Mode-S positions completely unreliable

Hello, I am a PPG pilot and I am using Safesky on my tablet via XCGuide.

I have today realised that the position of small planes in our area using Mode-S is completely unreliable. The same plane pops up a tens of kilometers away from it’s previously displayed position and jumps back-and-forth between completely unrelated positions.

This way even didplaying these positions is useless, moreover misleading.

Is there any particular reason why this is happening and is it only here around LHBP or elsewhere too?

The position of the S modes depends on the quality of the multilateration.
I invite you to read these articles to understand exactly how it works; you should find the necessary explanations there.
Mode S traffic is surrounded by a circle of uncertainty in order to make the pilot aware of a relative position. Perhaps we should grey out the graphic representation of the traffic to make the pilot more aware of this imprecision.

For information, an AIR AVIONICS connected to a G3X picks up mode S via the radio but with a very high degree of inaccuracy. To represent this imprecise traffic, Garmin has decided to show white diamonds swirling around your position, meaning: “Warning, Mode S nearby and position impossible to confirm”. You have to admit, it’s extremely stressful!

With SafeSky, no more than with other systems, we won’t be able to position Mode S traffic better unless we multiply the number of reception antennas at aerodromes. In Belgium, work has been done in this direction, with the federations contributing financially to the purchase and installation of traffic reception antennas at all the country’s aerodromes. The direct result of this operation is excellent visibility of ADS-B traffic and a better representation of MODE S than in any other European country.
There are no secrets, only solutions. Use compatible systems to make yourself visible, promote ADS-B in aircraft capable of transmitting with this technology (ADSB transmits a precise GPS position that is easily understood by traffic warning systems).

Here are the two links I mentioned above.

Yours faithfully