Definition of seamless point surface

A seamless point surface consists of de-conflicted point datasets with for every point the best value estimate. The seamless point surface is a virtual surface. Only the footprints of the de-conflicted point datasets in the seamless point surface are stored. The selection on the points is done when retrieving the seamless point surface for visualization and export. For each point datasets only the points inside the de-conflicted footprint are retrieved.  

A seamless point surface is defined by a SQL query. The WHERE clause of the query defines the point datasets to be selected for de-conflicting and the ORDER BY clause defines the point dataset priority.

To create a seamless point surface, navigate to the Bathymetry datasource and click Add Dataset. The dialog to add a new dataset opens. Enter "SeafloorDTM" as name. The description is optional. A seamless point surface is a point dataset so select GlPointDataset as Dataset class. It is also possible to select a user-defined subclass of GlPointDataset as dataset class if you want to store additional metadata for the seamless point surface. As driver select "Seamless Point Surface Driver". Select "Sounding" as Type class. All point datasets based on the selected type class are taken into account in the generation of the seamless point surface. Select "mm" as Resolution and pick a color for visualisation of the seamless point surface footprint.

Click Save to store the dataset definition. A new dialog opens to enter the parameters for the seamless point surface definition. The selection of point datasets can be restricted by the dataset class. Only point datasets with the selected dataset class will be taken into account in the generation of the seamless point surface. Select "Survey" as Dataset class. When clicking Add attribute a list with the metadata attributes of the selected dataset class is shown. A query on one or more metadata attributes can be entered to further restrict the list of point datasets taken into account in the seamless point surface generation. 

The last step is the definition of the priority rules. The priority rule defines which point dataset has the highest priority when surveys are overlapping. Click Add Sort Order Rule. A list with metadata attributes of the selected dataset class is shown. Select "SurveyYear" as metadata attribute to sort on and select "Descending" as sort order.

The sort order of the survey becomes:

Press Save to store the seamless point surface definition and Activate to submit the task to generate the seamless point surface. A list with tasks is shown with the task status. Click on the Filter icon to refresh the task list to monitor the task progress. The task is successfully completed when the task status is "Finished".

Navigate to the Bathymetry datasource. A new seamless point surface dataset SeafloorDTM is added to the list with datasets. Click on the name to open the preview. The surveys are de-conflicted, the overlap between the surveys is removed and the remaining footprints are seamlessly integrated into a single point dataset. The concept of the seamless point surface is illustrated in following figures. The first figure shows the overlapping surveys. The second figure shows the de-conflicted survey footprints in the seamless point surface with highest priority for the red survey and lowest priority for the green survey.

The illustrate the effect of the priority rules on the seamless point surface, add a second seamless point surface "SeafloorDTM_demo". Navigate to Bathymetry datasource and click Add Dataset. Add a new seamless point surface dataset with the following parameter values:

Click Save to store the dataset definition. A new dialog opens to enter the parameters for the seamless point surface definition. Enter the following definition:

Notice that the sorting order of the priority rule is "Ascending" instead of descending. The other parameters have the same value as in the SeafloorDTM seamless point surface.

Press Save to store the seamless point surface definition and Activate to submit the task to generate the seamless point surface. A list with tasks is shown with the task status. Click on the Filter icon to refresh the task list to monitor the task progress. The task is successfully completed when the task status is "Finished".

Navigate to the Bathymetry datasource. A new seamless point surface dataset SeafloorDTM_demo is added to the list with datasets. Click on the name to open the preview. The effect of changing the priority order is illustrated in figures below. The first figure shows the de-conflicted survey footprints in the seamless point surface with with highest priority for the red survey and lowest priority for the green survey. The second figure shows the de-conflicted survey footprints in the seamless point surface with highest priority for the green survey and lowest priority for the red survey. The lower the priority of a survey, the smallest of the survey footprint in the seamless point surface.

For SeafloorDTM seamless point surface the soundings are extracted from the red survey in the overlapping areas (first figure). For SeafloorDTM_demo seamless point surface the soundings are extracted from the green or yellow survey in the overlapping areas (second figure).