I ran into a GPS issue while integrating a TF Mini-S LiDAR into my drone — the GPS just couldn’t get a fix as long as the LiDAR was powered on. Below is a log of what happened and how I traced it down to EMI interference.

Speed spike from GPS glitch
A GPS glitch in the flight log: position jumped so far that the calculated speed exceeded the speed of sound. This is clearly a GPS error, not actual movement.

The Problem

After mounting a Benewake TF Mini-S LiDAR and a u-blox M8N GPS on the same frame, the GPS couldn’t acquire satellites. I disconnected the LiDAR and the GPS came right back — so the LiDAR was definitely the culprit.

The TF Mini-S fires its laser at high frequency, and that switching noise leaks into the L1 GPS band (~1.575 GHz). It’s a known issue in the ArduPilot community. The symptoms can look like:

  • GPS never gets a fix
  • Satellite count keeps dropping
  • Random GPS glitch errors mid-flight
Bottom line: You need to shield both the LiDAR and the GPS. Shielding just one side isn't enough if they're close together.

Shielding Experiments

Test 1 — Baseline: No LiDAR

GPS locked on quickly with no issues. Good baseline — the receiver itself is working fine.

GPS log — no LiDAR, no shield
Figure 1: GPS log — baseline with no LiDAR connected. Stable satellite count and position.

Test 2 — LiDAR Near GPS, No Shield

With the unshielded LiDAR placed near the GPS, the GPS lock became unstable. The LiDAR is clearly the noise source — shielding it is necessary.

GPS log — unshielded LiDAR near GPS
Figure 2: Testing GPS instability with unshielded LiDAR in close proximity.
Satellite count drop
Figure 3: Satellite count drop observed during LiDAR-on period.

Test 3 — Shielded LiDAR, GPS not shielded

Wrapping the LiDAR in copper tape helped a lot, but it wasn’t enough on its own — when I put the shielded LiDAR right next to the GPS, it still caused problems.

So the GPS also needs some shielding. The tricky part: if you shield the GPS, won’t it block satellite signals? The trick is to only cover the bottom and sides. A copper-clad plate mounted under the GPS canopy blocks noise coming up from the LiDAR while leaving the top of the antenna fully exposed to the sky.

Next question: What about the flight controller? It’s also sitting nearby. I tested this in Test 4.

GPS log — shielded LiDAR, no GPS canopy
Figure 4: Improved GPS lock with shielded LiDAR at normal separation.
GPS instability at close range
Figure 5: Residual instability when shielded LiDAR placed too close — GPS canopy also needed.

Test 4 — Does the Shield Work Near the Flight Controller?

I moved the shielded LiDAR right next to the flight controller (FC) and toggled it on and off. No issues — GPS stayed stable and the FC behaved normally. The copper-tape shield seems to contain the noise well enough even at close range.

Shielded LiDAR moved close to flight controller
Figure 6: Shielded LiDAR placed close to the flight controller for the interference check.
GPS log — LiDAR ON near FC
Figure 7: GPS log with LiDAR powered ON near the FC — no anomalies detected.

Test 5 — Final Setup

LiDAR back in its original position, both shields in place. GPS was stable throughout.

Shielded LiDAR and GPS canopy — final hardware
Figure 8: Final shielded LiDAR and copper-clad GPS canopy in the operational mount position.
Final LiDAR mount on drone frame
Figure 9: Final LiDAR mount under the drone frame with shielding applied.
GPS log — stable in final shielded configuration
Figure 10: GPS log showing stable position throughout the final shielded configuration test.

Flight Test

Took it out for an evening flight on March 18. GPS was solid the whole time — held a fix in both GUIDED and AUTO modes without any glitches.

Summary: What Worked

Configuration GPS Stability
No LiDAR ✅ Stable
Unshielded LiDAR, canopy unshielded ❌ Unstable
Shielded LiDAR, canopy unshielded ⚠️ Mostly stable (proximity-sensitive)
Shielded LiDAR + shielded canopy ✅ Stable

Wrap the LiDAR in copper tape (or single-sided PCB, copper side out) and add a copper-clad plate under the GPS canopy. Hot glue holds it all together. That’s it.

References

Drone Build Series