Drone Purchase Strategy

Drone policy and the question of whether it can fly

1.In China, drones weigh less than 250 grams, don’t need to be registered and a driver’s license (a bit like a bicycle, no license plate, no registration, no driver’s license, but still have to obey the traffic rules

The drone weighs more than 250 grams, but the take-off weight does not exceed 7000 grams. You need to register on the Civil Aviation Authority website, after completing the registration, you will be given a QR code, You need to stick it on your drone, which is equivalent to sticking an ID card on your plane(It is a bit like an electric bicycle, which needs to be registered, but does not require a driver’s license)

2. The take-off weight of the drone is greater than 7000 grams, and a drone driver’s license is required, Such drones are usually large in size and are often used for special operations, such as surveying and mapping, plant protection, etc.

All drones need to obey the rules and cannot take off in no-fly zones. Generally, there is a red no-fly zone near the airport, and there is a height restriction zone (120 meters) around the airport. Other non-restricted areas generally have a height restriction of 500 meters.

Tips for Buying a Drone

1. Flight Control  2. Obstacle Avoidance  3. Anti-Shake  4. Camera  5. Image Transmission  6. Time of Endurance

Flight Control

The flight control is easy to understand. You can imagine why we can stand firmly and why we don’t fall when we walk? Because our cerebellum will control the muscles in various parts of the body to tighten or relax in order to achieve the purpose of balancing the body. The same goes for drones. The propellers are its muscles, the drone can accurately perform hovering, lifting, flying and other operations.

In order to achieve precise control, drones need to have “eyes” to perceive the world. You can try it, if you walk in a straight line with your eyes closed, there is a high probability that you will not be able to walk straight. The same goes for drones. It relies on various sensors to perceive the surrounding environment, so as to adjust the power on the propeller, so as to maintain accurate flight in different environments, which is the role of flight control. Drones with different prices have different flight controls.

For example, some toy drones do not have any eyes that can perceive the environment, so you will find that the flight of this drone is very unstable, and it is easy to lose control when encountering a breeze, just like a baby. The baby walks unsteadily with eyes closed, but if there is a slight breeze in the air, it will go with the wind uncontrollably.

Most mid-range drones will have an extra GPS so it knows its way and can fly farther. However, However, this type of drone does not have an optical flow sensor, nor does it have “eyes” like a compass that can perceive the surrounding environment and its own state, so there is no way to achieve precise hovering. When hovering at low altitude, you will find that it will float freely, like a naughty teenager who has no self-control ability and loves to run around. this type of drone has high playability and can be used as a toy to fly.

The high-end drones are basically equipped with various sensors, which can continuously adjust the power of the propeller according to its own state and the surrounding environment, and can accurately hover and fly stably in a windy environment. If you own a high-end drone, you will find that it is like a mature and stable adult, allowing you to confidently fly the drone into the blue sky.

Obstacle avoidance

Drones rely on eyes all over the fuselage to see obstacles, but this function requires a large number of cameras and sensors, which will increase the weight of the aircraft. Moreover, high-performance chips are needed to process these data.

For example, bottom obstacle avoidance: obstacle avoidance is mainly used when landing. It can sense the distance from the plane to the ground, and then land smoothly and automatically. If the drone does not have bottom obstacle avoidance, it will not be able to avoid obstacles when it lands, and it will fall directly to the ground.

Front and rear obstacle avoidance: Avoid hitting the drone’s rear during frontal collisions and reverse shots. hen the obstacle avoidance function of some drones encounters obstacles, it will frantically alarm on the remote control and automatically brake at the same time; If you choose to go around, the drone can also automatically calculate a new route to avoid obstacles; If the drone has no obstacle avoidance and no prompt, it is very dangerous.

Upper obstacle avoidance: The upper obstacle avoidance is mainly to see obstacles such as eaves and leaves when flying at low altitude. At the same time, it has the function of avoiding obstacles in other directions, and can safely drill into the woods. This obstacle avoidance is very useful when shooting in special environments, but it is basically useless for outdoor high-altitude aerial photography.

Left and right obstacle avoidance: It is mainly used when the drone is flying sideways or rotating, but in some cases (such as automatic shooting), left and right obstacle avoidance can be replaced by front and rear obstacle avoidance. On the front of the fuselage, the camera is facing the subject, which can also produce a surround effect while ensuring the safety of the drone.

To put it bluntly, obstacle avoidance is more like the automatic driving of a car. It can only be said to be icing on the cake, but it is not completely reliable, because it is actually easy to deceive your eyes, such as transparent glass, strong light, low light, tricky angles, etc.,  So obstacle avoidance is not 100% safe, it just increases your fault tolerance rate, everyone should fly safely when using drones.

