PushBroomScanner Node

The Pushbroom scanner model describes the relation between points in image space and three dimensional points in a global reference system using satellite vendor specific metadata files. These files contain information about the satellites position and attitude in the orbit, the position of the camera within the satellite (referred as camera mounting) and the interior camera parameter. Note: Only geocentric coordinate systems can be use as global reference systems. Therefore, control points have to be in a geocentric coordinate system.

A PushbroomScanner node is created either during the Image import or direct Import of Metadata via the Image Node. After importing PushbroomScanner parameters a PushbroomScanner node will appear as a subnode of the corresponding image icon in the Barista thumbnail view.

PushbroomScanner node icon: ; PushbroomScanner node as current sensor model:

Double Click on the PushbroomScanner icon opens a PushbroomScanner dialog. The Pushbroom scanner dialog shows the parameters of the Pushbroom scanner model. These parameters can be shared with other PushBroom models. See satellite camera, satellite camera mounting, satellite orbit path and orbit attitudes for more information about the adjustable parameters.

PushBroomScanner dialog

The selection of additional ALOS PRISM camera parameters can only be done within the PushBroom scanner dialog. Select Adjust parameters to determine these additional parameters. Tick the boxes in the column fix if you do not want to determine all parameters. By default these parameters are not determined.

Note: There are some things to consider when determining these additional parameters. When working with ALOS PRISM level 1A and 1B1 data sets, 4/6 image strips per view direction (separate for nadir/forward/backward) are available. The additional parameters are modelling the relative position of each image stripe per view direction. That means that only for 3/5 of the 4/6 image strips additional parameters can be determined. Always keep one of the images without additional parameters! Besides the fact that for one image no additional parameters can be determined a good distribution of control points is required in order to make the parameters determinable for the other 3/5 images. Fixing the scale or quadratic parameter can improve the determinability if the distribution of the control points is not optimal.

Right Click on the PushbroomScanner icon opens a PushbroomScanner icon popup menu with the following options:

PushBroomScanner node popup menu

Using the item Set PushbroomScanner to current sensor model will set the PushbroomScanner node to the current sensor model for the corresponding image node. By default, the current sensor model will be used for all Barista functions involving a sensor model, e.g. orthophoto generation or monoplotting. The current sensor model of an image node will be highlighted by a red frame.

Generate RPCs

Using the item Generate RPC will open a dialogue for defining the height range for which the RPCs should be generated by specifying minimum and maximum heights. Within this height range the RPCs will be a good approximation of the mapping function. If the RPC generation is successful, a information message showing the RMS error of the weight unit will be displayed on screen. This can be interpreted as the RMS error of the differences between points back-projected using the pushbroom sensor model and points back-projected using the RPCs in [pixels]. The resulting RPCs will be stored to a RPC node.

The dialog for generating RPCs

To Image Node

To Thumbnail View