Basic Config Question

Reach Module / M+ / M2 Getting started
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I have been reading this forum and positioning information online for over a year. I think that using correction equipment is one of those things that for many of us, we will not fully understand until we are hands on and using it.
I am building a company with my own financial resources and so I am careful with spending. I have an opportunity to buy an RS+ survey kit at a good price. I know that I will easily be able to get excellent relative corrections, so I do not need help with this… yet. What I am not clear on is absolute accuracy without the use of an NTRIP network. I understand what it means, I am just not clear if the RS+ kit is a good choice if I want to do a lot of absolute accuracy corrections. What I do not understand perfectly is if the RS+ can be used as a base station and be considered a known location. For example, I contacted the GIS manager of the city I live in and he told me that the city does not have any marked known locations within the city. So I have no known location as a reference. I was pretty surprised. I think that what throws me is why the location acquired by the base stations from satellites cannot be considered as a known location and therefore the relative locations marked by the rover are considered as absolute accuracy. (taking into account expected error amount). I imagine that I am not alone struggling to assimilate this, so I hope someone who has worked through this question can comment.

I have also contacted Emlid about using the M2 on my M210’s asking if the M2 will behave like the factory RTK and provide corrections to the drone in real time for positioning control. I am only concerned with positioning control which behaves like the factory RTK in that it makes the drone more resistant to electromagnetic interference. The M210’s are amazing drones. The position hold quality is far better than I expected prior to buying them, but I am reluctant in many inspection situations when I am close to power stations and other environments that threaten the compass. Emlid did not answer my question, they just said I need to find a way to trigger writing info to the image files. That would be excellent to have working, but as I say, my goal is drone control. My intention is to use the RS+ survey kit to mark GCP’s and also connect the M2 to the base station for drone control. Most jobs do not require GCP’s so in those cases, I may just set up a base station and connect the drone with the M2 for drone control in environments where I think it would make sense. I may also just have a standard procedure of using an RS+ as a base station for drone control.

I am very appreciative of any help in understanding the questions.

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Hi Scott.

To establish a “known point” without the benefit of a correction network, you can use a “PPP workflow”.

Regarding using an M2 on your M210, you would not be able to integrate it into the navigation system of the drone. When set up with a proper kit, it would create an event time stamp for when and where images are captured. DJI did NOT provide this capability with the M200 series.

Yes, all of this seems really complicated, and it is, but you are in the best place for getting started and support.

Good Luck in your journey!

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Hi Scott, there is one limitation you should also be aware of when using the Reach R+ to establish an absolute point through PPP, is that being a single band receiver the expected accuracy will only be about 30cm. Also only NRCan CSRS-PPP and IBGE-PPP services support PPP for single-band receivers. This is from Emlid’s own docs:

Also, if using an Emlid M2 as a Rover to place GCP’s, you will need another multi-band receiver like the Emlid Reach RS2/RS+ for the Base. The RS2 can send corrections to RS+, although only using the L1 signals, but not the other way around. The RS+ to RS2 won’t work.

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Hi Scott,

When GNSS receiver defines its position based on data from satellites only, the final point has an accuracy of several meters. Satellites do provide all the data to define precise location, but the signals from them are getting disturbed while going through the atmosphere. That’s why accuracy of a standalone device is so low. And that’s why we use RTK or PPK technology: having the second unit (base) helps eliminate these atmospheric errors.

However, a base defines its position as a standalone device as well, with several meters of accuracy in relation to its global coordinates. It’s some kind of a shift. Therefore, all points taken with a rover are shifted too in terms of global coordinates.

If you don’t have any known points nearby, you can use PPP, but as @mark1st.john mentioned it provides 30cm of accuracy only for single-band devices. You better go with Reach RS2+.

Reach devices can’t control DJI drones as they simply don’t have an interface to receive position data. So, it can only be used for PPK Mapping while connected to a camera.

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