Shawn Billings, post: 389303, member: 6521 wrote: There are so many ways to do this, it's hard to determine one method. It will depend on your equipment and your capabilities.
If you have RTK:
Collect point (fixed solution) at origin stake. Create localization at origin point with Geodetic North as the orientation and 0,0 as the origin grid coordinates. Head Northerly to the desired distance for the azimuth stake. Watch coordinate values and stake with Easting as close to 0 as possible. Note, it doesn't have to be zero, you could use 5000,5000 or any origin value you prefer. The directional error, expressed angularly, will be directly related to the easting error of the two RTK points (origin and azimuth stake) and the distance between them. Some data collectors will show the geographic coordinates in real time (latitude, longitude) and some do not. If your data collector does express geographic coordinates, then you can simply note the longitude at the origin point, head North and stake the azimuth point at the same longitude.If you have only Post Processing:
Set receiver on origin stake, then set second receiver on distant, inter-visible point. Collect data for necessary time for fixed vector solution. Process data. In processor, create coordinate system with origin stake as origin of new system. Calculate inverse between origin and second point. Return to field with total station or theodolite and set up on origin, backsight second point and turn the angle to North. If you can't set up a coordinate system in the processor, use Grid. In your case, the convergence angle is -00å¡04'22". So the geodetic bearing from Origin to Second is going to be Grid Azimuth (inverse) - 00å¡04'22" (counter-clockwise rotation). Using this geodetic bearing, for Origin to Second, return to field, set up total station or theodolite and turn to geodetic North.If you have a Total Station and Celestial Ephemeris:
Setup total station on Origin point and perform celestial observation. For years, I've used time from an $100 Garmin e-Trex and position as well. It's served me very well. Polaris will provide the best accuracy due to it's low apparent movement (makes time less critical) and it's small size (improves pointing accuracy). Other stars can be used but give up accuracy due to apparent motion. The sun in generally more convenient, but requires a solar filter when used with a total station. A theodolite can be used without filter using a projection method (hold a white card under the focal lens and watch the projection of sun and cross-hairs intersect.If you have a gyro-scope:
Least likely because most mortal surveyors don't have one. I've never even seen one, but from what I've read, they produce results easily, but require about 20 minutes to do so and have an angular accuracy of about 20 arc seconds. This is old information and I don't know if the specs have improved for these devices with newer technology.Regarding GPS solutions:
All of the normal rules apply. You need open skies at the origin and azimuth point (and second point for post processed solution) as well as at the base (if you are using a base for RTK and not RTN). I would recommend with the post processing route that once you stake the azimuth point from the origin, you set up your static gear on the origin point and the new azimuth point and collect necessary data for a good vector and make sure that this new vector is North once post processed.
Ooops...didn't mean to do that.
If the coordinate system isn't geographic or ECEF, it's most likely grid. SPC is a flavor of grid, but not all grids are SPC. All grids have convergence, SPC or otherwise.
I may be wrong, but Carlson data collection doesn't allow users to work in geographic coordinates in real time.
John Hamilton, post: 389322, member: 640 wrote: Ooops...didn't mean to do that.
John, You may know this, but if you catch a bad post quickly enough you can delete it. I don't know how long the window is.
Shawn Billings, post: 389325, member: 6521 wrote: If the coordinate system isn't geographic or ECEF, it's most likely grid. SPC is a flavor of grid, but not all grids are SPC. All grids have convergence, SPC or otherwise.
I may be wrong, but Carlson data collection doesn't allow users to work in geographic coordinates in real time.
Won't let you work in geographic, or won't let you see geographic?
John Hamilton, post: 389320, member: 640 wrote: Take a polaris observation to a reference mark. Turn the angle to north (astronomic or geodetic if you use the laplace correction). Then use the double centering procedure (do people still remember how to do that?) to run the line north. At the north end, take a check observation to Polaris.
I was thinking exactly the same thing.
You have a convenient star up there, use it.
I did a science experiment...I turned a baseline off of Polaris and corrected astronomic to geodetic using the LaPlace correction. Then I observed with L1 GPS, processed and converted the grid bearing to geodetic. They agreed within 2".
@dave-karoly Dave: I know your comment in this thread was from almost four years ago, but I'm curious if you recall how long your baseline was (total station and target set up on the same pair of points as the GPS receivers?), what GPS equipment and processing were used, and what the terrain and sky views were like? Thanks!
The base line was about 750 feet. I setup over a 12" spike in my front yard looking east down the street to a drive into a school parking lot. We don't own that house anymore.
I used my Topcon GPT3005LW manual total station for Polaris. I don't own it anymore.
I used my ProMark 3 single frequency receivers in Static mode processed in GNSS solutions. I don't own them anymore either.
@dave-karoly Thank you for the information, Dave. It's very cool that you took the time to perform the comparison.
@tom-adams Right said
Do you remember what the laplace correction was?
Latest:
https://www.ngs.noaa.gov/GEOID/DEFLEC18/computation.html