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Orientation constraints - PIX4Dmatic

PIX4Dmatic provides Orientation constraints as a means to realign a project. Projects can be reoriented along the X, Y, or Z axes.

Important: There are three primary concepts for incorporating orientation constraints.
  • An Orientation constraint is a line defined by two Tie points.
  • An Orientation constraint has a direction.
  • An Orientation constraint can only be aligned on the X, Y, or Z axes.
  • If the project has images with geolocation, and the Orientation Constraint is too divergent from the orientation given by the image geolocation, the Orientation Constraint will not be taken into account. If the orientation given by the image geolocation is inaccurate, the geolocation should be removed to orient the project.

Axis and Direction

PIX4Dmatic can orient a project on the X, Y, or Z axes. The X and Y axes lie on a horizontal plane, with the X-axis indicating the east-west direction and the Y-axis representing the north-south direction. The Z-axis points upward, denoting elevations or the vertical aspect. Depending on the direction of the constraint, PIX4Dmatic will try to align the project according to the axis and direction of the constraint.

  • X-axis points due East.
  • Y-axis points due North.
  • Z-axis points straight up.
Tip: The vertical corners of a building are generally a plum line representing the Z-axis. Utilizing an orientation constraint in these areas can correct a tilted or inverted project.

Orientation constraints in the 3D viewer

Orientation constraints are symbolized in the 3D viewer as a magenta line with an arrowhead denoting the direction of the constraint.


Deleting or changing the direction of the Orientation constraint

The Orientation constraint can be deleted, or the direction can be flipped by right-clicking on the constraint while in the 3D viewer.


Properties panel

The Properties panel displays the axis of the Orientation constraint along with the computed angular error in degrees. When a new Orientation constraint is created, the correct axis (X, Y, or Z) information must be entered in the Properties panel.


How to orient a project

An Orientation constraint is defined by two MTPs.

  1. Select the Orientation constraint coordinate_system.svg icon or use the keyboard shortcut G.
  2. Begin by left-clicking on a Tie point and finish the constraint by left-clicking on another Tie point.
    Important: MTPs must be marked in the images for the orientation constraint to work.
  3. Select the axis (X, Y or Z) in the Properties panel.
  4. (Optional) The direction of the MTP will be displayed by the arrow of the constraint. If need be, right-click on the orientation constraint to flip the direction.
  5. After drawing the Orientation constraint, either Reoptimize or run Calibration (if not previously calibrated).
  6. Click Save...