4.5.6. Bounding box filterΒΆ

The bounding box filter takes a 2D bounding box as parameter that is given by the coordinate values of its lower left (xmin, ymin) and upper right (xmax, ymax) corner. It is evaluated against the ENVELOPE column of the CITYOBJECT table.

../../_images/impexp_export_bbox_filter.png

Fig. 4.38 Bounding box filter for export operations.

You can choose whether features whose envelopes overlap with the provided bounding box are to be exported (default), or whether their envelope must be inside. Alternatively, the export can be tiled by splitting the bounding box into a regular grid. The number of rows and columns of this grid can be defined by the user. Each tile is exported to its own output file. To make sure that every city object is assigned to one tile only, the center point of its envelope is checked to be either inside or on the left or top border of the tile.

Similar to the import operation, the coordinate values of the bounding box filter can either be entered manually or chosen interactively in a 2D map window. To open the map window, click on the map button map_select. A comprehensive guide on how to use the map window is provided in chapter Section 4.8.

Note

When choosing a spatial bounding filter, make sure that spatial indexes are enabled (use the index operation on the Database tab to check the status of indexes, cf. Section 4.3.3).

Note

If the entire 3D city model stored in the 3DCityDB instance shall be exported with tiling enabled, then a bounding box spanning the overall area of the model must be provided. This bounding box can be easily calculated on the Database tab (cf. Section 4.3.2).

Note

Using the center point of the envelope as criterion for a tiled export has a side-effect when tiling is combined with the counter filter: the number of city objects on the tile can be less than the number of city objects returned by the database query because the tile check happens after the objects have been queried. Therefore, the counter filter only sets a possible maximum number in this filter combination. This is a correct behavior, so the Importer/Exporter will not report any errors.