RTK - M8P vs F9P

Hi all,

I am currently using the Here 3 & Here+ RTK Base (M8P) Combo (https://irlock.com/collections/pixhawk2/products/here-3-here-rtk-base-m8p-combo)

The main issue I am having is I rarely/sporadically get a fixed lock (not for long though). Float is usually accurate enough for us, but the problem is it random drifts 1-6 feet from time to time. Typically this drift/jump happens when its transitioning from Float to Fixed, which happens all the time even with open sky.

From what I have researched F9P makes a big difference. I am thinking of purchasing a Holy bro H-RTK F9P (with the high gain GPS500 antenna) as a start for my base station:
Will I notice a difference just by changing the base station to F9P with a good antenna (while continuing to use the Here 3)?

I am hoping to wait out for the Here Pro GPS (mainly for CAN support) for the rover side which I am assuming will be F9P which will complete my system whenever that it. Or would you suggest not waiting and just buying another Holybro F9P or the Drotek Sirius F9P for the rover at the same time as the base?

The challenge is we fly in urban areas (Film production work) all the time, so the real question is will the F9P be able to hold a fixed lock in these areas or am I still going to suffer from the constant switching between Fixed and Float?


1 Like

F9P will make a night and day difference from a M8P in terms of getting a fixed solution. You need to have both F9P on rover and base to make a real difference. We use it on a very specialized work drone and it stays fixed all day long in places where M8P doesn’t even get a float solution. We don’t have a base, we get corrections from a cors service trough an onboard modem. Just for info we use drotek F9P unit.


why and when you decided to move on from using your own RTK base station setup to using CORS service ? i also looking to know when you saying one can achieve all day long RTK fix solution using F9P then what was the issue with not using your own RTK base station setup cause this seems a better option in terms of cost and portability as CORS service will not be available everywhere and one always have to pay for this service compared to one time investment for RTK base station setup

We are happy with cors. Never used a dedicated base. I am not saying a cors is better, i just shared my experience. We have a yearly subscription and service is available nationwide, never had an availability problem in places where we usually work.
Not having our own base is one less thing to carry around for us.

1 Like

Not true. I have free service here (States, Michigan) and pretty much the entire State is covered. The only trouble would be in the Upper Peninsular where there are large areas with limited mobile service.


1 Like

I see, I thought it must be only paid service, seems like only US is the exception with so many CORS service providers, I cannot seem to find any CORS service providers in India, but I know people do use services like it in India for accurate measurement of land area for government records but not sure what they are generally called here

It’s used extensively in Agriculture perhaps check into that. But it may be cost prohibitive unless you are making money flying.

1 Like

Thanks all. Can’t seem to find a free CORS service in Canada to try which is unfortunate. Any idea what kind of pricing I could expect for a yearly subscription for a private sector service?

@Corrado_Steri Your comment about using a CORS service with an onboard modem really intrigued me. I am assuming this means you don’t have to setup any type of ground station? Is the hardware to do this readily available or was this some sort of custom solution for you?

It would be a dream for us to just turn on the aircraft and have the aircraft start important RTK corrections from the nearest station. I am assuming it is not this simple though…

Now you have me thinking I should avoid the wait of the Here Pro and just pick up a Drotek F9P. I liked the idea of the Here Pro using CANBUS. Have you experienced any issues in high EMI areas with the Drotek using UART/I2C?

1 Like

It is this simple if you have a telemetry system with the range for your use case You do need a Ground Station to serve the data but you don’t need a Fixed GPS unit. That’s not what @Corrado_Steri is doing but it’s one way if it will work for you. A case we have seen used successfully with this technique with a Rover has been an autonomous mower.

Thanks Dave. Yea I am aware I can do this, but since we are already spending 2-3min to setup the ground station, the extra 30sec it takes us to setup a tripod for the the GPS isn’t that siginificant. The idea of “eliminating” the ground station was the intriguing part which would save a significant amount of time. We use our aircraft on large film productions and when its our turn 2min of setup time is significant. The idea of just turning on the aircraft and being able to get an RTK fixed solution in under a couple minutes would be game changing.

Just add a raspberry to your setup and plug an usb modem to it, than with str2str you can feed rtk corrections directly from onboard raspberry to f9p module. If you search the forum for ntrip you should find a post from me on how to do it. Than all you need is an rc control and your gps flight modes will be done in rtk. Essentially you don’t need a ground station.