LAS 1.4格式定义.pdf

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Open Geospatial Consortium Submission Date: 2017-06-27 Approval Date: 2017-10-02 Publication Date: 2018-03-01 External identifier of this OGC® document: http://www.opengis.net/doc/CS/las/1.4 Internal reference number of this OGC® document: 17-030r1 Version: 1.4 Category: OGC® Community Standard Editor: ASPRS LAS Specification 1.4 OGC Community Standard Copyright notice Copyright © 2018 Open Geospatial Consortium To obtain additional rights of use, visit http://www.opengeospatial.org/legal/. Warning This document is an OGC Member endorsed international Community standard. This Community standard was developed outside of the OGC and the originating party may continue to update their work; however, this document is fixed in content. This document is available on a royalty free, non-discriminatory basis. Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to provide supporting documentation. Document type: Document subtype: Document stage: Document language: English OGC® Community Standard Approved for Public Release 1 Copyright © 2018 Open Geospatial Consortium

License Agreement Permission is hereby granted by the Open Geospatial Consortium, ("Licensor"), free of charge and subject to the terms set forth below, to any person obtaining a copy of this Intellectual Property and any associated documentation, to deal in the Intellectual Property without restriction (except as set forth below), including without limitation the rights to implement, use, copy, modify, merge, publish, distribute, and/or sublicense copies of the Intellectual Property, and to permit persons to whom the Intellectual Property is furnished to do so, provided that all copyright notices on the intellectual property are retained intact and that each person to whom the Intellectual Property is furnished agrees to the terms of this Agreement. If you modify the Intellectual Property, all copies of the modified Intellectual Property must include, in addition to the above copyright notice, a notice that the Intellectual Property includes modifications that have not been approved or adopted by LICENSOR. THIS LICENSE IS A COPYRIGHT LICENSE ONLY, AND DOES NOT CONVEY ANY RIGHTS UNDER ANY PATENTS THAT MAY BE IN FORCE ANYWHERE IN THE WORLD. THE INTELLECTUAL PROPERTY IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND NONINFRINGEMENT OF THIRD PARTY RIGHTS. THE COPYRIGHT HOLDER OR HOLDERS INCLUDED IN THIS NOTICE DO NOT WARRANT THAT THE FUNCTIONS CONTAINED IN THE INTELLECTUAL PROPERTY WILL MEET YOUR REQUIREMENTS OR THAT THE OPERATION OF THE INTELLECTUAL PROPERTY WILL BE UNINTERRUPTED OR ERROR FREE. ANY USE OF THE INTELLECTUAL PROPERTY SHALL BE MADE ENTIRELY AT THE USER’S OWN RISK. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR ANY CONTRIBUTOR OF INTELLECTUAL PROPERTY RIGHTS TO THE INTELLECTUAL PROPERTY BE LIABLE FOR ANY CLAIM, OR ANY DIRECT, SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES WHATSOEVER RESULTING FROM ANY ALLEGED INFRINGEMENT OR ANY LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR UNDER ANY OTHER LEGAL THEORY, ARISING OUT OF OR IN CONNECTION WITH THE IMPLEMENTATION, USE, COMMERCIALIZATION OR PERFORMANCE OF THIS INTELLECTUAL PROPERTY. This license is effective until terminated. You may terminate it at any time by destroying the Intellectual Property together with all copies in any form. The license will also terminate if you fail to comply with any term or condition of this Agreement. Except as provided in the following sentence, no such termination of this license shall require the termination of any third party end-user sublicense to the Intellectual Property which is in force as of the date of notice of such termination. In addition, should the Intellectual Property, or the operation of the Intellectual Property, infringe, or in LICENSOR’s sole opinion be likely to infringe, any patent, copyright, trademark or other right of a third party, you agree that LICENSOR, in its sole discretion, may terminate this license without any compensation or liability to you, your licensees or any other party. You agree upon termination of any kind to destroy or cause to be destroyed the Intellectual Property together with all copies in any form, whether held by you or by any third party. Except as contained in this notice, the name of LICENSOR or of any other holder of a copyright in all or part of the Intellectual Property shall not be used in advertising or otherwise to promote the sale, use or other dealings in this Intellectual Property without prior written authorization of LICENSOR or such copyright holder. LICENSOR is and shall at all times be the sole entity that may authorize you or any third party to use certification marks, trademarks or other special designations to indicate compliance with any LICENSOR standards or specifications. This Agreement is governed by the laws of the Commonwealth of Massachusetts. The application to this Agreement of the United Nations Convention on Contracts for the International Sale of Goods is hereby expressly excluded. In the event any provision of this Agreement shall be deemed unenforceable, void or invalid, such provision shall be modified so as to make it valid and enforceable, and as so modified the entire Agreement shall remain in full force and effect. No decision, action or inaction by LICENSOR shall be construed to be a waiver of any rights or remedies available to it. 2 Copyright © 2018 Open Geospatial Consortium

