You can get into deep trouble with what is being done.
Like assuming the correct location is 9 feet from an original looking monument?
I'd be using a minimum of 3 points to localize. An exception to this is if I was localizing to provide myself with search parameters for more points to localize to. I would have no fundamental problem with localizing onto well monumented boundary corners.
I assumed that the data you call recovered is what you measured with your GPS on your control network.
We set up the base station on a new point, which we called 3001, and started locating with the rover. We will be using 3001 throughout the duration of the project. I'm wondering if we configured something incorrectly because I'm sure a good amount of the located points were falling to the south of the calculated points. Thanks for adjusting my data.
Once he localized or calibrated that base station coordinate is changed it is no longer what it was before the localization/ calibration.
Will this change be in the raw data?
You can occupy the CCR monument assume it's good, then check it's real-world location and adjust if needed.
We did this in case there was a typo. The coordinates we got were pretty close to the published coordinates on the CCR.
You can occupy the CCR monument assume it's good, then check it's real-world location and adjust if needed.
We did this in case there was a typo. The coordinates we got were pretty close to the published coordinates on the CCR.
It's always good to match closely, then you have to decide if it's worth it to shift over to the new location.
I will always hold site control if there are design plans or such involved. But, if the new job is fresh: property corners, building locations, topo, ect. there is no reason to hold older control. Each job is different. You can't force new numbers on a building site with existing control, building, parking lots and all that stuff based on the control.
I had a thread about just that and that thread went on forever. It was remarkable how many wanted to shift the coordinates to match OPUS on a construction project with dirt being moved. It's a case by case basis.
You can get into deep trouble with what is being done.
so true doing one now dealing with previous surveyor finding original mons set many years ago then computing a totally different location for the corners. We found all original and they work with the original survey yet this one survey is in the chain of title and new positions for corners lol got to love this job
Like assuming the correct location is 9 feet from an original looking monument?
@field-dog yes and no. Once a localization and calibration has been accepted that base station value changes to fit what you localized to. You can go out set up and get an autonomous position for the base. It can be 20 ft off from true state plane or whatever true datum. Your survey site control could be assumed it could literally be a guess of where north is but say your traverse on that assumed coordinate system closed and you localized or calibrated to it well that file best fits that 5000 5000 elevation 100 coordinates system. In complete truth that’s why calibration and localization where created was to get gps information to work with an assumed coordinate system. It’s so 1990’s. If a company establishes a control network today say state plane or even state plane scaled to ground or even a LDP. There is almost no reason to calibrate or localize. My crews are given some points coordinates to help them search for the property corners. These are all derived from all the plats compiled and the first go is sorta eyeballed on google earth and rotated. I give them a csv file and the dxf file of the compiles. Sometimes I guess within less than a few feet sometimes it’s 20 ft. They are given the plats and all research they need as well. Once the find a couple points and observe them they translate rotate those points or the dxf to there datum which is usually state plane. Plus or minus several feet because they usually do a HERE position and log data at same time. After they get some corners around the site I will usually update there control to OPUS version and also those search points and the dxf. By now we are within a tenth or so of finding corners depending on year survey was done and methods. Aka following a chain and 20” transit pre 1930’s on a survey up and down hills and through swamps and thickets we might be off more. That is not a problem we are looking for the monument originally set or called for and the evidence on the ground not the coordinate. But it works and most of the time helps us be productive. The problem is I didn’t start out surveying this way. I had been given plats I could not even spell coordinates back then. We followed the surveyor and his calls from plats deeds and field evidence. Now we live in a coordinate world. You can do a complete boundary and never compute a darn coordinate. Coordinates are just a way it makes for simple math that uses trig geometry algebra etc. plane coordinates are just an easy way to keep up quickly with where you are and where you want to go. Go out with a pocket transit. And tape. You can traverse reduce slope distances to horizontal using and old brunton pocket transit. Also the old brunton had the sign and tanjent on back. It’s a good exercise and you can do it all all the math without a calculator.
