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pcmapndt

Localization map based on normal distributions transform (NDT)

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    Description

    Thepcmapndtobject creates a normal distributions transform (NDT) map from a prebuilt point cloud map of the environment. The NDT map is a compressed, memory-efficient representation suitable for localization. The object converts the point cloud map into a set of voxels (3-D boxes), each represented by a 3-D normal distribution. Use theselectSubmapobject function to select a submap within the map from a coarse position estimate. Use thefindPoseobject function to localize the pose of the sensor based on the assembled map.

    Creation

    Syntax

    ndtMap = pcmapndt(ptCloudMap,voxelSize)

    Description

    example

    ndtMap= pcmapndt(ptCloudMap,voxelSize)returns an NDT map from a point cloud map,ptCloudMap.

    Properties

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    This property is read-only.

    Currently selected submap, specified as a 6-element vector of the form [xmin,xmaxyminymaxzminzmax] that describes the range of the submap along each axis. The elements of the vector describe the region of interest represented by the submap.

    This property is read-only.

    Size of the voxels, specified as a scalar value in world units.

    This property is read-only.

    Range of the map along thex-axis, specified as a 2-element vector of the form [xminxmax] .

    This property is read-only.

    Range of the map along theY-axis, specified as a 2-element vector of the form [yminymax] .

    This property is read-only.

    Range of the map along thez-axis, specified as a 2-element vector of the form [zminzmax] .

    This property is read-only.

    Mean value of each voxel, specified as anM3矩阵. Each row of the matrix contains the [xyz] values for a voxel.Mis the number of voxels.

    This property is read-only.

    Covariance of each voxel, specified as a 3-by-3-by-Marray forMvoxels.

    This property is read-only.

    Number of points in each voxel, specified as anM1的向量forMvoxels.

    Object Functions

    selectSubmap Select submap within map
    isInsideSubmap Check if query position is inside selected submap
    findPose Localize a point cloud within a map using the normal distributions transform (NDT) algorithm
    show Visualize normal distributions transform (NDT) map

    Examples

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    Open Live Script

    Load a point cloud view set, which was saved from apcviewsetobject.

    data = load('vSetPointClouds.mat'); vSet = data.vSet;

    Extract point clouds and absolute poses to build a map.

    ptClouds = vSet.Views.PointCloud; tforms = vSet.Views.AbsolutePose;

    Create a point cloud map by aligning the point cloud scans using the absolute poses.

    ptCloudMap = pcalign(ptClouds,tforms);

    Create and visualize an NDT map from a point cloud map.

    voxelSize = 1; ndtMap = pcmapndt(ptCloudMap,voxelSize); figure show(ndtMap) view(2)% Change viewing angle to top-view

    Figure contains an axes object. The axes object contains an object of type scatter.

    Open Live Script

    Load a normal distributions transform (NDT) map from a MAT file.

    data = load('ndtMapParkingLot.mat'); ndtMap = data.ndtMapParkingLot;

    Load point cloud scans and pose estimates from a second MAT file.

    data = load('parkingLotData.mat'); ptCloudScans = data.parkingLotData.ptCloudScans; initPoseEsts = data.parkingLotData.initPoseEsts;

    Display the NDT map.

    show(ndtMap)

    Change the viewing angle to top-view.

    view(2)

    Select the submap centered around the first estimate.

    center = initPoseEsts(1).Translation; sz = [70 50 20]; ndtMap = selectSubmap(ndtMap,center,sz);

    Set the radius for visualization of the current location and the distance threshold to update the submap.

    radius = 0.5; distThresh = 15;

    Loop over the point clouds, localize them in the map, and update the selected submap as needed.

    numScans = numel(ptCloudScans);forn = 1: numScans ptCloud = ptCloudScans (n);initPose= initPoseEsts(n); poseTranslation = initPose.Translation; [isInside,distToEdge] = isInsideSubmap(ndtMap,poseTranslation); submapNeedsUpdate = ~isInside...% Current pose is outside submap|| any(distToEdge(1:2) < distThresh);% Current pose is close to submap edgeifsubmapNeedsUpdate ndtMap = selectSubmap(ndtMap,poseTranslation,sz);end% Localize the point cloud scan in the map.currPose = findPose(ndtMap,ptCloud,initPose);% Display the position of the estimate as a circle.pos = [currPose.Translation(1:2) radius]; showShape('circle',pos,'Color','r');% Pause to view the change.pause(0.05)end

    Figure contains an axes object. The axes object contains an object of type scatter.

    References

    Biber, P., and W. Strasser. “The Normal Distributions Transform: A New Approach to Laser Scan Matching.” InProceedings 2003 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2003) (Cat. No.03CH37453)Vol. 3, 2743–48. Las Vegas, Nevada, USA: IEEE, 2003. https://doi.org/10.1109/IROS.2003.1249285.

    [1] Magnusson, Martin. "The Three-Dimensional Normal-Distributions Transform: An Efficient Representation forRegistration, Surface Analysis, and Loop Detection." PhD thesis, Örebro universitet, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-8458 urn:nbn:se:oru:diva-8458.

    Extended Capabilities

    C/C++ Code Generation
    Generate C and C++ code using MATLAB® Coder™.

    Version History

    Introduced in R2021a

    See Also

    Functions