Here's what's on the MK manual site. The GPS shield is an enlargement of the ground-plane of the GPS-Receiver to increase the signal strenght. Also it shields the antenna against electro magnetic fields of the other electronics. During the first start-up, the NaviCtrl will build a complete Almanac/Index. This contains satellite positions and paths. A complete cycle to build this Almanac takes 12.5 minutes. Based on the last known position the fix will from then on be built up much quicker. If the fix takes a longer time, it could be that the small battery on the GPS board is too weak. The battery is normally charged to about 3V. The battery is always charged when the GPS module is in operation. If the battery voltage is significantly lower than 3.0 V, it can be charged by providing power to the GPS module. One way is through the Naviboard's USB port (with the MKGPS connected). The ribbon cable to the FC should be removed. Another method is to power the MKGPS with 5V on one of the "5V-Pads" on the edge and 0V on ground (GND). Charging takes about 24 hours. The purpose of the battery is to keep the ephemerides in RAM and the realtime clock running after power off to shorten the re-aquire time.
I am now experiencing this. Last three flights I lost GPS. It went from 6 to 0 to 6 over a ten second period right upon power up. I checked connections to/from Navi board and all are tight. The latest GPX attached. See lines 9-19. Ideas on what to check? Colin
Were all 3 flights in the same location? Are you calibrating the compass at each location if the answer is no? I have personally seen a couple dead spots myself where I was flying and Mrs Graupner would tell me "GPS LOST". On the GPS log file you posted theres a nearby hospital that might be causing interference of some sort. At first I thought my issue was a bad calibration, or a bad cable, bad connection etc. But I found the problem to be the location I was flying which just happens to be a dead spot. The spot is in between two bridges that are about 1000 feet apart.
Colin lots of solar activity the last couple of days. Can't open the file right now but when were you flying?
It could be a few things could interference. Sometimes it could be a simple issue. The micro moles could be going bad even though the connections may seem good. A way to test is to turn on the system is wait for GPS latch up. Jiggle the cae a little to see if the GPS goes off line. Check the solar weather for that day. Also check to see the GPS coordinates were accurate before takeoff. Compass calibration won't affect GPS reception. Completely separate system. contrary to what you hear you calibrate your compass at every location. It's not that accurate. Magnetic variation does not change for a few hundred miles. Not only that you can calibrate your compass to be normalized to em interference on the ground but have messed up in flight in flight.
He was flying around 4pm and the solar data shows the KP index was good up to around 7 pm. But that could contribute to it as its very close.
I have heard that said before but to my experience I have seen the opposite. I traveled to a golf course about 75 miles away. First flight up I got GPS loss. I recalibrated the compass and never had below 6 sats after that with 4 hours of flying. Happened a second time when I went about 50 miles away to a state park. I know what your saying Shaun but personally I experienced a completely different reaction. It could be complete flukes, dunno.
Yes. All at this same location. The acquisitions seem slow (day before yesterday it was 3-4 min to get 6 Sats), so location may be an issue. It I'm suspicious of EM as well, since it always happens as I'm powering up for flight. Once I'm up it goes back to normal.
Colin looks like you were flying at about 1956GMT. Here's the chart from the 27th. Each bar is a 3 hour period. The Red bar would be for the period of 1800-2100GMT.
I never thought about the GMT conversion when looking at this chart. Wouldn't 15:56:00 Pacific time convert to 22:56:00 GMT? I know it doesn't matter for this situation because the KP is still at 4 until 03:00:00 GMT the next morning. Just trying to make sure I understand for my reference in the future.
