gis-tools-ts - v0.6.0
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    Interface LASFormat9

    Point Data Record Format 9 adds Wave Packets to Point Data Record Format 6.

    interface LASFormat9 {
        classification: string;
        classificationFlag: string;
        edgeOfFlightLine: number;
        gpsTime: number;
        intensity: number;
        numberOfReturns: number;
        pointSourceID: number;
        returnNumber: number;
        scanAngle: number;
        scanDirectionFlag: number;
        scannerChannel: number;
        userData: number;
        waveformLocationReturnPoint: number;
        wavePacketDescriptorIndex: number;
        wavePacketLength: number;
        wavePacketOffset: number;
        xT: number;
        yT: number;
        zT: number;
    }

    Hierarchy (View Summary)

    Index

    Properties

    classification classificationFlag edgeOfFlightLine gpsTime intensity numberOfReturns pointSourceID returnNumber scanAngle scanDirectionFlag scannerChannel userData waveformLocationReturnPoint wavePacketDescriptorIndex wavePacketLength wavePacketOffset xT yT zT

    Properties

    classification: string

    1 byte

    ASPRS Standard LIDAR Point Classes (See toLASClassification14)

    classificationFlag: string

    4 bits (bits 0 - 3)

    Classification Flags: Classification flags are used to indicate special characteristics associated with the point. The bit definitions are:

    • 0 Synthetic If set then this point was created by a technique other than LIDAR collection such as digitized from a photogrammetric stereo model or by traversing a waveform.
    • 1 Key-point If set, this point is considered to be a model key-point and thus generally should not be withheld in a thinning algorithm.
    • 2 Withheld If set, this point should not be included in processing (synonymous with Deleted).
    • 3 Overlap If set, this point is within the overlap region of two or more swaths or takes. Setting this bit is not mandatory (unless, of course, it is mandated by a particular delivery specification) but allows Classification of overlap points to be preserved.
    edgeOfFlightLine: number

    1 bit (bit 7)

    Edge of Flight Line: The Edge of Flight Line data bit has a value of 1 only when the point is at the end of a scan. It is the last point on a given scan line before it changes direction or the mirror facet changes. Note that this field has no meaning for 360° Field of View scanners (such as Mobile LIDAR scanners) and should not be set.

    gpsTime: number

    8 bytes

    The GPS Time is the double floating point time tag value at which the point was acquired. It is GPS Week Time if the Global Encoding low bit is clear and Adjusted Standard GPS Time if the Global Encoding low bit is set (see Global Encoding in the Public Header Block description).

    intensity: number

    2 bytes

    The intensity value is the integer representation of the pulse return magnitude. This value is optional and system specific. However, it should always be included if available. Intensity, when included, is always normalized to a 16 bit, unsigned value by multiplying the value by 65,536/(intensity dynamic range of the sensor). For example, if the dynamic range of the sensor is 10 bits, the scaling value would be (65,536/1,024). If intensity is not included, this value must be set to zero. This normalization is required to ensure that data from different sensors can be correctly merged.

    Please note that the following four fields (Return Number, Number of Returns, Scan Direction Flag and Edge of Flight Line) are bit fields within a single byte.

    numberOfReturns: number

    4 bits (bits 0 - 3)

    Number of Returns (given pulse): The Number of Returns is the total number of returns for a given pulse. For example, a laser data point may be return two (Return Number) within a total number of up to fifteen returns.

    pointSourceID: number

    2 bytes

    This value indicates the file from which this point originated. Valid values for this field are 1 to 65,535 inclusive with zero being used for a special case discussed below. The numerical value corresponds to the File Source ID from which this point originated. Zero is reserved as a convenience to system implementers. A Point Source ID of zero implies that this point originated in this file. This implies that processing software should set the Point Source ID equal to the File Source ID of the file containing this point at some time during processing.

    returnNumber: number

    4 bits (bits 0 - 3)

    Return Number: The Return Number is the pulse return number for a given output pulse. A given output laser pulse can have many returns, and they must be marked in sequence of return. The first return will have a Return Number of one, the second a Return Number of two, and so on up to fifteen returns. The Return Number must be between 1 and the Number of Returns, inclusive.

