1.1.1 External Environment and Conditions

✅ In the field, drone flight is an important factor in determining the quality of 2D orthophotos and 3D data. In addition, it is important to carefully consider the external environment and conditions for the drone to fly safely.

To plan a safe and efficient drone flight by taking into account these external environments and conditions, please refer to the following information.

Weather

The first thing to check before flying a drone is the weather.

In the field, I recommend using a website like Windy to check the weather conditions more accurately. Windy allows you to specify the exact location, not just the city, district, or ward, as a point.

Here are the requirements you need to check when checking the weather for drone flight:

• Wind Wind affects the flight stability and image data quality of the drone. It is advisable to refrain from flying if the wind speed is 5 m/s or more.

• Shadows Shadows affect the performance of the drone camera. It is best to shoot during the time when shadows are minimized, between 11 am and 2 pm.

• Fog Fog affects the performance of the drone camera. It is advisable to refrain from flying if the fog is thick.

• Real-time snow and rain

  Snow and rain can damage the drone's body and camera, and can affect the accuracy of the data results. Therefore, it is advisable to refrain from flying in the event of snow or rain.

• Temperature The performance of the drone battery is affected by the temperature. The performance of the battery can be degraded in too high or too low temperatures.

  • Too hot Lithium-ion batteries (drone batteries) are prone to short-circuiting or exploding if overcharged. To prevent this, a small chip is installed to prevent overcharging. The phenomenon that the power turns off automatically on a very hot day is a normal operation of the chip to prevent explosion.
  • Too cold If the outside temperature is too low, the mobility of lithium ions is reduced, resulting in internal resistance, which affects battery performance and causes the battery to be consumed faster than usual.

External Environment

The external environment of the place where the drone will be flown should also be considered. The following environments can affect the performance of the drone camera:

• Surfaces that reflect light due to water or snow

  • When light is reflected, the accuracy of the reflected part is reduced. In addition, the engine cannot recognize that the photos are connected in the process of analyzing the photos, resulting in a broken result.

  • Furthermore, in a snowy environment, the thickness of the snow included in the result value when acquiring surface data makes it impossible to measure the accurate value.

    

    2D Orthomosaic

    

    3D Point Cloud Model

    

    Broken Result Photo

• Trees

  • If trees or water fill up the entire photo, it may be difficult for the engine to recognize that the photos are connected during the analysis process, resulting in a broken result.

    

    

    3D Point Cloud Model - Broken Result Photo

• Number and Location of GCPs

  • GCP (Ground Control Point) is a reference point for precisely aligning images taken by a drone camera. The number and location of GCPs have a significant impact on the accuracy of drone surveying.

  • It is generally recommended to drop a total of 10 or more GCPs at intervals of 2 to 300 meters, based on 1 km², in a location with a flat surface and no elements that block the GCPs. The number of GCPs may vary depending on the size of the target site, the surrounding environment, and the surveying purpose.

    

    Construction site with GCPs

• What happens if you don't take good GCPs?

  • If you compare a project with GCPs to a project without GCPs in a section where no construction has taken place, you can see a significant difference. In other words, the error range of the data increases, making it difficult to obtain accurate field data.

  • For example, on the platform, you can see graph data that draws a line between two points and measures a cross-section to compare it over time.

  • The orange graph represents the graph with GCP data, while the green graph represents the graph without GCP data. As you can see in the photo below, there is a difference of about 30 cm when there is no GCP data.

    Comparison of the cross-section data with GCPs and without GCPs

Battery Management

• Drone batteries are an important factor that determines the performance and safety of drone flights. Therefore, it is very important to manage batteries properly.
• Prepare spare batteries. Drone batteries can fly for about 20 to 30 minutes on a single charge. Therefore, it is a good idea to prepare spare batteries if you plan to fly for a long time.
• Fully charge the battery. Fully charging the battery will allow you to fly for a longer period of time.
• Do not completely discharge the battery. Completely discharging the battery can shorten the battery life.
• Do not use the battery for too long. Using the battery for too long can cause it to swell. In this case, you should not use the battery and dispose of it.
• Store the battery at 30 to 40% charge. Storing the battery in a fully charged or fully discharged state can shorten the battery life.