2 Emlid RS2 for accurate heading

Hello there,

I researched a little bit on this problem but no answer clearly.
We intend to use somehow a system formed by 2 RS2 units to heave accurate heading in real time, mounted on a boat.
Could you please clarify is there is a way we can do this and if it’s possible?

Thank you!

There are several Android apps that I have used which include heading as a displayed value. Two that come to mind are GPS Compass Navigator and Polaris GPS Navigation.

Not sure how you would incorporate two receivers to do so

You would have to have a 2-channel mcu and software that support that functionality. Probably not a buy it off the shelf solution, but maybe someone could help. You could accomplish the same thing with an imu tied into the system.

Thank you for your answers. I do own an imu (Applanix) but this is not an option. I would like to tie 2 emlid receivers to output accurate heading for navigation purpose only.

It’s just a matter of software, but an imu and a receiver can provide heading. Just ask every major construction equipment manufacturer out there.

Won’t the Applanix IMU provide this information in conjunction with the RS2?

Theory says it is perfectly possible, given the right piece of software (or the skills to code using the NMEA streams of both receivers).
We can set up a few ground rules:

  • the more distance you provide between the 2 units, the lower the standard deviation of a given direction.
  • fix solution and baseline length will define the length between the 2 units. If you have a 2,5 cm std dev fix, 1 meter between the unit is mighty fine (a ratio of 0.025:1, lower is better). However with just a single solution, with 2.5 meter std dev, 1 meter would give you a ratio of 2.5:1, which is extremely poor. To obtain the same ratio in single -solution mode (and thus the same std dev in the heading), you would need 100 meters between the 2 units.

I don’t know if having two units on a boat will increase the accuracy that much. If you are on open water, I am assuming you will not be using corrections.

As Wizprod said with distance like on a ship I could see it making a difference with 2 units.

In the NEO-M8P info posted in another thread, there’s a function mentioned in section “1.6.2.2 Moving baseline mode” and provides an accuracy of <1 degree angular error for a baseline length of 1 meter. This is based on the L1 characteristics of the chip. I don’t know what the chip is in the the RS2 or M2 (dual frequency). I suppose these functions could be accessed via the command structure of their software “u-center”

Hi Mihai,

Our software doesn’t provide the heading calculation option. As Christian said, you may get the receivers’ coordinates and try to calculate the heading from them in a 3rd-party app.

I have created a program to complete this task in Windows. It will take the two strings and produce a heading output. It’s best to use this on RTK with both receivers for a more stable output.

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Just thinking how much more accurate would you be with 2 RS2 compared to 1 RS2? I mean you want heading as the post suggests so just 1 RS2 even with 0.05m RMS would still provide an accurate reading if taken every 1 sec or even faster and then average it out after every 10 m distance intervals.

The main advantage of dual receivers is that heading would be maintained at startup and a standstill. GPS-controlled construction machines that only have one antenna go through a startup process everyday to initialize their heading. Sometimes they pick up in 50ft and sometimes it takes a couple of minutes. I can see how this would be advantageous on a boat.

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I’ve attached a copy of my program to do this for anyone to try. It doesn’t do the filtering or averaging, which may be a good idea if traveling with some speed.Vector GNSS.zip (173.8 KB)

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Consider that a boat’s heading can be different from its apparent movement, due to current and wind drift. If the user wants a true boat orientation along its longitudinal axis, then two receivers are really needed if no other option is available.

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