readFrame
Read Velodyne point cloud from file
Syntax
Description
reads the next point cloud in sequence from the Velodyne® PCAP file and returns a ptCloud
= readFrame(veloReader
)pointCloud
object.
reads the point cloud with the specific frame number from the file.ptCloud
= readFrame(veloReader
,frameNumber
)
reads the first point cloud recorded at or after the given
ptCloud
= readFrame(veloReader
,frameTime
)frameTime
.
[
returns the timestamps for all points in the point cloud using any combination of
input arguments from previous syntaxes.ptCloud
,pointTimestamps
] = readFrame(___)
[
returns the positional information for each point cloud frame.ptCloud
,pointTimestamps
,positionData
] = readFrame(___)
Examples
Read Point Cloud from File Using Time Duration
Create a velodyneFileReader
object to read a Velodyne® packet capture (PCAP) file and select specific point clouds using a duration
scalar.
Read in point clouds by using a Velodyne® file reader. Specify the PCAP file to read and the Velodyne® device model.
veloReader = velodyneFileReader('lidarData_ConstructionRoad.pcap','HDL32E');
Create a duration
scalar that represents one second after the first point cloud reading.
timeDuration = veloReader.StartTime + duration(0,0,1,Format='s');
Read the first point cloud recorded at or after the given time duration.
ptCloudObj = readFrame(veloReader,timeDuration);
Display the point cloud using pcshow
.
figure pcshow(ptCloudObj)
Input Arguments
veloReader
— Velodyne file reader
velodyneFileReader
object
Velodyne file reader, specified as a
velodyneFileReader
object.
frameNumber
— Frame number of desired point cloud in the file
positive integer
Frame number of the desired point cloud in file, specified as a positive integer. Frame numbers are sequential.
frameTime
— Frame time of desired point cloud in file
duration
scalar
Frame time of the desired point cloud in the file, specified as a duration
scalar in seconds.
The first frame available at or after frameTime
is
given.
Output Arguments
ptCloud
— Point cloud
pointCloud
object
Point cloud, returned as a pointCloud
object.
pointTimestamps
— Timestamps for all points in point cloud
duration
vector | duration
matrix
Timestamps for all points in the point cloud, returned as a duration
vector or a matrix.
The function returns timestamps as:
An M-element vector for unorganized point clouds. M is the total number of points in the point cloud.
An M-by-N matrix for organized point clouds. M and N are the number of rows and columns in the organized point cloud, respectively.
Timestamps are between the values of StartTime
and
EndTime
, which are properties of the velodyneFileReader
object. Points in an organized point cloud
with a NaN
value is returned with a time stamp set to
NaN
.
positionData
— Position data
structure
Position data, returned as a structure with five fields:
Field | Description |
---|---|
GPSReadings | GPS reading data, returned as an
M-by-4 matrix of data type
If the GPS hardware is not connected,
then the function returns |
GyroscopeReadings | Raw gyroscopic rotation readings in radians per
second, collected from the three internal gyroscopes in
GPS hardware, returned as an M-by-3
matrix of data type
If the Velodyne device model is not
HDL-32E, then the function returns
|
AccelerometerReadings | Raw accelerometer readings, in
m/s2, collected from the
three internal accelerometers in GPS hardware, returned
as an M-by-6 matrix of data type
If the Velodyne device model is not
HDL-32E, then the function returns
|
PositionTimestamps | Timestamp for each position reading, returned as an
M-by-1 duration vector. |
GPSTimes | Time of the GPS in UTC, returned as an
M-by-1 duration
vector, used to synchronize the timestamps of the GPS
coordinates with their respective point clouds. |
positionData
returns []
when there
is no position data in the PCAP file.
References
[1] Velodyne LiDAR, Inc. "HDL-32E User Manual." 63-9113 Rev. M, 2018.
Version History
Introduced in R2018aR2023a: Returns positional information for each point cloud frame
The readFrame
function can return the raw position readings
of point cloud data for each frame as a structure with fields for the GPS locations,
gyroscope readings, accelerometer readings, position reading timestamps, and GPS
reading timestamps.
R2022b: Returns timestamps for all points in point cloud
The readFrame
function additionally returns the timestamps
for all the points in the point cloud as a duration
vector or matrix.
See Also
Functions
Objects
External Websites
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