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Plot scans and robot poses

Since R2019b



show(slamObj) plots all the scans added to the input lidarSLAM object overlaid with the lidar poses in its underlying pose graph.

show(slamObj,Name,Value) specifies options using Name,Value pair arguments. For example, "Poses","off" turns off display of the underlying pose graph in slamObj.

axes = show(___) returns the axes handle that the lidar SLAM data is plotted to using any of the previous syntaxes.


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Use a lidarSLAM object to iteratively add and compare lidar scans and build an optimized pose graph of the robot trajectory. To get an occupancy map from the associated poses and scans, use the buildMap function.

Load Data and Set Up SLAM Algorithm

Load a cell array of lidarScan objects. The lidar scans were collected in a parking garage on a Husky® robot from ClearPath Robotics®. Typically, lidar scans are taken at a high frequency and each scan is not needed for SLAM. Therefore, down sample the scans by selecting only every 40th scan.

load garage_fl1_southend.mat scans
scans = scans(1:40:end);

To set up the SLAM algorithm, specify the lidar range, map resolution, loop closure threshold, and search radius. Tune these parameters for your specific robot and environment. Create the lidarSLAM object with these parameters.

maxRange = 19.2; % meters
resolution = 10; % cells per meter

slamObj = lidarSLAM(resolution,maxRange);
slamObj.LoopClosureThreshold = 360;
slamObj.LoopClosureSearchRadius = 8;

Add Scans Iteratively

Using a for loop, add scans to the SLAM object. The object uses scan matching to compare each added scan to previously added ones. To improve the map, the object optimizes the pose graph whenever it detects a loop closure. Every 10 scans, display the stored poses and scans.

for i = 1:numel(scans)

    if rem(i,10) == 0

View Occupancy Map

After adding all the scans to the SLAM object, build an occupancyMap map by calling buildMap with the scans and poses. Use the same map resolution and max range you used with the SLAM object.

[scansSLAM,poses] = scansAndPoses(slamObj);
occMap = buildMap(scansSLAM,poses,resolution,maxRange);
title('Occupancy Map of Garage')

Input Arguments

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Lidar SLAM object, specified as a lidarSLAM object. The object contains the SLAM algorithm parameters, sensor data, and underlying pose graph used to build the map.

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: "Poses","off"

Axes used to plot the pose graph, specified as the comma-separated pair consisting of "Parent" and either an Axes or UIAxes object. See axes or uiaxes.

Display lidar poses, specified as the comma-separated pair consisting of "Poses" and "on" or "off".

Output Arguments

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Axes used to plot the map, returned as either an Axes or UIAxes object. See axes or uiaxes.

Version History

Introduced in R2019b