[TMGsi]

guys, i need help

when trying to take off to test the position hold flight mode, the quad already takes off without control and falls.

in flight mode without gps it took off normally

I think that at the homepoint set, where you need to enter "set home altitude" (in [m] referenced to wgs84) I only reported my altitude in relation to the sea level. could this be the cause of the problem?

help me solve this problem of taking off with gps and then immediately falling.

thanks and good flights.

[TheOtherCliff]

You generally should take off in non-GPS mode such as Attitude mode (Stabilized1) and switch to GPS mode such as PositionHold only once you are in the air.  Switch back to Attitude mode before landing.  Generally, never use GPS mode while on the ground or it may be directed to fly just 0.5m sideways, scraping along the ground and tipping over.

May I suggest that you use VelocityRoam mode instead of PositionHold mode.  If both sticks are in the middle, then VR is just PH, but you can move it around if you want.  It is a moveable PH.

Are all your motor power wire pairs twisted together and routed away from Revo board?

Do you have OpLink telemetry wired up?  It can help to understand the problem if you still have a problem.

I think that at the homepoint set, where you need to enter "set home altitude" (in [m] referenced to wgs84) I only reported my altitude in relation to the sea level. could this be the cause of the problem?

As I recall, setting this altitude wrong should not matter unless you are flying certain kinds of waypoints, or needing to see correct altitude on GCS map (requires telemetry to send back GPS to GCS to display on GCS map).

[TMGsi]

I start takeoff in stabilized mode, but it doesn't even take off,
when i didn't have gps installed on fc it flew normally. (I'm not trying to take off with positionhold enabled, I think you understood that in the previous message)

I don't have oplink

the motor wires are practically far from the fc, it's a 270mm frame

so my problem has nothing to do with the wgs84 altitude,

I'm going to change the flight mode for the velocityroam, but first I need to get it to take off.

[TMGsi]

I think my problem is related to this option:
attitude> settings> attitude estimation algorithm

which of these available options should i choose? (to fly with velocityroam as a flight mode)

could you explain to me what each of these options serves?

[TheOtherCliff]

Basic (Complementary): is the simpler code that was originally made for the simpler CC3D.  It uses only the gyro and accel sensors and so it doesn't have the problems that using mag sensor brings.  It can be wrong in some cases.

GPS Navigation (INS13): is much more complex and only works on Revo class board.  It uses gyro, accel, and mag sensors. It does not get confused like Basic does.  You must carefully twist motor power cables to reduce their mag field and allow mag sensor to see earth mag field.

In LibrePilot version 16.09 you should use GPS Navigation (INS13) if you want to use GPS flight modes.

To use GPS Navigation (INS13) you must:
- carefully twist motor power cables to reduce their mag field and allow mag sensor to see earth mag field
- set Home Location by going to Flight Data page, right clicking where you want to set Home Location and choosing "Set the home location" from the right click menu.  Altitude is not critical except for some kinds of waypoint flights, but you should probably look it up and use that number.
- calibrate the mag sensor.  This really should be done with OpLink telemetry, but I have done it very carefully with a USB cable.  Read Attitude->Help.  Do all the calibrations in Attitude -> Calibration.

For mag calibration information go to this page:
  https://librepilot.atlassian.net/wiki/spaces/LPDOC/pages/18382863/Aux+Mag+Setup+and+Calibration
and look for the heading:
  Mag Calibration (GCS -> Configuration -> Attitude -> Magnetometer Calibration)

You really should use an aux mag (built into GPS) to have mag sensor farther away from power wires.  Small drones are hard to get good clean earth mag readings with electromagnet motor wires so close unless you are using an aux mag that is mounted farther away.

