Landmarks Example 1
This page shows two examples of how to create a landmark relative to a segment (or to 3 markers) using a reference location (a target or existing landmark). In the first example, we use a location or landmark, Left Knee Static that was created previously. Left Knee Static exists in the standing trial for the same subject, but it doesn't exist in the motion trials.
Example 1: Landmark Relative to a Segment and reference
In this example, to create a landmark relative to a segment, we also use a location or landmark, Left Knee Static that was created previously as a reference. Left Knee Static exists in the standing trial for the same subject, but it doesn't exist in the motion trials. It is a Calibration Only Landmark.
First, create the Left Knee Static calibration only landmark. To create, the landmark relative to a segment, Left Knee Joint, use these landmark options below. The relative segment or offset to existing segment is LTH. The Left Knee Static is also selected as an offset to existing Calibration Target or Landmark.
Landmark Name= Left Knee Joint
Existing Segment= LTH
Offset to Existing Calibration Target or Landmark= Left Knee Static
Offset by Percent Not Checked
Calibration Only Landmark Not Checked
When you select the Apply button, you will note that the three combo boxes defining the offsets for the marker have been populated (but grayed out). For example:
Offset Using the Following ML/AP/AXIAL Offsets Not Checked ML=0.0615 AP= -0.0573 AXIAL= 0.1544
These combo boxes contain the location of the Landmark without referring to the reference landmark. If you select the check box to use these offsets after they have been populated
Offset Using the Following ML/AP/AXIAL Offsets Checked
You can now save the model template and apply it to another standing trial and this landmark can be tracked in the new file. This Landmark will now be tracked with the thigh segment (RTH) and will no longer need the reference landmark since the offsets have been calculated.
Example 2: Landmark Relative to 3 markers
In this example, we will create the landmark and offsets relative to 3 markers. First, we assume that the Left Knee Static landmark has already been created. This is a calibration only landmark. Then we create a landmark, Left Knee Joint, relative to 3 tracking markers LEFT.THIGH1, LEFT.THIGH2, and LEFT.THIGH3.
Landmark Name= Left Knee Joint
Starting Point= LEFT.THIGH1
Ending Point= LEFT.THIGH2
Lateral Object= LEFT.THIGH3
Offset to Existing Calibration Target or Landmark= Left Knee Static
Offset by Percent Not Checked
Calibration Only Landmark Not Checked
When you select the Apply button, you will note that the three combo boxes defining the offsets for the marker have been populated (but grayed out). For example:
Offset Using the Following ML/AP/AXIAL Offsets Not Checked ML=0.1544 AP= -0.0573 AXIAL= 0.0615
These combo boxes contain the location of the Landmark without referring to the reference landmark. If you select the check box to use these offsets after they have been populated
Offset Using the Following ML/AP/AXIAL Offsets Checked
You can now save the model template and apply it to another standing trial and this landmark can be tracked in the new file. This Landmark will now be tracked by the 3 markers attached to the thigh.