NOTES: The Open Geospatial Consortium (OGC) endorses LAS 1.4 as a Community standard. The NOTES below provide clarification to the LAS 1.4 specification document for the benefit of users of the OGC endorsed version of LAS 1.4. 1. The following normative references are included in the document. a. ANSI: [INCITS/ISO/IEC 9899:1999] 1999 ANSI C Language Specification, http://webstore.ansi.org/RecordDetail.aspx?sku=INCITS%2fISO%2fIEC +9899-1999+(R2005), 2005. b. OGC: [OGC 01-009] OpenGIS Coordinate Transformation Service Implementation Specification Revision 1.00, 2001. c. Ritter, N and Ruth, M.: GeoTIFF Format Specification, http://web.archive.org/web/20160403164508/http://www.remotesensing.o rg/geotiff/spec/geotiffhome.html, 2000. 2. The OGC Architecture Board (OAB) recommends that future versions of LAS include reference to the latest version of the OGC Well-known text representation of coordinate reference systems (WKT CRS) standard. a. OGC: [OGC 12-063r5] Geographic information - Well-known text representation of coordinate reference systems, 2015. 3. The OAB also recommends that future work consider use of multipoint coverages 4. It is clarified that this version of the LAS 1.4 specification does not include as a valid encoding. compression. 3 Copyright © 2018 Open Geospatial Consortium

LAS SPECIFICATION VERSION 1.4 – R13 15 July 2013 Approved: November 2011 Published by: The American Society for Photogrammetry & Remote Sensing 5410 Grosvenor Lane, Suite 210 Bethesda, Maryland 20814-2160 Voice: 301-493-0290 Fax: 301-493-0208 Web: www.asprs.org All rights reserved. Copyright © 2002-2011 American Society for Photogrammetry and Remote Sensing (ASPRS). All rights reserved. Permission to Use: The copyright owner hereby consents to unlimited use and distribution of this document, or parts thereof, as a specification provided such use references ASPRS as the publisher. This consent does not extend to other uses such as general distribution in any form, including electronic, by any individual or organization whether for advertising or promotional purposes, for creating new collective works, or for resale. For these and all other purposes, reproduction of this publication or any part thereof (excluding short quotations for use in the preparation of reviews and technical and scientific papers) may be made only after obtaining the specific approval of the publisher. Printed in the United States of America. American Society for Photogrammetry & Remote Sensing LAS SPECIFICATION Version 1.4-R13 Page 1 of 28

