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Overview / Example Scene

RGB

Here is the scene in which the following screenshots were captured.

DepthImage

Note the sensor_msgs/LaserScan overlayed in color on the sensor_msgs/Image. Red is close to camera, purple is far from camera.

LaserScan

sensor_msgs/LaserScan projected on top of the sensor_msgs/PointCloud2.

Top Down LaserScan

Top down view of the sensor_msgs/LaserScan.

Node

depthimage_to_laserscan

depthimage_to_laserscan takes a depth image (float encoded meters or preferably uint16 encoded millimeters for OpenNI devices) and generates a 2D laser scan based on the provided parameters. depthimage_to_laserscan uses lazy subscribing and will not subscribe to image or camera_info until there is a subscriber for scan.

Subscribed Topics

image (sensor_msgs/Image)

• The input image that must conform to REP 118. This can be floating point or raw uint16 format. For OpenNI devices, uint16 is the native representation and will be more efficient for processing. This is typically /camera/depth/image_raw. If your image is distorted, this topic should be remapped to image_rect. OpenNI cameras typically have little distortion and rectification can be skipped for this application.

camera_info (sensor_msgs/CameraInfo)

• Camera info for the associated image. Does not usually need to be remampped as camera_info will be subscribed to from the same namespace as image.

Published Topics

scan (sensor_msgs/LaserScan)

• The output laser scan. Follows REP 117, and will output range arrays that contain NaNs and +-Infs.

Parameters

~scan_height (int, default: 1 pixel)

• The number of pixel rows to use to generate the laserscan. For each column, the scan will return the minimum value for those pixels centered vertically in the image.

~scan_time (double, default: 1/30.0Hz (0.033s))

• Time between scans (seconds). Typically, 1.0/frame_rate. This value is not easily calculated from consecutive messages, and is thus left to the user to set correctly.

~range_min (double, default: 0.45m)

• The minimum ranges to return in meters. Ranges less than this will be output as -Inf.

~range_max (double, default: 10.0m)

• The maximum ranges to return in meters. Ranges greater than this will be output as +Inf.

~output_frame_id (str, default: camera_depth_frame)

• The frame id of the laser scan. For point clouds coming from an "optical" frame with Z forward, this value should be set to the corresponding frame with X forward and Z up.

Nodelet

Same usage as the Node.

Available as:

depthimage_to_laserscan/DepthImageToLaserScanNodelet

Installation

https://github.com/ros-perception/depthimage_to_laserscan