Can someone point me to a good document (or post the steps here) that explains in detail how to use the RS+ in RTK mode connecting to a local CORS station? I’ve read info on how to use CORS to do PPK, but where do you go to get the server information and how to enter it so the RS+ will connect? I was only able to find where to download data from CORS for PPK. I also discovered SNIP and RTK2GO but as far as the United States goes the RTK2GO NTRIP Casters are too few and far between. There’s much better coverage with CORS compared to RTK2GO but I can’t find info on how to connect to CORS in realtime RTK as opposed to PPK. I also don’t see any other public/free NTRIP caster networks for the USA with decent coverage? I want to use the Reach in multiple states and can’t afford to subscribe to each states correction network. I think Trimble has VRSNow but that’s pricey also.
I’m wondering if maybe it’s not even possible to connect to CORS for realtime correction data for RTK over the Internet?
I’m also wondering how to estimate expected accuracy based on the distance the caster is from where I am?
Jazee, I don’t think that the NGS CORS network provides any RTN casters for RTK, at least in my state. Your local state agencies may provide the service, but like here in SC it cost to use the service provided by SC Geodetic Survey. It’s very reasonable at $600/year. Some major cities and some state agencies (highway dept) may provide for free. There’s a lot of work involved in maintenance and keeping the RTN functional. Our state RTN has been down maybe 2-3 times in the last two years. It’s a dependable system thanks to the people that maintain it. Usually if they are upgrading or need to shut it down, they will notify the users.
Your accuracy will depend on the length of the baselines plus the receiver specs of error per ppm. Many RTN’s will compute a virtual reference station close to your actual position usually less than 10m. It also depends on the densification of the network. More stations equal shorter baselines and higher accuracy. Using our RTN, accuracy is usually 2-3 cm in both H/V components.
The CORS stations do provide RTK corrections, but that really depends on the states you are planning to work with. Nevertheless, you still need to request the NTRIP credentials from the CORS operator in your state. The map of CORS stations includes all the stations available with the contact info so that might be useful.
Our guide on how to work with NTRIP might be of use too.
Speaking of accuracy, it really depends on more factors than just a distance from the base station. As Brian noted, you can expect the centimeter accuracy from the RS+ if the base station is situated in the range of 6 miles. But the shorter the baseline is, the easier it is to calculate the solution for the receiver.
There are still some states that do not offer VRS. They use what is normally referred to as Nearest or closest tower. This is a single base solution instead of a multiple as with VRS.
Not sure where you are located or where you are looking at travelling but I have access to multiple states that have free access. They include: Alabama, Ohio, Indiana, Iowa, Michigan, Minnesota and Kentucky. There are also states that do not have one, Illinois for example. If you are doing it as a business, you might consider DigiFarm VRS. It is a subscription but a very good system and a very large coverage area if in the corn-belt area.