REVISION HISTORY R11 - Approved Version (Nov 2011) R12 - Errata (June 2012) - Typographical Corrections Corrected Public Header size in descriptive paragraph to 375 bytes Corrected two instances of Scan Angle Rank from "Unsigned Char" to "Char" R13 - Added Domain Profile Section (July 2013) LAS FORMAT VERSION 1.4: 1 Purpose, scope, and applicability The LAS file is intended to contain LIDAR (or other) point cloud data records. The data will generally be put into this format from software (e.g. provided by LIDAR hardware vendors) which combines GPS, IMU, and laser pulse range data to produce X, Y, and Z point data. The intention of the data format is to provide an open format that allows different LIDAR hardware and software tools to output data in a common format. This document reflects the fourth revision of the LAS format specification since its initial version 1.0 release. THE ADDITIONS OF LAS 1.4 INCLUDE: Backward compatibility with LAS 1.1 – LAS 1.3 when payloads consist of only legacy content LAS 1.4 Mode which supports o Extension of offsets and field sizes to support full 64 bit o Support for up to 15 returns per outgoing pulse o Extension of the Point Class field to support 256 classes o Definition of several new ASPRS standard classes o Extension of the Scan Angle field to 2 bytes to support finer angle resolution o Addition of a Sensor Channel bit field to support mobile mapping systems o Addition of Well Known Text (WKT) definitions for Coordinate Reference o Addition of an Overlap bit to allow indicating pulses in the overlap region while o Addition of an (optional) Extra Byte Variable Length Record to describe "extra maintaining the class definition Systems bytes" stored with each point Other minor changes o Added definitions for “LAS Domain Profile” and “LAS Domain Profile Description” American Society for Photogrammetry & Remote Sensing LAS SPECIFICATION Version 1.4-R13 Page 2 of 28

2 Conformance The data types used in the LAS format definition are conformant to the 1999 ANSI C Language Specification (ANSI/ISO/IEC 9899:1999 ("C99"). 3 Authority The American Society for Photogrammetry & Remote Sensing (ASPRS) is the owner of the LAS Specification. The standard is maintained by committees within the organization as directed by the ASPRS Board of Directors. Questions related to this standard can be directed to ASPRS at 301-493-0290, by email at asprs@asprs.org, or by mail at 5410 Grosvenor Lane, Suite 210, Bethesda, Maryland 20814-2160. 4 Requirements LAS FORMAT DEFINITION: The format contains binary data consisting of a public header block, any number of (optional) Variable Length Records (VLRs), the Point Data Records, and any number of (optional) Extended Variable Length Records (EVLRs). All data are in little-endian format. The public header block contains generic data such as point numbers and point data bounds. We refer to the data content of the file as the “payload.” The Variable Length Records (VLRs) contain variable types of data including projection information, metadata, waveform packet information, and user application data. They are limited to a data payload of 65,535 bytes. The Extended Variable Length Records (EVRLs) allow a higher payload than VLRs and have the advantage that they can be appended to the end of a LAS file. This allows adding, for example, projection information to a LAS file without having to rewrite the entire file. Table 1: LAS 1.4 Format Definition PUBLIC HEADER BLOCK VARIABLE LENGTH RECORDS (VLR) POINT DATA RECORDS EXTENDED VARIABLE LENGTH RECORDS (EVLR) A LAS file that contains point record types 4, 5, 9, or 10 could potentially contain one block of waveform data packets that is stored as the payload of any Extended Variable Length Record (EVLR). Unlike other EVLRs, the Waveform Data Packets (if stored internally to the file) have the offset to the storage header contained within the Public Header Block (“Start of Waveform Data Packet Record”). LEGACY COMPATIBILITY (LAS 1.1 – LAS 1.3): LAS 1.4 moves the file specification from a 32 bit file structure (maximum value of 232 – 1 == 4,294,967,295 == UINT32_MAX) to a 64 bit file structure (264 – 1). To maintain the ability to place a LAS 1.1 through LAS 1.3 payload (point record types 0-5, GeoTIFF coordinate reference system, referred to as “Legacy” payloads) in a LAS 1.4 file structure, it was necessary to duplicate some of the fields within the LAS 1.4 file structure. These duplicate fields are named “Legacy xxx” where “xxx” denotes the meaning of the field. American Society for Photogrammetry & Remote Sensing LAS SPECIFICATION Version 1.4-R13 Page 3 of 28

