Introduction
As part of the annual DJI Airworks 2019 event, the developer introduced a specialized drone built on the Phantom 4 RTK platform for precision farming and land management. Phantom 4 Multispectral — this is a high-precision drone model equipped with a multispectral image processing system that allows farmers and agronomists to quickly receive the most accurate data on the state of exploited land and cultivated crops, which brings the industry to a new intellectual level of interaction with the environment.
In addition to the P4 Multispectral drone, U10 UAV Based Laser Methane Leakage Detector and Wingsland Z15 payloads, solutions such as:
- The DJI Agras T16 is an advanced agricultural sprayer drone that can accurately apply liquids such as fertilizers and pesticides to field crops and orchards.
- The DJI Disaster Relief Program is a new initiative, a disaster relief program aimed at quickly equipping those responding to emergencies using DJ technology.
Peculiarities
- RTK module
- Centimeter positioning accuracy
- Multispectral imaging system
- TimeSync Correction System
- Spectral Sun Tracking Sensor
- NDVI real-time broadcast
- 6-way obstacle detection system
- Automatic flight modes
- GS PRO flight planning application
- OcuSync 2.0 video transmission system
- Fully compatible with D-RTK 2 mobile station
- Support for post-processing data using the PPK method
- Max. removal distance 10 km
- Max. flight time 27 minutes
Specification
Drone
Takeoff weight:
1487gr
Diagonal distance:
350 mm
Max. service ceiling at sea level:
6000m
Max. rate of climb
:
18 km/h (manual control)
Max. sink rate:
10.8 km/h
Max. horizontal flight speed:
50 km/h (P-mode)
58 km/h (A-mode)
Max. flight time:
about 27 min
Operating range temperatures:
0°C-40℃
Operating range frequencies:
2.400GHz – 2.4835GHz (Europe, Japan, Korea)
5.725GHz – 5.850GHz (Other countries/regions where there is no restriction)
Transmitter power (EIRP):
<20dBm(CE/MIC/KCC)
Hover Accuracy Range:
RTK is enabled and working correctly:
Vertical: ± 0.1m; Horizontal: ± 0.1m
RTK disabled:
Vertical: ± 0.1m (with visual positioning);
± 0.5m (with GNSS positioning)
Horizontal: ± 0.3m (with visual positioning);
± 1.5m (with GNSS positioning)
Image Position Correction:
The positions of the centers of the 6 cameras relative to the phase center of the onboard D-RTK antenna were calibrated and recorded in the EXIF data of each image.
Mapping features
Ground Pixel Size (GSD):
(H/18.9) cm/pixel, where H is the height of the aircraft in relation to the mapped area (unit: m)
Data collection efficiency:
Max. the working area for one sortie (at a height of 180m) is 0.47km², that is, the GSD is about 9.52 cm / pixel.
GNSS
Single Frequency High Sensitivity GNSS Module:
GPS + BeiDou + Galileo* (Asia)
GPS + GLONASS + Galileo* (other regions)
Usable frequency:
GPS: L1/L2
GNSS: L1/L2
Beidou: B1/B2
Galileo*: E1/E5
Initial-fixed time: < 50s
Positioning Accuracy: Vertical (RMS): 1.5cm + 1md
Horizontal (RMS): 1cm + 1md
1md means that the error increases by 1mm for every 1km of movement. Speed Accuracy: 0.3m/s
visual positioning
Speed range:
≤ 50km/h at 2 meters above the ground in good light
Height range:
0 – 10 meters
Working range:
0 – 10 meters
Detection range:
from 0.7 to 30 meters
FOV:
Front and rear sensors: 60°(horizontal), ±27°(vertical); bottom: 70°(forward and backward), 50°(left and right)
Frequency definition:
10Hz
Measurement frequency:
Forward/Reverse: 10Hz; Down: 20Hz
Conditions for normal operation:
lighting over 15 lux, landscape with a clear structure
infrared system
Detection range:
0.2 – 7 meters
FOV:
70°(horizontal), ±10°(vertical)
Frequency definition:
10Hz
Conditions for normal operation:
Surface with diffuse reflective material and reflectivity: > 8% (e.g. walls, trees, people, etc.)