    scanAngle: number

    2 bytes

    Scan Angle: The Scan Angle is a signed short that represents the rotational position of the emitted laser pulse with respect to the vertical of the coordinate system of the data. Down in the data coordinate system is the 0.0 position. Each increment represents 0.006 degrees. CounterClockwise rotation, as viewed from the rear of the sensor, facing in the along-track (positive trajectory) direction, is positive. The maximum value in the positive sense is 30,000 (180 degrees which is up in the coordinate system of the data). The maximum value in the negative direction is -30.000 which is also directly up.

    scanDirectionFlag: number

    1 bit (bit 6)

    Scan Direction Flag: The Scan Direction Flag denotes the direction at which the scanner mirror was traveling at the time of the output pulse. A bit 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).

    scannerChannel: number

    2 bits (bits 4 - 5)

    Scanner Channel: Scanner Channel is used to indicate the channel (scanner head) of a multichannel system. Channel 0 is used for single scanner systems. Up to four channels are supported (0-3).

    userData: number

    1 byte

    User Data: This field may be used at the user’s discretion

    waveformLocationReturnPoint: number

    4 bytes

    Return Point location: The offset in picoseconds (10-12) from the first digitized value to the location within the waveform packet that the associated return pulse was detected.

    wavePacketDescriptorIndex: number

    1 byte

    Wave Packet Descriptor Index: This value plus 99 is the Record ID of the Waveform Packet Descriptor and indicates the User Defined Record that describes the waveform packet associated with this LIDAR point. Up to 255 different User Defined Records which describe the waveform packet are supported. A value of zero indicates that there is no waveform data associated with this LIDAR point record.

    wavePacketLength: number

    4 bytes

    Waveform packet size in bytes: The size, in bytes, of the waveform packet associated with this return. Note that each waveform can be of a different size (even those with the same Waveform Packet Descriptor index) due to packet compression. Also note that waveform packets can be located only via the Byte offset to Waveform Packet Data value since there is no requirement that records be stored sequentially.

    wavePacketOffset: number

    8 bytes

    Byte offset to Waveform Packet Data: The waveform packet data are stored in the LAS file in an Extended Variable Length Record or in an auxiliary WPD file. The Byte Offset represents the location of the start of this LIDAR points’ waveform packet within the waveform data variable length record (or external file) relative to the beginning of the Waveform Packet Data header. The absolute location of the beginning of this waveform packet relative to the beginning of the file is given by:

    • Start of Waveform Data Packet Record + Byte offset to Waveform Packet Data for waveform packets stored within the LAS file
    • Byte offset to Waveform Packet Data for data stored in an auxiliary file
    xT: number

    4 bytes

    this parameter defines a parametric line equation for extrapolating points along the associated waveform. The position along the wave is given by: X = X0 + X(t) where X is the spatial position of the derived point, X0 is the position of the "anchor" point, and t is the time, in picoseconds, relative to the anchor point (i.e. t = zero at the anchor point). The units of X, Y and Z are the units of the coordinate systems of the LAS data. If the coordinate system is geographic, the horizontal units are decimal degrees and the vertical units are meters.

    yT: number

    4 bytes

    this parameter defines a parametric line equation for extrapolating points along the associated waveform. The position along the wave is given by: Y = Y0 + Y(t) where Y is the spatial position of the derived point, Y0 is the position of the "anchor" point, and t is the time, in picoseconds, relative to the anchor point (i.e. t = zero at the anchor point). The units of X, Y and Z are the units of the coordinate systems of the LAS data. If the coordinate system is geographic, the horizontal units are decimal degrees and the vertical units are meters.

    zT: number

    4 bytes

    this parameter defines a parametric line equation for extrapolating points along the associated waveform. The position along the wave is given by: Z = Z0 + Z(t) where Z is the spatial position of the derived point, Z0 is the position of the "anchor" point, and t is the time, in picoseconds, relative to the anchor point (i.e. t = zero at the anchor point). The units of X, Y and Z are the units of the coordinate systems of the LAS data. If the coordinate system is geographic, the horizontal units are decimal degrees and the vertical units are meters.

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