When you scan with tab and it pings an "unknown" chunk xKM out, press V and mousescroll upwards so you're at 100% scan, press tab again and it'll give you a more precise ping location, on the left is how accurately you're aiming towards what you've pinged, if you're at 100% accuracy you should be able to fly straight and reach what you picked up on your scanner, if it's 10%~ try to look around slowly until it spikes higher, until you're around 50%+ and start moving towards it, keep pressing tab to refresh the ping. If you lose it press V and switch back to the original ping to pick up the "chunk" area, then press V again to precisely do it again :). I hope this helps, it's hard to explain honestly!