Technical specification for underwater topographic survey of airborne lidar
other information
drafter:Xu Baolong, Shao Yongshe, Li Qingquan, Wei Ronghao, He Yan, Zheng Xuedong, Wang Chisheng, Ren Shaohua, Zou Shuangchao, Gao Hongzhi, Yan Bing, Song Li, Guo Kai, Wang Jing, Wang Zhaoxia, Lei Xin
Drafting unit:Beijing 4D Space Digital Technology Co., Ltd., Institute of Electronics, Chinese Academy of Sciences, Shenzhen University, Zhejiang Institute of Water Resources and Estuary Research, Shanghai Institute of Optics and Precision Mechanics, Chinese Acade
Focal point unit:National Geographic Information Standardization Technical Committee (SAC/TC 230)
Proposing unit:Ministry of Natural Resources of the People's Republic of China
Publishing department:State Administration for Market Regulation National Standardization Administration
Some standard content:
ICS07.040
National Standard of the People's Republic of China
GB/T39624—2020
Technical specification for underwater topographic survey of airborne lidar2020-12-14Release
State Administration for Market Regulation
National Administration of Standardization
Implementation on 2020-12-14
Normative reference documents
Terms and definitions
Abbreviations
Basic requirements
General provisions
Spatial reference
Time reference
Projection and framing
Graphical symbols
Point cloud density requirements
Point cloud plane accuracy
Point cloud elevation accuracy Degree
Metadata
Preparation
Requirement analysis
Data collection
Site survey
Equipment selection
Technical design document writing
Data acquisition
Comprehensive calibration
Route design
Data acquisition requirements
Data acquisition flight
Data re-measurement·
Data processing
Data processing flow
Data collation·
Waveform data processing
POS data Processing.
Point cloud data processing
Results production
Results quality inspection
GB/T39624—2020
GB/T39624—2020
Results quality inspection and acceptance
Inspection of original collection results
Inspection of post-processing results
10 Results collation and submission
Results submission requirements
Results submission content
Appendix A (Normative Appendix)
Appendix B (Normative Appendix)||tt| |Appendix C (Normative Appendix)
Appendix D (Normative Appendix)
Appendix E (Informative Appendix)
Appendix F (Normative Appendix)
References
Waveform Results Metadata
Point Cloud Results Metadata
Setting Angle Calculation Record
Eccentricity Component Measurement Record
Eccentricity Component Measurement Record Example
Flight Record
This standard was drafted in accordance with the rules given in GB/T1.1-2009. This standard was proposed by the Ministry of Natural Resources of the People's Republic of China. This standard is under the jurisdiction of the National Technical Committee for Geographic Information Standardization (SAC/TC230). GB/T39624—2020
Drafting units of this standard: Beijing 4D Space Digital Technology Co., Ltd., Institute of Electronics, Chinese Academy of Sciences, Shenzhen University, Zhejiang Institute of Water Resources and Estuary Research, Shanghai Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Yangtze River Scientific Research Institute of Yangtze River Water Conservancy Commission. The main drafters of this standard are: Xu Baolong, Shao Yongshe, Li Qingquan, Wei Ronghao, He Yan, Zheng Xuedong, Wang Chisheng, Ren Shaohua, Zou Shuangchao, Gao Hongzhi, Yan Bing, Song Li, Guo Cuo, Wang Jing, Wang Zhaoxia, Lei Xinm
GB/T39624—2020
Airborne LiDAR measurement is a new technology for quickly acquiring high-precision three-dimensional geographic information in space. It integrates LiDAR technology, high-precision inertial navigation measurement technology and high-precision dynamic GNSS differential measurement technology. Compared with traditional photogrammetry technology, it has the advantages of faster and more accurate acquisition of three-dimensional information of underwater landforms and objects. In recent years, airborne LiDAR measurement technology has developed rapidly and has begun to be applied in underwater topographic surveying and mapping fields such as coastal areas, waters near islands and reefs, and inland waters. This standard is aimed at the needs of underwater topographic measurement. On the basis of analyzing existing technologies, combined with the development level and characteristics of airborne LiDAR underwater topographic measurement technology at home and abroad, it puts forward standardized technical requirements for underwater topographic measurement operations using airborne LiDAR. IN
