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--- visual3d:documentation:modeling:segments:create_coda_pelvis_relative_to_anatomical_landmarks [2024/07/03 17:27] – removed sgranger
+++ visual3d:documentation:modeling:segments:create_coda_pelvis_relative_to_anatomical_landmarks [2026/06/09 21:22] (current) – Cleaned up section levels and added links. wikisysop
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+====== How to create a CODA pelvis relative to anatomical landmarks ======
+The [[visual3d:documentation:modeling:coordinate_system|segment coordinate system]] for the [[visual3d:documentation:modeling:segments:coda_pelvis|CODA pelvis]] is the mid-point between the ASIS markers. The anatomical landmarks are actually posterior to the ASIS markers because the motion capture system tracks the centre of the marker.
+===== Correcting the CODA definition =====
+This is a modest error, but it can be corrected by creating landmarks that are posterior to the ASIS markers by the radius of the motion capture marker.
+==== Step 1. Confirm the subject metric containing the marker radius ====
+If the metric doesn't exist, create a new metric. Switch to **Subject Data/Metrics** TAB.
+{{:SegmentExample4_1.png}}
+Select **Add New Item** and enter in the name **Marker_Radius** and the value.
+{{:SegmentExample4_2.png}}
+In this example, the marker has a diameter of 1.2 cm. Visual3D uses [[visual3d:documentation:pipeline:model_based_data_commands:units_of_measurement|MKS units]], so the value is 0.006 meters. **NOTE**: If the radius is not consistent with your marker radius, modify the value.
+==== Step 2. Create landmarks for the ASIS markers ====
+{{:SegmentExample4_4.png}} {{:SegmentExample4_5.png}}
+**NOTE**: the Medial-Lateral (ML) Edit box contains the [[visual3d:documentation:pipeline:expressions:expressions_overview|expression]] **-MARKER_RADIUS** to define the offset.
+==== Step 3. Create a CODA Pelvis ====
+Follow the usual steps to create a CODA pelvis segment.
+{{:SegmentExample4_6.png}}
+In this example, the locations defining the segment coordinate system for the pelvis are the landmarks **RT_ASIS** and **LT_ASIS**, and the marker **SACR** located at the midpoint of the PSIS markers.
+The tracking markers are **RASI**, **LASI**, and **SACR**.
+{{:SegmentExample4_7.png}}