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April-Tags and QR-Codes detection

Description: This tutorial shows how to use the April-Tag and QR-Code detection modules of the rc_visard.

Keywords: rc_visard, tagdetect, rosservice, web GUI

Tutorial Level: BEGINNER


The goal of this tutorial is to show how to trigger the detection of April-Tags and QR-Codes through rosservice calls and the Web GUI of the rc_visard.

Before we start

In order to go through this tutorial, the following prerequisites should be met:


The rc_visard’s image version is at least 1.5 and the rc_visard’s license includes the TagDetect module to be used (April-Tag or QR-Code). This can be verified on the web GUI’s system panel. The GUI can be accessed using rcdiscover.


Install the TagDetect client:

$ sudo apt-get install ros-melodic-rc-tagdetect-client

Setting up the scene

To verify the maximum distance from which a tag can be detected, go to the Tag reading section of the rc_visard's documentation.

Detection by the Web Gui

For trying out the tag detection from the web GUI, simply go to the correspondent TagDetect module page on the Modules Tab. There you can find the interface where you can optionally add the tag family and run the detection by clicking on "Detect" in the section Try Out.


Detection by rosservice call

In order to use rosservices for tag detection, the tag detection client has to be running and then a call to the corresponding rosservice has to be made. This can be done by using the following commands:

The parameter needed is either the device's id or its IP address. For illustration purposes, both are being displayed.

The device id can be either the rc_visard's serial number or its user defined name.

For QR-Code detection:

$ rosrun rc_tagdetect_client rc_qr_node _device:=<device id>

$ rosservice call /rc_qr_code_detect/detect "tags: []"

For April-Tag detection:

$ rosrun rc_tagdetect_client rc_april_node _device:=<device id>

$ rosservice call /rc_april_tag_detect/detect "tags: []"

Wiki: rc_visard/Tutorials/TagDetect Module (last edited 2019-07-23 10:02:45 by FelixRuess)