We have recently done a GPS closure on a property and are trying to add in some Total Station points. ?ÿAll of this is done in Carlson on the SurvNET program. ?ÿThe GPS closure was shot in with a Base/Rover set up localized on two state plane coordinates. ?ÿThe total station was set up on two control points set by the Base/Rover set up, backlighted, and then shot in two other pins. ?ÿDoes anyone know how to combine these in Carlson for a total overall closure? ?ÿWhen we only adjust the GPS part we get good residuals and no error messages holding the BP as control. ?ÿWhen we add the second RW5 file with the total station data, however, it brings up errors and the two control points backlighted on have really bad residuals.
I use both most of the time by taking static readings at locations that I will follow and run TS traverse into deep woods and out the other side with deadend ties between the static points.
My point to point distances are very accurate and are hardly over 0.08ft different in several thousand feet.
I use curvature of the earth adjustments for my TS traverse.
Everything checks great on north and south runs. It is the runs from east and west and the mid quadrant shots that directions fo not get matched. Still they are very close in distance.
Most of the time I will make a simple rotation of my TS data to match the GPS.
Starnet is the way to do it right when you are wanting nats accuracies on each point.
Usually, I am placing tpost along boundaries for fence and painted boundaries so I am not worrying about the nats.
We have recently done a GPS closure on a property and are trying to add in some Total Station points.?ÿ ... ?ÿThe GPS closure was shot in with a Base/Rover set up localized on two state plane coordinates.?ÿ
What do you mean by a GPS closure??ÿ Unless you moved two receivers in the same way you would a total station and prisms and use the vectors from point to point like a traverse, the GPS points are coordinates and any "closure" computation on them should appear perfect.
You didn't mention anything about grid to ground conversions.?ÿ If the GPS points are converted to state plane, then your ground measurements need to also be converted to state plane distances before combining them.?ÿ You need to find the Combined Scale Factor for a typical point in your project and use it to scale the distances measured with the total station.?ÿ Failing to do so will give serious residuals in most areas.
So I think the closure is actually just an adjustment. ?ÿWe are new to GPS in our office mostly, and I am pretty new to surveying so just trying to get it down. ?ÿIn SurvNET there is an option to create a .cls file, a closure file, like I normally would with a total station traverse. ?ÿPreviously I had been told that we do not need to create a .cls file with a GPS closure since the adjustment, and the combined grad factor for grid to ground was what was needed on a certificate. ?ÿThat being said, I also have been told that it is possible to create a .cls file for GPS adjustments, and if at all possible I would like to do so. ?ÿPLEASE correct me if that is incorrect.
The GPS coordinates should all be state plane since the original control points, on which we localized, we shot in with a MIFI connected to our local state plane. ?ÿWhat you are saying is I need to take the combined scale factor and multiply that by the distances shot with the total station to get corrected distances, then input that into the RAW file to correct the residuals?
Okay. ?ÿSo, our program Carlson Survey with SurvNET does have an option to apply curvature. ?ÿI will make sure that it is clicked tomorrow when I look at it. ?ÿAlthough I do think that it was clicked on when I tried this today. ?ÿIt seemed like when I tried to only adjust the GPS data it turned out just fine, but as soon as I added the RAW file for the TS data the residuals came up all wrong. ?ÿAnd only on the two control points that were also the MIFI points. ?ÿIt seemed to me that since they were the same points it should be fine, but it might be some error in the scale of the GPS to the TS data. ?ÿI will make sure that the curvature refraction and ground to grid factor is used.
A GPS network is a 3D solution. To add in a field traverse you have to carry good verticals. Bad instrument/rod and or antenna heights can throw a solution into disarray. Bad elevations can create horizontal discrepancies.
Check that out first and call back in the morning.
A GPS network is a 3D solution. To add in a field traverse you have to carry good verticals. Bad instrument/rod and or antenna heights can throw a solution into disarray. Bad elevations can create horizontal discrepancies.
Does his software work in 3D or in 2D + 1D??ÿ When he goes to State Plane, it may not be necessary to carry heights other than to know the average project elevation.
I use Star*Net to simultaneously adjust GPS vectors and terrestrial measurements routinely, and have done so for 20 years. I'm not super familiar with SurvNet, but I have seen enough of it to know that it has a lot in common with Star*Net. So I'm confident that SurvNet can do what you are trying to do with it.
As far as what might be wrong with your current data - that is very difficult to say. It might be that once you solve the mystery of your 6 foot bust in GPS data you presented in your other thread the source may become clear. Other likely sources of error are 1) incorrect measure ups, 2) incorrect point numbers, 3) Foot definition mixups, 4) grid zone mixups?ÿ - in order of decreasing likelihood, but these are by no means the only possible problems.
Wild ass guess, but when you localized did you hold the scale factor to 1.00? A localization (calibration in Trimble speak) will introduce a scale factor unless you check the hold scale factor to 1.0. Easy to forget to do.
Surveying "on the ground" will usually result in longer distances when compared to GPS inverses on the same point. Especially in higher elevations. Again, I say usually.
You need to convert your shots taken with the total station by applying the proper combined scale factor if you want to remain in state plane.
OR
Use the inverse to get your GPS measurements to be "on the ground."
You need to make sure what you need because holding "ground" distances on state plane can have repercussions. Boundaries were defined on the ground. Our green acre surveys must report grid and ground distances in higher elevation areas.
Sorry for the rough sketch. I whipped it up with my note while my 6 YO was hanging on me.
Surveying "on the ground" will usually result in longer distances when compared to GPS inverses on the same point. Especially in higher elevations. Again, I say usually.
You need to convert your shots taken with the total station by applying the proper combined scale factor if you want to remain in state plane.
OR
Use the inverse to get your GPS measurements to be "on the ground."
You need to make sure what you need because holding "ground" distances on state plane can have repercussions. Boundaries were defined on the ground. Our green acre surveys must report grid and ground distances in higher elevation areas.
Sorry for the rough sketch. I whipped it up with my note while my 6 YO was hanging on me.
I have always found GPS vectors to match my traverse ground distances. I take it too many people do not understand that a GPS vector is XYZ to XYZ and is therefore a slope measurement. Because the slopes are generally mild, one can even take ground elevations off a USGS quad map and not adversely affect the horizontal results.
