Drones are aerial cameras, and long-distance detection technology improves the comprehensive capabilities of drones. Here we will explain the principles and mechanisms of drone long-distance detection, as well as the roles and differences of visible light cameras, infrared thermal imaging cameras, and starlight cameras.
What is long-distance detection technology for drones?
Long-distance detection refers to the ability of drones to detect, identify, and track targets at a long distance through onboard sensors (such as visible light cameras and infrared thermal imaging cameras). This technology is crucial in scenarios such as police reconnaissance, search and rescue, and border patrols, and depends on camera performance, target characteristics, environmental conditions, and the comprehensive capabilities of the drone platform.
Principles and mechanisms of long-distance detection
Drones' long-distance detection is based on optical imaging (visible light cameras) and thermal radiation detection (infrared thermal imaging cameras). Sensors capture the electromagnetic radiation (visible light or infrared bands) of the target and convert the signal into images or data. Its core mechanism includes the following stages:
Detection:
The presence of the target is discovered, usually as a bright spot, shape, or thermal signature in the image.
The detection distance depends on the sensor sensitivity, the contrast between the target and the background, and environmental interference.
Recognition:
To determine the target type (such as distinguishing between human bodies and vehicles), higher image resolution is required.
The recognition distance is usually 1/3 to 1/2 of the detection distance.
Identification:
To determine the specific identity of the target (such as identifying a specific person or vehicle model), the highest clarity and detail are required.
The recognition distance is about 1/5 to 1/10 of the detection distance.
Key factors:
- Sensor performance: resolution, focal length, sensitivity, aperture size.
- Target characteristics: size, reflectivity (visible light) or emissivity (infrared), contrast with background.
- Environmental conditions: light, humidity, fog, smoke, background clutter.
- UAV platform: flight altitude, stability, zoom capability, data transmission distance.
- DRI model: The industry usually uses Detection, Recognition, Identification (DRI) to quantify the long-range detection capability of drones, based on Johnson’s Criteria, which is the minimum number of pixels of a target in an image:
Autel evo2 dual 640t v3's DRI distance
Detection: about 2-4 pixels.
Recognition: about 6-8 pixels.
Identification: about 12-16 pixels.
Autel drones for long-range detection
Currently, the Autel drone series that support long-range detection include the EVO Lite Enterprise series, Autel EVO II Dual 640T series, and EVO MAX series. These commercial drones are equipped with thermal imaging cameras or embedded with AI detection algorithms, which can perform long-range target recognition.
Differences in long-range detection of drone cameras
How long-range detection of visible light cameras works:
Visible light cameras capture light in the 400-700nm band (human visible spectrum), focus the light reflected or scattered by the target through the lens, and form a high-resolution image.
Relying on external light sources (such as sunlight, moonlight or artificial lighting), high sensitivity (high ISO) or auxiliary light sources (such as starlight cameras) are required in low-light environments.
Working principle of long-distance detection of infrared thermal imaging cameras:
Infrared thermal imaging cameras detect infrared radiation emitted by targets (usually in the mid- and far-infrared bands, 7.5-14μm), and generate thermal images based on target temperature and emissivity.
Not dependent on external light sources, suitable for all-weather (day and night) and low-visibility environments (such as fog and smoke).
The image shows temperature differences, often using white heat (bright in hot places), black heat (dark in hot places) or rainbow color plates.
Working principle of long-distance detection of starlight cameras:
Starlight cameras can capture weak light sources and perform clear night vision imaging, which is very effective for night patrols and search and rescue operations.
Starlight cameras are suitable for all-weather (day and night) and low-visibility environments (such as fog and smoke). Compared with visible light cameras and thermal imaging cameras, they have a wider range of applications and longer detection distances.
Key factors affecting long-range detection
Sensor performance:
Resolution: Visible light (50MP) provides high detail, thermal imaging (640x512) balances distance and clarity.
Focal length/FOV: Long focal length (narrow FOV) is suitable for long distances, wide angle (wide FOV) is suitable for close-range scanning.
Sensitivity: Low light sensitivity (high ISO) of visible light cameras and NEDT (<50mK) of thermal imaging determine the detection limit.
Target characteristics:
Size: Large targets (such as vehicles) can be detected farther than small targets (such as humans).
Reflectivity/emissivity: Visible light depends on target reflectivity, thermal imaging depends on emissivity and temperature difference.
Motion state: Moving targets (such as running vehicles) are easier to detect due to higher heat or contrast.
Environmental conditions:
Light/weather: Visible light is limited by light, and thermal imaging is affected by humidity and fog.
Background clutter: Complex background (such as urban heat sources, vegetation reflections) may interfere with detection.
Time period: Thermal imaging at night has a longer detection distance due to low background temperature and large temperature difference.
UAV platform:
Flight altitude: 100-200 meters balances coverage and image details. Too high may reduce resolution.
Zoom capability: EVO MAX 4N's 16x digital zoom (thermal imaging) and visible light zoom enhance long-distance identification.
Transmission distance: SkyLink 3.0 supports 20km transmission to ensure long-distance real-time monitoring.
Actual cases and applications of EVO MAX 4N long-distance detection
Night pursuit:
Thermal imaging camera detects suspect heat signatures at 1000 meters, starlight camera captures clothing details within 500 meters, and AI locks on targets.
720° obstacle avoidance and millimeter wave radar ensure safe tracking in complex environments.
Search and rescue:
Thermal imaging finds missing persons in the forest at 1500 meters, and the laser rangefinder (5-1200m) provides precise coordinates.
The visible light camera records details of the scene and assists the ground team.
Border monitoring:
Thermal imaging detects illegal vehicles crossing the border 2 kilometers away, and visible light cameras identify license plates during the day.
A-Mesh 1.0 networking supports multi-drone collaboration and covers a wide area.
Fire assessment:
Thermal imaging detects fire hotspots 1-2 kilometers away, and visible light cameras record smoke diffusion to assist in command.
Suggestions for optimizing long-distance detection
Choose the right sensor:
Daytime or low light: Prioritize the 50MP visible light or starlight camera of EVO MAX 4N.
Nighttime/low visibility: Switch to thermal imaging camera and adjust the white-hot/black-hot color plate.
Adjust flight strategy:
Maintain an altitude of 100-200 meters to avoid excessive loss of details.
Use narrow FOV lenses or digital zoom to focus on distant targets.
Environmental optimization:
Operate at night or early morning to maximize the temperature difference of thermal imaging.
Avoid dense fog or high humidity weather to reduce atmospheric attenuation.
Combining AI with multiple sensors:
Use EVO MAX 4N's AI recognition to fuse visible light and thermal imaging data to automatically track targets.
Use a laser rangefinder to accurately locate distant targets.
Maintain equipment:
Clean the lens regularly to ensure visible light and infrared transmittance.
Update firmware to optimize camera algorithms and AI performance.
Summary
The long-distance detection of drones is achieved through the implantation of visible light cameras, infrared thermal imaging cameras, starlight cameras, and AI detection algorithms, which use the reflected light and thermal radiation of the target to generate images. In long-distance detection at night, Autel EVO MAX 4N has a long-distance detection range of up to 5 kilometers, regardless of temperature changes or glass materials.
