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TagSLAM

Getting Started

Installation

TagSLAM has been tested on Ubuntu 16.04 and 18.04LTS. You will need a full ROS installation (Kinetic or Melodic). For installation instructions see the tagslam root repository.

Example

In the example folder of the tagslam repository you can find a simple example for a monucular camera setup. Here’s how to run it.

Running the example directly from the bag

The example bag file already contains the extracted tags, so you can directly feed the bag into tagslam. You need to set use_sim_time to true so tagslam can drive the clock.

rosparam set use_sim_time true
rviz -d `rospack find tagslam`/example/tagslam_example.rviz &
roslaunch tagslam tagslam.launch bag:=`rospack find tagslam`/example/example.bag

Rviz should show you a tag/camera configuration like the one on the image below, but without the camera image.

The program will complete too quickly to observe it in rviz, but you can ask tagslam to replay the sequence with a ROS service call (tagslam must still be running at that point):

rosservice call /tagslam/replay

Running the example in online mode

Run these three commands, each in a separate terminal when required

rosparam set use_sim_time true
roslaunch tagslam tagslam.launch run_online:=true
roslaunch tagslam apriltag_detector_node.launch
rviz -d `rospack find tagslam`/example/tagslam_example.rviz &
rosbag play --clock `rospack find tagslam`/example/example.bag --topics /pg_17274483/image_raw/compressed

If all goes well, your rviz window should look like this:

rviz online

Extracting tags from images in a bag

Unless you must run online, it is best to run the tag detector on the whole bag first, and then directly feed the detections into tagslam. The tagslam workspace contains sync_and_detect, a tool to extract tags and write them to a new bag. At the same time, it also synchronizes the detections that come from multiple cameras, i.e it filters frames that don’t have images from all configured cameras.

Here is an example of how to run it on the example bag:

roslaunch tagslam sync_and_detect.launch bag:=`rospack find tagslam`/example/example.bag

This will produce a bag in the example directory:

example.bag_output.bag

Under the topic /detector/tags the bag has the tag detections, so it can be used to directly drive tagslam. Besides that there is the topic /annotated_images/compressed which has the tags highlighted in the original image.

More examples

Many more examples can be found in the tagslam test repository.