If you are using an aux mag, you must configure several things correctly (Attitude -> Magnetometer page):
Mag usage, Mag type, and Auxiliary Magnetometer Orientation

[TMGsi]

i'm using a gps with a compass and it's on a post about 20 cm above the fc and about 27 cm from the pdb.  with ins13 it doesn't even take off (it loses control when taking off), so I switched to complementary + MAG + gpsoutdoor.  that way it takes off and I can even test the positionhold.  but it still needs to improve

[TMGsi]

I was not able to take off with the gpsins13 because the gps was fixed on the drone without the pole.
after i made a 20cm wooden post now gpsins13 is selected and best of all i am getting the drone in positionhold perfectly.

now is to test the velocityroam and rth.

my question with rth is the following, when i turn on the drone, does the fc mark this place where the drone was connected to rth or the place where i marked in the llibrepilot app?

[TheOtherCliff]

GPS should work correctly without the pole.

The very critical part is that the GPS/mag must be mounted with arrow pointing forward, and mag settings must be done correctly.  That is because the mag must point forward ... if not, the non-forward be accounted for in setup.

(For GPS/mag pointing forward) Note that for DJI/Naza GPS/mag, the default mag orientation setting (0,0,0) is correct, but for other GPS/mag type, you MUST set this differently (0,180,0) from what I remember.

my question with rth is the following, when i turn on the drone, does the fc mark this place where the drone was connected to rth or the place where i marked in the llibrepilot app?

There is an option for that in System->Settings->TakeOffLocation, but I recall an issue.  Maybe it was that it was always "Arming Location".

Wait for good GPS lock, then put model where you want it to return to, then arm it.  Be aware that RTB (we call it Return To Base because it is not returning to what we call home location, but takeoff location) is not done automatically unless you set it up that way.  You must get failsafe detection working, configure RTB as a flight mode, and then configure it to use that flight mode when failsafe is engaged.

[TMGsi]

The RTB is working properly too, that's great. (I mentioned before how RTH influences other firmware)

With regard to flight modes now, how can I have or how to configure my radio to have 4 or 5 flight modes, since my radio has keys that are at most 3 positions?

example, flight mode 1 for attitude
                 flight mode 2 for positionhold
                 flight mode 3 for velocityroam

now in another key of the radio flight mode 4 for RTB
and in flight mode 5 any other.

how could it be? or am I limited to having only 3 flight modes? the radio has several keys available.

[TMGsi]

another problem that I'm noticing.  in my osd it has 2 altitudes, altitude and home altitude, when I start to take off both altitudes are showing the altitude in relation to the sea level.  wasn't one to show the drone's altitude in relation to my ground?

[TheOtherCliff]

With regard to flight modes now, how can I have or how to configure my radio to have 4 or 5 flight modes, since my radio has keys that are at most 3 positions?

Currently, you must do that mixing setup in the transmitter so that the channel you use for FMS is affected by more than one switch.

another problem that I'm noticing.  in my osd it has 2 altitudes, altitude and home altitude, when I start to take off both altitudes are showing the altitude in relation to the sea level.  wasn't one to show the drone's altitude in relation to my ground?

I would hazard a guess that you entered "0.0" when setting Home Location and it asked "Altitude above WGS-84 geoid" (or whatever the exact wording is).  Try setting Home Location again and this time put the real altitude in there.  If I recall correctly, one way to do this is to simply clear the Home Location's "Set" checkbox with it all running and good GPS signal.  In a few seconds it will re-check the Set checkbox with the current drone location (including altitude) being set correctly.

[TMGsi]

could you please send me a link to a website that does the calculation for me to have the altitude according to wgs84?  because on the librepilot help site there is a link, but this link seems to have changed, a new page enters at the moment.

[jdl]

Here are some googled results for online geoid height calculators:

https://geographiclib.sourceforge.io/cgi-bin/GeoidEval

https://www.unavco.org/software/geodetic-utilities/geoid-height-calculator/geoid-height-calculator.html

Once you have the height in EGM96 (from GoogleEarth, for example) just add the Geoid separation value for the location of interest to get the WGS84 height.

[TMGsi]

man, thank you very much.  now i got the value for wgs84.  mine here was -1.58 I don't know if it's right, but I did a test flight and the result is that the positionhold was much better.  however, my altitude shown on the osd was in relation to the sea level.  the two altitude information are in relation to the sea level.  (860 meters)