Lots of good commentary in here that's beyond my limited years of experience, but from these responses I'm assuming that all are immediately taking into account that it's a partial topo of an existing r/w or roadway. If it were almost anything other than that, any kind of mortgage, boundary or even a fenceline survey, checking in with two corner monuments that are off by a "little" is not adequate for even construction site control. As others have mentioned (in different ways) there's a difference between relative positional accuracy - the accuracy of each point in a traverse in relation to its measurements from each of the other points and positional accuracies relating to a national grid, a datum or a subdivision. That said, I wouldn't base even something like a partial topo on just two points in most cases. If you can use that basis to check into at least one but, for elevation, two more property corners you're going to be able to do your translate and rotate with a lot better info, a thus higher confidence (and legal backup) than with just two. I have used two before but I've never believed I could back up that work if it were challenged and I'd never put my stamp on something I hadn't beaten up quite a bit more than that.
Thanks for adjusting my data
My pleasure. I checked the convergence at your job and it is - 0-16-14 (according to Corpscon v6) which means that you should have a bearing on that east-west govt lot line of N 89 33 00 E + 0 16 14 = N 89 49 14 E. My adjustment of your data shows N 89 46 10 E so it appears that your control is probably okay and that PLAT just needed to be brought in to your control.
Note: Convergence is always subtracted from true north azimuths so minus a minus is a plus. If you use azimuths you will not screw up when changing quadrants.
If you use azimuths you will not screw up when changing quadrants.
I’ve always preferred azimuths but, as you know, they aren’t used anymore in the U.S. except maybe by the military.
Looking at the plat which is a 1990 era survey, I don't see any valid option to do a calibration. All it would do is violence to the geometry. True north was held along the east line of Lot 1. That's fine for 1990, but what would be the point of a calibration or localization? Doing that is like activating the disconnecting sway bar in a jeep, locking in the front and rear differentials and plowing down the interstate at 70mph.
Well, those options are available so you got to use them.
It's simple to use accurate lat, longs from OPUS, project a well defined XY coordinate system, and rotate translate the plat to it. If you want to hold 0d0'0" along the east line of Lot 1 you can do it later in all the different programs. Can't see why you would but you can.
It's simple to use accurate lat, longs from OPUS, project a well defined XY coordinate system, and rotate translate the plat to it.
I use this approach, except perhaps for initial monument searches.
Project Update
We're not going to get back to this project until late next week. Due to the extreme Florida heat, we're doing stability B and C BM inventory this week. Monthly lake elevation checks begin tomorrow. The CAD guys in the office are drawing the plat and surrounding parcels. I'm anxious to get back to the project because it's so interesting. Many thanks to everyone who has contributed to this thread.
If you use azimuths you will not screw up when changing quadrants.
I’ve always preferred azimuths but, as you know, they aren’t used anymore in the U.S. except maybe by the military.
Hawaii regulations require all bearings in South Azimuth and subdivision POB based on the nearest NGS triangulation station, which I appreciate. They don't specify any grid or ground, though, so you get guessing on some of that - which brings up another question but I'll save that for another thread.
Hawaii regulations require all bearing in South Azimuth, which I appreciate.
Why south? Any idea to the history of this?
@jimcox For what it’s worth, for many decades the US Coast and Geodetic survey (now the National Geodetic Survey) reckoned azimuths from south, I think well into the 20th century. I suspect this derives from astronomical work such as observing bodies on the meridian to the south of the station (in the northern hemisphere), thus referring azimuths from south might have been convenient.
Hawaii regulations require all bearing in South Azimuth, which I appreciate.
Why south? Any idea to the history of this?
I'd bet there were many dips and turns that ultimately brought them to codifying it, but I've heard that it may have originated from navigation way back where, being South Pacific Polynesian ancestrally, that direction was the way "home".