Network GPS vs RTK

VRS is the cat's meow. Remember that VRS is not the same as just network RTK, it is like icing on the cake in addition to network RTK.

You can get either flavor (single base or VRS) from a VRS server.

VRS seems to have slightly better positions MOST of the time because of the interpolated atmospheric corrections. (edit: I forget if that is specific to VRS or if it is applied to all the base stations' data just by virtue of being tied to the VRS server)

WSRN has a clock correction that is applied to all the various base stations, derived from the network's receivers overall, that accounts for the network delay of however the base station receiver data is getting to the network server. WSRN also injects the rapid orbit data so that your RTK corrections are a little better than using the broadcast orbits alone (like with base-rover RTK).

Now, all that is great fun and maybe useful but the revolutionary part of having a well-run RTN nearby, especially a VRS server, is being able to download all that great time-corrected base station data and post process with it.

I did a lot of RSE's comparing WSRN to CORS and found that post processing with topcon tools usually the verticals were 1cm at 1sigma with WSRN base vs 4cm at 1sigma with CORS data. How did I test this? I trig leveled between about a dozen occupations and put it all in star*net.

(edit: note that this was 45-90 minute static. At my current work where we use the RTK VRS I would say the verticals are usually repeatable within a tenth or better one sigma. That's doing VRS in town with probably 5-6 base stations within ten miles. Dunno how it would inflate with longer baselines. Supposedly the VRS takes out the PPM more or less entirely when the atmospheric stuff is being predictable. )

If you are out of town and can't get cell signal but you can collect static, then post-process using the RTN's base station files you can get really good results, even at longer baselines, for the reasons I mention above. The VRS option can make a noticeable improvement most of the time, for RTK or static. And it really shines for under-canopy static.

Some research shows I might use an RTK Bridge and a UHF base radio and not need a base receiver. I would need to locate the Bridge where cell signal existed. I would need an VRS account. When I'm really out there (no cell signal at all) I'd need to use the base receiver and the UHF. I can probably do this for 6-7K. It appears the bridge, or a version of it, can link with the internet at the office without a cell signal and no need for a base receiver. That would be nice.

So what's the options for 35W UHF base radio's?

After that I suppose it's time to start saving for the R10 & TSC3.

I'm thinking something like http://www.universal-radio.com/catalog/tnc/5718.html
plugged into a lower-frequency radio, something in the 6m to 11m range, with a suitable antenna
at each end. Better for hilly terrain and canyons. The lower-frequency business bands are all sitting empty because it has been trendy for years to use the higher frequencies.

I'd like to try using NVIS antennas and HF radios for RTK but I don't think RTK will go slow enough for the 300 baud limit on HF radio. NVIS bounces stuff straight up and down off the ionosphere and so covers an area of 80-200 miles radius without being blocked by terrain.

Network GPS corrections to UHF radio

Is there software that would connect via the internet, get the VRS corrections, and output to the input of a UHF base radio say, at my office from a laptop or PC?

Same question for a smart phone. An App to connect to the VRS and output to the input of a UHF base radio to broadcast the corrections?

I find that it is critical to have both.

As far as needing modules, if you are talking about a modem, I would seriously consider doing the mifi thing, if your dc does wifi. I used to use Bluetooth from my cell phone, so there are lots of ways to get corrections.

Static comparing OPUS or NGS CORS with our network here (WSRN) reveals just how good a job gshrock and friends are doing. My experience mirrors that of above post.

However, my experience is that I could not live without my standalone base.

Network GPS corrections to UHF radio

One of the RTN bases is about 30 miles south down the valley from me. The other three RTN bases around me are definitely over mountain ranges in the next valleys (40-50 miles).

My TSC2 doesn't have WiFi.

We used the VRS in NC for years , but just went back to a base and rover setup . We had alot issues with verticals and horizontals not checking . If you want to use it for horizontal it may do what you want . I seen alot of sloppy surveying with it . We had regulated it to just setting pairs on the job to get on grid . I just traded my VRS rover set up for a new Hiper II setup a couple months ago after frustration with the accuracy with the VRS . Its not what you think.

In your area I wouldn't worry much about changing out your base etc. just to be compliant. Do you have a frequency scanner to see what the traffic is like? You can also do a frequency search on cityfreq to see who is licensed in your area. Chose a frequency that is never used, monitor your frequency before startup and be on your way.

Pablo B-)

Network GPS corrections to UHF radio

I called the dealer about the WiFi. I was told they all have it. For some reason the software for WiFi and Bluetooth is not installed on my DC. I'll need to take it in.

I can scan with the radio. Just roll through the frequencies and listen for the static blasts or voice traffic. I rarely hear anything, sometimes 1 or at most 2 other base stations (out of about 16 channels). Once in a while some voice traffic but I think cells phones have put an end to most of that, at least around here.

We have our Javad base setup to transmit corrections from the Verizon CDMA to a static IP address and/or the built in UHF radio. Pretty slick setup any number of rovers can login to the IP address and get corrections. We can also access the Leica network from the rovers or base but I find having a local base gives a much better and repeatable height solution than is possilbe from VRS or Network solutions.

ditto to Robert

RTN is great for bringing control into your project by averaging observations. local base/rover for topo and better repeatability on the project however. It kind of hurts to have to say that because I am close to the operation of our state RTN. It is what it is.

I am seeing a couple folks here saying the same thing, might as well use OPUS it would seem.

I am more of an OPUS / Static guy myself too, BUT I thought it was just me being "old school". Don't get me wrong, I think the RTN's are a nice addition, BUT I find the same, when you need tight stuff, rolling your own in some fashion just seems to provide better results.

In addition there are too many locations that a RTN or cell coverage is not going to cover you in some areas I work, not getting rid of the base/rover yet.

SHG

This is an interesting thought.
The higher the frequency, the more data it can carry, and vice versa. Our data packets are very small.
The lower the frequency, the more the signal will "bend" around terrain. I hear EMTs, police, and firemen all complain about the decreasing coverage, but they have all migrated up the spectrum.
We are used to getting what's left over, but in this case, it may be a good thing.