Measurement and Calibration of Plant-Height from Fixed-Wing UAV Images
Abstract
:1. Introduction
2. Materials and Methods
2.1. Trial Plots
2.1.1. Experimental Setup
2.1.2. Ground-Truth Measurements of Plant Height
2.2. Image Data Acquisition
2.2.1. UAV Platform
2.2.2. Sensor
2.2.3. Flight Control
2.2.4. Flight Procedures
2.3. Ground Control Points (GCPs)
2.3.1. Structure
2.3.2. Uses
2.4. Image Data Processing
2.4.1. UAV SfM Method
2.4.2. Crop Height Analysis
2.4.3. Comparison with Ground-Truth Measurements
2.5. Image Quality Assessment
3. Results
3.1. Plant Height Estimation with Fixed-Wing UAV
3.1.1. SfM Model Accuracy and Trends in Ground-Truth and Estimated Plant-Height Data
3.1.2. Accuracy Assessment of SfM Plant-Height Estimates
3.2. Plant Height Accuracy Improvement with Height Calibration
3.3. Plant Height Accuracy Correlation with Image Quality
4. Discussion
5. Conclusions
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Flight Date | Ground Truth Date | Days Difference | Number of Images | Number of Plots | Wind Speed |
---|---|---|---|---|---|
05/24 | 05/26 | 2 | 231 | 700 | 4.4 m/s |
05/30 | 05/31 | 1 | 242 | 700 | 2.2 m/s |
06/16 | 06/16 | 0 | 242 | 700 | 6.2 m/s |
06/29 | 07/03 | 4 | 233 | 700 | 4.0 m/s |
07/25 | 07/27 | 2 | 240 | 610 | 7.2 m/s |
Items | Specifications |
---|---|
Wingspan | 1.22 m |
Weight maximum | 2 kg |
Material | EPP foam, carbon fiber tubes, coroplast |
Battery | 6200 mAh, lithium polymer |
Flight planning software | Mission Planner |
Endurance | 40 minutes |
Minimum air speed | 16 meters per second |
Items | Descriptions | Specifications |
---|---|---|
Sensor | Sensor | APS-C type (23.5 × 15.6 mm) |
Number of pixels | 24.3 MP | |
Image sensor aspect ratio | 3:2 | |
Exposure | ISO sensitivity | ISO 100-25600 |
Shutter | Shutter speed | 1/4000 to 30 s |
Flash sync. speed | 1/160 s | |
Lens | Focal length Aperture range | 16 mm F22 to F2.8 |
Size and Weight | Dimensions (W × H × L) | 4.72 × 2.63 × 1.78 in |
Weight (with battery) | 0.34 kg |
Items | Specifications |
---|---|
Processor | 32-bit ARM Cortex M4 core with FPU |
168 Mhz/256 KB RAM/2 MB Flash | |
32-bit failsafe co-processor | |
Sensors | MPU6000 as main accel and gyro |
ST Micro 14-bit accelerometer/compass (magnetometer) | |
ST Micro 16-bit gyroscope | |
Dimensions (W × H × L) | 2.0 × 0.6 × 3.2 in |
Weight | 3.8 g |
Items | Descriptions | Values |
---|---|---|
Alignment | Accuracy | High |
Adaptive camera model fitting | Yes | |
Dense point cloud | Quality | High |
Depth filtering | Mild | |
DEM | Model resolution | Around 5.52 cm/pix |
Source data | Dense cloud | |
Orthomosaic | Coordinate system | WGS 84/UTM zone 14N |
Blending mode | Mosaic |
Flight Date | X_RMSE (cm) | Y_RMSE (cm) | Z_RMSE (cm) |
---|---|---|---|
5/24 | 2.52 | 1.72 | 1.88 |
5/30 | 2.23 | 2.12 | 0.96 |
6/16 | 2.29 | 1.96 | 1.83 |
6/29 | 1.83 | 3.09 | 2.22 |
7/25 | 1.87 | 2.55 | 2.18 |
Date | Performance | ||||
---|---|---|---|---|---|
Uncalibrated RMSE | Calibrated RMSE | Improvement RMSE | R2 | Relative RMSE | |
05/24 | 0.23 m | 0.19 m | 21.3% | 0.81 | 20.4% |
05/30 | 0.09 m | 0.07 m | 29.2% | 0.83 | 6.1% |
06/16 | 0.21 m | 0.18 m | 17.7% | 0.73 | 12.0% |
06/29 | 0.14 m | 0.12 m | 17.4% | 0.85 | 8.0% |
07/25 | 0.29 m | 0.26 m | 12.8% | 0.63 | 16.2% |
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Share and Cite
Han, X.; Thomasson, J.A.; Bagnall, G.C.; Pugh, N.A.; Horne, D.W.; Rooney, W.L.; Jung, J.; Chang, A.; Malambo, L.; Popescu, S.C.; et al. Measurement and Calibration of Plant-Height from Fixed-Wing UAV Images. Sensors 2018, 18, 4092. https://doi.org/10.3390/s18124092
Han X, Thomasson JA, Bagnall GC, Pugh NA, Horne DW, Rooney WL, Jung J, Chang A, Malambo L, Popescu SC, et al. Measurement and Calibration of Plant-Height from Fixed-Wing UAV Images. Sensors. 2018; 18(12):4092. https://doi.org/10.3390/s18124092
Chicago/Turabian StyleHan, Xiongzhe, J. Alex Thomasson, G. Cody Bagnall, N. Ace Pugh, David W. Horne, William L. Rooney, Jinha Jung, Anjin Chang, Lonesome Malambo, Sorin C. Popescu, and et al. 2018. "Measurement and Calibration of Plant-Height from Fixed-Wing UAV Images" Sensors 18, no. 12: 4092. https://doi.org/10.3390/s18124092