Purpose

This tool allows to detect ships or similar objects over water bodies.

Technical Note

The tool is based on a well-established 2-parameters CFAR (Constant False Alarm Rate) detector approach.

After masking land areas based on an input reference shape file (optional), the module is performing adaptive thresholding to identify areas (“targets”) of backscatter significantly (from the statistical point of view) larger than a surrounding background; a guard window around the potential target is discarded during this comparison to avoid spurious effects.

The position of targets of interest is then extracted from the binarized image by identifying objects with a given minimum average backscatter and size.

Input Files

Input file list

Input file name of the SAR images (*_geo). These files are mandatory. Note: Only _geo files are currently supported.

Optional Files

Land Mask Shape File List

The software avoids the areas inside the polygon(s) of the provided shapefile. If a list of shapefiles (derived from the Costaline Extraction tool) is provided, the tile elevation is considered to choose the proper land mask file according the date and central pixel coordinates of the image.

Please note: This feature is available only with geocoded input files. Users have to consider the resolution of the input SAR data and verify that the .shp file and the SAR image are in the same Cartographic System.

Parameters - Principal Parameters

Target Window Size

Dimension of the Target(s) to detect (in meters).

Guard Window Size

Defines a window around the target window that is not taken into account in the background estimation (in order to remove double targets) (in meters).

Background Window Size

Size of the window used to estimate background value (in meters).

Probability Of False Alarm

Probability of getting a false alarm (ship detected when there is no ship). This value ranges between 0 and 1.

Central Pixel Minimum Sigma0 (dB)

Target window central pixel minimum Sigma0 value in order to be considered as a target.

Minimum Ship size

Pixel group below this minimum threshold are not considered as ships (in pixels).

Generate KML

Setting this flag to true, a Google Earth .kml file of the results is created.

Land Mask Buffer Size

It creates a buffer polygon of a specified distance around the land mask provided.

Tide User Auth Key

The authorization key to access the the WorldTides website.

Do Classification

Specify if the the identified ships have to be classified. The classification can be performed in case the input image is in polarized VV with a resolution of 10 meters (pixel spacing in range and azimuth); it is performed with a neural network trained on Sentinel-1 data. The result of such classification (a vector of probabilities) is saved in the output shape file with a column for each ship type recognized by the neural network.

Parameters - Global

It brings to the general section of the Preferences parameters. Any modified value will be used and stored for further processing sessions.

Parameters - Other Parameters

It brings to the general section of the Preferences parameters. Any modified value will be used and stored for further processing sessions.

Output Files

Output file (*_ship_mask.shp)

For each image in the input file list, a corresponding point shapefile showing center of groups of pixels identified as ships is created.

Output file (*_ship_mask)

For each image in the input file list, a corresponding mask showing pixels assigned to ships is created

Output file (*_ship_mask.kml)

If the flag "Generate kml is set to true in the parameters, a .kml file is created showing the location of the detected ships in a proper software (Google Earth, ArcGIS Earth, ...)

Output file (*_ship_mask_land_mask)

For each image in the input file list, a corresponding mask showing pixels assigned to land is created. This file only appears when a land shapefile is ingested.

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.

Basic - Feature Extraction - Ship Features - Ship Detection

Basic - Feature Extraction - Ship Features - Ship Detection

Purpose