1 Scope
Technical Specification for Airborne Lidar Underwater Topography Survey GB/T39624—2020
This standard specifies the basic requirements, preparation, data acquisition, data processing, results quality inspection, and results collation and submission for airborne Lidar underwater topography survey
This standard applies to underwater topography survey operations in waters with a depth of no more than 50m using airborne Lidar measurement technology. 2 Normative References
The following documents are indispensable for the application of this document. For all dated references, only the dated version applies to this document. For all undated references, the latest version (including all amendments) applies to this document. GB12319 Chinese Nautical Chart Format
GB12327 Hydrographic Specifications
GB/T13989
GB/T17278
GB/T18316
GB/T19710
National Basic Scale Topographic Map Division and Numbering Basic Requirements for Digital Topographic Map Products
Quality Inspection and Acceptance of Digital Surveying and Mapping Results
Geographic Information Metadata
GB/T20257 (All Parts) National Basic Map format of this scale GB/T24356
GB/T32067
CH/T8023
Quality inspection and acceptance of surveying and mapping results
Ocean element diagram legend and symbols
Technical specification for airborne laser radar data processing CH/T8024—2011 Specification for airborne laser radar data acquisition Basic geographic information digital results 1:500, 1:1000, 1:2000 digital elevation model CH/T9008.2
CH/T 9009.2
Digital elevation model
Basic digital achievements of geographic information
1:5000, 1:10000, 1:25000, 1:50000, 1:100000CH/Z9026
Basic digital achievements of geographic information
Mathematical word water depth model
Terms and definitions
The following terms and definitions apply to this document. 3.1
airborne lidar
Airborne lidar
Laser detection and ranging system carried on an aviation platform, integrating lidar equipment, GNSS and IMU equipment Note: This standard specifically refers to the airborne lidar bathymetric system used for water depth measurement, which is used to obtain the geometric and physical characteristics of the target surface. 3.2
funderwatertopographical survey
The process of comparing underwater landforms and objects directly with known or indirect quantities using water depth measurement methods. Note: This standard specifically refers to obtaining information on the geometric characteristics of underwater terrain. 1
GB/T39624—2020
2000 National Geodetic Coordinate System ChinaGeodeticCoordinateSystem2000; CGCS2000 uses the 2000 reference ellipsoid and a right-handed earth-fixed rectangular coordinate system with the origin at the center of the earth. The Z axis is the reference polar direction of the International Earth Rotation Bureau, the X axis is the intersection of the reference meridian plane of the International Earth Rotation Bureau and the equatorial plane perpendicular to the Y axis, and the Y axis, Z axis and X axis form a right-handed orthogonal coordinate system.
[GB/T14911—2008, definition 2.32]
1985 National Vertical Datum1985 was promulgated and named in 1987. It is defined by the Qingdao leveling origin and the average sea level of the Yellow Sea determined by the tidal data of the Qingdao tide station from 1952 to 1979. The starting elevation of the leveling origin is 72.260m. [GB/T14911—2008. Definition 2.24]
Theoretical lowest tide level thelowestnormallowwater The specific implementation form of my country's nautical chart depth datum is the lowest tidal water level that may occur in theory. Its height is calculated from the local average sea level.
［GB/T17501—2017. Definition 3.6］
Mean sea level meansalevel
The ideal calm sea surface with an elevation equal to the average of the ocean water level observation results. It can be divided into daily average, monthly average, annual average and multi-year average sea level according to the observation time.
Note: Rewritten from GB/T15918—2010, definition 2.5.53.7
Local mean sea level localmeansealevel The average value of hourly observations of the local tide gauge station for more than 19 years. 3.8
Checkline
A route perpendicular to the flight collection route.
