L1 GPS Systems

They are very useful. I have 3 ProMark3s and they will perform as well as any dual frequency static GPS receiver. The only downside is you can't send the files to OPUS.

Hands down the simplest to operate and process is the Ashtech Locus units. They run for 100 hours on D batteries. Of course, since they pretty near perfect, they stopped being produced about 12 years ago. But if you can find some used units, that's the best IMHO.

Gary

I have 3 Promark 2's and have had great results 95% of the time. I always set 1 on a NGS marker to start.

Bruce

Yeah for a static unit all you really need is an on/off switch, a reasonably accurate watch and a notepad.

The Sokkia Stratus was a lot like the Locus, except with 12 channels. We bought a set of Stratus at my old job, after a couple of Locus went bad. However, the Sokkia software was no where near as good as Ashtech Solutions. In fact, I stopped using Sokkia Spectrum, converted all the Stratus files to Rinex, and imported them into Ashtech Solutions. A little more work that way, but well worth it, IMO.

I have to agree, the Locus are nice recievers. When I went solo couple of years ago, I picked up some Locus because they were cheap, good, and I was very familiar with them.

I like the Trimble 4600LS, solid, low power consumption units. But a thing of the past. Value on the market = very little. Will run them until they stop functioning.

:beer:

I've got 7 locus units now... I bought 3 new in about 2000 and have added the rest over time. You can get some great results running 7 units at a time. I still see them on ebay occasionally, usually in the $500-$1000 dollar range. I've been looking for some RTK units, but these get the job done for not a whole lot of investment.

Very happy here with Sokkia GSR 1700 CSX tough small lite RTK and static
10 hz update in rtk

not toyish like promarks or locus.

And yes a modern great L1 GNSS product made by novatel sold by sokkia

i think most L2 is for morons sucked in by salesmen

Peter K

>
> i think most L2 is for morons sucked in by salesmen
>

Sorry but that has to be the most ignorant thing I have heard in a long time.

I use 4 Sokkia stratus units. Nice and small. One button on/off. Excellent battery life!!! I'd guess 30+ hours per charge. Excellent results if you get a solution - which in always in very open conditions. Side by side with a ProMark 2 in the woods, the stratus won't work but the ProMark2 will. And as others have said, projects that don't process in Spectrum usually process fine in Ashtech Solutions.

I couldn't agree with this statement more. But the final straw for me with Sokkia Spectrum was catching vectors reported as "pass" when they were significantly off. You can usually catch this when all your vectors report as "pass" in processing, but "fail" in adjustment. I reprocessed the same data in Ashtech Solutions, got significantly different results at processing, and the Ashtech Solutions adjustment passed just fine.

This was to establish a BM at a remote site. Due to the confusion, we ended up running a level run to the site anyway, and found the Ashtech results within 0.02', and the Spectrum solution off 0.70' for elevation. But the Spectrun solution did report FAIL, just to be clear. But there was no reason for this. The benchmarks and site BM were wide open to the sky, and we had let the units run plently long. False positives on static GPS sessions, under great conditions, is too much ...

Trimble 4600's here. I think they're adequate for what I do, boundary surveys. I also have the benefit of open sky's (Great Plains). I've never had the desire to purchase L2 units, instead I purchased a robotic total station for areas that are impractical for L1. If I had to purchase again I'd go with either used Ashtech or used 4600's, should get 'em quite cheap off of Ebay.

I'll add my weight to L1.
I have both RTK and L1 and wouldn't be without my Stratus and Locus.
I agree with comments on processing but to repeat some info passed on to me from Sokkia support and which I have seen make huge improvement in results.

The key to processing Stratus data is to go into the “Process Parameters” option and in “Advanced” you need to deselect “Force unreliable fixes to float (TI test) and change the SVs used for processing to GPS Only. (Not Glonass & GPS)

I still prefer Ashtech Solutions.

Wow, lots of L1 lovers out there.

Probably time to dust off those old L1s and put them up for sale since they are never touched anymore.

Wow...lots of input. Thanks for all the info. General consensus seems as if people like there Ashtech systems out there, along with the Locus. Looked on Ebay over the weekend, a set of two Promark2 went for $2k. Not too bad. Seems they hold their value even after all these years.

Ken I think you would be well satisfied with L1 solutions (use of GPS ie) and over shortish distances (I've used mine out to 20km, but mostly 8-12km) and proper attention to where you set them up (as in any GPS)there is proven, to many of us, statistics that say they are worthy of their invention and continued use.

I've had 'knockers' but I doubt they have ever really used them and are probably of an RTK L1/ L2 and now Glonass and beyond ilk that to them anything less is like going back to a Gunters chain.
I don't say that to denigrate them one bit.

I saw a couple Locus on Ebay the other day - one a Topcon branded one, both at a grand each. I thought that too dear given their age.

If I recall well, for static observations/short baselines (sufficient coverage for a lot of jobs), the default settings of the processor would only used the L1 data. A L1/L2 system did not make any difference. This was a few years ago with TGO. Maybe it changed, I don't think so.

Based on that, I can see why a L1 only system would still attract today.

:beer:

I think you're thinking of C/A code carrier receivers - the early receivers used the C/A code only to acquire & lock on to the L1 carrier, and the C/A code is not modulated on L2. So if the receiver was an actual dual frequency one, it only measured the phases of the L2 carrier by a codeless technique (non P-code). It probably didn't make much of a difference (performance-wise) over a single frequency receiver. But a dual frequency P-code receiver, capable of locking on to both L1 & L2, makes a pretty sig. difference. L1 only def has its place though for static & rapid-static, and affordability is a huge plus too. Wish I had some!

> But a dual frequency P-code receiver, capable of locking on to both L1 & L2, makes a pretty sig. difference. L1 only def has its place though for static & rapid-static, and affordability is a huge plus too.

I believe Georges is referring to the fact that an L1 fixed solution is the gold standard for vector processing, and that the default baseline processing style in TGO attempts to produce an L1 fixed solution for all baselines under 5 km. The L2 data might allow the L1 integers to resolve a bit quicker, but for 5 km or less, L1 is as good as it gets.