L1 Limit RTK

RTK is only possible with a dual-frequency receiver.

> RTK is only possible with a dual-frequency receiver.

L1-only RTK is certainly possible, but has generally been avoided because of its sensitivity to SV numbers, lock loss and range limitations. Trimble sold L1-only RTK systems years ago, and Ashtech (then Magellan or Thales) revived the technology a few years ago with its BLADE processor, which uses SBAS and/or WAAS SVs in the solution.

Aschtech sells an L1 only RTK system.

I don't know about the range, though.

If you don't need to stake out, L1 stop & go works really well for topo. The good news is there is no communication issue because you post-process.

A good friend on mine uses the Promark 3 L1 RTK, and it is pretty slick, from what he tells me. I think he has about a half mile to possibly 3/4 mile range, but he has the stock radios.

He really likes it, and it well worth what the price tag is.

As other said it mainly depends on the radios bundled with the system and the stock radios (with the ProMark 3 RTK anyway) are basically line of sight (1/2 mile to mile max typically).

Pacific Crest has the HPB or LPB UHF radios for the base and a rover radio which can increase range. That being said, since it is L1 GPS (and SBAS) only, you will be limited to about 5-6 miles. Even at that range your TTFF and maintaining lock can be an issue.

The ProMark 3 RTK is great for small construction site surveying and anything under a 1-2 mile radius form base to rover.

Peter if your system comes with different base radio antenna types (ie short stub antenna and longer whip antenna) check the documentation for the broadcast characteristics of each to use the one best suited to your terrain and observing conditions. You also may find using a second radio as a repeater in some situations a significant production boost since you will be able to limit moving the base station with planning.

From experience using an L1 RTK system a few years ago... while you are initialized, drop control points frequently that you can use to reinitialize the system after losing lock...and you will...a lot.

I don't know about the initialization procedure with L1 RTK.

With PPK stop & go I simply start collection shots. I have gotten on-the-fly initialization with as little as 5 minutes of data collecting in the file. I usually go at least 15 minutes to be sure I will get OTF initialization later in post processing and most S&G jobs are longer than that and have good sky (otherwise I would use the total station).

L1 RTK initialization methods are basically the same as those used for post-processing. You can utilize the kinematic bar, on-the-fly, static on-the-fly or from a known point (known point must have raw data associated with it, if I remember correctly).

Does single frequency real time require the redundancy of rerunning the points at a later time before the data can be relied on?
jud

I used the bar for about the first two months until I figured out OTF works very well and is easier.

For known point I think you have to have collected the point and not deleted it from the receiver. The point has to be in there somehow. I haven't used this method.

"L1-only RTK is certainly possible, but has generally been avoided because of its sensitivity to SV numbers, lock loss and range limitations." My contention is that with the limitations of L1 RTK. Your time is much more valuable than the extra ~$10k that you would have to spend on a multi-frequency RTK system.

Hello All

To begin with the question would Gps makers like ???(your brand) cripple the
solution from fix to float to Protect sales of L1 L2 for greater than
say 5.0 KM.

Today had float solution with 1 watt radios at 21 km satel Modems

Note the point is the 1 watts where working over 21 km (13 mi)
and the above with some small mountain obstructions

To re ask the question Do manufactures cripple L1 RTK to
protect L1/l2 RTK For the long shot deep pocket user

To be blunt the Sokkia GSR 1700 CSX RTK with Carlson Is flawless and wondering
mostly on the theoretical limits of L1 RTK. The GSR 1700 CSX is light to the point
that in day to day RTK survey it beats The C--p out of robot or others heavy RTK L1-L2 bloat-hard-ware GPS..

Note The GSR 1700 CSX 30K$ require no stoned age init bars etc.. just turn on base and go to work RTK with rover not a junk budget system

Thanks

PK

I dont think it would be the equipment manufacturer and more the inability of a L1 only solution to be able to solve ambiguities over a 10-13 mile distance. That is what L2 is for. At that distance you are already pushing the manufacturers specs for L1 only static.

Same goes for L1/L2 gear. Using RTN I can get a fix over 50 miles from a base using cell corrections, however at 100 miles all I have been ever able to do is get a float solution.

And sorry, no matter what you say, L1 only will never perform as good as L1/L2 gear, especially at any kind of longer distances.

I agree, L1 is for relatively short distances. It would be better to get a control point for the base station near where you need a lot of RTK shots using Static methods then there wouldn't be an issue. If you only need one or two shots a long way from the base then a Static session won't really take that long especially when you consider the drive/hike time.

> To re ask the question Do manufactures cripple L1 RTK to
> protect L1/l2 RTK For the long shot deep pocket user
>
LOL! You can rest assured, this is not done by manufacturers. Either the receiver receives the L1 carrier wave, or it does not. It doesn't matter if you're doing static, rapid static, or kinematic, there is no "crippling" done to 'decrease range' to try to steer users to dual frequency gear. If you're getting 20K distance on some of your RTK work w/ L1 only, consider yourself fortunate.

> LOL! You can rest assured, this is not done by manufacturers. Either the receiver receives the L1 carrier wave, or it does not. It doesn't matter if you're doing static, rapid static, or kinematic, there is no "crippling" done to 'decrease range' to try to steer users to dual frequency gear.

I wish that were true, but it's not always the case. Topcon, for example, set up certain models of its Hiper receivers so that they would not transmit the correction data when the distance from the base exceeded a prescribed distance. It wasn't an L1 versus L1/L2 issue, but rather a means of charging users more money for more range.