updated readme with ov_secondary links

Author: rpng-guest

ReadMe.md

@@ -19,6 +19,7 @@ Please take a look at the feature list below for full details on what the system
 
 ## News / Events
 
+* **May 18, 2020** - Released secondary pose graph example repository [ov_secondary](https://github.com/rpng/ov_secondary) based on [VINS-Fusion](https://github.com/HKUST-Aerial-Robotics/VINS-Fusion). OpenVINS now publishes marginalized feature track, feature 3d position, and first camera intrinsics and extrinsics. See [PR#66](https://github.com/rpng/open_vins/pull/66) for details and discussion.
 * **April 3, 2020** - Released [v2.0](https://github.com/rpng/open_vins/releases/tag/v2.0) update to the codebase with some key refactoring, ros-free building, improved dataset support, and single inverse depth feature representation. Please check out the [release page](https://github.com/rpng/open_vins/releases/tag/v2.0) for details.
 * **January 21, 2020** - Our paper has been accepted for presentation in [ICRA 2020](https://www.icra2020.org/). We look forward to seeing everybody there! We have also added links to a few videos of the system running on different datasets.
 * **October 23, 2019** - OpenVINS placed first in the [IROS 2019 FPV Drone Racing VIO Competition
@@ -63,9 +64,27 @@ Please take a look at the feature list below for full details on what the system
 * Out of the box evaluation on EurocMav and TUM-VI datasets
 * Extensive evaluation suite (ATE, RPE, NEES, RMSE, etc..)
 
-## Demo Videos
 
 
+## Codebase Extensions
+
+* **[ov_secondary](https://github.com/rpng/ov_secondary)** -
+This is an example secondary thread which provides loop closure in a loosely coupled manner for [OpenVINS](https://github.com/rpng/open_vins).
+This is a modification of the code originally developed by the HKUST aerial robotics group and can be found in their [VINS-Fusion](https://github.com/HKUST-Aerial-Robotics/VINS-Fusion) repository.
+Here we stress that this is a loosely coupled method, thus no information is returned to the estimator to improve the underlying OpenVINS odometry.
+This codebase has been modified in a few key areas including: exposing more loop closure parameters, subscribing to camera intrinsics, simplifying configuration such that only topics need to be supplied, and some tweaks to the loop closure detection to improve frequency.
+
+* **[ov_maplab](https://github.com/rpng/ov_maplab)** - 
+This codebase contains the interface wrapper for exporting visual-inertial runs from [OpenVINS](https://github.com/rpng/open_vins) into the ViMap structure taken by [maplab](https://github.com/ethz-asl/maplab).
+The state estimates and raw images are appended to the ViMap as OpenVINS runs through a dataset.
+After completion of the dataset, features are re-extract and triangulate with maplab's feature system.
+This can be used to merge multi-session maps, or to perform a batch optimization after first running the data through OpenVINS.
+Some example have been provided along with a helper script to export trajectories into the standard groundtruth format.
+
+
+
+## Demo Videos
+
 [![](docs/youtube/KCX51GvYGss.jpg)](http://www.youtube.com/watch?v=KCX51GvYGss "OpenVINS - EuRoC MAV Vicon Rooms Flyby")
 [![](docs/youtube/Lc7VQHngSuQ.jpg)](http://www.youtube.com/watch?v=Lc7VQHngSuQ "OpenVINS - TUM VI Datasets Flyby")
 [![](docs/youtube/vaia7iPaRW8.jpg)](http://www.youtube.com/watch?v=vaia7iPaRW8 "OpenVINS - UZH-FPV Drone Racing Dataset Flyby")
@@ -76,6 +95,7 @@ Please take a look at the feature list below for full details on what the system
 [![](docs/youtube/ExPIGwORm4E.jpg)](http://www.youtube.com/watch?v=ExPIGwORm4E "OpenVINS - UZH-FPV Drone Racing Dataset Demonstration")
 
 
+
 ## Credit / Licensing
 
 This code was written by the [Robot Perception and Navigation Group (RPNG)](https://sites.udel.edu/robot/) at the University of Delaware.

ov_msckf/launch/pgeneva_ros_tum.launch

@@ -4,11 +4,11 @@
     <arg name="max_cameras" default="2" />
     <arg name="use_stereo"  default="true" />
     <arg name="bag_start"   default="0" />
-    <arg name="bag"         default="/home/patrick/datasets/tum/dataset-room2_512_16.bag" />
+    <arg name="bag"         default="/home/patrick/datasets/tum/dataset-room1_512_16.bag" />
 
     <!-- imu starting thresholds -->
     <arg name="init_window_time"  default="1.0" />
-    <arg name="init_imu_thresh"   default="0.75" />
+    <arg name="init_imu_thresh"   default="0.70" /> <!-- room1:0.70, room2:0.75, room3:0.70 -->
 
     <!-- saving trajectory path and timing information -->
     <arg name="dosave"      default="false" />

ov_msckf/launch/pgeneva_serial_tum.launch

@@ -32,7 +32,7 @@
         <param name="max_cameras"            type="int"    value="2" />
         <param name="dt_slam_delay"          type="double" value="3" />
         <param name="init_window_time"       type="double" value="1.0" />
-        <param name="init_imu_thresh"        type="double" value="0.8" />
+        <param name="init_imu_thresh"        type="double" value="0.70" /> <!-- room1:0.70, room2:0.75, room3:0.70 -->
         <rosparam param="gravity">[0.0,0.0,9.80766]</rosparam>
         <param name="feat_rep_msckf"         type="string" value="GLOBAL_3D" />
         <param name="feat_rep_slam"          type="string" value="ANCHORED_FULL_INVERSE_DEPTH" />