Prearm: Need Position Estimate

Helo i am configuring a matek OPTICAL FLOW & LIDAR SENSOR 3901-L0X, I already have the rangefinder working and now i am configuring optical flow sensor, i followed all steps on Optical Flow Sensor Testing and Setup — Copter documentation
i receive data from the sensor and i already calibrated it, but the problem comes on the Second flight step

Because when i try to arm in loiter mode mode it shows me this error

I can succesfully arm in stab or althold mode, but it dont let me arm in loiter mode.

MatekH743 001B0031 33305118 36353839
ChibiOS: 66e5de0d
ArduCopter V4.3.1 (22f45675)

It’s looking for a proper GPS fix still. Have you power cycled the flight controller after you set the EK3 parameters mentioned in the Wiki?

If the vehicle appearing on the ground station map? If not then the issue could be that the “Set Origin Here” hasn’t worked for some reason.

My next guess is that the rangefinder isn’t happy.

Probably best to provide an onboard log. To produce a log while the vehicle is disarmed you might need to set LOG_DISARMED = 1.

kindly tell me how to solve an error of Pre arm: AHRS waiting for home ???

Notice the message GPS:No GPS. You need to sort that out. If you are indoors then the GPS may not be getting enough signal to get a position. Or if you are powered by USB the GPS may not be powered up and needs battery to be working (depends on your flight controller)

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But I’m not using the GPS with pixhawk 2.4.8 flight controller and when i armed it gives an error of AHRS waiting for home…! or with GPS it shows green light and not armed and error of GPS not fix…

You’ll need to give the AHRS some kind of position information.

Look at Non-GPS Navigation — Copter documentation

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using gps, it also give an error of waiting for home.can u suggest me a proper documentation ???

You need to be outside with a clear view of the sky. Especially if the GPS module hasn’t had a full lock recently it will be a “cold” start and that just takes time.

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Hey @Mateo_Morales ,

I also facing the same problem. Did you get any solution for this?

Did you ever find a solution for this problem we have the same problem and can’t seem to fix it.

I’m having the same problem too, is there any solution yet?

You can check this Mode change to LOITER failed: requires position with only PX4flow

And at the end still, if you do not find the fix then let me know.

I’m not sure about my method, but I’ve solved it before.
In my case, the preARM condition was not released due to vibration (LIDAR) of the vehicle against external devices when the preARM condition was as shown above.
In some cases, the IMU determined that the vehicle was constantly moving and prevented ARM from being attempted, so I personally held the vehicle fully horizontal and stood by.

And these problems are also believed to have a significant impact on surrounding obstacles (such as metals).

Follow the guide, and I got this message also. " Prearm: Need Position Estimate"

How can I get postion when indoors?

If I don’t have Non-GPS Navigation modules, how can I use matek OPTICAL FLOW & LIDAR SENSOR 3901-L0X for postion hlod indorrs?

You need nonGPS navigation modules.

@amilcarlucas Thanks for your reply. Maybe I should try FlowHold

Is there any way to automatically switch between FlowHold(don’t need postion info) and PosHold(need postion info)?

here you go: