SyntheticAperture Radar
Under DevelopmentUnderstand backscatter polarizations, C-band radar echo responses, and active terrain deformation diagnostics from Sentinel-1.
Active Microwave Remote Sensing
Synthetic Aperture Radar (SAR) is an active sensor that transmits microwave pulses and measures the strength and phase of the reflected echo (backscatter). Unlike optical sensors, microwaves penetrate clouds, smoke, and vegetation cover, enabling day-and-night surface monitoring.
Backscatter Polarization Channels
VV Polarization (Vertical-Vertical)
Transmits vertical waves and records vertical returns. Highly sensitive to water surface roughness, sea waves, open soils, and flooding extents.
VH Polarization (Vertical-Horizontal)
Transmits vertical waves and records horizontal returns. Extremely sensitive to volume scattering, such as agricultural crops, forest branches, and complex biomass.
Radar Backscatter Calibration
Raw Sentinel-1 Ground Range Detected (GRD) files contain digital numbers that must be calibrated to physical backscatter values ($\sigma^0$) and converted to decibels (dB) for classification.
| 1 | # Python pipeline to calibrate raw Sentinel-1 GRD digital numbers to Sigma Nought (dB) |
| 2 | import numpy as np |
| 3 | |
| 4 | def calibrate_sar(digital_number, calibration_look_up): |
| 5 | # Convert digital integer numbers to backscatter amplitude power |
| 6 | power_coefficient = (digital_number ** 2) / (calibration_look_up ** 2) |
| 7 | |
| 8 | # Convert power to logarithmic Decibels (dB) |
| 9 | sigma_nought_db = 10 * np.log10(power_coefficient + 1e-10) |
| 10 | return sigma_nought_db |