Note: Used to check the accuracy of collecting point cloud data 3.9
Waveform data
waveformdata
The laser receiving system discretizes the echo of the signal according to the preset sampling rate, and the obtained echo intensity time series Note: The time resolution of the waveform data is not greater than the laser pulse width, and the original sampling data used to invert the water environment information and spatial geographic information is saved, thereby obtaining accurate underwater terrain data and rich water surface and water environment characteristics. 3.10
underwaterterrainmodel
Underwater terrain model
A spatial model such as a regular grid or triangulated network established based on underwater discrete elevation points. Note: Used to simulate the distribution of attributes such as the spatial position of continuously distributed underwater terrain. 3.11
Digital bathymetricmodelA spatial model such as a regular grid or triangulated network established using discrete water depth point data. Note: A digital spatial model used to describe continuous water depth changes within a region. 2
Diffuse attenuation coefficient of water bodyThe ratio of the change in optical irradiance transmitted in a unit length of water body to the optical irradiance. GB/T39624—2020
Note: It belongs to the surface optical parameter of water body, which characterizes the attenuation of optical irradiance in water body with the propagation distance of water body, also known as K, value bottomreflectivity
Bottom reflectivity
The ratio of the bottom reflected light radiance to the bottom received irradiance. GNSS lever arms
GNSS eccentricity component
The three coordinate components of the GNSS antenna phase center in the reference coordinate system. IMU eccentricity
IMU lever arms
The three coordinate components of the origin of the IMU device in the reference coordinate system. Lidar eccentricity
lidar lever arms
The three coordinate components of the origin of the airborne lidar in the reference coordinate system. 3.17
Bore sight angles deviation
The systematic angle deviation between the three corresponding axes of the airborne lidar coordinate system and the coordinate system of the carrier where the IMU is located. 3.18
point cloud density
Point cloud density
The average number of laser measurement points per square meter. 3.19
Maximum water depth
maximum depth
The maximum water depth that can be measured by the airborne lidar Note: It is expressed in multiples of the reciprocal of the diffuse attenuation coefficient of the measured water body at the laser wavelength (1/K.). 3.20
Swathwidth
Swathwidth
The measurement width perpendicular to the flight route when the airborne laser radar is operating. Note: It is expressed in multiples of the flight altitude.
Measurement rate
Measurement rate
The number of underwater topography measurement points obtained by the airborne laser radar per unit time. 4
Abbreviations
The following abbreviations apply to this document.
IMU: Inertial measurement unit GNSS: Global navigation satellite system POS: Position and orientation system PPS: Pulse per second second)GB/T39624—2020
5 Basic requirements
5.1 General provisions
Airborne laser radar underwater topography measurement shall comply with the following provisions: a) The power supply, load, flight time, speed, altitude and downward viewing window of the selected airborne platform shall meet the requirements of laser radar for underwater topography measurement;
b) Airborne laser radar and related auxiliary equipment shall be used within the validity period of metrological verification or calibration and be in normal working condition; The selected airborne laser radar shall transparently provide waveform, point cloud raw data and corresponding format description: d
Point cloud density, plane accuracy, elevation accuracy are suitable for marine environment and meet the sea conditions of level 3 and below, wind force of level 3 and below, K. less than or equal to 0.3m-1 and bottom reflectivity greater than or equal to 15%, etc. In difficult sea conditions, when the use conditions cannot be met, the indicator is allowed to be relaxed by 0.5 times; e) The work process should include preparation, data acquisition, data processing, quality control and results collation and submission: f) The production, distribution and use of results should comply with relevant confidentiality regulations. 5.2 Spatial datum
5.2.1 Plane coordinate system
The plane coordinate system should use CGCS2000. If other plane coordinate systems are used, they should be linked to CGCS2O00. 5.2.2 Elevation datum
The elevation datum should use the 1985 national elevation datum. If other elevation datums are used, they should be linked to the 1985 national elevation datum. For islands and reefs far away from the mainland, the elevation datum should also give the relationship with the local mean sea level. 5.2.3 Depth datum
The depth datum shall adopt the theoretical lowest tide level. If other datums are adopted according to the needs of the project, the relationship between the adopted datum and the theoretical lowest tide level and the 1985 national elevation datum shall be given. For islands and reefs far away from the mainland, the elevation datum shall be given in relation to the local average sea level.
5.3 Time datum
The date shall adopt the Gregorian calendar, and the time shall adopt Beijing time. 5.4 Projection and framing
The projection adopts the Gauss-Kruger projection. The 1.5° belt projection is adopted for mapping scales greater than or equal to 1:2000, the 3° belt projection is adopted for 1:5000 to 1:10000, and the 6° belt projection is adopted for less than 1:10000. Other projections may also be adopted according to actual needs. If no specific provisions are made, they shall comply with the requirements of GB/T13989. When there are specific needs, they can be freely divided into sections. 5.5 Graphical symbols
The graphical symbols for sea areas shall comply with the requirements of GB12319 and GB/T32067, and the graphical symbols for land areas shall comply with the requirements of GB/T20257.
