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Google Earth is Your Friend

Discussion in 'General Discussion' started by GreggC, Dec 31, 2015.

  1. GreggC

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    Good morning guys,
    I continually read about CFIT (controlled flight into terrain)
    Before I do a distance flight I use Google Earth to determine ground elevation of my intended route.
    For example;
    From my driveway I fly north approx 2 miles at 400' AGL,
    Ground elevation rises approx 60', at the turnaround point my altitude is 340' AGL.
    When I fly East ground elevation drops 130', I start my flights going east at 270' ,
    at the turnaround point my altitude is 400' AGL this keeps me in compliance with the 400' AGL rule.
    If I were to fly west the same 2 miles ground elevation rises 410',
    Looking west ground elevation does not appear to rise that much...
    But google earth tells me it does.
    Google Earth is your friend.
     
    FotoGeek likes this.
  2. FotoGeek

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    Interesting. I wish DJI would build that into the firmware so people like me don't have to do all of that ;)
     
  3. Fat City

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    I was hopeful that Google Earth on my PC could be used (with Litchi's Ground Station) to set the altitude of waypoints along a flight path over some rolling terrain. If you draw a path (Add -> Path) in GE, you can then view the elevation along that path (Edit -> Show Elevation Profile). Seems ideal for the purpose. Unfortunately I found that there are occasional, but substantial discontinuities at cetrain points in many elevation profiles. This is apparently a problem of long standing, so I'd urge you to do some sanity checking before you act on any elevations taken from GE.
     
  4. ianwood

    ianwood Taco Wrangler
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    It would require quite a bit of memory to contain all the terrain data for a given area. And that would most likely not include obstructions. The alternative would be sense and avoid / terrain following sensors. Expensive, limited range and adds weight and complexity.
     
  5. GreggC

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    I've compared my Garmin Montana 650t to Google Earth ground elevations at home, the desert where we ride our RZR's, our Durango campsite, our Taylor Park campsite...etc. and have found it to be reasonably accurate. Also I drove to the intersection west of my house where Google Earth showed the ground elevation rising 410', it was spot on.
    Anyway,
    I just wanted to put this info out there, Google Earth can be used as another tool when planning a flight.
     
    #5 GreggC, Dec 31, 2015
    Last edited: Dec 31, 2015
  6. FotoGeek

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    I was thinking it could leverage Google and 'feed' that data to apps as needed based on current location.
     
  7. Sirwilliam70

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    Aren't we forgetting about the line of sight rule? If you're flying out 2 miles, abiding by the 400 ft altitude rule is kinda pointless if you're breaking other rules. Not trying to call anyone out, just saying the point is moot.
     
  8. ianwood

    ianwood Taco Wrangler
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    It would still have to cache it much like Google maps does on mobile phones. And the uplink bandwidth is limited so most likely it would have to store data for its entire range (not small).

    The only way it would work is with a pre-programmed waypoint route which it can check before flight.
     
  9. FotoGeek

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    Not more than any basic mobile GPS app already does.
     
  10. FotoGeek

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    LOS rules are so lame and can't really be enforced until something happens.
     
  11. ianwood

    ianwood Taco Wrangler
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    Your phone has a lot more memory in it than your P3 does. P3 probably has <100Mb of NVRAM. Equally important is the processing power needed to compute the distance in 3 dimensions to each point several times per second.

    The next iteration of flight controllers may contain a GPU variant to manage such heavy computation but it's not there now.
     
  12. FotoGeek

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    very true.. I wonder if there's a way they can leverage the gpu on mobile devices? I think the Shield has 192 core gpu :eek:
     
  13. Fat City

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    In my case I wanted to plan a route where the P3 would always be visible, flying just a few meters off the rolling, sloping ground. There aren't any obstructions -- it's all manicured grass -- but after a few hundred meters it's hard for me to be sure of the P3's altitude. Using Ground Station there's no need for the quad or the tablet to know the terrain. So it's a case where it's always VLOS, but presetting waypoints and altitudes is valuable.
     
  14. jimerb

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    Where does google earth show altitude? I've never noticed that? Does it show it on the app and pc software too?
     
  15. Fat City

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    On the PC it shows the lat, lon, and elevation of the pointer position at the bottom right of the screen. Don't know about the app.
     
  16. Sirwilliam70

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  17. GreggC

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    I pick my poison,
    Over 400' is a real and considerable risk, FAA designated airspace starts at 500'.
    As for LOS, these things were designed and built to fly past LOS,
    I didn't spend $2500 to fly down the block and back.
    With GPS, barometric altimeter, IMU, compass and a flight app
    going past LOS IMO is far less of an issue than getting into FAA designated airspace.
    Just my .02
     
    #17 GreggC, Dec 31, 2015
    Last edited: Jan 1, 2016
  18. snerd

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    I think you're just fooling yourself. Both/either will get you the same fine. And I believe the FAA controls "all" of the airspace, not just above 500 feet.

    ETA, I don't care what you do, just telling you my reasoning.
     
  19. GreggC

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    Understood,
    And I suspect you are correct,
    Either one will result in a fine.
    However, this thread has gone off topic,
    Even flying LOS Google Earth can be a useful tool.
     
  20. WetDog

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    At least around where I live, GE isn't accurate enough to make me feel comfortable doing this. The other problem is biology - mapping solutions are very unlikely to calculate tree heights and an Controlled Descent into Vegetation is just about as bad as a Controlled Descent into Terrain.