I’m totally new to all of this. I’m considering purchasing a mavic 3M drone with an RTK module.
I’m getting a little confused about the use of base stations with and without a modem vs just using a Network Correction Service.
Can someone explain to me if a base station is even required if the drone RTK module is connected to a local Netwrok Correction Service? Advantages and disadvantages?
I’m just having a hard time trying to understand things with base stations and local correction services and which one to chose, or if I need both. Also the modem or no modem receivers is a bit confusing as well.
Is anyone able to clarify these concepts and questions for me because my small brain is having trouble understanding it all!
To obtain centimeter-accurate coordinates on your RTK drone, you need to provide it with corrections. As a source of corrections, you can use either your own base or corrections from the local NTRIP Service.
Getting corrections from the NTRIP service requires a stable internet connection at your work site. Also, you need to ensure you have NTRIP stations in the 60 km range for RTK. Plus, keep in mind that NTRIP services sometimes charge a fee.
Using your own base station, for example, Reach RS3, helps you not depend on these factors. You can place the base in a convenient location for you. It’ll shorten the baseline, which is good for results. To pass the corrections via the internet, you can use the free Emlid Caster. But you can also use the local NTRIP feature and pass the corrections without the internet. Here you can find a more detailed guide about the possible integration.
So, if I’m just using a rover receiver (say an RS3), then I am required to have access to a local NTRIP service provider to get accurate georeferenced data points?
But if I’m not using a local NTRIP service, am I still able to obtain relative accuracy instead? Especially if I set my first data point as a zero benchmark point and take further levels using your Castor of Flow apps?
You don’t need to use RTK at all. You can take the log from the drone and a log from a base station and apply the corrections on your computer. It will be more accurate than RTK and frees you from needing a connection during flight.
You can either use your own base station (RS3) or download logs from a CORS or other public base station. If you use an RS3 you have to make sure the coordinates are accurate for the station. I know a lot of surveyors rely on benchmarks but their accuracy will depend on where you live. For example here in Hawai’i we are moving at about 10cm per year away from North America so our surveyed point coordinates are not accurate.
If you leave the base station in place for a long enough time collecting a log, you can then take that log and a) calculate the position of the base and b) use the logs + calculated position to correct the drone log and fix the photo positions
Yep. You can work with real-time corrections or, as @daygeckoart mentioned, in PPK. For the latter, you’ll need to process the logs from the drone and the logs from the NTRIP service.
Emlid Flow doesn’t support working with arbitrary coordinate systems for now. But you can use localization to work in a coordinate system with a false origin. It’s possible both when you receive corrections from the NTRIP service or your own base. Here is a post to learn more about the workflow.
