Set Reference Point

Photo4D needs the coordinates of at least two points to determine a world coordinate system. Therefore, users need to set two or more reference points.

The steps to set up a reference point are the following:

1. Open the Point Info Window if it has not been opened.
2. Select a point on the object as the current point (click the left mouse button on a mark). This causes the information for this point to appear in the Point Info Window.
3. Enter the reference coordinates in the X, Y, Z fields and Change the type to "reference" by clicking the reference (R) button next to each field.
4. Click the "Save Change" button to update the change into the Photo4D database.

Do not forget to press "Save Change" in the Point Info window after changing the value!

Photo4D uses a right-hand coordinate system. The coordinate values of the reference points should be measured in this system either by actually measuring the reference point locations or sometimes by guessing.

The exact unit for the coordinate of reference points is not important. Photo4D will compute the coordinates for the rest of the points relative to the reference points. However, the reference points must be consistent. The first two reference points will always be consistent in Photo4D. Three or more reference points may cause inconsistencies if not set properly.

It is always a good practice to use more than two reference points when a situation allows you to obtain their accurate coordinate values. Two reference points cannot uniquely define the world coordinate system. More important, additional reference points can increase accuracy and robustness when Photo4D computes 3D information.