Using an LS as base

James Suttles

Active Member
We've been using an LS to LS solution for a year now. Great setup, however the workflow of base to rover is somewhat daunting at first. I have ran into a small issue. We normally us a 2m Tripod and a fixed 1.5m pole. Both require the black adapter that is 0.25mm or 0,082'. The units were setup to add this distance as a vertical offset. That all worked well until this past week. I did a project and we used a regular tripod and a regular prism pole. The adapters had to be used, but when the HI's were measured they were to the Bottom of the LS not to the Bottom of the Adapter, like before. So we have both HI's 0.082' too long. Adam and I are working on a solution to make sure the points I collected all are correct. What I have learned is you cannot change the HI in the base file, it has to be written when the GNSS file is written. The Rover Heights can be corrected. Just not sure about the GNSS file. Anyone have any experience in changing the Base height, in the GNSS file?

The adjusted Base Height was correct, so the RTK points should be relative, after the Rod Heights are adjusted, its just the PPK points I am not sure of. Does anyone know how the Base HI is utilized in the DPOS process?

This may sound very confusing, and from my perspective so far, it is. When you recover your base point, the HI comes in a 0.375, not the actual measured HI, that is were it gets tricky. If you send the GNSS file to Web DPOS, it will use the HI measured, with the Vertical Offset included, and that is great, unless you need to change it. I know Web DPOS will let you it manually, but not so when the LS sends it to DPOS.

Any idea would be greatly appreciated.

Lastly, I know there is a push for other options, mainly other constellations, which is front and center.; however, the LS base to LS Rover interface is desperately needed. If LS to LS interface implemented, correcting a situation such as this may be a few clicks and done.

Adam feel free to add any info I may have missed to mention.

Thx
 

Matthew D. Sibole

Well-Known Member
5PLS
I do not generally care what my elevations are while on site. With that said when you recover base point from the rover it populated the 0.37’ height for the base. Attach the raw gnss file to that point. Now edit the rod height to be the correct rod height measure to the bottom of the LS. When sent to DPOS through the LS all will be good.
 

James Suttles

Active Member
So is the HI in the GNSS file ignored? and only the Antenna Phase center the 0.375' height used. If so, then correcting this, will simply require changing the rover heights. Correct?

I just want to make sure I fully understand the process, as its sounds like its simply adjust the Rover heights, to the bottom of LS measurement.

Thx
 

Matthew D. Sibole

Well-Known Member
5PLS
To be honest I have not put a ton of thought into it. I only wanted the DPOS file to come back correct and this was my way to do it.

If you try and change the base HI before attaching the raw gnss file it will case the LS to crash and you will have to reboot.
 

Adam

Well-Known Member
5PLS
I have two points that are the same elevation via leveling. I plan on running a test tomorrow to freshen my memory a bit.

As I remember the base hi has the opposite sign that the rover height has in the equation. So by having the erroneous.082 as an offset in the base hieght and as an offset in the rover hieght they cancel out.
 

Wes Cole

Active Member
I've been using 2 LS's for base/rover over TCP the past couple of days. I'd really like to see the development team work on two things:

  1. The workflow for starting the LS as a base. It's not too cumbersome at this point with Jfield, just mainly would like the process of setting the base position and rod height to be a bit more like the normal base/rover setup with a T1M/T2.
  2. I'd also like to see the process of DPOS-ing the files collected at the base a bit more streamlined so that I get a real ground elevation at my base point instead of at the APC. Admittedly I haven't tried to do this yet, just discussed the how-to with @Adam
All this to prevent the inevitable screw-up on my part!

Three big things I like about having an LS as a base over the T1M,etc.:
  1. You can view the base LS on RAMS from your phone and reboot if necessary (learned that today from @Adam ), make sure you are recording a static file, view DOP's, check for plumb, etc.. With RAMS and turning on the camera you can also make sure the base is still in it's desired location and upright.
  2. No up-charge to start utilizing Galileo as soon as it's enabled in the release of Jfield (i'm not a pre-releaser!)
  3. Flexibility...you can split the two LS's up and use on RTN if needed.
All in all pretty pleased with this set up.
 
Last edited:

Adam

Well-Known Member
5PLS
The Base setup issue with the APC offset and Antenna height have been fixed in the last release versions. Now, simply select the base point and enter the antenna height under advanced - antenna. RTK and DPOS work correctly. Please check into points to confirm. I like to stake out the base and get right beside it and look at the cut/fill. It should be near zero.
 
Top