# Dimensions

PDAL dimensions describe the combination of data’s type, size, and meaning. The following table provides a list of known dimension names you can use in Filters, Writers, and Readers descriptions.

Name | Type | Description
--- | --- | ---
Alpha | uint16 | Alpha
Amplitude | float | This is the ratio of the received power to the power received at the detection limit expressed in dB
Azimuth | double | Scanner azimuth
BackgroundRadiation | float | A measure of background radiation.
Blue | uint16 | Blue image channel value
ClassFlags | uint8 | Class Flags
Classification | uint8 | ASPRS classification. 0 for no classification. See LAS specification for details.
Curvature | double | Curvature of surface at this point
Density | double | Estimate of point density
Deviation | float | A larger value for deviation indicates larger distortion.
EchoRange | double | Echo Range
EdgeOfFlightLine | uint8 | Indicates the end of scanline before a direction change with a value of 1 - 0 otherwise
ElevationCentroid | double | Elevation Centroid
ElevationHigh | double | Elevation High
ElevationLow | double | Elevation Low
Flag | uint8 | Flag
GpsTime | double | GPS time that the point was acquired
Green | uint16 | Green image channel value
HeightAboveGround | double | Height Above Ground
Infrared | uint16 | Infrared
Intensity | uint16 | Representation of the pulse return magnitude
InternalTime | double | Scanner’s internal time when the point was acquired, in seconds
IsPpsLocked | uint8 | The external PPS signal was found to be synchronized at the time of the current laser shot.
LatitudeCentroid | double | Latitude Centroid
LatitudeHigh | double | Latitude High
LatitudeLow | double | Latitude Low
LongitudeCentroid | double | Longitude Centroid
LongitudeHigh | double | Longitude High
LongitudeLow | double | Longitude Low
LvisLfid | uint64 | LVIS_LFID
Mark | uint8 | Mark
NormalX | double | X component of a vector normal to surface at this point
NormalY | double | Y component of a vector normal to surface at this point
NormalZ | double | Z component of a vector normal to surface at this point
NumberOfReturns | uint8 | Total number of returns for a given pulse.
OffsetTime | uint32 | Milliseconds from first acquired point
OriginId | uint32 | A file source ID from which the point originated. This ID is global to a derivative dataset which may be aggregated from multiple files.
PassiveSignal | int32 | Relative passive signal
PassiveX | double | Passive X footprint
PassiveY | double | Passive Y footprint
PassiveZ | double | Passive Z footprint
Pdop | float | GPS PDOP (dilution of precision)
Pitch | float | Pitch in degrees
PointId | uint32 | An explicit representation of point ordering within a file, which allows this usually-implicit information to be preserved when reordering points.
PointSourceId | uint16 | File source ID from which the point originated. Zero indicates that the point originated in the current file
PulseWidth | float | Laser received pulse width (digitizer samples)
Red | uint16 | Red image channel value
Reflectance | float | Ratio of the received power to the power that would be received from a white diffuse target at the same distance expressed in dB. The reflectance represents a range independent property of the target. The surface normal of this target is assumed to be in parallel to the laser beam direction.
ReflectedPulse | int32 | Relative reflected pulse signal strength
ReturnNumber | uint8 | Pulse return number for a given output pulse. A given output laser pulse can have many returns, and they must be marked in order, starting with 1
Roll | float | Roll in degrees
ScanAngleRank | float | Angle degree at which the laser point was output from the system, including the roll of the aircraft. The scan angle is based on being nadir, and -90 the left side of the aircraft in the direction of flight
ScanChannel | uint8 | Scan Channel
ScanDirectionFlag | uint8 | Direction at which the scanner mirror was traveling at the time of the output pulse. A value of 1 is a positive scan direction, and a bit value of 0 is a negative scan direction, where positive scan direction is a scan moving from the left side of the in-track direction to the right side and negative the opposite
ShotNumber | uint64 | Shot Number
StartPulse | int32 | Relative pulse signal strength
UserData | uint8 | Unspecified user data
WanderAngle | double | Wander Angle
X | double | X coordinate
XBodyAccel | double | X Body Acceleration
XBodyAngRate | double | X Body Angle Rate
XVelocity | double | X Velocity
Y | double | Y coordinate
YBodyAccel | double | Y Body Acceleration
YBodyAngRate | double | Y Body Angle Rate
YVelocity | double | Y Velocity
Z | double | Z coordinate
ZBodyAccel | double | Z Body Acceleration
ZBodyAngRate | double | Z Body Angle Rate
ZVelocity | double | Z Velocity