GPS Tips and Tricks

Many people who followed my gps on Betaflight guide have not had the best experience with gps. Here are some tips for getting the most out of your gps setup.

  • Make sure you have an m8n chip. The reason you want an 8 and not a previous version (i.e. a 7) is that the 8 can do two different satellite constellations at once. Specifically, GLONASS and GPS. You effectively double the number of satellites you can see, which makes the gps lock much faster. The way to check for this: in u-center, go to Messages View. Then select UBX -> MON -> VER.

    Beitian BN 880
  • If your GPS takes a while to lock, you may want to power it up with 5V while you’re driving to your flying spot. Some flight controllers supply 5V when plugged in to USB (the Omnibus F4 does, for example) and others don’t. For the ones that don’t, you could attach a small connector to power it with an external 5V source.
  • Mount your GPS unit such that it has as much line of sight as possible to the sky. If you have a 1.3GHZ video transmitter, get your gps as far as possible from it.
  • It’s possible to use a GPS with only the RX pin of a UART, if it has non-volatile configuration. You have to first configure it via u-center so that it sends all the messages Betaflight needs (see here ). Obviously auto-config from BF won’t work, but that’s fine.
  • If your gps is connected with TX and RX, you can connect u-center directly to it via the flight controller without the need for an FTDI interface. In the Betaflight CLI, type “gpspassthrough” and then disconnect so that the configurator releases the port. Go to U-center and connect to the same port.
  • My two preferred gps modules so far: 1) Beitian BN-880 for 6″ and larger builds. It also has compass. 2)  Ublox m8n for 5″, because it’s small and light.

[more tips to come, check this page once in a while]

Miniquad long range pre-flight checklist – this will save you money and pain

Long range with a miniquad is unforgiving. Make a mistake, lose the craft. This checklist is intended to minimize preventable losses, based on experience.

  1. Flip the quad upside down, check motor screws. You do not want to lose a motor mid-air while flying over a lake or mountains.
  2. Check that all your propellers are in good shape. A bent prop could cause a motor to fail, a damaged prop could explode mid-air.
  3. Check your transmission frequency and power. Specifically, you’re using Crossfire make sure you’re on the right frequency for your region (e.g. 915Mhz in the US), and that your transmission settings are adequate for the flight about to take place.
  4. Plan your flight. Surprises in long range are usually not good. Look around, study the terrain, know where you can and cannot go, have an understanding of line of sight between you and your expected course. Checking the area on Google Maps and having an idea of the distances and landmarks is always a plus.
  5. Make sure DVR is on. If your quad goes down and the battery comes unplugged, DVR is your best hope to find it. I personally DO NOT take off for a long range flight unless I know I’m recording it on my goggles.
  6. GPS not locked = no go.  Same as above. I want gps every time not just for finding the quad, but to make sure I can find my way back. Distance to home is invaluable, don’t leave home without it.
  7. If your receiver / base station is on a tripod, make sure it will not get knocked over. This is actually a good reason to have a spotter. You can have the best video system, yet lose a quad because of a gust of wind.

[more to come]

This is not really part of the checklist, just some learnings from experience:

  • Never go too far on a maiden. Even if you’re the world’s best builder, you never know what components are faulty. Fly around for at least four or five packs before venturing into the distance.
  • A quad that crashed badly is not a long range quad. You never know what hidden damage exists, and you don’t want that damage to become evident as you fly one mile out over water. If you have a bad crash, inspect the quad thoroughly (particularly all the solder joints and wires).
  • Know your battery well. Turn around before it’s half spent.
  • Consider using redundant mechanisms for finding the quad: e.g. gps and a bluetooth beacon such as a Tile. Don’t rely on the battery to remain plugged in.
  • If you can, scan the spectrum. Make sure nobody is using the video frequencies you plan to use.

Miniquads and Safety – Rational Analysis Attempt

Miniquad safety is a murky subject. At first glance it seems obvious that a miniquad is a potential dangerous object, perhaps even lethal. A quadcopter traveling in a straight line at the height of  a person’s head has the potential to seriously hurt or kill somebody. There is a fair amount of offline discussion around this topic, but unfortunately most of it is based on speculation and feelings as opposed to reason and hard numbers. This post is an attempt to do the latter.