I believe Colin is on the West coast which is GMT-7 currently. Changes with daylight savings time. EST is -4
Dave: If you open up the GPX file as a text file (which is all it is) using, say, Notepad or Wordpad, you'll see lines of the form: <time>2013-08-27T19:56:31Z</time> The trailing "Z" means Zulu Time -- which is also known as UTC (an out-of-sequence acronym for Universal Coordinated Time -- see http://en.wikipedia.org/wiki/Coordinated_Universal_Time if you want to know why it's not CUT). There's a conversion chart at http://hurricanes.noaa.gov/zulu-utc.html . When you ask "Wouldn't 15:56:00 Pacific time convert to 22:56:00 GMT?" the answer is yes -- but it's already UTC in the GPX file. (Tell me this isn't confusing!) It gets worse. If you send me a GPX file, MK_GPXTOOL, in an effort to be helpful, looks in your computer, determines the time zone, and converts the GPX file data into your computer's local time zone! So Colin's GPX file looks like this when MK_GPXTOOL displays the summary (I'm in the Pacific Time Zone and, of course, we have Daylight Savings Time in effect -- so the time is in PDT): Flight date: 2013-08-27 12:56:31 PMFlight time: 12:56:31 PM - 1:03:26 PM (415 secs, 00:06:55)So, to look at the n3kl.org Kp Index data you either have to look at the GPX as a text file to find the Zulu time, or look MK_GPXTOOL time and at the NOAA link about to convert it back to UTC. Hope this helps. Andy.
Gary: Agreed. The entire Internet and all aviation operates on UTC. Wow. It's 04:03. Almost bed time... Andy.
That means your battery in the GPS is dead. That little button battery. It saves the sattlilte almanac so when you turn the system back on it already knows which sattelites to be looking for. Mine is out as well. Becasue of that it has to try search the sattelites so it can take a few minutes. Not sure causal to your issue but it could be because it has not had enough of a chance to load that into the GPS memory.
Sure, the only reason why the compass needs to be calibrated to magnetic north is so that the Nav system can correlate the magnetic course to the GPS course. This is only when the copter is moving in flight. If the compass too much of an error such as being 10 degrees off it will get confused with what GPS is giving it. That can cause that wired toilet bowel effect. When the copter is not moving GPS cannot provide a heading with accuracy. The GPS has no idea where north is in relation to the Copters front until it starts moving. If there is too much of a discrepancy the nose will start to weathervane back and forth and the copter is going to try to keep flying in the course direction. Lets say you want to travel north i.e 360 in dynamic position and you front boom at that heading as well. If the copters compass is off significantly in the control which will allow for some error. The nose will rotate to one side then instead pitch down movement it will partially bank into the position. If you manually have to make significant yaw corrections the situation gets aggravated and will start oscillating from side to side while trying to move forward. It will keep doing this until you disengage the PH function. In lower parts of the hemisphere its relation to magnetic change is not a whole lot until you move a significant distance away to east or west. In the upper or lower parts getting closer to the poles this change is more rapid, but were talking about bening in Alaska and moving 50 miles to make a significant change. Going from the middle of the US to California, there really is about only 5 degrees ish that this will change. The field is not static and can change on its own, but usually that change relatively small in a single area over a significant amount of time as the earths iron sloshes around in the corps. So that is why its not necessarily that important to recal every time you fly. IMO External magnetic interferences are to dynamic and wont matter one way or anther unless you are flying in tight area for a long period of time. I have taken off at places with a noticeable magnetic disturbance and as I moved away from the source it went away. If I had done a recalibration. I would have negated that calibration after I was away from the disturbance so my compass would be off flight. That is why they recommend t calibrate in an open area away from external influences and kkep things like your cell phone off etc. My technique is to turn on all electric equipment on the aircraft so that I normalize the magnetic field to internal on the aircraft as best as possible. Obviously with a three axis gimbal you will not be 100% perfect because you will move the field around a bit. But for the most part since those transmitters move. Since the radios are close to the aircraft any way they generally dont effect a radical change as they rotate hence why there is not too much of an issue. If transmitters are off when you calibrate then they will put additional field that was not there when you turn them on. Big picture that is really the only importance to compass calibration is to make sure it is normalized to the GPS as best as possible. The best way to know for sure is to get VFR flight charts or google magnetic variation and see what it is for the area you are going to fly. I don't consider an issue unless I see a 5 degree or more change.