Documentation of the T365 specific options

Author: radfordi

doc/t265.md

@@ -117,6 +117,14 @@ Yes, T265 can work both indoors and outdoors. Just like a person, it can be blin
 
 No, you can use as many T265 devices in a space as you like.
 
+### Are there any T265 specific options?
+
+Yes, there are.
+
+ - `RS2_OPTION_ENABLE_MAPPING`  - The internal map allows the device to recognize places it's been before so that it can give a consistent pose for that location.   The map has a fixed finite size and will keep the most often/recently seen locations.  Without this it will be operating completely open loop (i.e. just doing VIO) and will have more drift.   The device will use the map to close modest loops and recover from small drifts.  Enabling this option will not cause pose jumps without `RS2_OPTION_ENABLE_POSE_JUMPING`.
+ - `RS2_OPTION_ENABLE_POSE_JUMPING` - This option allows the device to discontinuously jump its pose whenever it discovers its pose is inconsistent with one it has given before.   For example, after walking in a circle or covering the camera (getting a small drift) and uncovering it.  Currently this will only affect the translation and not the rotation nor any of the velocities or accelerations.
+ - `RS2_OPTION_ENABLE_RELOCALIZATION` - This allows the device to solve the Kidnapped Robot Problem, i.e. it will allow connecting the current map to a loaded map or connecting the current map to itself after accumulating a large drift, say after closing a large loop or covering the camera and walking around.  This is independent of jumping the pose.  When fooled this feature can lead to much larger errors than are likely via the basic mapping.
+
 ## Appendix
 
 ### Wheel odometry calibration file format