====== Aerial Triangulation ======

==== In This Chapter ====

  * [[control_points]]
  * [[image_points]]
  * [[interior_orientation]]
  * [[object_points]]
  * [[bundle_block_adjustment]]
  * [[relative_orientation]]

===== Introduction =====

This chapter leads you through the different steps of the Aerial Triangulation procedure.

After performing an Aerial Triangulation you will find the following results:

  - The exterior orientation parameters for each image:
    * The projection center coordinates expressed in the destination (ground or terrain) coordinate system.
    * The orientation parameters Omega, Phi and Kappa.
  - The ground coordinate values for all object points.
  - Some result files reflecting the accuracy of the adjustment.

===== Necessary Data =====

Some basic information must be available to start the Aerial Triangulation:

  * Interior Orientation (IO):\\  All images used in the triangulation must have an IO.
  * Tiepoint measurements.
  * Terrain coordinates of GCP's. \\  These Ground Control Points are also measured as tiepoints.
  * Approximate values for projection centers and orientations. \\  These values have been defined in step 2 of the [[..:project:Step_B_Exterior_Orientation#Step 2 Exterior Orientation|'Project Wizard']].
  * Approximate values for the object points. \\  These approximate values can be calculated with the 'Calculate approximations' function.

===== The Aerial Triangulation Procedure =====

The different steps in the 'Aerial Triangulation' menu lead you through the triangulation procedure like using a wizard:\\ \\ {{adjustment_menu.gif?345x177&nolink}}

Follow the next steps:

  - It is assumed that all the images have already an approximate coordinates for the Projection Centre and approximate orientation angles.\\  These values are already entered in the project during the project creation phase.
  - Prepare the [[Interior_Orientation#Interior Orientation|Interior Orientation]].
  - Prepare the [[Image_Points#Image Points|Tiepoints]].
  - Prepare the [[Control_Points#Control Points|Control points]].
  - Prepare the [[Object_points#Object Points|Object points]] by calculating an approximated value.
  - Execute the Bundle Block Adjustment.