Cznnnn Pids..

[foxtrot_xray]

I noticed a local mark to me that referenced some 'CZnnnn' PIDs. Looked them up, and they're all (the three CZnnnn referenced PIDs are CZ4850 - CZ4852) listed without datasheets, with reason of 'No Geodetic Control at this mark'. So, someone explain to me what that means?

 

Is that referencing a physcial control disk that's missing, or that process 'control' to ensure quality/accuratness wasn't present? (The desc says the disks are there, I'm going to check for these a little later this afternoon..)

 

I notice that a few sequential CZnnn marks are all listed in the same manner. So does this mean that when PIDs were first being assigned, they left a few letter combinations for destroyed/invalid marks?

 

Cheers,

Me.

Edited August 4, 2006 by foxtrot_xray

[mloser]

First of all, I love the name of that station--HICK. Since there is no mention of anyone by that name in the datasheet I am just imagining that the crew got to that area and decided it was just a hick town, and named the mark accordingly.

 

Your CZ marks are reference marks to the triangulation station, which is a horizontal control station. They are described in the datasheet also. Reference marks are normally present at a triangulation station and provided two functions--they were extra marks to help find the main station in case it got covered, etc, and they provided angles and distances to be certain that the main station was in the correct location. Tri-stations most often have two reference marks, but can have none, one, or more than 2. I have found a few with 3 but no more.

Some reference marks are surveyed as vertical control and will get their own PIDs when they are submitted. These are simply 2 extra points described on the datasheet, with no precise surveying value. Why they exist in the NGS database is beyond me--I think that has happened in the last few years because if you link to the original datasheet from the GC page they are not named, but if you look at a current datasheet from NGS they are. I am guessing they are placeholders of some sort in the database.

 

My personal opinion is that looking for a triangulation station and not the reference marks means I didn't do my job. I always search for every mark mentioned in a tri-station datasheet. This includes the azimuth mark also, which HICK doesn't have. The azimuth is yet another disk set at a distance from the main station, often a half mile or even more. It was used to verify a confirmed angle from the station after equipment was set up. Azimuth marks are often the hardest to locate as they have no coordinates and are often described poorly, using features that have disappeared or changed over the years. If old reference marks are described I will often look for them too, just to satisfy my own curiousity.

[Bill93]

One clue for hunting azimuth marks is (duh) the azimuth. I have found (easy) azimuth marks from just the azimuth and approximate distance alone when I hadn't printed the whole data sheet (bad idea).

 

Set your GPS to go to the main tri station, but travel to the general area described for the az mark. Find the azimuth value given in the box score and add or subtract 180 degrees to get the reciprocal bearing. Look for places that have the correct reciprocal azimuth as shown on the GPS and fit with whatever description you have.

 

At a quarter mile (common for 1934 stations), the one degree increment in most GPS displays gives a 25 foot swath to search. If, as often occurs around here, the az mark is near the fence line along a road that intersects the one the tri station is on, that isn't too bad a search job. The high spot along the fence line, or 33 feet N/S and 33 ft E/W from a road intersection in this general area is a good place to start.

 

This technique won't work if the az mark is buried and no witness post, but it is quite successful when there is something above ground to see.

 

For the hard ones you can go home and use the NGS program FORWARD to compute coordinates for a couple points in the neighborhood of the azimuth mark and at precisely the correct azimuth. Then go back to the site and set a goto on one of those points. Because it is close, 1 degree is very little distance. Set stakes at points that your GPS tell you have the correct azimuth or 180 from it. This will give you a line that the az mark must fall on within the accuracy of your handheld GPS.

Edited August 4, 2006 by Bill93

[foxtrot_xray]

First of all, I love the name of that station--HICK. Since there is no mention of anyone by that name in the datasheet I am just imagining that the crew got to that area and decided it was just a hick town, and named the mark accordingly.

The town is considereed 'hick' now, I can only imagine what it was like back then! (It's okay, I live in the town, so I'm included in that..!) However, the name of the mountain it's on is 'Hickory Log', so I imagine that's where the name came from.

 

Your CZ marks are reference marks to the triangulation station, which is a horizontal control station. They are described in the datasheet also. Reference marks are normally present at a triangulation station and provided two functions--they were extra marks to help find the main station in case it got covered, etc, and they provided angles and distances to be certain that the main station was in the correct location. Tri-stations most often have two reference marks, but can have none, one, or more than 2. I have found a few with 3 but no more.

They are in the datasheet, so does that mean while they HAVE a PID, (CZ....) they don't have their individual entries? Again, is this on purpose, or just because? (Before, I've never worried about finding the reference marks, only the main one. Now, however, since they're supposedly nearby, I figured I'd find them all.)

 

Me.

[foxtrot_xray]

One clue for hunting azimuth marks is (duh) the azimuth. I have found (easy) azimuth marks from just the azimuth and approximate distance alone when I hadn't printed the whole data sheet (bad idea).

[...snip...]

Holy cow, thanks for the technical pointers. Never been good at the bearing stuff, but that did help- at least help me understand some of it.

