Scaling: Max Marker Error and Visualizer Discrepancies
Posted: Sat Feb 13, 2021 10:23 am
Hi all,
I am working to scale several subjects using the GUI and I keep running into two issues regarding the max marker error. I have reviewed the scaling documentation, tutorials, and dug through previous forum posts, but have thus far had no luck finding an explanation. I am hoping to get clarification on the following discrepancies between the max marker error in the messages pane and the experimental and virtual marker offsets in the visualizer window:
(1) Of the 8 subjects I have scaled, all have a max marker error around 10cm, however, when I overlay the virtual and experimental markers in the visualizer window the markers are a good match (screenshot below). I think this may be a unit problem, but both the .osim file and .trc files specify the units as meters (sample files attached). Is there some other place units are specified, or something else I missed that would explain such a high marker error compared to what I am seeing visually? If not, which should I believe, the visual or the max marker error output in the messages pane?
Messages Output: total squared error = 0.128967, marker error: RMS=0.056085, max=0.107094 (L.SH1)
(2) During scaling, regardless of the max marker error value, sometimes the identified marker doesn't seem to be the "poorest" match. For instance, if the messages pane identifies a left shank marker as having the max marker error, when I overlay the virtual and experimental markers and look at the whole model, the right shoulder markers look to have a greater offset. Similar to my first question, which should I trust, the output in the messages pane, or what I'm seeing in the visualizer window?
Any insight/suggestions into these discrepancies and how to proceed would be immensely appreciated! Thank you in advance for all the help!
I am working to scale several subjects using the GUI and I keep running into two issues regarding the max marker error. I have reviewed the scaling documentation, tutorials, and dug through previous forum posts, but have thus far had no luck finding an explanation. I am hoping to get clarification on the following discrepancies between the max marker error in the messages pane and the experimental and virtual marker offsets in the visualizer window:
(1) Of the 8 subjects I have scaled, all have a max marker error around 10cm, however, when I overlay the virtual and experimental markers in the visualizer window the markers are a good match (screenshot below). I think this may be a unit problem, but both the .osim file and .trc files specify the units as meters (sample files attached). Is there some other place units are specified, or something else I missed that would explain such a high marker error compared to what I am seeing visually? If not, which should I believe, the visual or the max marker error output in the messages pane?
- Overlaid markers
- Scaling_Shank_MarkerError.PNG (295.65 KiB) Viewed 258 times
(2) During scaling, regardless of the max marker error value, sometimes the identified marker doesn't seem to be the "poorest" match. For instance, if the messages pane identifies a left shank marker as having the max marker error, when I overlay the virtual and experimental markers and look at the whole model, the right shoulder markers look to have a greater offset. Similar to my first question, which should I trust, the output in the messages pane, or what I'm seeing in the visualizer window?
Any insight/suggestions into these discrepancies and how to proceed would be immensely appreciated! Thank you in advance for all the help!