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Trying to map a quite big open space but some values returned from the node is 'nan' which i suspect are areas which has no obstacle or whatsoever at max distance. How can i turn this 'nan' into a defined value so gmapping can mark it as free space?
Are you using the urg_node or the hokuyo_node? The lasers send error codes telling what types of erroneous readings they are getting. The urg_node turns all error readings into NaN, but the hokuyo_node turns errors that are reported as "outside of max distance" into INF. Check out this chunk of code from the hokuyo_node to see where they are setting INF values. Having INF values will allow you to specifically know that there are no objects in range, then you could use a LaserScanRangeFilter to move all INF values to a max_range+1 value. Then you can use ~maxRange and ~maxUrange params in gmapping to properly handle these readings.
In summary, I've had much better luck with hokuyo_node than urg_node for specifically the reason you are describing.
played with the filters. amazing. it's working now. thank you very much.
edit: i was using the urg_node before. going to use hokuyo_node from now on since it can support the old uhg-08lx
jarvisschultz' answer above is right, but for those who want an example, a starting point for me was changing from this
<launch>
<node name="pioneer_driver" pkg="p2os_driver" type="p2os_driver">
</node>
<node name="hokuyo_node" pkg="hokuyo_node" type="hokuyo_node">
</node>
<node pkg="tf" type="static_transform_publisher" name="laser_broadcaster" args="0.1 0 0.1397 0 0 0 1 base_link laser 100" />
<node pkg="tf" type="static_transform_publisher" name="camera_broadcaster" args="0.1 0 0.1397 0 0 0 1 base_link camera_link 100" />
</launch>
to this
<launch>
<node name="pioneer_driver" pkg="p2os_driver" type="p2os_driver">
</node>
<node name="hokuyo_node" pkg="hokuyo_node" type="hokuyo_node">
</node>
<node pkg="laser_filters" type="scan_to_scan_filter_chain" name="laser_filter">
<rosparam command="load" file="[path]/hokuyo_config.yaml" />
<remap from="base_scan" to="scan" />
</node>
<node pkg="tf" type="static_transform_publisher" name="laser_broadcaster" args="0.1 0 0.1397 0 0 0 1 base_link laser 100" />
<node pkg="tf" type="static_transform_publisher" name="camera_broadcaster" args="0.1 0 0.1397 0 0 0 1 base_link camera_link 100" />
</launch>
with [path]/hokuyo_config.yaml like;
scan_filter_chain:
- name: range
type: LaserScanRangeFilter
params:
lower_threshold: 0.2
upper_threshold: .inf
See http://answers.ros.org/question/20901... and http://answers.ros.org/question/20899... .
Asked: 2015-01-09 03:38:49 -0500
Seen: 2,488 times
Last updated: Jun 01 '17
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