====== Example - Landmark Relative to a Segment and Reference ======

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.

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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

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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.