Camera
Matrices:
6 × 1.29-inch CMOS; including one matrix of visible RGB radiation and five monochrome ones for multispectral imaging. Number of effective pixels of each sensor: 2.08 million (total number of pixels: 2.12 million)
Filters:
Blue (Blue, B):
450nm±16nm
Green (Green, G):
560nm±16nm
Red (Red, R):
650nm±16nm
Red Edge (Red Edge, RE):
730nm±16nm
Near infrared (Near-Infrared, NIR):
840nm±26nm
Optics:
Field of View (FOV) – 62.7°
Focal length: 5.74mm (40mm equivalent to 35mm format), f/2.2, autofocus at ∞
Matrix ISO range:
200 – 800
Monochrome matrix gain:
1-8x
Email speed global shutter:
1/100 – 1/20000s (standard camera); 1/100–1/10000s (multispectral cameras)
Max. picture size:
1600×1300 (4:3.25)
Photo formats:
JPEG (standard images) + TIFF (multispectral image processing)
Supported file systems:
FAT32（≤ 32GB);
exFAT(> 32GB)
Supported SD cards:
MicroSD, maximum capacity: 128GB. Class 10 or UHS-1. Required write speed ≥ 15MB/s
Working temperature range:
0°С- 40℃
suspension
Stabilization:
3-axis
Operating range:
tilt angle: — 90° to +30°
Battery
Type of:
lithium polymer (LiPo)
Capacity:
5870mAh
Voltage:
15.2V
Qty. cans:
4S
Weight:
468 grams
Working temperature range:[
/one_half]
-10°C to +40°C
Maximum charge current:
160W
Intelligent charging station
Input voltage:
17.5V
Operating range temperatures:
from +5°to +40℃
Remote Control
Working frequency:
2.400GHz – 2.4835GHz (Europe, Japan, Korea)
5.725GHz – 5.850GHz (USA, China and other countries and regions)
Transmitter power (EIRP):
2.4GHz
CE/MIC/KCC: <20dBm
5.8GHz
SRRC/CE/MIC/KCC: <26dBm
Max. transmission distance:
FCC:
10 km
SRRC/CE/MIC/KCC:
6 km (in interference-free area)
Power consumption:
16 W (typical)
Food:
2S 7.6V 6000mAh LiPo
Slave. current/voltage:
1.2A at 7.4V
Mobile device holder:
Tablets/Smartphones
Operating temperature range:
0°C-40℃
Appearance
Multispectral imaging system
Agricultural image collection is made possible by a built-in stabilized system that collects a comprehensive set of data right out of the box. Information input via 1x RGB camera and 5-camera multi-spectrum array covering Blue, Green, Red, Red Edge and Near Infrared (NIR) all running at 2MP CMOS sensors with a global shutter, the entire camera system is stabilized by a 3-axis mechanical gimbal.
Spectral Sun Tracking Sensor
The built-in spectral sunlight sensor on the top of the drone captures solar radiation, which ensures maximum accuracy and consistency of data collection at different times of the day. Combined with post-processed data, this information helps provide the most accurate NDVI results.
NDVI (Normalized Difference Vegetation Index) – Normalized Relative Vegetation Index – is a simple indicator of the amount of photosynthetically active biomass (commonly referred to as the vegetation index).
RGB and NDVI translation
The system allows the operator to switch between a pre-normalized relative vegetation index (NDVI) and an RGB (visible light) model to identify problem areas that need to be addressed in order to quickly make targeted treatment decisions.
centimeter accuracy
The DJI TimeSync Accurate Acquisition System allows the operator to obtain real-time location data for each image captured by all six cameras, thus ensuring centimeter-level accuracy. The system constantly aligns the flight controller, RGB and NB cameras, and the RTK module, capturing positional data at the CMOS center, and ensures that each photo uses the most accurate metadata. All cameras go through a rigorous calibration process where the radial and tangential lens distortions are measured. The collected distortion parameters are stored in the metadata of each image, allowing the post-processing software to be customized for each user.
Compatible with D-RTK 2 and NTRIP
You can improve the accuracy of RTK positioning without an Internet connection by connecting the P4 Multispectral to a high-precision D-RTK 2 GNSS mobile station and NTRIP (network transmission of RTCM corrections over the Internet protocol), or you can save satellite observations to be used later in the post-processing method kinematics (PPK).
OcuSync 2.0
Top-of-the-line OcuSync digital video transmission technology that allows you to switch between 2.4GHz and 5.8GHz based on channel congestion, providing outstanding noise immunity and latency at FPV distances up to 10 km (for P4 Multispectral).
Intelligent agricultural missions
Flight plan
The operator can perform automated missions and control flight operations through the advanced DJI application – GS PRO, running on IOS devices.
Data Capture
P4 Multispectral allows the user to efficiently collect multispectral images over a large area and get an objective view of problem areas.
Data analysis
Easily access and process aerial imagery using plant-specific metrics and parameters to achieve desired plant health outcomes.
Actions based on the received data
Based on the data received from the drone, the user can make the necessary decisions aimed at improving the condition of agricultural land and crops.
Application
precision farming
Multispectral imaging can be useful throughout the growing season by providing information through the electromagnetic spectrum invisible to the human eye. With access to this data and Vegetation Index data such as NDRE and NDVI, farmers can make informed crop management decisions in a timely manner, reducing costs, conserving resources and maximizing yields.
Environmental monitoring and inspection
Regular plant monitoring and inspection can be made even smarter and more efficient with the P4 Multispectral drone. The resulting multispectral data can be used to monitor forest health, measure biomass, map coastlines, or manage coastal vegetation while protecting habitats or ecosystems, and more.
