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2016-04-11 17:19:23 -0500 commented answer Combine position estimates from Lidar SLAM and PTAM

Okay great there's lots to think about in there, thanks. I had heard of the pub_odometry parameter but not looked into it so will give that a look. Also just looked at the robot_localization package and it looks good. Cheers!

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2016-04-10 18:17:08 -0500 commented question Combine position estimates from Lidar SLAM and PTAM

hector_slam is building up a map as it goes along and giving out that map and a pose estimate. The PTAM slam is working out increments I think as it gets its key points when it starts up and then goes from there, (it also uses control inputs for the drone for the pose estimate)

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2016-04-10 15:20:37 -0500 asked a question Combine position estimates from Lidar SLAM and PTAM

Hi all,

I have an AR drone with a Lidar attached. I have hector_slam running giving out a position estimate for the drone which is working fine. I also have a PTAM node running which is also spitting out a position estimate.

What is the best way to combine these position estimates to give a best guess for the location of the drone?

2016-04-09 05:03:04 -0500 commented answer Hector mapping not creating map

Ah nice, thanks

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2016-04-08 05:41:48 -0500 commented question Hector mapping not creating map

I've added it, but says I need >10 points to accept my own answer

2016-04-08 05:40:46 -0500 answered a question Hector mapping not creating map

Turns out the drivers I was using on the AR drone were giving out millimetres instead of the meters that LaserScan is expecting. After dividing the output by 1000, I get a map and pose as expected. Thank you to DavidN for pointing it out

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2016-04-07 15:41:01 -0500 commented question Hector mapping not creating map

Don't know how to mark this as answered either as these are only comments to the original question

2016-04-07 15:39:28 -0500 commented question Hector mapping not creating map

Yes that was it! The numbers were in millimetres instead of meters. Thanks for the pointer

2016-04-07 09:21:29 -0500 commented question Hector mapping not creating map

I cannot visualise with rviz, it counts up the messages coming in so is definitely receiving them. Very true, when I run it with the actual drivers all the numbers are much smaller. I will check the code and post back

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2016-04-06 03:06:06 -0500 commented question Hector mapping not creating map

Knew I'd forgotten something! Added launch file and he publishing node

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2016-04-05 16:04:06 -0500 asked a question Hector mapping not creating map


I have a LIDAR connected to an AR drone, with drivers running on the drone to read the laser data, and send it to my ros master computer using netcat. I have written a ros driver in python that listens to the network and reads the incoming laser data, creates a LaserScan message, populates all the fields and then publishes this to /scan.

I can see /scan in rostopic list, and can see populated messages in rostopic echo /scan. However when I run my launch file which runs hector_mapping, no map is created. I know the launch file works as I have tested it with the LIDAR connected directly to the master computer using the official drivers and it builds a map fine.

So I think there must be a problem when I populate the LaserScan message and publish it. I have included one of my populated messages below, can anyone see anything wrong with it or suggest something else which I can try? I have noticed the seq fields in the header are always 0 but have read I shouldn't set that myself and leave ros to deal with it.

Node: /laserlistener
Time: 21:56:49.521363019 (2016-04-05)
Severity: Info
Published Topics: /rosout, /scan

  seq: 0
    secs: 1459889809
    nsecs: 520699977
  frame_id: laser
angle_min: 3.14159265359
angle_max: -3.14159265359
angle_increment: 0.0174532925199
time_increment: 0.000515921866295
scan_time: 0.18521595
range_min: 0.15
range_max: 6
ranges: [0.0, 0.0, 1274.25,  ... ] omitted as lots of numbers, all look correct though
intensities: [ ... ] ditto

The angle_min and angle_max fields are meant to be like that (at least that is what the official driver spits out) I have also tried 0 to 2*pi

Launch file:

<node pkg="tf" type="static_transform_publisher" name="map2odom" args="0 0 0 0 0 0 map odom 100" />

<node pkg="tf" type="static_transform_publisher" name="odom2base_frame" args="0 0 0 0 0 0 odom base_frame 100" />

<node pkg="tf" type="static_transform_publisher" name="base_frame2base_footprint" args="0 0 0 0 0 0 base_frame base_footprint 100" />

<node pkg="tf" type="static_transform_publisher" name="base_footprint2base_stabalized" args="0 0 0 0 0 0 base_footprint base_stabalized 100" />

<node pkg="tf" type="static_transform_publisher" name="base_stabalized2base_link" args="0 0 0 0 0 0 base_stabalized base_link 100" />

<node pkg="tf" type="static_transform_publisher" name="base_link2laser" args="0 0 0 0 0 0 base_link laser 100" />

<node pkg="tf" type="static_transform_publisher" name="map2scanmatcher_frame" args="0 0 0 0 0 0 map scanmatcher_frame 100" />

<include file="$(find hector_slam_launch)/launch/tutorial.launch"/>

<param name="use_sim_time" value="false" />

<param name="hector_mapping/pub_map_odom_transform" value="false"/>

<!-- Map size / start point -->
<param name="hector_mapping/map_resolution" value="0.050"/>
<param name="hector_mapping/map_size" value="2048"/>
<param name="hector_mapping/map_start_x" value="0.5"/>
<param name="hector_mapping/map_start_y" value="0.5" />
<param name="hector_mapping/map_multi_res_levels" value="5" />

<!-- Map update parameters -->
<param name="hector_mapping/update_factor_free" value="0.4"/>
<param name="hector_mapping/update_factor_occupied" value="0.9" />    
<param name="hector_mapping/map_update_distance_thresh" value="0.01"/>
<param name="hector_mapping/map_update_angle_thresh" value="0.06" />
<param name="hector_mapping/laser_z_min_value" value = "-1.0" />
<param ...
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2016-03-16 16:00:53 -0500 commented answer Convert network Lidar data to LaserScan

Is there a way to listen to stdin in ROS or somehow otherwise pipe into a node, so that I can let netcat deal with receiving the data and just let the node convert it into the LaserScan format?

2016-03-16 14:41:04 -0500 commented answer Convert network Lidar data to LaserScan

Great, thanks for the info. Will give that a read

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2016-03-15 12:54:14 -0500 asked a question Convert network Lidar data to LaserScan

Hi there!

I am trying to stream data back from my Parrot AR Drone 2.0, which has a LIDAR attached, to my PC (which has ROS running) in order to run Hector Slam.

I currently have code running on the quad which is reading the Lidar (connected to the USB port on the quad) data and streaming this to my PC using netcat. This is all working well and I can see the data coming in on my desktop. I now need a way to listen to this data and convert it into the LaserScan messages that Hector Slam uses.

I am very new to ROS and although have learnt a lot already, I do not know how to do this and can't seem to find any similar posts made here. I may well just be searching for the wrong things but any help would be greatly appreciated!

Cheers, Andy

PC - Ubuntu 14.04 AR Drone - BusyBox I think