Anti-Shake

Because the wind at high altitude is usually relatively strong, it is also very important to stabilize the drone when taking aerial photography. The more mature and perfect is the three-axis mechanical anti-shake.

Roll axis: When the plane flies sideways or encounters left and right side winds, it can keep the camera steady.

Pitch axis: When the aircraft dives or lifts upwards or encounters strong frontal or rear wind, the camera can be kept stable.

Yaw axis: Generally, this axis will work when the aircraft is turning, and it will not make the screen shake left and right

The cooperation of these three axis can make the camera of the drone as stable as a chicken head, and can take stable pictures under various conditions.

Usually low-end toy drones do not have gimbal anti-shake;

Mid-end drones have two axes of roll and pitch, which are sufficient for normal use, but the screen will vibrate at high frequency when flying violently.

The three-axis gimbal is the mainstream of aerial photography drones, and it can have a very stable picture even in high-altitude and windy environments.

Camera

A drone can be understood as a flying camera, and its mission is still aerial photography. The large-size CMOS with a large bottom feels lighter, and it will be more advantageous when shooting low-light objects in the dark at night or in the distance.

The camera sensors of most aerial photography drones are now smaller than 1 inch, which is similar to the cameras of most mobile phones. There are also some 1-inch ones. While 1 inch and 1/2.3 inch don’t sound like much difference, the real area is four times the difference. This four-fold gap has opened up a huge gap in night photography.

As a result, drones equipped with large sensors can have brighter images and richer shadow detail at night. For most people who travel during the day and take photos and send them to Moments, the small size is enough; For users who require high image quality and can zoom in to see details, it is necessary to choose a drone with a large sensor.

Image Transmission

How far the plane can fly depends mainly on the image transmission.  Image transmission can be roughly divided into analog video transmission and digital video transmission.

Our speaking voice is a typical analog signal. When two people are talking face to face, the exchange of information is very efficient and the latency is low. However, voice communication can be difficult if two people are far apart. Therefore, the analog signal is characterized by short transmission distance and weak anti-interference ability. The advantage is that the short-range communication delay is low, and it is mostly used for racing drones that do not require high delay.

Digital signal image transmission is like two people communicating through the signal. You have to translate it to understand what others mean. In comparison, the delay is higher than that of the analog signal, but the advantage is that it can be transmitted over a long distance, and its anti-interference ability is also better than that of the analog signal, so digital signal image transmission is mostly used for aerial photography drones that require long-distance flight.

But digital image transmission also has advantages and disadvantages. WIFI is the most common digital image transmission method, with mature technology, low cost and wide application. This drone is like a wireless router and will send out WIFI signals. You can use your mobile phone to connect to WIFI to transmit signals with the drone. However, WIFI is widely used, so the road channel for information will be relatively congested, a bit like a public national road or expressway, with too many cars, serious signal interference, poor image transmission quality, and a short transmission distance, generally within 1 km.

Some drone companies will build their own dedicated digital image transmission, as if they have built a separate road for themselves. This road is only open to internal personnel, and there is less congestion, so the information transmission is more efficient, the transmission distance is longer, and the delay is lower. This special digital image transmission usually transmits information directly between the drone and the remote control, and then the remote control is connected to the mobile phone to display the screen through a data cable. This has the added benefit of not interfering with your phone’s mobile network. Communication messages can be received normally.

Generally, the interference-free distance of this kind of image transmission is about 10 kilometers. But in reality, many aircraft cannot fly this distance.There are three reasons:

The first is that 12 kilometers is the distance under the US FCC radio standard; But it is 8 kilometers under the standards of Europe, China and Japan.

Secondly, the interference in urban areas is relatively serious, so it can only fly 2400 meters. If in the suburbs, small towns or mountains, there is less interference and can transmit farther.

Third, in urban areas, there may be trees or tall buildings between the aircraft and the remote control, and the image transmission distance will be much shorter

Time of Battery

Most aerial photography drones have a battery life of around 30 minutes. That’s still battery life for slow and steady flight in no wind or hovering. If it flies out normally, it will run out of power in about 15-20 minutes.

Increasing battery capacity can increase battery life, but it’s not cost-effective. There are two reasons: 1. Increasing the battery capacity will inevitably lead to larger and heavier aircraft, and the energy conversion efficiency of multi-rotor drones is very low. For example, a 3000mAh battery can fly for 30 minutes. 6000mAh battery may only fly for 45 minutes, and a 9000mAh battery may only fly for 55 minutes. The 30-minute battery life should be the result of comprehensive consideration of the size, weight, cost, and battery life of the drone under the current technical conditions.

If you want a drone with a long battery life, you must prepare a few more batteries, or choose a more energy-efficient dual-rotor drone