The "Extract Water" tool in ArcGIS Pro 3.3, available under the Image Analyst extension, is designed to identify and delineate water bodies using input synthetic aperture radar (SAR) data and a digital elevation model (DEM). The tool analyzes the radar backscatter to classify pixels as either water or land, subsequently creating corresponding polygon feature classes. The process includes calibration of the radar data to gamma nought using the "Apply Radiometric Calibration" tool to enhance accuracy, particularly in large radar scenes.
For precise alignment and optimal transformation of the output feature class, it is recommended to orthorectify the input radar data. If the input data is not orthorectified, the tool uses the provided DEM Raster parameter to perform this transformation. In the absence of a DEM, an ellipsoidal surface transformation is applied. For best results, the input DEM should be in the WGS84 (EPSG:4326) geographic coordinate system.
The tool also allows the creation of water or land polygons that can be utilized in other SAR analysis tools, such as "Detect Bright Ocean Objects" and "Detect Dark Ocean Areas."
Key parameters of the tool include:
1. Input Radar Data**: The radar dataset or layer to be analyzed.
2. Output Feature Class**: The resulting polygon feature class representing water and land areas.
3. Minimum Area** (optional): Specifies the smallest water body size to be extracted, with a default value of 50,000 square meters.
4. DEM Raster** (optional): Used for orthorectification and optimizing polygon construction if the input radar data is not orthorectified.
5. Apply Geoid Correction** (optional): Determines whether to transform the DEM's vertical reference system to ellipsoidal height, with a default correction based on the EGM96 geoid.
This comprehensive tool facilitates detailed and accurate extraction of water bodies from SAR data, supporting a wide range of remote sensing applications.
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