A LAS 1.4 file writer who wishes to maintain backward compatibility must maintain both the legacy fields and the equivalent non-legacy fields in synchronization. Of course, this is not possible if the number of points exceeds UINT32_MAX, in which case the legacy fields must be set to zero. If a file writer is not maintaining backward compatibility, the legacy fields must always be set to zero. If there is a discrepancy between a non-zero legacy field and the equivalent LAS 1.4 field, the LAS 1.4 reader should use the legacy value to maintain the same behavior as a LAS 1.1 through LAS 1.3 reader. Best practice is to also throw an informative error so that the file can be repaired. COORDINATE REFERENCE SYSTEM (CRS) REPRESENTATION: GeoTIFF is being replaced by Well Known Text (WKT) as the required Coordinate Reference System (CRS) representation for the new point types (6-10) introduced by LAS 1.4. GeoTIFF is maintained for legacy reasons for point types 0-5. A “WKT” bit has been added to the Global Encoding flag in the Public Header Block. If this bit is set, the CRS for the file will be located in the WKT (Extended) Variable Length Records (EVLR, VLR). A file writer who desires to maintain backward compatibility with legacy LAS for point types 0-5 must add a GeoTIFF VLR to represent the CRS for the file and ensure that the WKT bit is false. The CRS representation is summarized in Table 2 Table 2: Coordinate Reference System Representation Point Type 0-5 6-10 WKT bit == False WKT bit == True GeoTIFF Error WKT WKT It is considered a file error to have more than one GeoTIFF (E)VLR or more than one WKT (E)VLR in the file. A writer can append a new CRS EVLR to a file by “superseding” the existing CRS (E)VLR. Superseding is performed by changing the LAS_Spec ID of the record to “Superseded”, a new LASF_Spec defined in this release. DATA TYPES: The following data types are used in the LAS format definition. Note that these data types are conformant to the 1999 ANSI C Language Specification (ANSI/ISO/IEC 9899:1999 ("C99"). long (4 bytes) ● char (1 byte) ● unsigned char (1 byte) ● short (2 bytes) ● unsigned short (2 bytes) ● ● unsigned long (4 bytes) ● ● unsigned long long (8 bytes) ● ● double (8 byte IEEE floating point format) ● string (a variable series of 1 byte characters, ASCII encoded, null terminated) float (4 byte IEEE floating point format) long long (8 bytes) American Society for Photogrammetry & Remote Sensing LAS SPECIFICATION Version 1.4-R13 Page 4 of 28

PUBLIC HEADER BLOCK: Table 3: Public Header Block Item File Signature (“LASF”) File Source ID Global Encoding Project ID - GUID data 1 Project ID - GUID data 2 Project ID - GUID data 3 Project ID - GUID data 4 Version Major Version Minor System Identifier Generating Software File Creation Day of Year File Creation Year Header Size Offset to point data Number of Variable Length Records Point Data Record Format Point Data Record Length Legacy Number of point records Legacy Number of points by return X scale factor Y scale factor Z scale factor X offset Y offset Z offset Max X Min X Max Y Min Y Max Z Min Z Start of Waveform Data Packet Record Start of first Extended Variable Length Record Number of Extended Variable Length Records Number of point records Number of points by return Any field in the Public Header Block that is not required and is not used must be zero filled. File Signature: The file signature must contain the four characters “LASF”, and it is required by the LAS specification. These four characters can be checked by user software as a quick look initial determination of file type. American Society for Photogrammetry & Remote Sensing LAS SPECIFICATION Version 1.4-R13 Page 5 of 28 Format char[4] unsigned short unsigned short unsigned long unsigned short unsigned short unsigned char[8] unsigned char unsigned char char[32] char[32] unsigned short unsigned short unsigned short unsigned long unsigned long unsigned char unsigned short unsigned long unsigned long [5] double double double double double double double double double double double double Unsigned long long unsigned long long Size 4 bytes 2 bytes 2 bytes 4 bytes 2 byte 2 byte 8 bytes 1 byte 1 byte 32 bytes 32 bytes 2 bytes 2 bytes 2 bytes 4 bytes 4 bytes 1 byte 2 bytes 4 bytes 20 bytes 8 bytes 8 bytes 8 bytes 8 bytes 8 bytes 8 bytes 8 bytes 8 bytes 8 bytes 8 bytes 8 bytes 8 bytes 8 bytes 8 bytes Required * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * unsigned long 4 bytes * unsigned long long unsigned long long [15] 120 bytes 8 bytes * *

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