Using an LS as base

Nate The Surveyor

Well-Known Member
As Galileo, and Biedou get closer to being available, I consider that there are 3 options to be available for a new base.
Right now, we can use T-1M.
Or the LS.
And, in the future, the T-3.
I can see an advantage of getting another LS, with internal radio. 1 watt. (Broadcasting)
If the new constellations prove to help only some, then I can use 2 rovers, with the T-2. This could improve many things.
If the new constellations help a lot, then the base having a LS on it, could simply speed things up. Later, a set of 3 LS's could form a dynamic setup, with 1 on base, and leapfrogging the other 2.
In any case, how hard is it to use an LS on base? Is it as automated as the T-2?
I just want to talk about it, for planning purposes.
What do you think?
Or, buy another LS for base, for now, and a T-3 later. This really could expand the usefulness of things.
Some other users also seem to favor the idea of an LS on base.
Nate
 

Adam

Well-Known Member
5PLS
It's not terribly difficult. It is not the same setup procedure as the T2. The hr or hi and the antenna phase center offset has to be taken care of by the user by adjusting the elevation of the base point to coincide with the apc. It's a simple formula.
 

Adam

Well-Known Member
5PLS
Apc (antenna phase center) The offset from the arp (antenna reference point). It is -0.375ft.
 

Symon

New Member
Our solution with two LS's is just not to ever set the base up over the mark and use the m-local to adjust as getting the pole height right is easier for us.

We didn't really get all the ins and outs from the guy we bought the LS's off so still learning as we go. We follow the same process as in Adams document to start the base with the added step of recording a point in the collect screen (usually just 10 epochs) of code data (make sure you action profile isn't requiring a fixed solution etc.) and then using the "select from list" option rather than enter "enter position"
 

Matthew D. Sibole

Well-Known Member
5PLS
The way I do it is after I start the base I then switch to a WAAS float profile and go into collect on the base and start collecting a point. Then when you are done for the day you stop collecting that point on the base. You then go to files and tap collected with points and transfer the static file of the point you collected with the base to a flash drive.

In the rover you hit one of the RTK points and hit recover base point. Then you attach the static file of the base to that base point. You then hit recover DPOS session and then it can be sent to DPOS.

I know it sounds like a lot but it is pretty fast and works well.
 

Nate The Surveyor

Well-Known Member
Does it allow the weighted average, between the shots, taken via different rovers?
I can see simply adding a letter designator to the point names. Rover 1 is direct point numbers. Rover 2 is n1..n750, and so forth.
@Matthew D. Sibole , so this is how you get multiple LS's, to post process off the same base file. I'd guess the base NEZ could be slightly different, if some time elapsed, between DPOS sessions. (For the different rovers) In that case, you'd have to assign the base value to some of the sessions.
 

David M. Simolo

Active Member
Great thread guys and all stuff that's been on my mind too moving forward. I have been avoiding using an LS as a base because it had been purported to be not the easiest but it sounds like some of the hurdles have been figured out. Right now we have 2 LS's, a T2 and a T1M. Something's going to change when we get Galileo up and running so I'll be giving this further thought.
 

James Suttles

Active Member
Use 2 LS's exclusively, and there is a procedure to follow, but once you do it once or twice, its not bad. If they write an interface to take care of those steps, that will just be icing on the cake.
 

Symon

New Member
We've got comfortable now with the random base setup and m-local on another control mark method.

We also would like to be able to install a mark and then set the LS base over it, enter a height above the mark (this looks like a nice to have given the workaround in Adam's very helpful pdf above), start the base logging static and then go off and m-local on a known point. At the end of the survey then store the static at the base and then output a RINEX file to use https://www.linz.govt.nz/positionzpp (similar to AUSPOS or OPUS I think) that has the correct height above the mark.

What I'm unclear about is what to we do about a height for the base mark for the shot we take. I see Adam's complicated (and prone to mistake in the hands of staff, hence why we prefer the m-local) method for setting the height to get the base to broadcast correctly but we don't need to do that as the m-local sorts out correct height for the rtk work (and much more reliably). We only need to ensure the observation at the base has the correct pole height; do we just enter the pole height as we would on the rover in the observation screen? I think it is as simple as that but the complicated method to start the rtk base has left me wondering if there's more to it?

The other question is how then to extract the stored point from the base in RINEX format? Also it would be good to know how best to get the base observation data into the rover so we can have try of DPOS?
 

Symon

New Member
Opps missed that, will have a crack at that. Its a great learning curve, always something you discover that you can do better with this kit!
 

Symon

New Member
The way I do it is after I start the base I then switch to a WAAS float profile and go into collect on the base and start collecting a point. Then when you are done for the day you stop collecting that point on the base. You then go to files and tap collected with points and transfer the static file of the point you collected with the base to a flash drive.

In the rover you hit one of the RTK points and hit recover base point. Then you attach the static file of the base to that base point. You then hit recover DPOS session and then it can be sent to DPOS.

I know it sounds like a lot but it is pretty fast and works well.
Hi Matt,

Tried the above today. Started RTK on base, then using standard WAAS profile (had to edit it to 'stop with stop button' rather than stop after 10 epochs) started observing, at end of job stopped and accepted observation, tapped 'files', tapped 'collected with points', clicked the radio button for 'GNSS Raw' but nothing shows up? Not sure what I missed?

When I tap 'points' and then tap that table screen I can see it has 11432/11431 epochs (5Hz) so it seemed to store those epochs but not raw data? Suspect I missed something else?
 

Symon

New Member
Right that's the key step that we missed, its obviously not a default setting for the WAAS Float action profile and I assumed because it was logging epochs it was storing the data. Bother, don't get to try out the DPOS/Positionz-PP this time I guess.

To used to a Leica mindset that if the epochs are storing your getting the (raw) data in the background.
 

Symon

New Member
Adam,
Working through your pdf above I'm wondering why you subtract the offset to the APC? Looking at the receiver I would have thought the APC was above the top of the pole/tribrach+legs height you measure to bottom of the LS being used as the base? Also we're metric in NZ so assume we'd be using 114mm?
Thanks
 

Adam

Well-Known Member
5PLS
Adam,
Working through your pdf above I'm wondering why you subtract the offset to the APC? Looking at the receiver I would have thought the APC was above the top of the pole/tribrach+legs height you measure to bottom of the LS being used as the base? Also we're metric in NZ so assume we'd be using 114mm?
Thanks
Puzzling isn't it. I don't know the answer but I have proven it against marks that I leveled between. 114mm sounds correct but I don't want to bet the farm. I don't have it in front of me.
 
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