VRS Subscription or Single Base

I doubt you need used equipment to meet your budget. To start just set up a new receiver at the office all day and use your RTK base and rover as you do now. One hour static? I cannot imagine you can locate and measure all you have to for an EC in such a short time. Once you have established your own CORS elevation you can post process immediately when you return to the office. You will most likely just be downloading other CORS as a quality check. $3500 first year gets all varieties of static receivers. $3500 second year gets you all the connection gizmos.

Paul in PA

I doubt you need used equipment to meet your budget.

I agree. A Javad Triumph-2 with L1/L2 and GLN plus RTK is a bit less than $5k. You'll probably want to get a fixed IP address for the outgoing corrections, and you'll need a SIM card and account or portable WiFi hotspot for your rover (assuming your rover is capable of making the connections). A portable hotspot (e.g. Verizon Jetpack) is only about $150. I think you're still under $6k out the door with new gear.

Thanks Paul. 90% of my ECs are single story, slab on grade or mobile homes. So no basement or crawl space measurements. Easy to get all those measurements in less than an hour.

I already have a static IP at my office. Can the Javad be setup on my office internet or would I need to use other software like SNIP to setup a ntrip server?

My rover is a Trimble R2 and the Slate data collector already has a SIM card. That's what I use with VRS right now.

andrewm, post: 430204, member: 10888 wrote: I already have a static IP at my office. Can the Javad be setup on my office internet or would I need to use other software like SNIP to setup a ntrip server?

The T2 has WiFi and Bluetooth capability; WiFi would probably be the easiest connection if you can locate the receiver close enough to your access point. I'm much fuzzier on the NTRIP server setup, as I don't use one. The T2 can output direct to TCP, and that's the way I do most of my base-rover work now, with the T2 sending TCP corrections over a Verizon Jetpack to my Triumph-LS. If the R2 can work with a TCP connection, your can skip the NTRIP server entirely.

You might want to talk to John Evers ([email protected]), as he seems to be the most knowledgeable about Javad gear and IP connections. Or post something over on the https://support.javad.com/index.php?forums/triumph-2.5/&apos ;">Javad T2 board, where others are likely to chime in.

A javad Delta 3N receiver ($4,150) and GrAnt-G3T antenna ($1,800) might be a good solution. Pair that with SNIP ntrip caster software and I should be set I think.

I'll post on their forums for opinions.

As long as you are OK with the limitations of single baselines at 20 km, the better solution long term is probably running your own reference station, even the best run networks have issues from time to time and they are all out of your control, when something goes wrong with your own, at least you can only blame yourself.

SHG

I think your statement about 0.2 to 0.7 feet variation in elevation using the LSU C4G is a bit alarming. I have used their system, i think it works great. You should be getting repeatability of around 0.03 m in the vertical in a well run system, which i think theirs is.

One of the main selling points of using C4G is that many (most?) of the benchmarks in that area of the country are highly suspect due to regional subsidence. From C4Gnet home page: In 2006, Louisiana State Legislation made C4Gƒ??s CORS network the vertical control standard for the State of Louisiana (http://c4g.lsu.edu/index.php?option=com_content&view=article&id=95:la-r-s-50-173-1-vertical-control-standards&catid=21&Itemid=198&apos ;">LA Rev Stat ?? 50:173.1). This infrastructure is currently the backbone for surveying in Louisiana...

So using C4G should get you a consistent set of elevations that are related to reality. If you put up your own base station in an area that is subsiding, the base will subside as well, and over time you will need to correct for that. And tying in to local benchmarks (i.e. "localizing") could be very problematic in that area.

I will add that we recently did a job using a VRS and the results were pretty noisy, I believe the problem was with the VRS, so they are not always perfect. When you have short lines (5 to 10 km max) it is probably better to use a local RTK base, data is less noisy. I still get corrections from the local base over a cell connection, so it appears the same as VRS, no radio limitation. That can be dangerous, you want to watch your base-rover distance with single base RTK.

I agree with John... I wouldn't be that surprised by 0.2' fluctuations in the vertical but that should be worst case. If you're typically seeing that or more there might be something else going on.

My statement regarding LSU VRS is compared to 1-hr static processed with Trimble RTX-PP. I have sat on several benchmarks in the area that were established as part of the height modernization study and the Trimble RTX-PP results are always within 0.1 of those benchmarks. Here are a couple examples:

DP2512 - 77.33'
Static (RTX) - 77.38'
Static (OPUS-RS) - 77.17'
LSU VRS - 77.14'

DP2520 - 48.88'
Static (RTX) - 48.83'
Static (OPUS-RS) - 48.67'
LSU VRS - 48.52'

My process for ECs is to collect a 180 epoch observed control point using VRS before and after the 1-hour static. The VRS is consistently 0.1-0.3' lower than the Trimble RTX-PP. But I have seen it up to 0.7' lower on one occasion. Who knows what could have been going on at that point.

Sounds like that point was an outlier, there's no telling. The numbers above confirm my thought that the VRS would match OPUS better than it would RTX-PP.

Interesting that RTX-PP is closer to the published values though. I think what you may be seeing there is in part the result of subsidence.

I would take a look at the SmartNet subscription services. I believe a statewide subscription is $2,400 per year. Looks to me like Louisiana is completely covered by their service.

https://www.smartnetna.com/coverage_network.cfm

I've looked into SmartNet before. But if I'm going to use a VRS service, it will be LSU C4G. I have personal contacts there that can help if something isn't working.

I am so glad that VRS in Kentucky is free......

rberry5886, post: 430429, member: 232 wrote: I am so glad that VRS in Kentucky is free......

Oh it's not free, the people of the Great State of Kentucky are paying for it one way or another.

The late great Dr. Roy Dokka once told me that his rates were based on the fact that it cost him $500,000 per year to own, operate, and maintain the Gulfnet VRS, and that if he could find someone to sponsor him in that amount he would happily open it up free of charge.

A suggestion, which is what I do, is use a base and broadcast by radio. I've got enough control points around and there are enough points published that I am almost always within RTK radio distance on my work.

No fee to use the VRS in Vermont.

I would be very nervous to base a piece of my business infrastructure on the whim of political budget funding. Especially with Louisiana politics! I'll gladly pay for a quality service like LSU C4G.

When you guys start talking about free VRS I get jealous. I guess its all about economies of scale. More residents, more tax, more is done. Little old South Australia is lagging well behind much of this continent. If I look at CORS stations in S.A. you could swing a cat and not hit anything. Eastern seaboard is a completely different story. Rumour has it powers that used to be decided that this was not worth investing in. We are paying the price now... literally.

not sure about the low cost of owning and operating your own base station. I have been running a RTK base station for about 16 years using Leica hardware and software broadcasting corrections over a static ip. Had there been a RTK service at that time, I probably would have joined. If I was faced with a service vs running my own base today, I would chose the service.

There are pros and cons for each. The plus for us is that most all our work is relative to an antenna on our tower. The con is that the further we get away from our office, the more the RTK accuracy degrades (static and post processing keeps us accurate).