LAS文件

文件结构

LAS文件是一种存储点云数据的二进制格式。它由一个文件头和多个数据记录（点数据）组成。

文件头包含LAS文件的格式版本、点数据记录的数量、范围和精度等元数据信息。点数据记录则包含了每个点的位置、颜色、分类以及其他任意属性。LAS文件的数据记录按照一定的顺序组织，同时支持数据的压缩和索引。

具体的LAS文件格式结构如下：

LAS_FILE_HEADER {
    char FileSignature[4];
    unsigned short FileSourceID;
    unsigned short GlobalEncoding;
    unsigned int   ProjectID_GUID_data_1;
    unsigned short ProjectID_GUID_data_2;
    unsigned short ProjectID_GUID_data_3;
    unsigned char  ProjectID_GUID_data_4[8];
    unsigned char  VersionMajor;
    unsigned char  VersionMinor;
    char           SystemIdentifier[32];
    char           GeneratingSoftware[32];
    unsigned short FileCreationDayOfYear;
    unsigned short FileCreationYear;
    unsigned short HeaderSize;
    unsigned int   OffsetToPointData;
    unsigned int   NumberOfVLRs;
    LAS_VLR        VLRS[NumberOfVLRs];
    unsigned char  PointDataFormat;
    unsigned short PointDataRecordLength;
    unsigned int   NumberOfPointRecords;
    unsigned int   NumberOfPointsByReturn[5];
    double         XScaleFactor;
    double         YScaleFactor;
    double         ZScaleFactor;
    double         XOffset;
    double         YOffset;
    double         ZOffset;
    double         MaxX;
    double         MinX;
    double         MaxY;
    double         MinY;
    double         MaxZ;
    double         MinZ;
};

规范链接

LAS文件格式由美国杰出空间数据权威 (ASPRS) 组织制定，目前最新的版本为1.4。该标准提供了LAS文件格式的详细规范和相关工具，ASPRS的官方网站（https://www.asprs.org/）提供了LAS文件格式的官方规范链接和参考文档。

规范链接如下：

• LAS数据格式标准（PDF）：https://www.asprs.org/content/dam/asprsorg/WorkingGroups/LASLASER/LAS_1_4_r14.pdf
• LAS工具套件（LAS Tools）：https://rapidlasso.com/laszip/
• LASlib 库：https://github.com/LAStools/LASlib

示例文件：

下面是一个示例LAS文件，它包含一个地区的点云数据。这个文件的点记录格式为1（存储X、Y、Z、Intensity、Return Number、Number of Returns和Scan Direction Flag），记录长度为28字节。文件头信息中的X、Y、Z范围和计量单位都是米。

LAS_FILE_HEADER {
    FileSignature           = "LASF";
    FileSourceID            = 0;
    GlobalEncoding          = 0;
    ProjectID_GUID_data_1   = 0;
    ProjectID_GUID_data_2   = 0;
    ProjectID_GUID_data_3   = 0;
    ProjectID_GUID_data_4   = { 0, 0, 0, 0, 0, 0, 0, 0 };
    VersionMajor            = 1;
    VersionMinor            = 4;
    SystemIdentifier        = "Example LAS File";
    GeneratingSoftware      = "Unknown";
    FileCreationDayOfYear   = 1;
    FileCreationYear        = 2019;
    HeaderSize              = 227;
    OffsetToPointData       = 227;
    NumberOfVLRs            = 0;
    PointDataFormat         = 1;
    PointDataRecordLength   = 28;
    NumberOfPointRecords    = 100000;
    NumberOfPointsByReturn  = { 93950, 540, 10, 0, 0 };
    XScaleFactor            = 0.001;
    YScaleFactor            = 0.001;
    ZScaleFactor            = 0.001;
    XOffset                 = -10455;
    YOffset                 = -19476;
    ZOffset                 = 0;
    MaxX                    = -10450.342;
    MinX                    = -10686.42;
    MaxY                    = -19189.24;
    MinY                    = -19476.23434;
    MaxZ                    = 299.23;
    MinZ                    = 0;
};