Tie point entry modes

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Tie point entry modes

Tie point entry modes

Tie points are defined by using different levels of automation. These different levels can be described as three entry modes:

Manual - you enter the tie point manually in all images. The application just displays each raw image the sees the tie point location automatically in the detail views.

Semi-automatic - you enter the tie point manually in the active image. The application finds matches in other images automatically. This mode is active if Find matches automatically is switched on in Tie points / Automation of the TerraPhoto Settings. This mode applies to Ground tie points only.

Automatic - the application searches for tie points automatically. You start the search by selecting Search points command from the File pulldown menu in the Tie points window. The automatic search enters only Ground tie points.

Automatic - feature points - feature points replace the automatic tie point search mentioned above. They are computed based on the raw images and converted into Air tie points. However, they can be located on above-ground objects as well as on the ground.

Whenever you start working on a new project, you normally start with the manual mode. If mismatch distances become relatively small (about 2-3 * pixel size of the raw images), you may change to the semi-automatic mode. If that mode is successful in finding correct matches and if the camera parameters are stable, you can run the automatic search.

Alternatively, you start the feature point computation first, preferable in TerraSlave. While the process is running, you can continue with the normal TerraPhoto workflow.

General workflow of entering a tie point

1. Select an image in the upper list box of the Tie points window.

The image is displayed on the Active full view.

2. Select a tie point type from the Point pulldown menu of the Tie points window.

3. Define an approximate location with a data click in the Active full view. Select a location where you think you can place a tie point of the selected type.

For Known tie point types, the known point location must be entered first instead of the approximate tie point location.

The selected location in the active image is displayed in the Active detail view.

4. Search for a good location for the tie point in the Active detail view. Place the tie point in the Active detail view with a data click.

The tie point is created and displayed in the lower list of the Tie points window. It is defined in the active image while all secondary images have empty pixels for this tie point.

The tie point location is displayed in the Secondary detail view.

5. Enter the tie point in all other images in the Secondary detail view. The images are displayed one after one in the Secondary detail view whenever the tie point has been entered.

In semi-automatic entry mode, Ground tie points are placed automatically in all secondary images after they have been entered in the active image. If a tie point location can not be found automatically in an image, this image is displayed in the Secondary detail view for manual entry. However, the setting for Bad matches in Tie points / Automation of the TerraPhoto Settings determines the handling of situations, where tie points can not be found semi-automatically.

Alternatively to the mouse pointer, you can navigate in the lists of the Tie points window by using the <Arrow-up> and <Arrow-down> keys. The key commands select the previous/next image in the list of images or points. A selected tie point pixel can be deleted by using the <Delete> key. The usage of keys is automatically focused on the tie point list if the setting Focus point list automatically is switched on in Tie points / Automation of the TerraPhoto Settings.

A detailed description of entering tie points of different types is provided in Section Point pulldown menu.