 

And I would use it, if I could. Downside is that the station is near the top of a mountain, the closest directions say "about 150 feet", and the directions are muddled. (See my note in the mark now, I believe - and it's only an opinoin - that the directioons are duplicated.) With all that, was inable to find it this evening. I will be going back of course, (because now it's personal). Oh, and there is no Az mark. So it's going to be a fun find.

 

Me.

[mloser]

Before you trust the Goto totally take a look at Google maps, Mapsource if you have it, or USAPhotoMaps to see where the station is located. It looks to me like there is a clear road running up the hill to about 365 feet east of the mark. I am guessing that is the road to the water tower.

For a tri-station, trust your GPSr to get you to within 10 feet or so of the mark, then look for the landmarks in the description. Remember, you have 3 marks to look for up there, so hopefully something will show up. I would guess that the station itself will be buried under leaves and possibly dirt. RM1 is in an oddly shaped boulder--2 feet by 8 feet, and unless the hill is covered with that kind of outcrop you might be able to walk right to it. RM 2 is also in a boulder, less well described, but at least it projects 2 feet so it probably won't be buried. I would ignore the references to the road, unless it turns out you can see it more clearly than I can on aerial photos. After reading the datatsheet better, RM 3 turns out to be the azi mark, and is along the main road that goes southwest to northeast. I would be willing to bet it is the one marked BM 1352 on topo maps, at the base of the road leading uphill.

 

Take a 100 foot tape, a decent compass, a prod of some sort and a metal detector if you have one, and the datasheet. The "box score" at the top of the datasheet tells you what you need to know to find all the marks:

 

EE1753| HICK RM 3 0145726.3 |

EE1753| HICK RM 1 17.321 METERS 02919 |

EE1753| HICK RM 2 18.438 METERS 12953 |

 

The reference marks are in degree order, from 0-360. RM 3 is at 14.56726 degrees from the station. There is no distance because no distance was measured. Like Bill93 said you can go to where you think the mark is and measure the angle back to the station. You can also use the GOTO function of your GPSr to tell you this. RM 1 is 17.32 meters from the station at 29.19 degrees. If you find RM 1 first, you can follow the arrow as well as reverse the azimuth to the main station. If you find the station you can pace or measure to RM 1. The same applies to RM 2 which is at 129.53 degrees. These are TRUE NORTH measurements so don't forget to adjust for magnetic north, which at this location is 4 degrees WEST of north, so add 4 degrees to every angle (I found this by clicking on the Topozone map from the GC.com page. The declination is at the bottom).

 

I often head out looking for elevation marks without much research, but usually look at maps and photos extensively for tri-stations. They are often harder to reach, and any clue I can get will help.

[foxtrot_xray]

Before you trust the Goto totally take a look at Google maps, Mapsource if you have it, or USAPhotoMaps to see where the station is located. It looks to me like there is a clear road running up the hill to about 365 feet east of the mark. I am guessing that is the road to the water tower.

It is. I went up there last week, a little after first posting. Cloudcover and treecover made it rather difficult to get a good reading, (+-100ft) so I didn't find anything. I HAVE determined that the last section of the description (starting with "Turn Sharp Right...") is duplicated, and not to be followed. Now, having said that, the "About 150 feet" is a PITA, 'cuz the "dim woods road" is no longer a road.

 

unless the hill is covered with that kind of outcrop

Unfortunately, it is..

 

But, this does bring up my original question. I randomly looked at a few OTHER "CZ..." marks, and they were all RM's, and listed as having "No Geodetic Control at this location.". Even a mark referenced in another post has "CX..." marks, which are not in the database for the same reason. I/m just curious to what exactly that means?

 

Take a 100 foot tape, a decent compass, a prod of some sort and a metal detector if you have one, and the datasheet. The "box score" at the top of the datasheet tells you what you need to know to find all the marks:

[...snip...]

I often head out looking for elevation marks without much research, but usually look at maps and photos extensively for tri-stations. They are often harder to reach, and any clue I can get will help.

I'll find these, definately. The downsides right now are the heat and storms. (Hey, it's Georgia. In summer.) I will say tho, doing all the research on this one (Google Earth, Mapping software, etc) just added to the fun, tho. Much more enjoyable than seeing a water tower and going, "'K, next.".

 

Me.

[tosborn]

The reference marks are in degree order, from 0-360. RM 3 is at 14.56726 degrees from the station.

 

Are you sure this is the correct interpretation of the azimuth.....isn't it 14d 57m 26.3s (in other words, the box scores azimuths are expressed in dddmmss.s and not decimal degrees)?

[mloser]

Yep, you are right. I knew that but for some reason mis-typed it.

[foxtrot_xray]

Now, how come some references have bearing, and some don't? (I.e. Reference Marks, and Azimuths?) (I mean, it'd be helpfl if they gave both, yanno?)

 

Cheers,

Me.

[foxtrot_xray]

w00t! Went out today and found them all. The directions were verily messed up (something I'm finding much more common than I would think, including one in NC I found over the weekend that the USPQD couldn't find, because of invalid instructions.) Entered log and entered new directions to NGS. Make it a /little/ easier to find.

 

Thanks for the explanation on the RMs, all!

Fox.