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Everything posted by jwahl

  1. Somewhere between satellite triangulation and GPS there was the transit doppler system that I expect also played an important role. We used doppler in surveying applications even though it was only sub meter at best and that with extreme effort and time. It still proved useful. - jlw
  2. I did a control survey for photogrammetry in that area in about 1978 and probably used that station. I remember the road up there, but don't remember the station specifically although I think I have some pictures taken then from the mountain. We traversed south and the westerly along a road to some place called Black Meadow Landing as I recall. While on a high rock pinnacle turning angles an airplane came down the river and turned up out little valley, barely clearing our point, I think I could see the whites of the pilots eyes on that one. A very spectacular environment that is for sure. - jlw Upon examination of the datasheet and the quad I see that I misinterpreted your photo and was imagining your mountain being on the south side of the River. Anyway that is where I was and the station was called METAL and is on the Mountain just west and a little north of Parker Dam.
  3. Most systems like this labelled as "Local Coordinates" are not on a formal projection but are based upon a true north azimuth somewhere in the area and possible false northing and easting for a given point. There is an example in the DC areas known as WSSC Coordinates which are based upon the dome of the capitol being 0/0 and true north out of there. A plane grid is then carried forward by the terrestrial surveys over time. While these types of systems were not originally based on a projection, there are a number of custom projections that can be set up that will closely approximate them. Of course to "get on to " the system requires deducing the base point and getting a lat long for it, or developing a transformation between other systems and known or recovered points in the local system. What software to use to do this can vary widely, and I cannot specifically recommend some, but with the proliferation of mapping programs for GPS any that allow setting up a custom projection might be made to work. Even your GPS itself probably has a custom or user projection option that can be manipulated for the purpose. Things llike OZI Explorer and a multitude of other programs also have capabilities to define custom projections. I need to look at that map again, but the presence of the True Meridian near the 100,000 Easting line suggests the possibility that the origin of the system is on that line. There is usually no scale factor in these systems and if they are near sea level you would use a scale factor of 1.0000 at the origin. A mercator projection set with the central meridian at that location with a 100,000 easting and scale of 1.000 might work reasonably well over the area and is available in almost every GPS unit's user projection options. - jlw PS I doubt that they have anything to do with UTM, MGRS or state plane. 2nd PS: If someone wants to provide me a list of the coordinates as mentioned above I can try to outline a procedure to set up a user grid that will convert them for you.
  4. BLM has plats that often show USLM or MM's but don't necessarily trust them. Sometimes they have been misplotted and the Mineral surveys tied to them can be plotted miles off from where they are. Sometimes you have to diligently follow the notes the LM description and the MS notes and gradually figure out things from workings on the ground. I found a large cone shaped LM down along the edge of the Panamint valley that was misplotted by more than 6 miles. Getting a good location on one of these can really help BLM clean up their records, MTP's and maps, if they listen to you. - jerry
  5. My intuition is that datums and orientations are minor issues. You can probably achieve a reasonable degree of accuracy simply by doing an arithmetic transformaion. That is differences in lat longs between common stations in the general region. It is going to be within feet or better.
  6. They aren't classified as bench marks and only very rarily will one be in the NGS database which is the basis for this site. There is a "Public Land Survey" section on the Waymarking site that is your best bet. - jlw
  7. Second PS about S7 on the brass cap. In the normal course of events in the survey of the PLSS that 1/4 corner along the line between two townships would be run first and marked for the sections which are expected to be established later when each township is surveyed. So for a normal township it would be section 7 to the east and 12 to the west. For some reason the township to the east was never surveyed and so an actual section 7 was never created whereas the township to the west was surveyed and resurveyed and there is a section 12. Areas of Federal Public Domain lands remain unsurveyed for a number of reasons. One would be that there is no intent to ever sell or 'patent' the land because it has already been designated or 'reserved' for another purpose such as a National Forest, wilderness reserve, National park or the like. Since a complete original survey of a township costs money and takes time, they are/were sometimes not done because there was no necessity. Later on, particularly if there is some administrative activity like mineral exploration, oil and gas leasing and the like, it may be determined that a protraction will come in handy in order to legally describe lands within these unsurveyed areas. A lot of vacant federal land were protracted in the 1960 era. Again those protractions are simply diagrams which represent a plan for how the surveys would be done, if done, and were computed from the best knowledge of where the surveyed exterior lines were. One difficulty with them was in figuring out where your lease was by means of them. The newer APD mentioned above simplified protraction by establishing a fixed geographic coordinate on most of the 'corners' of the protracted sections. No corners are ever set and no field survey is done. Where this cookie cutter fixed grid meets the surrounding surveys protracted blocks are created as sort of a buffer because the exact relationship between the fixed (by coordinates) protracted sections and the existing surveyed lines on the exterior of the area which are very often older surveys and not precisely known. Reviewing the timeline, the idea was put forth around 1987 or so and officially put in place around 1990 a little further back in time than I said previously. - jlw double PS: a lot of these APD's were done for the USFS for some reason so that they could complete their cooperative mapping and updating of the quads with USGS. The fact that these show on the quad leads me to believe that is where these came from.
