Help Content > Basic Module > Feature Extraction > Ship Features

Purpose

This tool is used to extract a series of shape files containing the coastline detected in the input images, grouped by tide height.

To use this tool it is necessary to create a WorldTides account (https://www.worldtides.info/). An authorization key can be obtained by creating a free account. The tide information is retrieved for free not using any credits, as specified in the website.

Technical Note

This tool is used to extract the coastline from a list of images, all the input images must be geocoded, on the same area and the center of those images must be suitably close to open waters (less than 1 degree).

The input images will be grouped based on the tide height in the time of acquisition. From the resulting groups a new image will be created to account for possible interferences and moving objects.

These resulting "grouped" images will then be used to determine the coastline that will be extracted in the relative output shape files. Once the shape has been extracted some filters are applied to smooth the results and remove false positives in the acquisition.

To the resulting shape files three different filters are applied:

•the first filter smooths the results to remove gridded edges from the shape file

•the second filter removes every shape that is completely within an area of a defined size.

•The third filter remove every shape with area size lower than a defined size.

All the values pertaining to these filters can be modified from the panel to achieve different levels of filtering.

Input Files

Input file list

Two or more geocoded images on the same area. This file is mandatory.

Parameters - Principal Parameters

Tide Base URL

URL of the WorldTides website.

Tide User Auth Key

The authorization key to access the the WorldTides website.

Tide height span

The height span in meters that will be used to group the images.

Minimum group size

Number of images that need to be in a group to be declared valid. If a group contains less that this number of images it will be merged with the previous one.

Smoothing window size

Smoothing value for the first filter.

This value should usually be greater than 1 and less than 10 for optimal results.

Aggregation group size

Aggregation size used by the second filter.

This value should usually be greater than 1 and less than 20 for optimal results.

Filtering size

Aggregation size used by the third filter.

This value should usually be either 0 or a value between the Aggregation group size value and 150.

This is the most aggressive filter and will remove the most features if set, useful for very noisy shapes.

Minimum db threshold

This is the value that will determine the threshold between what will be considered water and land, everything under this value will be outside of the coastline shape.

Keep intermediate files

Flag to determine if intermediate files should be kept or deleted.

Output Files

Output Root Name

Name of the output root. This file is mandatory.

The output files will contain a number between 0 and the number of groups ordered by tide height in ascending order.

General Functions

Exec

The processing step is executed.

Store Batch

The processing step is stored in the batch list. The Batch Browser button allows to load the batch processing list.

The window will be closed.

Help

Specific help document section.

Specific Function(s)

None.