It’s important to acknowledge that all of us partake in activities that are dangerous to others. Some are arguably necessary; if you have to drive to work, you are a statistical contributor to the roughly forty thousand road deaths that happen in the US on a given year. But what about the unnecessary driving all of us do? From a statistical perspective, going on a recreational 1000-mile road trip has 1/100,000 odds of resulting in one death. This is very significant, because a large amount of driving in the US is of this type. Recreational driving kills at least hundreds of people each year. Nobody is on a crusade against unnecessary driving, just because we are not robots that think about the public good. We are imperfect, selfish, and get emotional about things that are often not the ones that matter most.

I imagine some people may be put off by the comparison with driving. Driving is accepted and part of our culture, like alcohol and guns. Miniquads are not. They are new and scary. Because they are a recent development, there is not enough data to write a paragraph like the above. How many people die per million miniquad flights? We do not know. The close we could get to this number would be by estimating the number of batteries flown every day, and finding records of all people killed by miniquads. I personally have not found any records of deaths caused by miniquads, but that does not mean they have not happened (I would honestly welcome that information).

It is possible that a miniquad is not as dangerous as some people believe. Let’s consider all the things that need to go wrong for someone to be killed by a miniquad. Here is an example scenario:

Miniquad near road

An operator is flying a miniquad near a road, trying to keep some distance (let’s say no closer than 20 feet). If the operator has no intention of going over the road, some type of failure must occur. The most common failures with fpv miniquads are:

  • power train failure (motor, esc)
  • loss of video
  • loss of control

In the first case, most likely the miniquad will drop. Unless it was traveling relatively fast and in the direction of the road, it is very unlikely that it will land on it. In the second case, the operator has the responsibility to deactivate the miniquad right away (or set it into a mode that would stabilize it and climb out of danger). Video loss should not cause the miniquad to hit a road unless the operator makes a mistake.

Loss of control is the most likely reason the miniquad could impact the road. This is largely preventable. Again we do not have data to back this up, but empirically most control losses in radio control are due to various operator mistakes such as flying out of range or having damaged antennas. Interference is also possible, but this mostly happens when several miniquads fly in close proximity and in a hostile RF environment. Out in the open this is still possible but unlikely, especially if the operator is staying well within the known range boundaries and line of sight.

Let’s imagine the operator has taken all possible precautions for this flight, just like a normal aircraft pilot would. The miniquad is in good shape: no damaged antennas, no questionable components. There is a contingency plan for video loss, control loss is unlikely. There is still an unknown chance that something will go wrong and the miniquad will somehow end up hitting the road. I can only speculate as to what could cause this, but let’s say it happens.

We are now in an uncommon scenario: we got unlucky and the quad is hitting the road. What would need to happen for someone to die? The typical miniquad weighs roughly 600 grams. A miniquad impacting a car cannot change its trajectory. What can it do? It could startle the driver, which in turn could lead to an accident. How likely is this? If we want to know, we would have to dive into statistics of traffic accidents and see how many of those were caused by unexpected hazards startling drivers. We would have to know the total number of events in which drivers were startled, and divide the known accidents by that to find the odds of an accident.

Let’s say that 99 out 100 times, when a car gets hit by an object the driver gets startled but no accident happens. It could be more or less, but the point is that an accident is not the most likely scenario when a driver gets startled. How about a fatal accident? That depends highly on the type of road and the road conditions. A miniquad landing on a car in gridlock traffic at rush hour is likely to cause some property damage, but extremely unlikely to result in a death.

Miniquad in park

When flying in a public place such as a park, the worst possible scenario is hitting an unexpected passerby with lethal force. Let’s examine what would need to happen for someone to die or get seriously injured in this case. Once again, the primary suspects are video loss, control loss and powertrain failure.

