Question - Recording of Home Point on Powering Up

Posted by Jacques Eloff on August 29, 2015 at 11:02pm

Hoping someone can halp me here. I did post this question in Pixhawk group but thought I would post here as my problem may be more relevant to Plane. 

I’ve already had a few successful flights with Pixhawk in my Skywalker X-5 flying wing – all flights were in a park right next to my house. I decided to go to my local flying club yesterday but I could not get the Pixhawk to arm (flashing yellow). In Mission Planner I looked at the Flight Data map and it shows 6Km to home! I then look at the Flight Plan tab and see the “H” over my house!

So, it’s obvious that my home point has not been reset when I powered up the Pixhawk at my club. I can confirm that I did get a valid GPS fix and there was no reason shown in the little telemetry/horizon box in Mission Planner. I did have a good internet connection at the flying club and brought up the map which showed my plane sitting right where I was.

I can only presume that the distance to home is what denied me the ability to arm because when I got home I tried again and was able to arm. But what's interesting is that I was in my back garden when I powered it up and noticed that the Flight Data map showed the model on the other side of my house which is where I first powered up the Pixhawk (first ever after buying it). I'm stumped!

When I was at the model club field I did try right click the plane symbol in the Flight Data map and selected “Set Home Here” but that did nothing.

Thanks in advance,

Jacques

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Replies

  • Jacques Eloff October 31, 2015 at 12:34am

    I thought I would just close out this issue in case any other confused Plane users end up here in their searches! Firstly, there was likely another issues as to why I could not arm my model at my local flying club (and probably a fault of mine). The fact that Mission Planner was still seeing my home point as my house (when I was at my model flying club) is normal and expected. It is only when one Arms the plane that the new home point will show in Mission Planner - ie. where the model is currently sitting. However, insofar as the Flight Controller is concerned, the home point is where the plane first acquired GPS. So if you moved your plane after it acquired GPS and arm it elsewhere then you get 2 versions of home and your distance to home will show differently in your OSD and Mission Planner, However, the actual home point the plane will return to in RTL (the important one!) is the one stored in your flight controller. Note that Copter works slightly differently.

    This is what the wiki (http://copter.ardupilot.com/wiki/common-planning-a-mission-with-way...) says:

    "For Copter the home position is set as the location where the copter was armed. This means if you execute an RTL in Copter, it will return to the location where it was armed, so arm your copter in the location you want it to return to."

    "For Plane the home position is the location of the plane where the GPS was locked. This means if you execute an RTL in Plane, it will return to the location where it first acquired the GPS lock, so only power up your plane in the location you intend it to return to when performing an RTL."

    I actually read in one of the wikis that one can get around the potential ambiguity by re-setting the home point in Mission Planner by dragging the "H" (in the flight screen) to the location that your flight controller sees as home point. But this seems a really strange way of doing things and this whole issue should be sorted out in my opinion. Unless someone can offer a valid reason as to why you would want a situation with 2 home points??

    I was totally confused before I knew of this issue, because I would connect up my model in the pits area of my flying club then walk out to the runway and arm it just before take off. The "H" in Mission Planner would show on the runway, but the model circles over the pits when I hit RTL! 

    Please note that I am not criticising/knocking Pixhawk/APM/Plane in any way. I'm actually loving the capabilities that it allows and enjoying the "journey" and now even considering of replacing my multirotor flight controllers (DJI) with Pixhawk.

    Jacques

  • Jacques Eloff September 25, 2015 at 8:18am

    Back on this issue of home point, I noticed something today that's got me confused:

    I armed my plane which reset the home point as expected and this showed up in Mission Planner and OSD (both showing zero distance to home). I then went into the Flight Plan tab of MP and dragged to a new home point about 50m away. As expected, this showed in the Flight Data tab where new distance to home is 50m. However, the OSD is still showing zero distance to home. Why are they showing differently? What would happen if I hit RTL - where would the plane go?

    Thanks,

    Jacques

  • Moderator
    Graham Dyer August 30, 2015 at 12:33am

    As I understand it the firmware won't allow arming without a solid 3D GPS lock, this can take some time when moving to a new location. The little button cell on the GPS is there to do a warm start so that the GPS normally finds it's position within a minute or less.

    When it gets a 3D lock it still won't set the Home position until the plane is actually armed, (this was added for pilots who didn't want home to be set where the plane/copter obtained 3D lock as this might be in the pits at a club overwhich it is not allowed to fly).

    So the home position will still show older home positions until armed which can't happen until a 3D lock is obtained (6 satellites or more)

    • Jacques Eloff > Graham Dyer September 8, 2015 at 3:08pm

      Hi Graham

      Thanks for your reply. I must admit I was sceptical at first because this is what the Wiki for RTL mode says:

      For Plane the home position is the position of the Plane when you first get GPS lock whether it was armed or not.

      • This means if you execute an RTL in Plane, it will return to the location where it was when it first acquired GPS lock.
      • For Plane: Plug in the battery and let it acquire GPS lock where you want it to return to: (Not the Pits). 

      Anyway, I did some tests yesterday and you are 100% right! Would be good if someone could update the Wiki.

      Thanks,

      Jacques

  • Jacques Eloff August 30, 2015 at 12:32am

    Many thanks Richard - that is a very useful video!

    Jacques

  • Michael Pede August 29, 2015 at 11:29pm
    Hey. The Home is tricky. It is also misleading. When you connect your tablet or PC at the field, and it reads the Home position before the GPS lock, it will give the Home position that was last valid.

    When it DOES get a GPS lock, it will set the new Home location, but will NOT update your tablet. You need to disconnect and reconnect your telem after a new home is set.

    As to why your home was once again set to home, perhaps you connecred your telem once it had armed, and the drift from your GPS lock inside a house caused it to jump to the other side of the house.

    More data is needed before you can rule out if the Home is being set properly or not.

    Do you have a OSD?
    • Jacques Eloff > Michael Pede August 30, 2015 at 12:12am

      Michael - thanks so much for your reply. That's really helpful and I'll go try that shortly. In answer to your question - I do have a Minim OSD but not yet installed, will get it in later today.

      However, I was fiddling again this morning and something interesting happened. The plane was sitting in my back garden (where GPS was acquired and still showing 30m or so to the home point in my workshop where it first acquired GPS after buying it). So I remove the SD card from the Pixhawk and suddenly the home point is where the model is sitting!

      Jacques

This reply was deleted.