS is the basis, in part, for the NAD 83 Datum. They were also the basis, in part, for the NAD 27 Datum. The differences between the two Datum is the mathematics and methodology behind the observations and calculations. So, You see, these markers are the physical items that represent NAD 83 in the world. Not to confuse this, yet it is very important to note, If the survey marker was not included in the NSRS, then NGS did not adjust, or calculate its value for NAD 83, or in the case of the Vertical Elevation NAVD 88, which superseded NGVD 29. In the case of a lot of the old USGS Bench Marks, which are printed on USGS Maps, If we do not find them in the NSRS, which is the NGS Database, then if they were monumented prior to 1986, (the year NAD 83 was rolled out) it is likely the working Datum for that marker is NAD 27, However, if you are using an updated USGS Mapping product, and the Datum on that map is NAD 83, then the location of the BM on the map has been at the very least, Cartographically corrected. You would need to write to the USGS for more information than that. Now in the case of the VIGO stations, the DNR could have submitted their Data to the NGS for inclusion in the NSRS if they had chose to. If the data met the standards, the NGS could have included it. All 50 states have an interest in survey at the Geodesy level and will submit many of their newly monumented stations to the NGS for inclusion in the NSRS. elcamano could probably share a few stories about that in his career at Michigan DOT. I wrote up definitions for the 3 major horizontal Datum in use in the US today. At the highest levels of accuracy they do not interchange. To Quote Kenewah's signature; "New tools are no replacement for old rules". For the most part, it really is a good idea to observe the Datum being used by the system or map, the reason for this is because each Datum is derived in it's own unique way, and there can be quite a shift between them if you try to use them interchangeably. NAD 27's Datum shift can be large and widely variable based on the location it is taken, when compared to NAD 83 and WGS 84. Between WGS 84 and NAD 83 the Shift is also variable but within one (1) meter taken both vertically and horizontally. Ok, the definitions: NAD 27 NAD 27 stands for North American Datum 1927. Originally developed by the agency now known as the National Geodetic Survey, an agency overseen by the U.S. Department of Commerce. Based horizonally on a single fundamental point known as Meade's Ranch, located in Kansas, it was primarily derived through theoretical, mathematical models of the earth's shape and highly precise land surveying of the United States. The Vertical Component for use with NAD 27 was known as NGVD 29, (The National Geodetic Vertical Datum of 1929) since superseded, a Datum fixed to a series of Tidal references in the United States and Canada which was for use when precisely measuring vertical elevations.NAD 27 was the precursor to the NAD 83 Datum which is Satellite based and still being perfected through improved observed mathematical models and real time national monitoring to this day. For the highest accuracy, Datums should NOT be used interchangeably. Always remember to set your GPS to match the Datum that the map you are using is based on, Whether that is NAD 27, NAD 83, or WGS 84. NAD 83 NAD 83 stands for North American Datum 1983. Developed by the National Geodetic Survey, an agency overseen by the U.S. Department of Commerce. This is an earth centered, 3 dimensional Datum, but is highly accurized horizontally, and is primarily for use in the United States and North America. It is derived from highly accurate, continually improved mathematical models of the earth, highly precise land surveying, sattelite observations, and a large network of real time national ground station monitoring to this day. The Vertical Component for use with NAD 83 is known as NAVD 88, (The North American Vertical Datum of 1988) a Datum which is fixed to one Bench Mark located in Quebec Canada, for use when precisely measuring vertical elevations. Depending on the order of accuracy, the accuracy of these Datum generally ranges from 1 millimeter to 5 centimeters. For the highest accuracy, Datums should NOT be used interchangeably. Always remember to set your GPS to match the Datum that the map you are using is based on, Whether that is NAD 27, NAD 83, or WGS 84. WGS 84 WGS 84 is a Department of Defense (DOD) owned Datum, developed primarily for worldwide U.S. Military use, yet has many world wide users. It's precursors were WGS 72 and WGS 66. It is an earth centered 3 dimensional Datum which handles Horizontal and Vertical all-at-once, is Satellite based and is the basic convention for use with GPS. Very little physical infrastructure is included, yet it is still being perfected and adapted for accurization through the National Geospatial-Intelligence Agency. It is further improved, and observed with third party mathematical models, and localized, realtime worldwide monitoring by various U.S. agencies and world wide countries to this day. It is derived and monitored in a similar manner to that of NAD 83, but uses different Mathematical models and earth station monitoring. Accuracy is high, however, it varies based on where in the world you are. It is Important to note however, that though NAD 83 and WGS 84 are both based from the same Satellite Constellation, they used different mathematical models and are NOT the same Datum. For the highest accuracy, they should NOT be used interchangeably. Always remember to set your GPS to match the Datum that the map you are using is based on, Whether that is NAD 27, NAD 83, or WGS 84. The bottom line is that the WGS 84 Datum has little to do with these particular survey markers at all. The only ones I know of that would, would have been placed by the USAF's geodetic Squadron, which was taken over by the Defense Mapping Agency, now doing business as, yet skipping over a name change or two, the National Geospatial-Intelligence Agency or NGA, they are overseen by the DOD. The Survey Markers they set are pretty rare, and the data for them is not available. This is only part of the big picture, and it is a pretty big picture. I hope that helps explain it. Rob