Most miniquad pilots make a good faith effort to avoid flying in populated areas. However, we don’t always fly in wide open spaces with no obstacles. Parks with trees are one example of a location where people can unexpectedly appear in the trajectory of a miniquad.

The number one mitigation factor for this type of risk is having a spotter continuously scanning the area for unexpected persons. This is not a protection when flying behind obstacles, as neither the spotter nor the operator would see behind, but it does decrease the odds of a collision. The second mitigating factor is a thorough pre-flight inspection of the miniquad to avoid loss of control, and a knowledge of the RF environment to avoid video loss. The third one is a contingency plan (“if I see a person in front of me I will immediately ground the quad and disarm”). The fourth (and arguably most important one) is speed. Because the energy of an object is proportional to the mass as well as the square of the velocity, a quad going 60 mph will impact with four times the energy of the same quad flying 30 mph. When flying in areas where humans are likely to appear, flying fast is flying irresponsibly in the same way driving above the speed limit is irresponsible.

Conclusion: if we as a community want the activity to be safer (not just appear to be safer, which is in itself a goal but not the point of this discussion), we need to think rationally and critically about the risks posed by miniquads. We need to inform ourselves regarding the likelihood of failures, and we have the responsibility to treat our quadcopters like regular aircraft. Flying a poorly maintained miniquad is irresponsible. Planning a flight adequately, thinking of the risks involved and having contingency plans is something all of us should do at all times.




How to log gps coordinates on the Taranis

[This post is a work in progress, feedback welcome].

In a previous post I discussed how to set up GPS with Betaflight 3.2. If you don’t have telemetry, you have to rely on DVR to locate a lost quad. However, if you have telemetry working on Betaflight you can take full advantage of gps. You can log gps data on the Taranis, have your current location on your telemetry screen (extremely useful for finding a downed quad) and even plot your flights on Google Earth! Here’s how.

If you’re using TBS Crossfire (recommended): First, make sure you connect your Crossfire receiver to the flight controller using CRSF and not SBUS. CRSF is a bidirectional protocol, and includes telemetry. I’m using the Crossfire Micro RX v2. If you already use CRSF, skip to “Discovering sensors.”

[Note: I tested this under firware version 2.0.6, had to revert from 2.0.7 because it didn’t work. Also, I tested this with BF 3.2 rc5 and rc6 only].

How to connect CRSF: you will need to connect your micro rx to the controller like this: gnd and 5v, channel 1 to a uart rx and channel 2 to a uart tx. If you’re connecting ch1 to the sbus uart, make sure you go to the Betaflight command line and type

set sbus_inversion=OFF

On your Crossfire transmitter go to the receiver configuration menu -> Output Map. Set CH1 to CRSF RX. CH2 will automatically switch to CRSF TX:

Go to Betaflight configurator and enable Telemetry under features. Under serial protocol, enable CRSF. Make sure the proper uart is set in ports.

If you can control your quad with CRSF, you are almost there. Next thing set up telemetry.

Discovering sensors

Plug in your quad and go to the Taranis telemetry page. Select the “Discover new sensors” option and wait a few seconds. You should see several new sensor appear on the sensor list. Here comes a surprise: flip your Taranis and look at the Crossfire screen (assuming you have the full size Crossfire). You’ll see something like this:

[if your gps is not locked to the satellites the coordinates will be 0, but at least you’ll know it works].

If you’re using Frsky with Telemetry: all you have to do is discover new sensors (see Discovering sensors in the Crossfire section above).

Enabling black box logging on the Taranis. Here’s a short video than explains it well:

Next up: Plotting flights on Google Earth.




How to add GPS to a miniquad with Betaflight 3.2

With the 3.2 release, Betaflight finally has decent GPS support. Here are some of the navigation features you can have on Betaflight OSD:

  • Latitude
  •  Longitude
  • Distance to home
  • Speed
  • Arrow pointing home

Even better: if you have a telemetry-enabled receiver such as the X4R or XSR, you can send your location to the Taranis in real time. The Taranis will log your position, and keep the last known position available in case of a crash. This means it could save you time and maybe money in the long run.

