So DJI support recommended I recalibrate my compass and IMU and then re-link my controller to the Spark because I had a "Lost Transmission" error that lasted 5 seconds. I did all of those things and took it outside to test it out. It was getting dark (7:30pm) when I lifted off from my driveway. It went to it's 4 foot hover and immediately started drifting to the right towards the house (10' away). I had to give it left stick to bring it back and land.

I figured the IMU cal didn't work right and maybe I was too close to the house...so I did the cal again and took off in an area farther from the house. It didn't drift like before but it certainly wasn't locked into a normal Spark hover that I'm used to. It was moving around a foot or 2 in any direction, even altitude..kind of like it had been drinking!

I had 16 satalites connected, so is this because the vision system struggles in the dark or is there a problem with my Spark?

This might be caused by the vision system due to low lighting.  I had the same behavior a few weeks ago when showing my dad my spark.  It was getting dark and it wasn't responding to hand gesture, hovering was not as stable as in normal daylight.  When i used my iphone to controls it responded well but not hovering normally.  This might be your issues too or maybe not.  In either case, try it during regular daylight and see if it behaves normally.

To dark for the vis.system, methinks

If you don't have a GPS lock (home point recorded on the map) the drone will use it's downward vision positioning system to hold it's position in a hover. This is very dependant on sufficient light and the surface/pattern of the ground which is why flying indoors can lead to crashes and where the prop guards come in handy. If VPS is also lost with no GPS the drone will auto switch to ATTI mode and this will cause it to drift in line with the wind. I upgraded my iPhone 7+ to IOS 11.2 recently and this caused a few issues too. I refreshed the firmware in Assistant 2, the NFZ geo fencing in GO 4 and reinstalled the app on my iPhone then recalibrated the remote controller sticks, IMU and compass - no problems since. There seems to be a definite link between the IOS updates and the drone - everything seems to need to be reconfigured as if new each time Apple update - it's getting quite boring.

I sounds like it was too dark for vps. Without it, gps hovering may drift +-1.5 m (according to specs).

It may be the result of magnetic interference.  If you have any type of metal siding or power lines near your house, it may cause your Spark to fly as such. Have you tried to fly in a different spot?

I just tried it again today while it is still light out, but quite windy. I took off from the same location and this time it was rock solid in its hover. I guess the vision system does quite a bit!

Thanks for the replies, guys!

I think the vision system is what really locks Spark into a solid hover.  The warnings about flying over surfaces that don't have patterns or are certain colors or reflective really seem to show that the camera is looking for something it can distinguish and uses that picture to maintain a very absolute position.   The lighting range does show fairly low lighting conditions and apparently if the sun goes supernova the light will be too bright to get a good lock while we wait to vaporize.   But yeah low light conditions and a surface without clear patterns of some sort to help it see how it is doing are important.

Good things to know for future troubleshooting, as I'm quite new to all of this as well! Thank you.

That is pretty normal.. at a certain light level in the evening as the sun goes down spark tends to drift a little.

Mark Blaide Posted at 2017-10-10 13:38
I just tried it again today while it is still light out, but quite windy. I took off from the same location and this time it was rock solid in its hover. I guess the vision system does quite a bit!

Thanks for the replies, guys!

Glad to hear that you have figured it out. Enjoy it and happy flying!

I been having drifting for sometime now and today decided to see if I could find anything. I always put it down to wind, possible GPS signal. After reading this post and the comments I realised that as far as I know the drifting started when I decided to do a mini project on the canal locks in the area I am staying in. I will test the theory soon but I believe I am experiencing most of my drifting when filming along the canal and this obviously is not a good surface for the VPS to use.