Users Manual

After a number of tag detection runs, previously detected tag instances will be discarded if they are not detected
in the meantime. This can be configured by the parameter forget
_
after
_
n
_
detections.
7.3.5 Interfaces
There are two separate components for tag detection of the sensor, one for detecting AprilTags and one for QR
codes, named rc
_
april
_
tag
_
detect and rc
_
qr
_
code
_
detect, respectively. Apart from the component names
they share the same interface definition.
In addition to the REST-API, the TagDetect components provide tabs on the Web GUI, on which they can be tried
out and configured manually.
Parameters and status values
In the following, the parameters and status values are listed based on the example of rc
_
qr
_
code
_
detect. They
are the same for rc
_
april
_
tag
_
detect.
This component offers the following run-time parameters.
Table 7.3.6: The rc
_
qr
_
code
_
detect component’s run-time parameters
Name Type Min Max Default Description
detect
_
inverted
_
tags bool False True False Detect tags with black and
white exchanged
forget
_
after
_
n
_
detections int32 1 1000 30 Number of detection runs
after which to forget about a
previous tag during tag
re-identification
max
_
corner
_
distance float64 0.001 0.01 0.005 Maximum distance of
corresponding tag corners in
meters during tag
re-identification
quality string - - H Quality of tag detection (H,
M or L)
use
_
cached
_
images bool False True False Use most recently received
image pair instead of waiting
for a new pair
This component reports the following status values.
Table 7.3.7: The rc
_
qr
_
code
_
detect component’s status values
Name Description
state The current state of the node
The reported state can take one of the following values.
Table 7.3.8: Possible states of the TagDetect components
State name Description
IDLE The component is idle.
RUNNING The component is running and ready for tag detection.
FATAL A fatal error has occurred.
Services
The TagDetect components implement a state machine for starting and stopping. The actual tag detection can be
triggered via detect.
7.3. TagDetect 80