LAS1.4标准：lidar点云数据格式详解

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LAS14标准文档是Lidar（激光测距仪）点云数据的标准格式，由美国摄影测量与遥感学会（American Society for Photogrammetry & Remote Sensing, ASPRS）制定和维护。该文档的版本1.4-R13发布于2013年7月15日，旨在提供一个公开、统一的数据交换格式，促进不同软件之间的lidar数据共享和处理。LAS文件被广泛应用于各种遥感应用，如地形测绘、地理信息系统（GIS）、城市规划和环境监测等领域。 LAS文件的核心内容包括点云数据的结构定义、字段描述、坐标系统和数据编码规则。它包含了点的三维坐标（X、Y、Z）、强度、反射率、时间戳、归一化返回强度、分类信息等关键属性，这些属性能够提供关于地面和物体的精确几何信息以及物理特性。此外，LAS标准还规定了数据的组织方式，如文件头部的元数据部分，用于描述数据集的总体信息，如扫描设备类型、传感器配置等。 LAS1.4-R13版在前一版本的基础上进行了更新和完善，可能涉及数据压缩方法、精度要求的提升、新的数据类型支持，以及对旧有格式的向下兼容性保证。版权方面，ASPRS允许用户在指定范围内使用该文档，但明确禁止任何形式的未经许可的广泛复制或商业用途，除非用于学术研究或技术论文的引用。对于从事lidar数据处理的专业人士和开发者来说，理解并遵循LAS14标准至关重要，它不仅确保了数据的互操作性和一致性，而且有利于提高工作效率和数据质量。通过学习和应用LAS标准，用户可以更好地管理和分析来自不同源的lidar数据，推动行业内的标准化和技术创新。

American Society for Photogrammetry & Remote Sensing Page 6 of 28

LAS SPECIFICATION

Version 1.4-R13

File Source ID: This field should be set to a value ranging from 1 to 65,535. If this file was

derived from an original flight line, this is often the flight line number. A value of zero (0) is

interpreted to mean that an ID has not been assigned. In this case, processing software is free to

assign a number. Note that this scheme allows a LIDAR project to contain up to 65,535 unique

sources. A source can be an original flight line or it can be result of merge and/or extract

operations.

Global Encoding: This is a bit field used to indicate certain global properties about the file. In

LAS 1.2 (the version in which this field was introduced), only the low bit is defined (this is the bit,

that if set, would have the unsigned integer yield a value of 1). This bit field is defined as:

Table 4: Global Encoding - Bit Field Encoding

Bits Field Name Description

0 GPS Time Type The meaning of GPS Time in the point records. If

this bit is not set, the GPS time in the point record

fields is GPS Week Time (the same as versions

1.0 through 1.2 of LAS). Otherwise, if this bit is

set, the GPS Time is standard GPS Time (satellite

GPS Time) minus 1 x 10

(Adjusted Standard

GPS Time). The offset moves the time back to

near zero to improve floating point resolution.

1 Waveform Data

Packets Internal

If this bit is set, the waveform data packets are

located within this file (note that this bit is mutually

exclusive with bit 2). This is deprecated now.

2 Waveform Data

Packets External

If this bit is set, the waveform data packets are

located externally in an auxiliary file with the same

base name as this file but the extension *.wdp.

(note that this bit is mutually exclusive with bit 1)

3 Return numbers

have been

synthetically

generated

If this bit is set, the point return numbers in the

point data records have been synthetically

generated. This could be the case, for example,

when a composite file is created by combining a

First Return File and a Last Return File. In this

case, first return data will be labeled “1 of 2 ” and

second return data will be labeled “2 of 2 ”

4 WKT If set, the Coordinate Reference System (CRS) is

WKT. If not set, the CRS is GeoTIFF. It should

not be set if the file writer wishes to ensure legacy

compatibility (which means the CRS must be

GeoTIFF)

5:15 Reserved Must be set to zero

Project ID (GUID data): The four fields that comprise a complete Globally Unique Identifier

(GUID) are now reserved for use as a Project Identifier (Project ID). The field remains optional.

The time of assignment of the Project ID is at the discretion of processing software. The Project

ID should be the same for all files that are associated with a unique project. By assigning a

Project ID and using a File Source ID (defined above) every file within a project and every point

within a file can be uniquely identified, globally.

Version Number: The version number consists of a major and minor field. The major and minor

fields combine to form the number that indicates the format number of the current specification

itself. For example, specification number 1.4 would contain 1 in the major field and 4 in the minor

field. It should be noted that the LAS Working Group does not associate any particular meaning

to major or minor version number.

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