Interested? Let’s do it.

The first thing you need is an integrated GPS receiver / antenna that’s small enough to fit on a miniquad. The one I have been using is the Micro Ublox M8N that you can buy at RTFQ for $16. It weighs only 6 grams, which is negligible for most miniquads capable of going relatively far.

Ublox M8N gps unit

This unit comes preconfigured and ready to wire to a flight controller. However, if you want to mess with the settings you can configure it via a serial UART and u-center for Windows. This video is still mostly relevant if you need to do that.

Wiring the gps unit is easy: just connect it to a free UART on your flight controller. Make sure that the wires are long enough that you can mount the gps on top of your quad.  If you are running a bottom mounted battery, the top of your HD camera mount is the best spot. I run a top mount, so I prefer heat shrinking the gps to a battery strap so I can have it on top of the battery.

Once wired, configuring the gps is easy.  On the ports tab of Betaflight, select gps as a peripheral for the UART to which it’s wired. In this case I used UART 3.

Then in the configuration tab:

And if everything is wired correctly, when you restart betaflight you should see the GPS indicator light up at the top of the screen.

Now there are two things you can do. If you have Betaflight OSD, you probably want to enable gps coordinates, distance to home and direction to home. I also like having the satellite count and gps speed, even though it’s not very accurate. My screen looks like this:

The home arrow indicates that I’m flying mostly away from myself and 145 meters away. The GPS coordinates show that I am in… [left as an exercise for the reader].

The second thing you could do is set up your Taranis to log gps coordinates (assuming your receiver has telemetry, won’t work with an xm+). I won’t cover that now because this is enough for one post, I’ll save it for a future one. Happy flying and hope this saves you from losing a quad or two!


Diagnosing Quad Issues

So your quad doesn’t fly right. It has strange oscillations, vibrations, falls out of the sky, etc. Here’s what you do:

  • Check that all frame screws are tight.
  • Make sure all standoffs are straight.
  • Check all the screw motors. Make sure they are not touching the windings. Test continuity between screws and leads with a multimeter (there should be no continuity). If there is continuity, use shorter screws.
  • Inspect the frame for cracks. Make sure it’s solid everywhere.

If you have tuned the quad, try the stock tune to rule it out as a cause of vibrations. A quad on stock tune should not vibrate unless it is a very unusual setup.

If none of the above solves it, test individual components. If you have a firmware that allows motor testing, remove the props and spin each motor independently. Hold each arm while spinning its motor and feel the vibrations. If a particular motor vibrates, either try replacing the bearings or just put in a new one.

Quad falls out of the sky

Watch this video by Joshua Bardwell. Most likely it’s a motor and / or an ESCs.

Frame review: VH qav210-style

In my experience with FPV freestyle, the frame of a quad is not very important in terms of flight characteristics. So long as it has a reasonable shape and weight distribution (particularly top-mounted battery), a frame will fly fine. When buying a frame, I care mostly about the following:

  • Price
  • Durability
  • Ease of maintenance

So far my go-to frame has been the qav 210 clone in its many incarnations. You cannot beat the price ($20 or less). It’s a pretty simple frame: unibody bottom plate, six standoffs, top plate. The main drawback has been durability. The plates break relatively easy, which isn’t a big deal to me because they are cheap and and easy to replace.

I recently found this “qav210 style” frame from Valuehobby which is almost a clone of the Astro X X5. The main difference is the unibody bottom plate, which I much prefer. At $20 it was an extremely good deal. It fixes the durability issues of the qav210 with no drawbacks that I can think of. See my video review for more.

KISS ESCs fire with new firmware

I have been flying KISS 24A ESCs for a while, and they have performed really well. However, I recently upgraded a couple of my quads to version 110b RC7. Since then, I have lost three ESCs to fires. Not sure if this is just bad luck or if it is related to the firmware update, but I would stay clear of it just in case. I will be downgrading my remaining ESCs to the previous release.

This seemingly innocuous landing cost me two burnt ESCs and motors.

