Problem with shearing and misalignment

[Allseeingeye]

I'm running a dji m300 with alphaair 450 and a emlid rs2+ base and I'm having a problem. The base was about 10 miles from the site I was surveiling and I was constantly getting shearing and misalignment which was especially noticeable around the edges. I was told the distance won't be a problem, so I'm thinking it could be a configuration issue? Looking for any recommendations and tips?

 

[SunDriedDad]

I'm running a dji m300 with alphaair 450 and a emlid rs2+ base and I'm having a problem. The base was about 10 miles from the site I was surveiling and I was constantly getting shearing and misalignment which was especially noticeable around the edges. I was told the distance won't be a problem, so I'm thinking it could be a configuration issue? Looking for any recommendations and tips?

Have you tried processing with PPK instead of relying solely on RTK in flight? That can sometimes clean up edge distortions

 

[A. Forrest]

Yeah, 10 miles is pushing it hard for a single base setup, especially if you're after tight alignments even though people say the RS2+ can stretch that far, in real world terrain or with atmospheric noise, you're gonna get drift, and

 

[PulseMap]

Good points from both,10 miles might be "okay on paper" but in practice, conditions make a big difference. I'd definitely test a PPK workflow to clean up those edges, and maybe consider setting a closer base or adding a repeater if tight alignment's critical. What software are you processing with?

 

[reetie]

Have you tried processing with PPK instead of relying solely on RTK in flight? That can sometimes clean up edge distortions

I've worked with similar setups, and I totally get how frustrating misalignment issues can be, especially when you're confident in your hardware.

While it's true that the Emlid RS2+ can handle baseline distances of up to 60+ km (about 37 miles) in ideal conditions, a 10-mile (16 km) baseline can still introduce accuracy drift if everything isn't perfectly dialed in — especially for high-precision LiDAR like the AlphaAir 450 on an M300.

A few things you might want to double-check:

1. Base Configuration
   • Was your base in an open-sky location with minimal multipath interference?
   • Were you logging raw data properly for PPK (if using that workflow)?
   • If doing RTK, were your correction settings (e.g., mountpoint, elevation mask, antenna height) accurate?
2. Antenna Height and Offset Settings
   • This is a common source of shearing. Make sure the antenna height and coordinate system on both the drone and base are correctly entered.
3. Time Sync
   • Any slight desync between LiDAR and GPS data can create shear artifacts. Ensure your system is properly time-synced, especially when using the Emlid with DJI/AlphaAir.
4. PPK Workflow
   • If you're relying on post-processing, make sure you're using high-quality base logs and correctly importing them. Software like Emlid Studio or Applanix POSPac (depending on what you're using) requires precise settings.
5. Check the Edge Shearing
   
   • Edge shearing often comes from slight trajectory drift, so it might be worth checking if your trajectory file (INS/GNSS) is stable throughout the flight.

Tips:

• Try bringing the base a little closer next time to test if the shearing reduces.
• Run a short test mission near the base to eliminate the long-baseline variable.
• If available, try using a known CORS station closer to the site for better comparison.

Let us know how it goes — happy to help troubleshoot more if needed!

Best Regards,
Reetie

 

[McNelly]

A 10 mile gap between your Emlid RS2+ base and drone site can cause the shearing and misalignment that youre seeing, even though it's technically doable. It's likely a setup or signal issue, doublecheck your RTK correction settings, antenna placement, and communication link quality. Improving your signal and tweaking settings usually should clear up those problems.