Gnikhog

According to the link provided by DaveD, the webinar is being run on Wednesday, Dec 9th. The topic holds an interest for me so I plan to be a participant.

MY3792 was first documented in the datasheet with 7 RMs and is the reset of MY3791 . Circumstances grew the number of RMs to 13. I'm sure Papa-Bear-NYC is probably the most up to date in regards to the history of these stations and their role in the triangulation of Masachusetts and the Eastern Oblique Arc.

I've used a Katadyn Pocket filter for a number of years and have been very satisfied. Keep in mind that all filters are not the same. There are mulitple tradeoffs including filtered particle size, initial cost, replacement filter cost, weight, in-field serviceability, stroke volume, etc. Do your homework, then make your purchase.

In my area, I have often found the stamping to be found clockwise from the work "MARK" stamped on the rim. This would be in about the 12 to 1 o'clock position in your picture. Here is an example:

As far as the disk is concerned, I would call it POOR as it is certainly not in GOOD condition. You could also query Deb Brown to see if it should be considered DESTROYED. On a slightly different subject, I cannot verify that this photo is actually KW1913 because I cannot verify that the disk is stamped "W 153 1942".

My list: NGS datasheet GPSr compass camera probe (a long shaft philips head screwdriver) screwdriver (straight blade) channel-lock pliers (for removing stubborn caps) 100 ft tape metal detector corn starch water (for cleaning disks if necessary) whisk broom plastic trowel small garden hand clippers 2 ft shovel orange flagging paper towels (to dry disks if necessary) 3 ft rope w/ mini D-rings (for use with 100 ft tape in special circumstances) cell phone or ham radio work gloves (poison ivy protection) first-aid kit pencils (not pens) extra batteries topographical map (for extended hikes or bushwhacking) All of this fits in my backpack except for the metal detector which can be strapped to the outside. One item I occasionally wish I had, but can never seem to remember to put in my pack is an old tablespoon. I often bring my laptop along in the vehicle for navigation purposes but rarely use it. I have loaded all the marks into Delorme's Street Atlas so I can see not only the roads but the location of the marks as well.

slippeddisk, One of the techniques I would use in a case like this is to measure from the found RM 2 disk to the drill hole that I believe to be RM 1. (From the JW1441 datasheet I calculate the distance and bearing from RM 2 to RM 1 to be approximately 47.4 ft at 30.5 dgr, true). Once I confirm the direction, distance, and that the drill hole is indeed where I expected the missing RM disk to be, I measure and mark from each reference mark back to where the station should be located - as noted by Holtie22. Using 2 (or more) RMs will generally improve search efficiency especially if you must dig beyond your probe or metal detector's detection depth. My theory is to dig smarter, not harder! By the way, I always try to report the condition of RMs in my NGS and GC reports because I think it provides value to others who will attempt to recover and/or use a mark in the future. Good luck!

Camper1, I had noticed our shared initials (JLH) some time ago and often wondered if some of our recoveries might have been incorrectly tallied. Fortunately we operate on opposite coasts! I too appreciate Holoscenes efforts, as I would have to spend an inordinate amount of time to determine just my own stats! Holoscenes, thank you for you continued diligence in resolving these types of problem. We all do like to see where we stand from time to time. Your ability to parse and reduce all this data in such a timely manner is nothing short of amazing!

Personally I believe that is always appropriate to report what you observe. If the mark is currently in good condition, that is what I would report. The bottom line is that you have no way of knowing what really happened in 1979 ... someone could have even been at the wrong mark! I would think that any professional considering the use of this mark would read the complete history and determine the usefulness for his or her project.