Getting Better at FPV Freestyle

There are two kinds of people in the world of FPV: those who fly miniquads, and those who don’t. Among those of us who fly miniquads, there are again two kinds of people: those who primarily race, and those who mostly freestyle (like me). I’m sure you could keep zooming into subcultures forever, as XKCD once put it:

I’ll stop at this level, and define what I mean by freestyle for the purpose of this post. My interpretation of freestyle is to fly in a way that generates a pleasant HD video experience (either as the product, or as a side effect). To me, the only way I can enjoy someone else’s freestyle is by watching their footage. Obviously many will disagree, and that’s fine. This is about getting better at the thing I just defined, call it what you may.

I’ve been trying to improve at this for the past few months, and I believe it’s working. Here are some of the things I did and still do:

  • Record every single flight of mine with an HD camera whenever possible. This is because the only way I have to analyze my flights is by watching them on the screen, sometimes over and over. I see things that I missed when flying all the time, or moves that seemed graceful at the time but look awkward on video.
  • Watch as much flight footage as possible, immediately after a flying session. While the flights are still fresh in my memory, I want to learn from them. Did I repeat myself too much? Could I have tried something different? Did something not go the way I wanted it? Why?
  • Practice the same move over and over for the duration of a pack. For example, a few months ago I had a hard time performing powerloops consistently. This type of practice helped me quite a bit.
  • Analyze videos that I like. What makes them interesting? Are there tricks or moves I could not do? Do I understand how they are performed?

What works for you? Let me know in the comments, or in my Youtube channel.




The Drone and the Sequoia – Epilogue

Part I and Part II if you’d like to catch up. This is part III.

Day 5

Grandpoobah (the owner of the cannon) wanted to give it a shot himself, so he came over to Oakland with a more powerful electric pump, supposedly capable of 180 psi. We worked as a team: he held the cannon and aimed it, I pulled the trigger (a two-position gas valve requiring a quick smack). We were getting better with every attempt, but unfortunately the $20 pump from Amazon gave out after eight tries. The smell of burnt plastic signaled its quick demise. At that point I decided to give up on the cannon.

I went to the Arborist subreddit (not to be confused with r/trees) and explained my situation. As luck would have it, a redditor who lives nearby offered to come take a look and maybe climb the tree for me.

Day 6

At 3pm on Monday, I met with Chris at the tree. An arborist by trade, he brought a ton of specific gear for climbing the most challenging trees one could find. Super nice guy, it turned out that he’s also a rock climber who climbs at the same gym as I.

Chris getting ready to climb

The hardest part for him was throwing his arborist weight into the right branch. I was surprised by his technique; he threw the line by hand about as high as we could go with the fancy air cannon. It took him maybe ten attempts to get the line over the branch he wanted to use as an anchor. He then wiggled it until the weight came down on the other side and tied a rope to the end. Pulled the rope over, tested it to make sure the system wouldn’t give out, and proceeded to ascend.

A few minutes later he made it to where princess Garuda was patiently waiting for her hero to rescue her from the maw of the evil Cth… ok enough with this metaphor.

So high

At 4pm on February 13th, 121 hours after getting stuck, the Garuda was finally down on the ground. Chris did not want any compensation for his ascent so I bought him a case of my favorite beer (thanks so much dude!). I wouldn’t ask him to do this again, so I’m staying clear from those trees until I learn the ropes myself.

The Garuda was intact, ready to fly. Not even the props were damaged. The GoPro was still mostly charged. The battery was down to 0.8V, but I carefully nursed it back to health and it flies just fine (believe it or not).

Out of the tree, ready to fly.

And this concludes the epic of the drone and the sequoia. Moral of the story: arborists are great people and drone enthusiasts should be nice to them!

I’d like to say the Garuda lived happily ever after, but a few days later the Great Garuda Fire of 2017 happened (ESC, camera, canopy and motor perished in it). I fixed it up but I’m still waiting for a new canopy to fly it again.

If you enjoyed this series, check this site often for more adventures. In the meantime, find me on Youtube.