update speed estimation docs

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Josh Hawkins 2025-05-14 14:08:25 -05:00
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@ -165,7 +165,7 @@ These speed values are output as a number in miles per hour (mph) or kilometers
#### Best practices and caveats
- Speed estimation works best with a straight road or path when your object travels in a straight line across that path. Avoid creating your zone near intersections or anywhere that objects would make a turn. If the bounding box changes shape (either because the object made a turn or became partially obscured, for example), speed estimation will not be accurate.
- Speed estimation works best with a straight road or path when your object travels in a straight line across that path. Avoid creating your zone near intersections or anywhere that objects would make a turn. A large zone can be used, but it's not required and may even cause issues - if the object's bounding box changes shape (such as when it turns or becomes partially hidden), the speed estimate will be inaccurate.
- Create a zone where the bottom center of your object's bounding box travels directly through it and does not become obscured at any time. See the photo example above.
- Depending on the size and location of your zone, you may want to decrease the zone's `inertia` value from the default of 3.
- The more accurate your real-world dimensions can be measured, the more accurate speed estimation will be. However, due to the way Frigate's tracking algorithm works, you may need to tweak the real-world distance values so that estimated speeds better match real-world speeds.