Precise Positioning in Nitrogen Fertility Sensing in Maize (Zea mays L.)

Area of Science:

• Agricultural Science
• Geospatial Science
• Remote Sensing Technology

Background:

• Accurate coordinate data for ground control points (GCPs) are essential for reliable unmanned aerial vehicle (UAV) photogrammetry.
• Standard Global Navigation Satellite System (GNSS) without augmentation provides insufficient accuracy for precise mapping applications.
• Unmanned aerial vehicle (UAV) photogrammetry offers potential for detailed field crop research but requires accurate spatial referencing.

Purpose of the Study:

• To evaluate the contribution of precise positioning systems, specifically real-time kinematic (RTK), for establishing accurate GCPs in UAV photogrammetry.
• To compare the positional accuracy of RTK-enhanced GNSS with ordinary GPS devices for agricultural applications.
• To demonstrate the impact of precise GCPs on monitoring nitrogen deficiency stress in maize using UAV-derived Normalized Difference Red-Edge Index (NDRE).

Main Methods:

• Comparative analysis of coordinate data acquired using RTK-enabled GNSS and a standard GPS device.
• Application of precise GCPs derived from RTK for UAV photogrammetry in a maize field study.
• Analysis of UAV-based NDRE data to assess crop response to varying nitrogen levels.

Main Results:

• The RTK system achieved a positional accuracy bias of 4 cm, significantly outperforming the non-augmented GNSS technique (311 cm bias).
• Precise GCPs enabled UAV-based NDRE data to effectively characterize maize crop responses to nitrogen nutrition.
• Nitrogen deficiency was accurately linked to reduced canopy cover and compromised chlorophyll content, as revealed by precise data.

Conclusions:

• Real-time kinematic (RTK) positioning is indispensable for obtaining accurate GCPs in UAV photogrammetry for agronomic research.
• The use of precise GCPs is critical for avoiding misleading results and ensuring the scientific validity of UAV-based crop studies.
• Accurate spatial data from RTK-enhanced UAV photogrammetry facilitates detailed analysis of crop physiological status and stress factors.