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diff --git a/topics/04_mechanical/index.md b/topics/04_mechanical/index.md
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--- a/topics/04_mechanical/index.md
+++ b/topics/04_mechanical/index.md
@@ -58,9 +58,12 @@ Optically tracked touch probes
 
 <img src="images/gom_touch_probe.jpg" alt="GOM touch probe">
 
-<div class="youtube-embed-wrapper"> <iframe src="https://youtube.com/embed/wt4PLgbwxQI?t=92" frameborder="0" allowfullscreen=""></iframe> </div>
+<iframe width="560" height="315" src="https://www.youtube.com/embed/wt4PLgbwxQI?si=A0yDBFneMn1wFotE&amp;start=98" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>
 
 
+Bridge Coordinate Measuring Machines (CMM)
+<img src="images/bridge_cmm.jpg" alt="Bridge CMM">
+
 ### Digitizer Arms
 
 Passive Robot Arm
@@ -85,16 +88,27 @@ Add Dennis Shelden Dissertation content
 
 <img src="images/gehry_scanning_exterior_model.jpg" alt="Source: Gehry Technologies">
 
+
+<img src="images/shelden_digital_surface_representation_p299.jpg" alt="Source: Dennis Shelden">
+
 ### Digital Templating
 
-Add proliner
+Wire based templating devices take measurements from rotary encoders
 
 <iframe width="560" height="315" src="https://www.youtube.com/embed/9dd1w9VAxw0?si=9kcd6ggq5RGd8YOL&amp;start=67" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>
 
 ### Robotic Survey Prisms
 
-https://www.sumpoint.io/#services
+A survey prism is a glass reflector that is used in surveying and engineering to reflect the Electronic Distance Measurement (EDM) beam of a total station.
+
+<img src="images/survey_prism_railroad.jpg" alt="Survey Prism">
+
+[SumPoint](https://www.sumpoint.io/#services)
+
 
 [Small Robots and Big Projects](https://papers.cumincad.org/data/works/att/acadia21_462.pdf), Maria Yablonina & James Coleman, ACADIA 2021
 
-### Digital Twins
+
+
+Labor costs more than steel
+Digital Twins