5 Point cloud density requirements
The point cloud density shall meet the requirements of the production digital elevation model and Table 14
Result scale
1:1000
1+2000
1:5 000
1:25000
Point cloud density requirements
Grid spacing of digital elevation model results/m
Note 1: Calculate the point cloud density according to no more than 1/2 of the grid spacing of digital elevation model results GB/T39624—2020www.bzxz.net
Point cloud density/(points/m)
Note 2: For underwater topographic surveys with special requirements, the technical requirements of the visual engineering shall specify the density in the technical design document. Note 3: Point cloud density refers to the density of the point cloud of underwater topographic surveys. Point cloud plane accuracy
Point cloud plane mean error shall meet the requirements of Table 2Table 2
Result scale
1:1000
1:2000
1:5000
125000
Point cloud plane mean error
Note 1: The accuracy of special underwater topographic survey projects depends on the specific engineering technical requirementsNote 2: d is the water depth (in meters).
Note 3: The point cloud plane accuracy is limited to 2 times the point cloud plane mean errorPoint cloud elevation accuracy
The point cloud elevation mean error shall meet the requirements of Table 3. Table 3
Result scale
1:1000
1:2000
Point cloud elevation error
Plane error
≤0.5+0.025d
≤1.0+0.025d
≤2.0+0.025d
≤2.5+0.025d
≤5.0+0.025d
≤10.0+0.025d
Elevation error
≤0.05*+(0.005d)
≤Vo.1+(0.005d)3
≤V0.15+(0.005d)*
Unit: meter
Unit: meter
GB/T39624—2020
Result scale
1:5000
1:10:000
1:25000
Table 3 (continued)
Note 1: The accuracy of special underwater topographic survey projects depends on the specific engineering technical requirements. Note 2: d is the water depth (in meters).
Note 3: The elevation accuracy of the point cloud is limited to twice the median error of the point cloud elevation 5.9
Metadata
Median error in elevation
≤/0.17+(0.005d)
≤0.3+(0.005d)
≤0.5*+(0.005d)
Unit: meter
Product metadata can determine the specific metadata content and produce it based on GB/T19710. The waveform result metadata should include but not be limited to the contents of Appendix A. The point cloud result metadata should include but not be limited to the contents of Appendix B. 6 Preparation
6.1 Requirements Analysis
Before the project starts, a requirements analysis should be conducted to fully understand the user's needs, reach an agreement with the user, determine the scope of the survey area, acquisition method, type of results, quality and form of results, and form a requirements analysis report. 6.2
Data Collection
The following data should be collected: a) Information on the survey area, natural geography, and cultural data; b) Information on hydrometeorology, tide level, water depth, bottom quality, water refractive index, water diffuse attenuation coefficient of laser wavelength, etc.; c) Existing field control point results;
Topographic maps of various scales and related results of the survey area and surrounding land areas, such as digital elevation models, orthophotos, topographic maps, administrative division maps, traffic maps, etc.: nautical charts or waterway maps of the survey area and surrounding water areas; other relevant information.
3 Site Survey
The site survey requirements are as follows:
Conduct on-site survey of the GNSS base station locations in the survey area;a)
Analyze and make on-site judgments on the reliability and accuracy of the collected data;b)) If conditions permit, conduct on-site verification of water environment parameters such as tide level and water diffuse attenuation coefficient in the survey area. Selection of Instruments and Equipment
Lidar
The selection of lidar should meet the following requirements:a)
Based on the water depth profile, bottom reflectivity and water diffuse attenuation coefficient of the operating area, as well as the requirements for laser point cloud density and accuracy, select a suitable flight platform and lidar, and select equipment and aircraft based on the point cloud density;b) The lidar should be calibrated for ranging, angle measurement and zero position. 6.4.2POS system
The selection of POS system should meet the following requirements:
GB/T39624—2020
The airborne GNSS receiver should be a high-dynamic measurement dual-frequency GNSS receiver with high-dynamic, high-frequency data receiving capability and stable phase center. The sampling frequency should not be less than 1Hzb) The IMU roll and pitch angle accuracy should be better than 0.005°, and the yaw angle accuracy should be better than 0.02°;c) The IMU data recording frequency should not be less than 100Hz; it has a PPS output interface, which can output PPS to the lidar and provide time synchronization;d)
The POS system memory should meet the requirements of long-term recording and storage of GNSS/IMU data, signal marker input data and other necessary data.
