Shorelines and Islands

Shorelines and Islands (Map Boundaries)

Map boundaries are user-defined paths that are added to a map project which serve to define the region in which the map is created and can, optionally, also provide depth information that is used during map generation.

Lake, river and ocean shorelines and islands can be defined through the use of Map Boundaries. Map boundaries can also be used to precisely define the mapped area.

A typical use of a map boundary would be to define the shoreline of a body of water, with a known depth of zero. The zero depths associated with the shoreline are included in the map calculation as if they were recorded track-points, enabling depth values to be interpolated between the shore and recorded track-points.

There can be at most one shoreline per map project, and any number of islands.

Note that adding a new map boundary, or editing an existing one, does not trigger automatic regeneration of the map. To re-generate the map after adding or changing a boundary, redraw the map area with the Define Map Area tool.

Map Boundary Properties

Map boundaries can be added and edited in the Project Properties Window and in the Define Map project view.

Move between boundaries in the project using the forward and back buttons (1). The properties for the currently selected boundary are shown in the boundary properties panel (3). Buttons to create a new boundary, import a boundary or delete one or all boundaries are contained within panel (2).

Adding a Map Boundary to a Project

Importing Map Boundaries

Map boundaries can be imported directly into a project from Google Earth™ KML and KMZ files, Shapefile polygons or lines, or from tracks contained within GPX files.

To import map boundaries, click the Import Boundary button (circled). A file selection window will be shown, from where one or more KML, KMZ, GPX or Shapefile files can be selected. Any number of files can be selected, with any mix of file types. Click Open in the file selection window to import the selected files.

By default, imported boundaries are treated as islands. This is simply because there are typically more islands than shorelines in a project, and reduces the workload significantly when importing large numbers of island boundaries.

Importing Boundaries From Google Earth Files

Tracing shoreline outlines in the Google Earth application is a good way to create boundaries:

·Trace the required boundary in Google Earth as either a polygon or a path. Both polygons and paths are treated the same in ReefMaster, which considers all boundaries to be closed loops.

·Save the polygon or path object; ReefMaster supports both KML and KMZ Google Earth file formats.

·Import the boundary into ReefMaster by following the import process described above.

Tracing boundaries in the field - the most accurate source of map boundaries

On-line map sources such as Google Earth can be very good, but are not always absolutely accurate. The most accurate way to create a map boundary is to walk a shoreline with a hand-held GPS unit and record the trail. It should be possible to convert the recorded track to a GPX file, which can be imported into ReefMaster for use as a boundary.

Using a Track as a Map Boundary

Any track within the workspace can be used as a map boundary. To add a track to a project as a boundary, use the context menu of a (single) selected track in the Asset Library, or right click a single track in the Global View. Select the option Add track to Project as Boundary.

To use a track that is already part of the project as a boundary, right-click the track within the Define Map view and select the option Use Track as Boundary. A new boundary will be added. Note that the original track will not be removed from the project in this case; remove the track manually if only the boundary is required.

Boundaries created from tracks do not retain the depth information that was present in the track.

Creating a Map Boundary within ReefMaster

Map boundaries can be created directly in the Define Map view, and drawn with the Pencil tool, or by adding path points individually to the list-box shown in the edit pane.

Drawing a New Map Boundary

To create a new map boundary using the pencil tool, simply select the Pencil mouse mode and draw a boundary. Ensure that no existing boundary is currently selected before starting the new path, or else the newly added points will be added to the selected path. The boundary can be drawn using a continuous mouse movement with the left mouse button held down, or individual points can be added by clicking the left mouse button. Path points can be deleted by using the right-click activated context menu or the path-point list box in the edit pane. Boundary editing uses the same editing functions as path editing in User Maps, where it is described in detail.

Creating a New Map Boundary with Explicit Path Points

Click the New button in the map boundaries properties panel (1) to create a new boundary. Individual points for the boundary path can be entered in the latitude and longitude edit boxes (3); to add a new point, click the Add (+) button (4). To edit an existing path-point, first select the path point in the points list (2), edit the latitude and longitude in the latitude and longitude boxes (3) and commit the change using the Edit button (5).

