# Checking the distance bwtween two STL models in order to exaluate the accuracy between virtual planning and actual surgery

**URL:** <https://discourse.slicer.org/t/checking-the-distance-bwtween-two-stl-models-in-order-to-exaluate-the-accuracy-between-virtual-planning-and-actual-surgery/29584>\
**Category:** Support\
**Tags:** segmentation\
**Created:** [May 22, 2023, 2:44pm UTC](https://discourse.slicer.org/t/checking-the-distance-bwtween-two-stl-models-in-order-to-exaluate-the-accuracy-between-virtual-planning-and-actual-surgery/29584 "2023-05-22T14:44:47Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![wael\_telha](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/wael_telha/32/16914_2.png) [@wael\_telha](https://discourse.slicer.org/u/wael_telha)\
**Post date:** [May 22, 2023, 2:44pm UTC](https://discourse.slicer.org/t/checking-the-distance-bwtween-two-stl-models-in-order-to-exaluate-the-accuracy-between-virtual-planning-and-actual-surgery/29584/1 "2023-05-22T14:44:47Z")

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hi dear all , I would like to confirm the accuracy of my evaluation through sharing with you some of the steps I used for the measurement of accuracy between the virtual planning model and the actual post-operative model, I need your valuable opinion in this regard

1. the first step after I did the registration between the pre-operative planning and post-operative  

2. After the registration, with the help of pick’n Point I choose the reference model, which is a post-operative model  
I made a point on the reference model as shown below at the area of interest to measure the distance between the same points between the two models, and later I chose the propagate the non-mesh model  

3. then through Model to Model Distance the source model is the post-operative Model and the target model is the pre-operative model and the calculation was done  

4.the fourth and last step was to get the measured value through Mesh Statistics. I chose the absolute value and X AXIS, Y, AND Z AXIS

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/a/3/a32e7bdb5d2fc033988383c62023ff58de1f5d33.jpeg)

my question is this step are accurate for measuring the distance between 2 models ?