  8. PB is a relatively new thing called a 'protracted block'. A township protraction is usually only created in an unsurveyed area. Because this type of designation is relatively new it must mean that there is a new protraction in that township. Which would mean that the township to the east was unsurveyed. Protractions are shown on diagrams which may cover part of a township to multiple townships. A protraction is sort of a paper plan for survey that is used to describe federal lands for leasing purposes. It cannot be used to sell or patent lands. A new form of protraction was created about 15 years or so ago called an 'Amended Protraction Diagram' or 'APD' which provided for creation of some parcels around the edges called 'Protraction Blocks' which are similar to a protracted section roughly a mile square, but they are odd ball. I am not sure if plats for Arizona are on line or not, they have been scanned. However APD's may or not be included. I would check here: http://www.glorecords.blm.gov/SurveySearch Once you are equiped with the township and range. If they don't have it you can call Cadastral Survey office in the Arizona BLM State office. - jlw PS: Yes it appears that plats for Arizona can be viewed at the sight I gave the link to above. T2N R7E appears to be the township to the west and T2N R8E is to the east and the protraction diagram does not appear to be shown.
  9. Seems more likely to be faded surveyor's paint, if not some unique lichen.
  10. Just to add a tidbit. That is a typical quarter section corner of the Public Land Survey System. Set by the General Land Office in it looks like 1930. The GLO became part of the Bureau of Land Management when it was formed in 1946, so records of these boundary surveys can be found in the BLM office for the state it is in. These surveys are described in documentary form called field notes and the sections they mark are portrayed on plats, and often shown on USGS topo maps. The GLO started setting iron post monuments around 1908, the quarter corner monuments are usually 1 in. diam pipes with the brass cap attached and section corners are 2 in. diam. pipes. Before that monuments were more often stone or other natural material. Occasionally one does have horizontal or vertical control on it, but that would not be the general rule. There is a Waymarking group for PLSS corners.
  11. That one has me wondering why it has a scaled position, and why the setting is listed as "unspecified". Not to mention that while it may not be ideal for GPS, it seems like it could be occupied and a position obtained with a little patience. Wonder what the story is on this one. - jlw
  12. Just to be argumentative, suppose the original observations of a station were with a bilby tower over it and target lights on top, and and the ground mark also has an undeground mark. Which is the station? In a manner of speaking the bilby tower was 'intersected' and occupied not the station mark on the ground. Is the station destroyed when the tower was removed? It all depends on how the observations were made. -OR- you could say there were all part of the station. It seems clear that the main thing that differentiates an intersection station from a 'real' or other 3rd order station is that it was not occupied. My point is the mere fact that the object described is a steeple, or a tower or a fire tower does not by itself mean it is an intersection station. I would say that in many cases a disk set underneath a fire tower was probably set fairly closely and if it is marked as the station and still exists it is not destroyed. The target tower can move, be rebuilt and destroyed but the station may not still be there. And of course in many cases no such monument was set and nothing at the station was ever occupied. The bingo post above exactly describes one such example, the tower was destroyed but the mark which is the station can still exist. At any rate describing what you found seems to me to be important but I'm not keeping score. One could assume something like the Washington Monument on the mall was an intersection station by it's nature, but no they occupied it!
  13. There are a number of cases that I am familiar with where there is a monumented station, and a structure also which would be like an intersection station. The descriptions could make this unclear. Without looking at the data sheet, one example is the old Daniels and Fisher tower in Denver that was a tower and it was also occupied and perhaps monumented at a point below the top. Similarly a lot of fire towers have the tower and a monument placed underneat. So description of a station as on object like a tower does not necessarily mean it was strictly an intersection station or was not occupied. You have multiple functions at a station, targets, lights, instrument stands and monuments. - jlw
  14. A few key elements of the description are that it is described as "3.6 METERS (12.0 FT) SOUTHEAST OF THE CENTERLINE OF THE HIGHWAY. THE MARK IS 0.18 M ABOVE HIGHWAY." Makes it sound like it was on a concrete edge of the travelled portion of the bridge. Perhaps in line with the easterly pier, but pictures I find on the internet do not really show a normal bridge abutment extending from shore. So this on first intuition makes me think it was part of the actual roadway and thus probably already destroyed. Pictures of the blown bridge show that most of it is still there with collapsed sections draped over the piers except for the center section which probably dropped straight down. I am relying some on the scaled position. I'll see if I can add in some links to the bridge before and after that might show the area. There is also roadway level google imagery which might be interesting to look at, and what I see is a low concrete platform on the edge of pavement which supports a guard rail. It would be a longshot to see the mark, and I didn't look extensively. That whole component could have been replaced in the last 25 years easily. - jlw PS link additions: One picture (7) after implosion showing bridge construction structure. Some older pics. Most from NY end. Bottom line from those pics there is really no concrete or stone structure above the roadway except that supporting the guard rail as part of the roadway itself. The rest is all steel.
