Crashpilot1000 wrote:.... If trash GPS signals are detected (bad reception, most likely in urban areas etc and def. expected with no gps groundplate) Harakiri will disable the current GPS flightmode and you are stuck with what you have defined when that GPS function is turned off. .....
I didn't know that. I'd always activate Baro in GPS so at least it won't drop suddenly.
Regarding GPS, here's a few things important to know if newer folks haven't spend much time on it:
1. work with u-center and notice the "3D-uncertainty" number. When only one or two SV locked in, that number would be large in the thousands of meters, but quickly reduce as the 3rd and 4th SV lock in. HOWEVER, watch it as you get the 6th SV lock in and you will see that the REMNANT UNCERTAINTY will still remain large (perhaps even 10 meters). It will reduce given more time, but make note of how long it would take to reduce to 2-3meter uncertainty. It takes a while, doesn't it?
What this means: you should better not be flying as soon as you get the 6th SV, even though you've met requirement. Wait some 20sec more, so that Residual Uncertainty/deviation would reduce some more. When I practice that, I'd get solid GPS PH vs. not doing so.
2. I believe backplane/backplate is a MUST for GPS antenna. IF you've taken apart a DJI Phantom, you would notice a rather thick Copper foil embedded in sticky plastic, just under the GPS module, separating it from all circuit below. And you should also notice that ALL FC mfgrs (Naza, Vector, WooKong, etc.) even SKYlark OSD, will supply their own GPS module. You just can't buy one from Ebay and slap it on. That's done for a reason. Programming GPS module to meet your FC functionality req'm is a Must.
Furthermore, I've found that virtually ALL of my <$20 GPS purchases on Ebay have problem keeping programmed configs. They'd lose data afte >2days of non-activity !! Some worked after battery replacement (but $3 battery) in case of 6M module, but I haven't been successful reviving 7M modules. The story here, is that you're better off with $25 module with a larger back plane, dependable SV locks and keeps configs.
3. When there's a failure in GPS hold, check through this list:
-recal your Mag sensor (Left stick TOP RIGHT, Right stick DOWN, white light turns on for duration of data gathering). Rotate the craft about its THREE axis, al least once. Leave it alone to white light Off, and auto reboot.
-make note of your Environment. RF interference is a problem. Cell Phone towers. Hi-power Wi-Fi. A Shopping center parking lot where I tried must have a 5w wifi because I can get max wifi signal at least 300m away. My quad would always wander around while in GPS PH. Consider that "No Fly Zone". LOL Pick another place to fly and test.
Also, wind vortex from buildings and home can play unpredictable turbulence on your craft, even 40-50meters away. Be aware of that.
-plug your GPS back into u-center. Is your programmed config still in there ???? My ebay units reset to 9.6kbaud, etc...stock settings when FC expect differently.
All these things assume that you've already made your craft RF-sound.
Note that SV formation in the sky is constantly changing. They orbit the earth around 12,000 miles, significantly less than the geo-stationary orbit of 22,300miles. So what you get today is different from yesterday, even 4 hours earlier. Less than 4hr from last power up, is considered "warm" GPS boot.
Some people use a small battery to power up for gathering current GPS almanac data. Then unplug that, and plug in the main battery for flying... (hot boot).
Here's my F450 on GPS PH. It works.
http://youtu.be/R5ZRlWyCvwg