6.4.3 Ground GNSS receiver
The selection of ground GNSS receiver should meet the following requirements: a) The ground GNSS receiver should match the performance of the airborne GNSS receiver; b) It should be a measurement-type dual-frequency GNSS receiver with a sampling frequency of not less than 1Hz; c) The selection of memory capacity should meet the requirements of complete data storage for the maximum flight operation time; d)
The selection of power supply should meet the requirements of uninterrupted power supply for the maximum flight operation time; e)
The GNSS receiving antenna should be equipped with a radial suppression plate or radial suppression ring and have good anti-interference ability. 6.5 Preparation of technical design document
The technical design document should be prepared based on the overall requirements of the project, the analysis results of existing data, the goals of the project, etc. The main contents of the technical design document are as follows:
a) Key task indicators are formed through demand analysis;b) Task source or purpose and survey area overview;c)
Existing data and previous survey situation;
Overall task requirements, including survey area scope, adopted benchmark, survey scale, map sheet and survey accuracy requirements;e)
Measurement equipment and instrument inspection items and requirements; Flight plan and implementation of airborne laser radar, requirements for ground base station installation: Data processing content, including processing of raw data, POS data processing, point cloud data solution and flight strip splicing; Flight data quality inspection and results evaluation methods and contents: Requirements for results submission and work summary.
Data acquisition
Comprehensive calibration
7.1.1 Calibration field
The calibration field should be selected in a flat road area with pointed roof houses and straight roads.7.1.2 Angle calibration
The flight route planning for angle calibration is carried out according to Figure 1.3 Ground GNSS receiver
The selection of ground GNSS receiver should meet the following requirements: a) The ground GNSS receiver should match the performance of the airborne GNSS receiver; b) It should be a measurement-type dual-frequency GNSS receiver with a sampling frequency of not less than 1Hz; c) The selection of memory capacity should meet the requirements of complete data storage during the maximum flight operation time; d)
The selection of power supply should meet the requirements of uninterrupted power supply during the maximum flight operation time; e)
The GNSS receiving antenna should be equipped with a radial suppression plate or radial suppression ring and have good anti-interference ability. 6.5 Preparation of technical design document
The technical design document should be prepared based on the overall requirements of the project, the analysis results of existing data, the goals of the project, etc. The main contents of the technical design document are as follows:
a) Key task indicators are formed through demand analysis;b) Task source or purpose and survey area overview;c)
Existing data and previous survey situation;
Overall task requirements, including survey area scope, adopted benchmark, survey scale, map sheet and survey accuracy requirements;e)
Measurement equipment and instrument inspection items and requirements; Flight plan and implementation of airborne laser radar, requirements for ground base station installation: Data processing content, including processing of raw data, POS data processing, point cloud data solution and flight strip splicing; Flight data quality inspection and results evaluation methods and contents: Requirements for results submission and work summary.
Data acquisition
Comprehensive calibration
7.1.1 Calibration field
The calibration field should be selected in a flat road area with pointed roof houses and straight roads.7.1.2 Angle calibration
The flight route planning for angle calibration is carried out according to Figure 1.3 Ground GNSS receiver
The selection of ground GNSS receiver should meet the following requirements: a) The ground GNSS receiver should match the performance of the airborne GNSS receiver; b) It should be a measurement-type dual-frequency GNSS receiver with a sampling frequency of not less than 1Hz; c) The selection of memory capacity should meet the requirements of complete data storage during the maximum flight operation time; d)
The selection of power supply should meet the requirements of uninterrupted power supply during the maximum flight operation time; e)
The GNSS receiving antenna should be equipped with a radial suppression plate or radial suppression ring and have good anti-interference ability. 6.5 Preparation of technical design document
The technical design document should be prepared based on the overall requirements of the project, the analysis results of existing data, the goals of the project, etc. The main contents of the technical design document are as follows:
a) Key task indicators are formed through demand analysis;b) Task source or purpose and survey area overview;c)
Existing data and previous survey situation;
Overall task requirements, including survey area scope, adopted benchmark, survey scale, map sheet and survey accuracy requirements;e)
Measurement equipment and instrument inspection items and requirements; Flight plan and implementation of airborne laser radar, requirements for ground base station installation: Data processing content, including processing of raw data, POS data processing, point cloud data solution and flight strip splicing; Flight data quality inspection and results evaluation methods and contents: Requirements for results submission and work summary.
Data acquisition
Comprehensive calibration
7.1.1 Calibration field
The calibration field should be selected in a flat road area with pointed roof houses and straight roads.7.1.2 Angle calibration
The flight route planning for angle calibration is carried out according to Figure 1.
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