RTK GPS Base Stations

Support GPS
1

Hi all,

We have mobile field rover units uBlox M8P modules with a constant LTE connection to the internet.

We are looking to setup our own fixed RTK base station and then transmit corrections over the internet for the field rover units to connect. The rover units will be within 30km of the fixed base station.

Does anyone have experience with either of these products for this use case?

Or can recommend a different product for this use case?

Thanks in advance,
Sam

2 Likes
2

Hi Sam,

Welcome :smiley:

Super interesting bits! Do you rovers have line of sight to the base station?
Just to confirm were you looking for a communication method or increase the accuracy of the GPS?
If the former I’d check out LoRa/LoRaWAN :smiley:

3

Hi Liam

At 30kM unless there is a pretty good hill at both ends I very much doubt it.
Allowing for an earth bulge of 4/3 earth radius (Radio waves will bend a bit but the actual amount depends somewhat on your position on the planet) the radio “horizon” in miles is the square root of twice the height in feet above the surrounding terrain (if it were flat). Example: at sea level if your eyes were 6 feet above the water the optical horizon is √(1.5 x 6) (3) in miles and the radio horizon is √(2 x 6) (3.46) in miles.
Cheers Bob
PS: Added to this you have a thing called Freznel Zone to stay clear of. If you enter “fresnel zone” into your browser you should actually find a fresnel zone calculator.

2 Likes
4

Hey Bob,

Thanks for mentioning the Freznel Zone, looks super interesting!
Just having a look into it now but I always thought signals would act like a laser but makes sense, you learn something new every day!

1 Like
5

Hi Liam

Yes it is. Any reflected signal on the fresnel zone can arrive at the destination 180Âș out of phase with the primary signal and result in partial (or almost complete in some cases) cancellation or serious fading. Directivity or gain in the antennas will play a role in reducing this effect, that is why you may see high gain antennas used where there is no obvious need for the gain in itself.

So you can appreciate that the design of a good point to point system has a little more to it than just pointing 2 antennas at each other. This aspect is almost a branch of electronics in its own right. There is lots of maths and hard work involved. Sometimes even walking the propagation path. A survey (radio) of the path is a must and when called on to carry out this task we used to do a “height gain” test where signal strength at different heights above ground (at both RX and TX ends) were measured and this gave the boffins some figures to work with when predicting behaviour over a certain path.

At my pay grade all I needed to know was the existence of some of these little quirks and I quickly learned not to be too surprised at any unusual results. They were always explainable at the end of the day. Nothing really happens for no reason.
Something for those intending to dabble in RF systems to think about.
Cheers Bob

2 Likes