A company I work with three days a week has had a Reliance for sevral years. Since their Psion went on the fritz a year ago and they began using a Husky they have had more problems than results. But they have not gotten new cables, so who knows what. I have done several projects for them with my ProMarks, but recently they purchased a Leica RTK setup as well as the DGPS conversion setup for one unit. This DGPS setup has a similar antenna to the Reliance, L1 only.

Isn't that like shooting yourself in the brain so it is easier to use just one side? Is it not possible to use the DGPS signal to solve an L1/L2 solution rather than doing an L1 only solution?

That one receiver only was just used in DGPS mode for a tree location survey. Heavy canopy to be sure. Holding the two aerial targets that were started from, several checks to field staked traverse and centerline points missed by 20'+, one was 70' off. Having RTK capabilities, I do not know why it was not used, but my question here is regarding DGPS capabilities and possibilities.

They want me to help out in the field on an RTK boundary and wetlands survey, but do not want me to bring my ProMarks along to throw in the mix. GPS control benchmarks are under 3 miles from site and include the project I did for them with the ProMarks 3 months ago.

That project was, eight aerial control targets, 2 GPS benchmarks, 2 NGS verticals and a traverse PK I found at an intersection. Long occupations at the 4 corners, 3 aerials and the PK. Four of the 8 hit within 0.04' H & V to my traverse, the others averaged 0.1' H & V with the 30 minute occupations on some intermediate points. I held the GPS to correct a traverse error, closure off by 0.10' and I had a good hunch which was the problem setup. We had traversed to an adjoining road one day, I set mag nails and shot the PK found as a traverse point at the end of the day. One of their one man field crews, was next in the area and did a location survey of a new cul-de-sac road. He left a mag in the new curb and near the same intersection to later tie it in. We get back there 3 days later and 1200' of road and the cul-de-sac have been paved, double overlay it look like. We dug out the mag which we had occupied to shoot the PK at the intersection, set a new mag as it was less time than digging out, located the mag in the curb, the sound of the mag set by the other crew, a MH and a fence post, so the points could at least rotate to some known features and then reshot all the EP and BC shots.

Tree clearing is being done today and I asked the crew to make a traverse tie across the tract. I wanted to do this during the field traverse, but I was slower than they expected, and they wanted the job done to their standards, not mine.

I am not trying to convince them to run their business differently, but want to get opinions for my own benefit at least.

Paul in PA

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Buried in the rhetoric above somewhere.

Given a beacon signal allows a more accurate real time position for an L1 signal, can that better L1 position be combined with the L2 data to give an even better L1/L2 position?

Paul in PA

LPL said ..."Given a beacon signal allows a more accurate real time position for an L1 signal, can that better L1 position be combined with the L2 data to give an even better L1/L2 position?....


Beacon corrections are based on range corrections for SV's in code positioning. Carrier smoothing of code positions happens on good quality receivers, but is not part of the DGPS correction signals sent out by Coast Guard beacons.

So, if you configure your dual frequency unit to receive beacon corrections you MAY get better carrier smoothed positions on your personal unit BEFORE the code corrections are applied to the ranges, but you won't see beacon signals applied to any L2 data.

Why? Because L2 code is encrypted for military users only. Your L1L2 receiver only looks at L2 carrier and tries, through widelaning or other techniques to correlate the L2 carrier with the L1 signals and use them all for faster ambiguity resolution.

Your wish is actually occuring through the newer starfire decimeter signal subscriptions, etc. They use a correction signal based on a virtual network to give you more accurate corrections than a single point based correction such as USCG DGPS.