Personally I have been using a spreadsheet for horizontal control stations with reference marks since returning from recovering my first mark. My spreadsheet, which has evolved a bit over time, includes only data that are important to me and are not already available either from the NGS datasheet or by using my GPSr proficiently. My spreadsheet simply calculates the azimuth and distance from RM to RM based on the NGS boxscore information and generates a scaled plot of the station and the RMs. I used simple trig functions as the formulas like those used in FORWARD and INVERSE offer precision and accuracy beyond that which I can measure angularly or in a straight line (or need). Besides, I didn't need lat/lon data for the RMs. In other words, my spreadsheet offers data with sufficient accuracy for locating RMs that are typically less than 50 meters from the station. Although I believe that I am probably more proficient with map and compass than most, I know that nothing lies like a magnetic compass especially when the user ignores the environment. (A possible exception is an overdriven FET probe but that is a discussion for another time and place.) While I too preset the declination on my compass, I consider it to be only a relative direction indicator. While some may believe that their compass always points to magnetic north, I know mine doesn't. Because of this, I prefer that my azimuths remain in true north format. I am willing to share my spreadsheet if there is an interest. It isn't elegant, doesn't come with instructions or support, but it has served my needs very well. Of course, it is not immediately evident to me that the message board is set up to allow files to be attached but I dont have a reason to look hard yet. /John

1) BMs (What's a Geocache?) 2) Both

1- Yes. The description seems to generally agree with the station coordinates. In other words, by following roads in my travel software, I could find the station general location. I cannot verify all of the actual road names and actual start/ending location of the SRs, but the description works. There is a boundry mark on the topographic map at approximately 500 meters at 111 dgr from DG7950. Naturally I cannot tell you if it is DG7954 NC VA GRANITE MONUMENT NO 30 with out actually looking at it. 2- No. I would put the mark in Mecklenburg county, VA /John

lumpynose, I would generally say that the detection depth is directly proportional to price and the operater's skill. I have a low end BFO-type detector ($65) that has a maximum detection depth in the 8 inch range (based on empirical data). Factors like soil composition and moisture do affect my results. Search coil size, oscillator frequency, and discrimination also differentiate a wide range of detectors. I have heard that PI-type detectors are capable of detecting objects at much greater depths but I have no experience with them. While a metal detector can be a time saver for marks near the surface, there is no subsitiute for careful measurements as per the datasheet for deeply buried marks like the one you mention (HT2454). In fact, recovery of this mark should only require careful measurements from the two RMs and a shovel! /John

The guideline I have been using is much less comprehensive ... it is the DATA ITEM: Description and Recovery text section of NGS's dsdata.txt /John

BDT - Thanks, I now know that this methodology has a name: quadrant notation. It is intuitively logical now that I know that my initial interpretation was correct! mloser - Actually this is an additional mark to search for while I'm looking for MZ1582. Using INVERSE, I determined that MZ1572 is only 27.6 meters distant. Besides, I am not intimidated by earlier failed recovery attempts (or D-coded non-published PIDs for that matter). I enjoy the challenge. It certainly would not be my first experience to find a mark that others could not. (Nor would it be my first experience to not find a mark that others could not find!) /John

I will be searching for MZ1572 in the not too distant future but I need to confirm that I have correctly translated two 1885 vintage azimuths. Have I interpreted the following correctly: " BEARING S 6 DEG 45 MIN E" = 173 deg 15 min " BEARING N 81 DEG 45 MIN E" = 81 deg 45 min /John

Thanks Rob, you confirmed what I suspected that the pros do (or don't do in this case): they don't rely on the compass for anything critical. Also, my note to Deb was not about the magnetic anomaly, it concerned a transcription error from the original monumentation text regarding the RM azimuths to what appeared in the box score. Two of the three box score RM azimuths are off by exactly 100°. The third is correct. Fortunately this datasheet contained the azimuth and distance data for the RMs in the original station description … not an uncommon practice for marks set and documented by the Massachusetts Geodetic Survey in the 1930's. /John

