DJI Naza GPS X,Y,Z co-ordinates
The shots below show my settings in the DJI Naza Assistant software for the X, Y & Z co-ordinates and what that translates to on the Quad. The first time I flew with the GPS, I didn't bother to set any parameters and GPS mode wasn't very good. As soon as I activated it, the quad would bank left and drift quickly until I re-engaged attitude mode.
I made three changes before the next flight. 1. Mount the GPS on the stick provided, 2. Point the arrow on the GPS towards the front and 3. Enter the co-ordinates in the software configuration. After another test flight, the GPS holds position pretty well. What I don't know is what had the most effect (the mount, direction or co-ordinates). I'm hoping it's the co-ordinates in the software because I'd prefer not to use the stick mount because it makes it bulkier to pack and more prone to damage on a hard landing. I think I'll try going back to double sided foam tape and mount it directly to an arm.
The pictures below show these settings X = -4cm, Y=4cm and Z=-9cm and what they look like in the real world.
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EagleTree Logger V4 on the DJI Naza F450
The first full flight with the EagleTree Logger v4 running on the DJI Naza F450 with GPS. The first 140 seconds show little activity while I plug things in and wait for GPS lock. When I eventually takeoff with a 4S 2200 Nano-tech LiPo, the voltage drops to 15.4 Volts and within 40 seconds drops down to 14.8 Volts as you'd expect from a 4S battery. It seems to hold the voltage fairly well throughout the flight keeping in mind it was fairly sedate backyard hovering with the GoPro onboard and recording. The voltage seems to start decling quickly after about 500 seconds where there's a few spikes in current and corresponding drops in voltage where I did a few short sharp rapid ascents with the throttle wide open. At about 670 seconds, the voltage drops too far and the second level protection kicks in where the Naza automatically descends. For my liking, it descends too rapidly but I'm not sure if that might be the result of setting the second level voltage protection level too low so there's nothing left in the pack to land safely. I wonder if I up the Voltage level, will the descent be more controlled when the Naza takes over.
I got about 2,000 mA out of the 2,200 pack which seems fairly good. The quad is loaded up with a GoPro, Naza GPS, Eagletree logger and Eagletree GPS so it's carrying a little more weight than usual. 8.5 minutes hover time seems pretty good I reckon. Average current draw with the 8" props is around 13 amps with a peak at 24.5. The 30Amp ESCs should be more than comfortable to handle that load.
This was the second flight with the DJI Naza GPS and all went well. There's been many rumours floating around the forums that the GPS doesn't work so well in the Southern Hemisphere (SH) and after my first flight I was worried they were right. During that flight, whenver I activated GPS mode the Quad would veer off to the left and never recover. After entering the X,Y,Z co-ordinates in the software configuration and mounting the GPS on the stick, it works great. At most the drift was maybe 1 meter but most of the time it seemed to hold position withing bout 30-50cm.
Next mission - Test the Return to Home (RTH) feature. I'll need a bit more space than the backyard though because it's supposed to ascend 20 meters, return to base, then land. Need to make sure there's no trees in the way. At the moment, the only way I have to trigger failsafe mode is to switch off my transmitter. That could be a bit nerve racking. In all my years of RC flying, I've never deliberately (or accidentally) switched off my Tx in mid-flight. I might have to make sure to have the video camera recording that one.
DJI Naza GPS installation on F450 Flamewheel
The DJI Naza GPS arrived today from Queensland, ordered from Quinton Marais (info@multiwiicopter.com). I must say his postage time is quick. I ordered it Wednesday night and it arrived at work in Melbourne Friday morning, just in time for the weekend.
The unit comes with a little 2 inch mounting pole that I guess helps elevate the GPS and Magnetometer from surrounding interference. Somewhere in the manual it talks about sensitivity to both vibration and magnetic field. I reckon the vibration would be worse when mounted on the supplied pole so I've gone with directly to the arm. I used some doubled sided foam tape to hold it on the arm.
A quick test in the backyard and it took maybe a minute from coldstart to acquire a full GPS lock. You can tell that by the colour and sequence of the flashing VU. When the controller is set to GPS mode, and before satellites are acquired, the VU will blink RED, RED, RED, GREEN. As more and more satellites are acquired, the number of RED flashes decreases until the VU flashes GREEN about once every two seconds.
No test flight to report yet.
** Update 6th July.
I've since moved the GPS onto the stick, faced it forward, entered the X,Y & Z co-ordinates and calibrated the magnetometer. It works much better now.
http://fangin.com/blog/2012/06/26/dji-naza-gps-xyz-co-ordinates/