  15. I have travelled over this bridge many times en route to visit relatives in VT and Quebec, and it was blown up last week. I thought I would check and see if there were any BM's destroyed. PG1604 seems like a candidate. If it is still there I suspect it is likely to be destroyed soon as demolition of the stone piers and probably abutments will take place to make way for new construction. It may be an interesting one for someone to check out. - jlw
  16. We must all be doing something different. I go to this page: USGS US Topo Then I select from the menu on the left: " Download Maps" Map Store. I then follow the directions to the right of the map, navigate to where I am interested, zoom in until I get the map outlines, put a little pin in it, and click it and a list of all the USGS Raster maps that exist are show available for download as a PDF. The 1 24K, the 1:100K and the 1:250K As far as I've been able to tell it is about as complete a coverage as you can get anywhere. Perhaps there are some kind of 'layers' when you use the special GeoPDF view which I haven't done. They show up as identical to the DRG's in acrobat. - jlw
  17. The "geopdfs" I have downloaded for the 1:24K series maps were simply the usual DRG's in PDF format. In fact I convert them to jpegs and use them as such all the time. My impression of the National Map data is that it seems to me like it came from 1:100K mapping based on the themes provided. So the mystery continues. - jlw
  18. jwahl


    The monument is visible in the google street level imagery and seems like to me to be in the right position. The county line is clearly marked with road signs and the monument is relatively certain a county line monument. A BM elevation taken on the top of the monument when it was upright seems possible. I think the DB description is likely erroneous unless a disk was placed in that drill hole which seems unlikely since the top of the monument is not level. There could be or could have been a small metal plug or pin in that hole, and that was close enough for someone to code it as DB into the system. Since the description is county line monument, there is unlikely another one nearby that would properly fit that description. My opinion anyway.
  19. I don't know if there are other videos on this topic, but I just came across this one. I wrote them a note about this forum. - jlw
  20. If these things are on points readily visible from the waterway, they could have been part of a system of navigational aids. These would have been sighted by ships using various techniques to determine a position or a line. They might be falling into disrepair with the advent of GPS. When they were in use, I would expect a large red and white target to be mounted on top. This is however, just a guess. - jlw
  21. BLM has measured the distance to it's bearing trees, set on PLSS corners to the center for many years. The procedure is to hold your tape on the side of the tree at a perceived right angle to the line from the tree to the monument. There is some estimation error involved there, but not much unless it is a very large tree. I suspect that is how C&GS would have done it too. A slightly more precise method could be to measure to the face of the tree and then using the circumference of the tree, determine it's diameter and radius and add that together. There is likely to be some uncertainty in any case because of where on the tree you chose to make the measurement. Also remember the measurement is usually assumed to be horizontal.
  22. I also vote for not found. They may have searched for it and even submitted a modified 'go to' description of how to get to the place. Just enough ambiguity to make you wonder though.
  23. Some perception I have seen mentioned here I would like to comment on. That is that surveyors who use either horizontal or vertical control monuments log them to NGS. That is not my experience. I would bet that 95% of surveyors do not or have not logged a report to NGS even though they are using marks. This was particularly true before we had internet forms, so before 5 years ago?. I think I might log a station if I found it destroyed or damaged so that it would not be useable and reporting that would save someone else time, but most of the time that effort is not made sorry to say. - jlw
  24. BLM Markers are most likely to be corners of the Public Land Survey System marking section and 1/4 section corners which control property boundaries. Property corners are a whole other class of monuments that are not generally included in the 'benchmarking' NGS derived database. There may be a few as mentioned that happened to be tied in, but generally speaking they are a separate thing. So short answer would be no, they are not logable here. However you should find 1 or 2 categories on Waymarking site to log them. I believe there is a BLM group as well as a Public Land Survey group. j. l. wahl
  25. I wonder why geologists seem to be consulted on these things. A geologist or two were involved in much of the recent 4-corners dust up. - jlw
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