Multispectral Imagery Explained: From Basics to Application

Multispectral imagery captures data across multiple light spectrums, unveiling information that can't be seen with the naked eye. This technology is revolutionizing various fields by enabling early detection of issues and providing insights into environmental conditions. In this comprehensive guide, we'll explore the fundamentals of multispectral imagery, its applications, and how it can benefit different industries.

What is Multispectral Imagery?

Multispectral imagery involves capturing data across different wavelengths of light. This technology allows for the observation and analysis of features that are not visible to the human eye, making it a powerful tool for various applications such as agriculture, environmental monitoring, and archaeology.

Challenges Solved by Multispectral Imagery

• Early Detection: Identify diseases, water stress, pest infestation, and nutrient deficiencies early.
• Land Use Monitoring: Reveal changes in land use, vegetation trends, and agricultural production cycles.
• Water Quality Assessment: Monitor chlorophyll concentrations and sediments in water bodies.
• Advanced Research: Utilize machine learning for crop counting and advanced vegetation research.

How Does Multispectral Imagery Work?

Vegetation reflects and absorbs different wavelengths of light based on their health. Healthy plants reflect more near-infrared light due to higher chlorophyll levels. Changes in water content and cellular structure alter how plants interact with infrared light, revealing their health status. Multispectral cameras detect these wavelengths and translate them into visible light to color-code problems and deficiencies.

Multispectral Bands

Each spectral band captures different types of information based on how surfaces reflect or absorb energy at different wavelengths. Here are the most common spectral bands built into drone sensors:

Vegetation Indexes

Vegetation indexes are combinations of different spectral bands to provide insights into plant health. Here are some common vegetation indexes:

Hardware for Multispectral Imagery

AgEagle Aerial Systems

• RedEdge-P: High-resolution RGB and multispectral imaging, covering five multispectral bands (blue, green, red, red edge, and near-infrared). Compatible with a wide range of drones.
• Altum-PT: Combines thermal, multispectral, and RGB imagery with five multispectral bands and a built-in thermal sensor.

DJI

• Mavic 3 Multispectral: Designed for precision agriculture and environmental monitoring. Features an RGB camera and four multispectral cameras (Green, Red, Red Edge, Near Infrared).

Software for Multispectral Imagery

Pix4D

• Pix4Dfields: Ideal for agriculture mapping, creating prescription maps, orthomosaics, elevation models, and more.
• Pix4Dmapper: Advanced photogrammetry software for converting images into georeferenced 2D maps and 3D models.

Multispectral Drone Workflow

1. Calibrate the Camera: Capture a picture of the calibration panel to adjust for light conditions.
2. Configure the Camera: Connect your device to the camera's Wi-Fi for programmed image capture.
3. Plan the Mission: Use your application to launch the drone for autonomous flight.
4. Process Data: Use software like DJI Terra or Pix4D to analyze the data post-flight.

Use Cases

Irrigation Management

Problem: In vineyards, vines need to get stressed to produce better grapes. A water leakage can overwater causing the plants to produce more leaves and worse grapes, while also increasing water consumption costs.

Solution: WingtraOne with a Micasense Altum camera can quickly detect broken pipes and determine which need to be fixed to maximize yield and minimize input cost.

Step by Step:

1. Acquire all aerial data in one flight.
2. Process in Agisoft Metashape.
3. Identify potential leakage locations based on colder spots on thermal images.
4. Prioritize repair based on chlorophyll levels (NDRE), targeting pipes that have leaked longer.

Precision Agriculture

Problem: Managing crop growth and controlling invasive weeds and pests is challenging. Uneven crop growth and the presence of thistles and wireworms can lead to crop failure.

Solution: Detailed drone insights enable effective management by identifying zones with varying crop growth and weed infestation, allowing for balanced crop inputs.

Step by Step:

1. Acquire aerial data with the DJI Mavic 3M.
2. Process data in Pix4D or similar software.
3. Analyze data to identify problematic areas and adjust crop inputs accordingly.

Eucalyptus Plant Counting

Problem: Replanting is crucial for maximizing yield and minimizing costs in cultivated areas, but accurate planning is challenging and time-consuming.

Solution: WingtraOne's multispectral data with Micasense Altum payload enables quick plantation overviews and accurately quantifies replanting requirements.

Step by Step:

1. Acquire all aerial data in one flight.
2. Process in Pix4D.
3. Calculate NDVI for reliable automated plant counting.
4. Identify problematic lines and areas.
5. Calculate costs of replanting based on NDVI data.

Forestry Management: Bark Beetle Detection

Problem: Bark beetle infestations can devastate forests, but early detection is difficult.

Solution: Multispectral mapping can identify stressed trees before visible damage occurs, helping to prevent the spread of beetles.

Step by Step:

1. Acquire aerial data with WingtraOne and Micasense Altum.
2. Process data in Metashape or Pix4D.
3. Identify anomalies and stressed canopies.
4. Determine which trees need treatment or removal.

Conclusion

Multispectral imagery offers a wealth of benefits across various industries, from agriculture to environmental monitoring. By capturing data across different light spectrums, it provides insights that are invisible to the naked eye, enabling more informed decision-making and effective management of resources. Whether you're monitoring crop health, managing irrigation, or detecting early signs of disease, multispectral imagery is a powerful tool that can transform the way you work.