Use the Relative Water Depth tool to calculates a product depicting relative water depths for water regions from a multispectral raster with at least blue, green, and near infrared bands. The calculation is based on a bottom albedo-independent Bathymetry algorithm developed by Stumpf and Holderied (2003). The bottom albedo-independent nature of the algorithm means that sea floor covered with dark sea grass or bright sand is shown to be at the same depth when they are at the same depth.

You can also write a script to do calculate relative water depth using the CalculateRelativeWaterDepth task.

To calculate relative water depths:

  1. From the Toolbox, select Spectral > Relative Water Depth. The Relative Water Depth dialog appears.
  2. Select an input raster, perform optional spatial and spectral subsetting and/or masking, then click OK.
  3. Select a filter from the Median Filter drop-down list. The default is 3x3, which removes high-frequency noise that often occurs in the water depth results. You can select a different kernel size from the drop-down, or select None to turn filtering off. Setting the median filter to larger sizes creates smoother results, but may smooth over small submerged features.
  4. Enter a filename and location for the Output Raster.

  5. Enable the Preview check box to preview the settings before processing the data. The preview is calculated only on the area in the view and uses the resolution level at which you are viewing the image. To preview a different area in your image, pan and zoom to the area of interest and re-enable the Preview option. Depending on the algorithm being used by the tool, the preview result might be different from the final result of processing on the full extent, full resolution of the input image in the following scenarios: 1) If you zoomed out of the input raster in the view by 50%, or a percentage less than 50%, ENVI uses a downsampled image at the closest resolution level to calculate the preview, or 2) If the entire image is not visible in the view, ENVI uses the subset in the viewable area of the input image to calculate the preview.

  6. Enable the Display result check box to display the output in the view when processing is complete. Otherwise, if the check box is disabled, the result can be loaded from the Data Manager.

  7. To reuse these task settings in future ENVI sessions, save them to a file. Click the down arrow next to the OK button , select Save Parameter Values, then specify the path and filename to save to. Note that some parameter types, such as rasters, vectors, and ROIs, will not be saved with the file. To apply the saved task settings, click the down arrow and select Restore Parameter Values, then select the file where you previously saved your settings.

  8. You can run the process in the background on your computer or in the background on an ENVI Server (if available). Click the down arrow next to the OK button and select one of the following:

    • Run Task in the Background: Runs the process on your computer. This method does not use an ENVI Server. The job progress will show in the ENVI Job Console's Background Jobs tab.
    • Run Task on envi_server_name. Runs the process on the selected ENVI Server. The job progress will show in the ENVI Job Console's envi_server_name tab.

    See ENVI Job Console for details on monitoring ENVI Server jobs and viewing results. See ENVI Servers for details on configuring and using an ENVI Server.

  9. Click OK.

See Also

Spectral Tools