Range of RTCM using RTK Here+ GNSS?


I am using a hexacopter with HexAero Pixhawk 2.1 with RTK Here+ GNSS-modules. Anyone know the range between base- and copter-GNSS-modules? They are using RTCM-protocol for update.



I have no experience with here+ but what I was told is that single frequency gnss isn’t good for corrections over 10-15 km as it can’t account for atmospheric differences between the satellites and rover/base.
That doesn’t mean that it’s bad or doesn’t do anything, but it means you won’t get as good results as you get with multi frequency gnss.
If you need very long range the better option would be either use CORS or multifrequency gnss

If you are asking what the range is on the correction signal, then as far as your telemetry radio’s is.

Its not the Pixhawk Telemetry, that wouldnt work, too useless signal.
I mean the RTCM-signal from copter-GNSS to base-GNSS.
See picture:

Anyone have any information on that Standard RTCM Stream? =)

not sure what system you are using, but most of these rely on the standard telemetry link between the GCS and the drone or have their own dedicated 915mhz (in the states) link. Either way your range is limited by the link between your base or gcs and the drone.

Do you need RTK accurately position your drone or are you using RTk to GEOTAG?

Using 433MHz telemetry (Eruope) between the HexAero/ProfiCNC Pixhawk 2.1 and the laptop with Mission Planner.
And using the RTK Here+ http://www.proficnc.com/system-kits/77-gps-module.html for geotagging the photos.
Using the groundstation on a spot that is accurately positioned.
I am not that used to this equipment yet, but it flies well and the photos are geotagged. I build and testfly, another person uses it.
I have understand that the RTCM protocol between the antenna on the multicopter/plane talks with the antenna on the ground. I dont know the distance it can handle. Not using PPK, so the signal needs to be good.

This distance is limited to the range of your radios. As long as the rover is getting the RCTM message youre good. Accuracy decrease as your baseline increases, but it’s neglible in the range of most radio systems.

We use Futaba 2.4GHz FASST/FASSTest (T10CP and T14SG) and its said they have max 2km LOS range.
The transmitters just lays on the table, the multicopters and planes starts, flys and lands by them selves. Except the planes that we always land in FBWA or Stabilize Mode.
The standard 100mW telemetry have a lot shorter range than the RC-link. A few hundred meters on multicopters and a bit longer with planes.
Well, have to test… :slight_smile: Was wondering if anyone knew the “RCTM”-range.

there is no “RCTM” range. As long as the rover is getting a message the GPS will be corrected.

Here is what trimble has to say about it.


As I have understand, there is two ways to get the positions. One is live RTK and one is after the flight with some work PPK? PPK seems more accurate but more time consuming?

Its RTK we are using, for a start.

What you said “As long as the rover is getting a message”… what message and from where?

I may have to sit down and read some manuals… =) but isnt there any signals sent between the “pucks” at the base station and the one on the rover (multicopters and planes in this case)?

Im confused by the picture mentioned earlier in this thread: RTCM Stream. From where to where? Is it physically?


The RTCM message is transmitted to the rover / plane via your telemetry radio. For example if you use the 433/900 MHz SIK-radios, this is where your RTCM will be sent. There is no communication between the GPS recievers is (or pucks as you call them).

So you´ll need a telemetry link between your plane /copter / rover and the ground station to get RTK positioning. This is the same link that transmits data from the plane / copter / rover down to the GCS and back again. (Altitude, speed, position, waypoints etc.)

If you have your base on a position that you have a very accurate fix on, you’ll have very accurate absolute positioning. If not, you’ll have very good relative positioning and fairly good absolute (1 meter or better, depending on how long you do the survey -in).

We use this system at work, and it is pretty good considering the price tag. Please don’t hesitate to ask if there is anything.

I did not know that it uses the 433 SIK! Great to know. We do use 433MHz SIK radios on our multicopters and planes, but it is very short range of it (another thread I guess), at least on the multicopters. Guess this thread is solved. =) Thanks! Regarding questions, I have many along the ride. :smiley:

We have flown 2-3 kilometers with the standard SIK-modems without glitch. If you look into your antennas you might have better luck. A yagi antenna on the ground does wonders :wink:

Just got a Arkbird Antenna Tracker. But dont have any good antennas yet for 433MHZ telemetry. Links? The original 100mW SIK-radio should handle up to 500 meters with standard antennas (those black short ones that comes with the kit).

Also have a TBS Crossfire 868Mhz-kit (with all antennas they have) on its way that I think can handle APM/Pixhawk telemetry. Dont know much more.

Hello everyone,
I use fixed wings for mapping most of the time and as we all know gcp are very difficult to collect. So using RTK gps system we can reduce no. of GCP we take.
I recently got my TBS crossfire and it is compatible with pixhawk, so i connected pixhawk telemetry with crossfire receiver and my radio module(Crossfire) can connect to my Tower application via bluetooth.
Now i wonder if i can use this as RTK gps SKI radio and i can connect ground station via bluetooth. Would that work? Has anyone tried it? Rather than using a 1W SKI tx for better range on rover this is a good option.
Need some suggestions.

Hello Antriksh,
Did you try the RTK with TBS Crossfire?
Does it work?
I’m trying same setup but cannot Float or Fixed RTK on mission planner.
Thanks in advance,