Base Rover Newbie
I am about to dip my toes into the base rover world for my first time. I will be using Carlson SurvCE field software. I will appreciate any tips for unattended base security. Also, please correct my thinking below regarding the process:
1. Setup base and radio and accept whatever initial position it gives me.
2. Connect the rover first to the Indiana VRS like I am used to, then shoot a “good” SPC position on a project specific marker.
3. Then connect the rover to the local base and “force” the “good” SPC position from the rover back to the base.
4. Rock and Roll.
Fire away friends, I have flame protection at the ready.
I am not an expert, so feel free to ignore ....
If all that matters is relative positioning in your project, then you could just use a quick position on the base and forget about any VRS.
If accurate absolute coordinates are needed, then getting a position from VRS on a rover point might supply that. Is that going to be accurate enough?
If you later get a better position on the base (maybe submit base to OPUS) can you correct the rover measurements?
You could do it the way you propose, and if you needed NSRS correct coordinates on your first site visit it would be a good way. But my preferred work flow (for the first visit to a site) is this:
1. Setup the base over a random point.
2. Set the base to collect raw data for OPUS as it sits.
3. Establish an autonomous position for the base, and proceed to RTK.
4. At the end of the day download the satellite data and submit to OPUS.
5. Shift the (Autonomous based) coordinates you collected onto the true (OPUS) base position. The shift should be on the order of 5-10 feet. You could do that in CAD or in Excel, I like to use StarNet to recalc the coordinates from the vectors with the corrected base position held.
Now you have a correct (or as near correct as OPUS can make it) position for your base station. On subsequent visits to the same site you can just set up over the same point and specify the base position. But you can still collect OPUS data again and average the results of the 2 sessions. Or just take solace in the assurance that the first was good.
As for security - in every instance of bases getting stolen that I know of the base was set up right beside the road. As in on the shoulder. Get it 20 feet off the road and your chances of having it taken go way down. Get it on the other side of the right of way fence and you are nearly golden. Church yards on weekdays and schoolyards in summer (in non-COVID times) are my preferred locations. Infields of highway interchanges are often suitable. It doesn't have to be right in the middle of your work area, just within radio range.
Step.3- I usually take the “good” RTK coordinates derived from CORS solution. Move the base to this point, then choose set base over known point. If I have an external battery or not doing a job over 45minutes-1 hour I always collect raw. since you are using SurvCe and if you are using Carlson Survey. Process the raw vectors thru Survnet. A 30 minute phone conversation with a Carlson rep and I could calculate my Relative Position values from the “good” base control point to any point I stored. Carlson is good stuff!
My base/rover work flow is pretty similar to what Norman Oklahoma described. I'll scout the area looking for a good open spot within easy radio range of the work, preferably higher in elevation to get better range and fire up the base using an autonomous point. I'll code this first autonomous position as Point #"_HERE" and carry on with collecting shots or setting out some points for the gun. After a few days I'll convert the base raw data to a Rinex format and submit it to OPUS and key those coordinates into the job as Point#_OPUS and translate everything done off the autonomous position to the OPUS position, generally not more than 5-10'. If I have OPUS based control already within radio range, I may localize on it to get going, but nearly always follow up with an OPUS solution as a check. As far as security goes, it depends on how bad the neighborhood is. I can usually put my base up in a location that would require someone to go to some effort to get to it and not pull right up and toss it in their trunk. I'm partial to fire station parking lots or anywhere there's a CC camera around (in a perfect world). I do nearly everything in SP these days. All the control gets wiped I can OPUS in and match up with old work within a couple centimeters. Virtual control using CORS (via OPUS) is the way to go and you need a couple hours of good base data to pull that off. Avoid using local projections unless there's a good reason. Can always postprocess those into a standard projection later.