Digitising channel damages

Channel damages are managed through the view tww_app.vw_tww_damage_channel.

This view calculates the damage geometry from:

  • the geometry of the channel referenced by the examination;

  • the recorded channel distance; and

  • the direction travelled by the examination camera.

When a damage is digitised manually, the point geometry selected in QGIS is discarded when the feature is saved. The geometry is then recalculated from the examination and the recorded channel distance.

Prérequis

To create a georeferenced channel damage, a corresponding examination must exist. Examinations can be created using tww_app.vw_tww_maintenance_event.

The examination must have:

  • a valid link to a channel; and

  • a valid link to a reach point that is either at the start or the end of that channel and is referenced by the uppermost/lowermost reach of the channel.

The wastewater network geometry used to position a damage is obtained from the materialized view tww_app.mvw_tww_channel.

Avertissement

tww_app.mvw_tww_channel is a materialized view and may be out of date.

If a channel was recently created, modified, reconnected or assigned to different reaches, refresh the materialized view before digitising damages. Otherwise, the channel may be missing or its geometry and topology may no longer correspond to the current network data.

How the damage position is calculated

A channel damage is stored as an attribute-based location along a channel. The point geometry shown in QGIS is generated by tww_app.vw_tww_damage_channel.

The view determines:

  • the examination associated with the damage;

  • the reach point from which the examination was carried out;

  • the wastewater structure associated with the examination;

  • the corresponding channel in tww_app.mvw_tww_channel;

  • the inspection direction, based on the examination reach point; and

  • the relative position along the channel.

The inspection direction is derived as follows:

downstream

The examination reach point corresponds to the fk_reach_point_from of the uppermost reach linked to the channel.

upstream

The examination reach point corresponds to the fk_reach_point_to of the lowermost reach linked to the channel.

unknown

The examination reach point matches neither of the above.

The relative position is calculated by dividing channel_distance by the length of the channel geometry. Values greater than the channel length are limited to the end of the channel.

For downstream inspections, the distance is measured from the beginning of the channel geometry. For upstream inspections, it is measured from the end of the channel geometry.

Note

Only examinations with recording type channel_TV are included in tww_app.vw_tww_damage_channel. The corresponding code is 3686.

Creating a channel damage

Select tww_app.vw_tww_damage_channel in the QGIS Layers panel and enable editing.

Use the QGIS feature creation tool configured for the channel damage layer.

The position clicked on the map is not the authoritative location of the damage. The final situation2d_geometry is calculated by the database from the damage attributes.

Place a temporary point and enter the required attributes. After saving and refreshing the layer, the calculated position replaces the temporary point.

New values are written to both:

  • tww_od.damage; and

  • tww_od.damage_channel.

Values entered in fields that are not stored in these tables are not persisted. Such fields are calculated by the view, primarily from the examination referenced by fk_examination.

Selecting the examination

The examination assigned through fk_examination must:

  • represent the relevant inspected channel;

  • have recording type channel_TV with code 3686;

  • be connected to the correct wastewater structure; and

  • have a valid examination reach point.

The examination reach point must correspond to either fk_reach_point_from or fk_reach_point_to of the most upstream/downstream reach of the channel.

Entering the channel distance

The value for channel_distance is usually obtained from the TV inspection recording or inspection report and must be entered manually.

The value represents the distance travelled by the inspection camera in meters, starting at the examination reach point.

Saving and checking the damage

Save the new feature and refresh tww_app.vw_tww_damage_channel.

Verify that:

  • the damage point lies on the expected channel;

  • direction is either upstream or downstream;

  • ws_identifier identifies the inspected wastewater structure; and

  • the point is located at the expected distance from the inspection start.

If direction is unknown, correct the examination or network relationships before continuing.

Note

The fields situation2d_geometry, direction, ws_identifier and tww_is_primary are calculated by the view and should not be edited manually.

Adding pictures or videos

Damage pictures and examination videos can be managed through tww_app.vw_file.

The channel damage view displays up to two associated pictures in:

  • picture_1; and

  • picture_2.

It also displays the associated examination video in video.

Pictures are linked directly to the channel damage. Videos are linked to the examination associated with the damage.

The picture and video fields are calculated from active file records. They are display fields and should not be edited directly in the channel damage view.

The channel damage view ignores outdated files when displaying pictures and videos. It also ignores outdated examinations when selecting videos.

Note

The current database query does not define an explicit ordering for the picture aggregation. If more than two pictures are attached, it is not guaranteed which files appear as picture_1 and picture_2.

Creating a new file record

Create a new record in tww_app.vw_file and set at least the following fields:

object

The obj_id of the object to which the file is linked.

For a damage picture, this is the obj_id of the channel damage. For an examination video, this is the obj_id of the examination.

kind

The file kind.

Damage pictures must use picture with code 3772. Examination videos must use one of the video kinds supported by the damage view, video with code 3775 or digital_video with code 9146.

classname

The class name of the object referenced by object.

_url

The complete path to the picture or video file.

Complete identifier, dataowner, provider and remark where required.

Important

The file path entered in _url must start with a repository path configured in tww_od.data_media.

When the file record is saved, the database selects the longest matching repository path. It stores the corresponding data-media object in fk_data_media and the remaining part of the URL in path_relative.

If no matching repository is found, the file record is not inserted and the database raises a warning.

Outdated files

The file selection used by the channel damage view excludes records for which tww_outdated is TRUE.

However, tww_outdated is not exposed by the supplied definition of tww_app.vw_file. A file therefore can only be marked as outdated through tww_od.file.

Refreshing the displayed media

After adding or modifying a picture or video:

  1. Save the file record.

  2. Refresh tww_app.vw_tww_damage_channel.

  3. Verify that the file appears in picture_1, picture_2 or video.

  4. Verify that the generated path can be opened from QGIS.

If a picture does not appear, check that:

  • object contains the channel damage’s obj_id;

  • kind is picture with code 3772;

  • tww_outdated is not TRUE;

  • the URL uses a path configured in tww_od.data_media; and

  • the channel damage layer has been refreshed.

If a video does not appear, check that:

  • object contains the examination’s obj_id;

  • the video kind has code 3775 or 9146;

  • neither the file nor the examination is marked as outdated; and

  • the examination is linked to the channel damage.