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Changing home point at battery swaps

Is it still true that changing the home point location during battery swaps could mess up the data collected if the home points are at different elevations?   I am flying a large area with 4 battery swaps and while I can maintain VLOS from a single home point, I would be more comfortable with moving to three different home points during the mission.  The elevation changes between these point would be relatively minor (a few feet) as the site is relatively flat.  

William Pender

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It depends. To get the most accurate results possible Maps Made Easy uses a Ground Reference image to correct the GPS derived altitude values based on the the SRTM elevation of the ground and the relative altitude as measured from the takeoff location. With a single takeoff location this works great. But, if you are moving around a bunch between takeoffs then this process gets complicated.

If the elevations of the takeoff locations are the same it is not an issue, so do that if you can.

However, if you can't keep the takeoff locations at the same elevation you should not include any ground reference images in your dataset. This will leave the elevation to be processed using the GPS derived tags which can vary 100+ meters between takeoffs even on flat ground.

Since your data is relatively flat I would go ahead and include it. You only need one ground reference image. If more than one are included then the last one the system detects is the one that gets used. 

Zane
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Really?   100+ meters difference in elevation in GPS tags?  Never heard of that before in using other mapping apps like Pix4D that don’t even use ground reference images like this app does (nor do they use them in processing).  Do you have a source where I can read up on that for my own education?

William Pender 0 votes
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