How to create a zone ?

Please find at first the drill for creating a new zone, and below details and additional information for correctly defining the zone.

Step by step

  1. Create a new zone by a click on the "plus" button.
  2. Immediately set the type of zone: release or recruitment zone.
  3. Change the name of the zone
  4. Add as much points as necessary to define the polygon.
  5. Choose the color of the zone (for later visualization)
  6. Optional step : refine the zone area with the bathymetric mask : set inshore and offshore line.
  7. Optional step, for 3D simulation only : define a zone thickness by setting upper and lower depth.

What is a zone ?

In the application, a zone is a marine restricted area whose every point belongs to the domain of the simulation. Part of the zone can cover the land, but it cannot be exclusively over the land. At least a fraction of the area has to overlap sea water.

Closed polygonal chain

The geographical area is defined as a polygon, with as much point as necessary. This means the possibilities in terms of shape are potentially infinite. A point is a Geo-position (longitude, latitude) with latitude expressed in degree North and longitude in degree East.
Points must be defined in a way to have a closed polygonal chain, without and segment intersecting. But there is no need to duplicate the first point of the polygon at the end of the chain, the application will do it automatically.
As mentioned above, the points do not have to be in the water, but make sure they all belong to the geographical domain of the hydrodynamic model.

Bathymetric mask

Zone definition can be refined by specifying two bathymetric lines: inshore line and offshore lines. The application isolates the area of the polygon that is contained between the inshore and the offshore lines.

Thickness

For 3D simulation, the zone is not only a surface but a volume. It is possible to define the thickness of the zone, with upper depth and lower depth. If thickness is activated, the application isolates the sea water layer that is contained between the upper depth (close surface) and the lower depth (close bottom). Otherwise it includes the whole water column.