PALSAR-2¶

Overview¶

PALSAR-2 is an L-band synthetic aperture radar (SAR) sensor onboard the ALOS-2 satellite operated by JAXA. It provides high-resolution, all-weather radar imagery suitable for vegetation structure analysis, forest monitoring, and land cover classification. Its longer wavelength enables deeper penetration into forest canopies compared to C-band SAR systems.

In GeeFetch, PALSAR-2 data is accessed via the Google Earth Engine collection JAXA/ALOS/PALSAR-2/Level2_2/ScanSAR (Level 2.2 orthorectified, terrain corrected).

Processing¶

Filtering by date range and area of interest
Refined lee filter is applied to remove noise
Resampling to target resolution
Mosaicking of overlapping acquisitions
Scaling to maximize precision within the requested data type. Pixels outside of the range \((-30, 0)\) saturate. For instance, if the requested datatype is uint8, the image is scaled by \(x \mapsto (x + 30) \cdot 255/30\).

Available Bands for download¶

Band	Description	Native resolution	Download by default
HH	Horizontal transmit, horizontal receive (dB)	25m	yes
HV	Horizontal transmit, vertical receive (dB)	25m	yes
LIN	Local incidence angle (between radar direction and slope normal)	0.01 deg	no
MSK	Data quality bitmask	25m	no

Refer to JAXA/ALOS/PALSAR-2/Level2_2/ScanSAR for more details.

Configuration Options¶

See common configuration options for non PALSAR-2-specific configuration.

Attributes:

Name	Type	Description
`orbit`	`P2Orbit`	Orbit direction to filter PALSAR-2 acquisitions. Can be ASCENDING or DESCENDING. Defaults to DESCENDING.
`refined_lee`	`bool`	Whether to apply the Refined Lee filter to reduce speckle noise. Defaults to True.

Example Usage¶

Command Line¶

Write the following config.yaml:

data_dir: ~/satellite_data
satellite_default:
  aoi:
    spatial:
      left: 2.2
      bottom: 48.7
      right: 2.5
      top: 49
      epsg: 4326
    temporal:
      start_date: "2024-06-01"
      end_date: "2024-06-30"
  gee:
    ee_project_ids: ["your-gee-id"]
  tile_size: 2000
  resolution: 10
palsar2:
  orbit: DESCENDING
  aoi:
    temporal:
      end_date: "2024-12-30"

then download with

geefetch palsar2 -c config.yaml

Python API¶

Though this is not geefetch main intended use, you can bypass the configuration and directly download Palsar-2 data with the geefetch.data.get.download_palsar2 function. For instance, the CLI command above is roughly equivalent to

import logging
from pathlib import Path

from geobbox import GeoBoundingBox

from geefetch.data.get import download_palsar2
from geefetch.utils.gee import auth
from geefetch.utils.log import setup

setup(level=logging.INFO)

data_dir = Path("geefetch_data/")
data_dir.mkdir(exist_ok=True)

auth("your-gee-id")

download_palsar2(
    data_dir,
    bbox=GeoBoundingBox(2.2, 48.7, 2.5, 49),
    start_date="2024-06-01",
    end_date="2024-12-30",
    tile_shape=2000,
)

See the API reference of geefetch.data.get.download_palsar2 for more details.

Relevant library code¶

Palsar2
geefetch.data.get.download_palsar2