Hi everyone,
I’m working with Sentinel-1 SLC IW2 VV data in SNAP and trying to perform Nyquist resampling and export as GeoTIFF. However, having the I and Q bands as two separate real channels instead of one complex channel seems to prevent proper Nyquist sampling (Nyquist = ratio = pixel resolution / pixel posting = 1).
Here’s my workflow so far:
- Applied the Orbit File.
- Performed TOPSAR Deburst.
- Created a Subset
- Used SAR Utilities → Undersample for Nyquist resampling, based on the following calculations (from the Sentinel Wiki):
Range:
Resolution: 3.1 m / Pixel spacing: 2.3 m
Oversampling factor: 3.1 / 2.3 = 1.348
Percentage for undersampling: 1 / 1.348 = 0.742 (74.2%)
Azimuth:
Resolution: 22.7 m / Pixel spacing: 14.1 m
Oversampling factor: 22.7 / 14.1 = 1.610
Percentage for undersampling: 1 / 1.610 = 0.621 (62.1%)
These percentages were used as the ratio for the undersampling operation.
- Exported the result as GeoTIFF.
But the exported GeoTIFF contains two channels instead of a single complex channel and Nyquist resampling doesn’t seem to work as expected.
Also there’s a discrepancy between the pixel spacing shown in SNAP and the values stated in the Sentinel Wiki…
Is there a way in SNAP to combine the I and Q bands into a single complex band so that Nyquist resampling works as intended, and the GeoTIFF export results in a single complex channel?
The background is that I want to perform SVA filtering on Sentinel-1 and therefore need Nyquist criteria and GeoTiff format.
Thank you for your help!