Splitting large maps using map boundaries

When mapping a very large area, it can be useful to split the map between several map projects, and recombine the contours in a single, large, User Map. This can be done by using map boundaries created with explicit path points (see above), which can be used to define the mapped area of a project very precisely.

·Create boundary rectangles for each different map project to define the mapped area, using precisely entered path-point values to describe the corners of the rectangle. The boundaries of each project should be adjacent, so that the boundaries of all the required map projects combine to create a single large area.

·Set the boundary type of each boundary rectangle to Shore.

·Set the properties of the rectangle boundaries; Is Boundary and Closed Loop should be set to true, and Provide Depth and Show Boundary in Map should be false.

The map projects will generate contours only within the defined boundary areas. Contours from the adjacent map projects can then be recombined in a single User Map to create a finished map.

Map Boundary Configuration

1. Name

Optional name field can be used to provide a descriptive name for a boundary. This field is populated with the name of imported polygons or paths when importing boundaries from Google Earth™.

2. Is Boundary

Specifies whether or not the boundary acts as a barrier during map generation. When this option is set, no contours are generated in the excluded areas. Typically, this value is set to yes, although it can be useful on occasion to provide depths from a path that does not act as a boundary (see Provide Depth, below).

3. Shorelines and Islands

Boundaries are always treated as closed polygons, and act to exclude data points from the generated depth map from either inside or outside the boundary area.

Shore

When a boundary is set to act as a shoreline, all data outside of the defined polygon is excluded. Note that this behaviour means that it is not possible to define, for example, two distinct shorelines within one map project. ReefMaster enforces this by allowing only a single shoreline per map.

Island

When a boundary is set to act as an island, all data within the defined polygon is excluded.

Configuring shorelines and islands

The configuration of shorelines and islands makes a big difference to the finished map. For example, accidentally configuring an island as a shoreline could end up excluding the vast majority of your map area from the finished map.

The Map Definition view makes it easy to see which areas of your generated map will be populated with data, by shading the excluded (land) areas, as shown in the image above. Excluded areas can often be seen more clearly with background maps off, especially when using aerial imagery backgrounds.

Provide Depth

Boundaries can contribute depth information to the map generation process by using the Provide Depth setting and providing a depth value. Depths are provided at 1m intervals along the path, for the value provided. Zero depths are typically used for shorelines, but any depth value can be used; for example, the known depth of a dam wall could be used where the dam provides the map boundary.

When defining a region for map generation that is not related to natural features such as shorelines, set Provide Depth to off. This will create a boundary that limits the map area but does not interfere with the map data.

Using Boundaries to Add Spot Depth Data to the Map Project

Spot depth data can be added to a map project by creating a boundary that provides depth, but does not act as a barrier during map generation.

To add spot depth soundings to a map:

·Create a boundary with options Is Boundary and Show In Map set to off, and Provide Depth to on.

·Assign the required depth to the boundary. All points within a boundary are the same depth.

·Draw or enter the required boundary points on the map project.

Show Boundary in Map

This option determines whether the boundary is visible in the contour view of the map project.

For shorelines and islands, this is typically set to on. When defining map areas to combine map projects, or adding spot depth data, this value is usually set to off.

Closed

Select this option to close the selected path. The loop is closed by joining the first and last path points. Although paths are always treated as closed internally by ReefMaster, it can be useful for display purposes to complete the boundary.

Map Boundaries and Map Exports

Map boundaries can be added exported to GPS devices or User Maps in the same way as map contours.

Humminbird™ Tracks

When exporting a user map with boundaries to a Humminbird™ track file, there is an option to export the boundaries as a separate track. Exporting to a separate track allows the style to be defined differently to the contour line style for display on the Humminbird™ unit.

Lowrance™ LCM files

When exporting a user map to LCM files, map boundaries are treated as lake shorelines, giving blue lake outlines on a yellow land mass, as shown in the image below.

Shapefiles for AT5 Maps

Shoreline and islands are exported as polygons that define the land area of the map. These polygons are filled in the selected land colour. Shorelines and islands are also exported as major contour lines.