PIX4Dfields supports green-on-green detection through high-resolution imagery and the Magic Tool. Follow this article to efficiently detect weeds within crop fields.
Introduction
Green-on-green detection in agriculture allows for identifying weeds among crops, which allows spot-spraying and minimizes blanket herbicide applications. By targeting only the affected areas, this method not only reduces herbicide costs but also minimizes environmental impact.
GSD Requirements
Orthomosaics with a GSD between 1 and 3 cm are ideal for detailed, plant-level weed detection. This ensures high-resolution detection of individual weeds within crop canopies.
If weeds occur in larger patches or zones, a lower resolution (GSD of 4-8 cm) is generally acceptable.
Consider weed condition
Weed growth stage affects detection efficacy:
Early stage: Green weeds blend with crops in the early stages and require higher image clarity for accurate identification.
Advanced stage or treated weeds: Weeds that are more mature or have been treated with herbicides may appear yellowish, improving detection due to color contrast.
Detecting weeds with the Magic Tool
- Create a boundary (mandatory). This helps limit the detection area to a specific region within your crop field, ensuring that the Magic Tool focuses only on the targeted area.
If there are parts of the field that will interfere with the detection (trees, ponds, etc.), make sure to create holes inside the boundaries. -
Access the tool by clicking the
Magic icon next to the 
Index icon. - Select the Layer and Boundary.
- Set the Cell Size:
Your GSD influences the minimum cell size. A very small cell can degrade selection performance.
Recommendation: Adjust the cell size to your crop and weed size, with values often ranging from 0,5 to 1 meter for high-resolution detection. - Select Sample Points:
Manually identify areas of weeds and crops by clicking on them within the boundary:- Weeds: Click on at least 10 cells representing weed areas.
- Crops: Click on at least 10 cells representing crop areas.
- Purpose: These sample points help the Magic Tool distinguish weeds from crops based on visual patterns and color differences
- Convert to Operation:
After setting the sample points and other parameters, convert the results into an operation layer. This action finalizes the weed detection, creating an operational layer that can guide targeted herbicide applications or further analysis.
Green-on-green detection examples
PIX4Dfields has been successfully used in various scenarios for green-on-green weed detection. Here are a few practical examples that highlight the method's effectiveness in detecting weeds amidst crops:
Peanut infested with Sorghum halepense.
A DJI Air 2 drone flew at a 2 cm GSD. Thanks to the high-resolution imagery and contrast between plant types, the Magic Tool helped identify the Sorghum halepense plants within the peanut crops relatively straightforwardly.
The Magic tool cell size was of 
Rice Infested with Sedges (Cyperaceae family)
Using a DJI Mini 3 Pro, a flight was conducted at 1.5 cm GSD over rice fields infested with sedges. The Magic Tool enabled the precise detection of sedge patches within the rice field. This detection accuracy facilitates efficient, targeted treatment of sedge-infested areas.