Earlier this week while recovering MZ1477, I discovered an unusual localized magnetic variation of about -13° (over an above the normal local declination of -15°) at the station. Having found the station first, I was getting pretty frustrated when I could find neither RM 1 or RM 2 (24.7 and 25.6 meters distant respectively). Fortunately RM 3 was set in a boulder above ground and I was able to find this even though I had been looking for it some 4.6 meters away. As it turns out this was what led me to figure out what was going on. I couldn't believe that my compass work was this poor so I stood at RM 3 and took an azimuth reading of the station - it was exactly 180° from what the datasheet indicated - just as it should be. Next I went back to the station and took an azimuth reading of the now visible RM 3 and noticed the -13° variation. When I applied this local error to the azimuths for RM 1 and RM 2, they were quickly uncovered. Interestingly, this magnetic variation was repeatedly measured to be about -5° at RM 1, 0° at RM 2, -4° at RM 3, and -13° at the station using this forward and reverse azimuth methodology. (I acknowledge that my compass skills contribute an error term as well.) I could see nothing visually (out in the forest) to create this very localized magnetic variation. Perhaps a local vein of lodestone or magnetite? Anyone had any similar experiences? What methods do professionals use to avoid these types of problems or would they be avoided all together through the use of distant (multi-kilometer) azimuth marks? [by the way, this is not related to the azimuth errors in the box score for RM 1 and RM 3. The azimuths (and distances) provided in the 1937 station description are correct. I know that you know that they are 180° from todays 0° = North convention! Yes, I did send Deb Brown a note on the box score errors.]

Actually the Mass Highway Geodetic Data Sheets identify location using the Massachusetts State Plane Coordinate system. You can convert these coordinates to the standard ddd mm ss.sssss format using the program spcs83.exe which can be found on the NGS website. The program can be used interactively or in batch mode. Be sure to read the accompanying user's guide! My experience has been that these datasheets are useful for horizontal controls only as there are no coordinates provided for vertical controls - at least in my area. Also, beware of out-of date Data Sheets that are still in NAD27 (U.S. Survey Foot) format as these coordinates are not compatible with spcs83.exe /John

Stem still intact in the drill hole = POOR according to the FAQs. You can put the details in your recovery text ... at least that is what I do.

Actually NGS has had this page up for at least a couple of weeks: NOAA Technical Report 50: Rates of Vertical Displacement at Benchmarks in the Lower Mississippi Valley and the Northern Gulf Coast Plenty of data to peruse.

Rob, My apologies … I thought you were suggesting that the NGS FAQ be unpinned and closed. /John

I would like to suggest that the NGS FAQ topic remained pinned. I think this is an important topic for all newcomers (and a good reminder for others with short memories). Allowing this to sink into the archives means it will be more difficult to find and read less frequently than if it was to be maintained in a prominent location - like the top of the forum. Considering that the majority of these topics are truly an educational exchange, keep the basics up top and easily accessible. In my opinion, of the 3 pinned topics in this forum, the NGS FAQ offers the most 'value' to the reader. Alternatively, pinning and locking a "read me first" type of topic with links to the NGS FAQ and other important topics might also be a reasonable approach. /John

I'm not sure what value a list of PIDs that 'might' be destroyed based on the datasheet text provides to NGS. Unless there is evidence collected and presented to make the 'destroyed' determination, I think the PID should remain active in the database. I'm sure a professional needing a nearby mark will simply choose another, not wanting to waste time looking for something that may no longer exist. On the other hand, perhaps this is where we can add some value by either recovering the mark or confirming, documenting, and reporting its destroyed status.

Personally, I really don't have a problem with what people are logging on this site. I think (hope) they are logging their finds here for fun. I have found and logged marks that others have previously logged incorrectly (ex. identifying a single RM find as a station while overlooking the actual station and other RMs). My thinking is that others can learn by my example if they are so inclined. (I have had email inquires for help.) Am I an expert? Certainly not! But I have become a student of the hobby and have a few tricks up my sleeve. I can tell when a mark that I have visited has been incorrectly identified by others - and that's good enough for me. I will not be contacting anyone to tell them that I disagree with their 'finds' and logs. I think it's important to remember what the Geocaching site is all about and not to confuse its purpose with that of the NGS. /John