FAQ
Drone
Q. How is P4 Multispectral different from Phantom 4 RTK?
A. Both — RTK compatible drone platforms. The main difference is the camera. The P4 Multispectral comes with a camera that consists of one RGB and five arrayed multispectral cameras, each 2MP resolution; while the Phantom 4 RTK comes with a single 20MP RGB camera.
Q. What propellers does the P4 Multispectral use?
A. It uses low noise 9455S propellers. Phantom 4 series drone props are also suitable, but they will degrade the P4M’s flight performance.
Q. What should be done to ensure the integrity of the Spectral Sunlight Sensor?
A. Keep it away from hard, sharp objects to avoid scratching.
cameras
Q. What are the capabilities of the P4 Multispectral Camera Array?
The P4 Multispectral multispectral imaging system detects the emissivity of various objects, which is recorded by each of the cameras and analyzed to calculate vegetation index values. A common index used in agriculture and forestry for plant health is the NDVI. Meanwhile, the spectral sunlight sensor located on the top of the drone compensates for the sunlight received at different times of the day, improving the consistency of data obtained from the same area of vegetation.
Q. How is the radiometric calibration of cameras implemented?
A. Your images are radiometrically calibrated when you process them using the Vegetation Index features in DJI GS Pro and DJI Terra.
Q. Have the cameras on the P4 Multispectral gone through image position compensation?
Oh yeah. The positions of the CMOS centers of the six cameras relative to the phase center of the onboard D-RTK antenna were calibrated and recorded in the EXIF data for each image.
Q. Have the camera lenses gone through distortion correction?
A. The original images are not corrected for distortion, but each camera lens has been measured for distortion during production, and all correction parameters are recorded in each of the images.
Q. Have the cameras gone through vignetting correction?
A. The vignetting of the original images is not corrected, but the parameters for correction are recorded in each of the images.
Q. How is consistency between multispectral camera arrays and spectral sunlight sensors on different drones ensured?
A. All P4M drones undergo standard camera and sensor calibration to DJI manufacturing standards, minimizing differences between drones.
Q. What is stored in image pixel values, DN values, or reflectance values?
A. DN values.
Control equipment
Q. What remote control is compatible with the P4 Multispectral?
A. Currently, the P4 Multispectral is only compatible with the control hardware SDK that comes with the aircraft.
signal transmission
Q. What is the resolution of the P4 Multispectral video stream?
O. 720p.
Food
Q. Can I use the P4 Multispectral battery on the Phantom 4 RTK?
Oh yeah.
Q. How long does it take to charge the P4 Multispectral battery?
A. About 58 minutes.
ON
Q. Is there a limit on the number of waypoints per departure?
A. There is no limit to the number of waypoints in each flight mission, but the drone can only operate up to 99 waypoints. When a flight mission has more than 99 waypoints, the DJI GS Pro automatically divides the waypoints into groups, each containing a maximum of 99 waypoints.
Q. What are the altitude and speed limits?
O. Max. flight height: 500m, minimum: 1m. Max. flight speed: 54 km/h, minimum: 3.6 km/h.
Q. Which flight mode should I use if I want to switch between live RGB and NDVI modes?
A. You can switch between live RGB and NDVI manually. We recommend that you stay in RGB mode and do not switch between channels while in flight. JPEG images will be automatically saved in RGB or NDVI depending on the camera mode. Most third-party mapping programs require RGB images for aerial triangulation before overlaying NDVI maps.
Q. What are the recommended camera settings?
A. For novice users, the developer recommends setting the multispectral mode to Auto, choosing “Average Metering” as the metering mode, and choosing AE unlock.
Q. Does P4M software support developers?
A. DJI Mobile SDK support will be available soon.
Q. What vegetation parameters are supported in DJI Terra?
A. DJI Terra supports NDVI, GNDVI, NDRE, LCI and OSAVI, but does not have a vegetation index calculator function.
Application
AT.
Can I reconstruct maps using third party software?
O. Yes.
Q. How do I calculate an appropriate flight altitude based on the Ground Pixel Size (GSD) value?
A. The GSD for the P4 Multispectral is (H/18.9) cm/pixel. You can calculate the flight altitude with the accuracy you need.
Q. What is the maximum mapping area per flight?
A. In a single flight, at an altitude of 180 m, the P4 Multispectral has a maximum display area of about 0.47 km², i.e. GSD is approximately 9.52 cm/pixel.
Q. Do mission waypoints show any altitude information?
A. Relative altitude information (relative to your takeoff point) is stored in photos taken at waypoints.
Q. Is the P4 Multispectral compatible with third party base stations?
A. No, you cannot connect third party base stations to the P4 Multispectral or to a radio remote control. However, you can receive data from a network RTK server using the NTRIP protocol in a 4G/Wi-Fi network environment. Satellite observation data can also be stored by the user in the drone, for subsequent post-processing by kinematics (PPK).