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Hotfix calibration #53

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Merged
Achaad merged 3 commits into from
Sep 8, 2025
Merged

Hotfix calibration #53

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22ddfdf
fix: fixed an error in calibration metadata extraction
Sep 8, 2025
9a6e145
Fix APS scaling and missing AP mode scaling factor index usage.
priit111 Sep 8, 2025
0a257cc
style: fix too long line
Sep 8, 2025
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18 changes: 12 additions & 6 deletions asar_xarray/envisat_direct.py
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Original file line number Diff line number Diff line change
Expand Up @@ -114,7 +114,6 @@ def parse_direct(path: str, gdal_metadata: dict[str, Any], polarization: str) ->
# antenna gain
n_samp = gdal_metadata["line_length"]
spreading_loss: np.ndarray[Any] = np.array([])
gain_arr: np.ndarray[Any] = np.array([])
if gdal_metadata["sample_type"] == "DETECTED":
gain_arr = np.ones(n_samp)
spreading_loss = np.ones(n_samp)
Expand All @@ -130,7 +129,7 @@ def parse_direct(path: str, gdal_metadata: dict[str, Any], polarization: str) ->
sat_x = osv[0]["x_pos_1"] * 1e-2
sat_y = osv[0]["y_pos_1"] * 1e-2
sat_z = osv[0]["z_pos_1"] * 1e-2

gain_list: list[float] = []
for n in range(n_samp):
# https://github.com/senbox-org/microwave-toolbox/blob/master/sar-op-calibration/src/main/java/eu/esa/sar/calibration/gpf/calibrators/ASARCalibrator.java
r = r_first + n * range_spacing
Expand Down Expand Up @@ -158,15 +157,22 @@ def parse_direct(path: str, gdal_metadata: dict[str, Any], polarization: str) ->
# dB -> linear
gain = math.pow(10, antenna_gains[elev_idx] / 10)

np.append(gain_arr, 1 / gain)
gain_list.append(1 / gain)
gain_arr = np.array(gain_list)

# calculate spreading loss compensation

spread_loss_power = 3.0
if "APS" in gdal_metadata["product"]:
spread_loss_power = 4.0
for n in range(n_samp):
r = r_first + n * range_spacing
factor = math.sqrt((range_ref / r) ** 3)
np.append(spreading_loss, 1 / factor)
factor = math.pow((range_ref / r), spread_loss_power)
spreading_loss = np.append(spreading_loss, 1 / factor)

cal_factor = gdal_metadata["records"]["main_processing_params"]["calibration_factors"][0]["ext_cal_fact"]
factor_offset = gdal_metadata["polarization_idx"]
cal_factor = gdal_metadata["records"]["main_processing_params"]["calibration_factors"][factor_offset][
"ext_cal_fact"]

metadata["cal_factor"] = cal_factor
metadata["cal_vector"] = np.array(spreading_loss) * np.array(gain_arr)
Expand Down
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