Specifications for low-altitude digital aerial photography and data processing
Some standard content:
ICS07.040
National Standard of the People's Republic of China
GB/T39612—2020
Specifications for low-altitude digital aerial photography and data processing
Specifications for low-altitude digital aerial photography and data processing2020-12-14Issued
State Administration for Market Regulation
National Administration of Standardization
Implementation on 2020-12-14
Normative reference documents
Terms and definitions
Basic requirements
Framing and numbering
Result accuracy
5 Aerial photography
Aerial photography preparation
Aerial photography equipment requirements
Aerial photography plan and aerial photography design
Aerial photography implementation
Flight quality and image Quality requirements
Quality inspection and collation of aerial photography results
Aerial photography results data
Photo control measurement
Photo control point layout
Basic control point measurement
Photo control point measurement
Photo control measurement results inspection
Photo control measurement results data
Triangulation
Image preprocessing
Accuracy requirements
Relative orientation
Free network adjustment
Absolute orientation and regional network adjustment
Result quality inspection||t t||Data of aerial triangulation results
Production of basic geographic information products,
Production methods and requirements
Results quality inspection
Data of basic geographic information products
Appendix A (Informative Appendix)
Appendix B (Informative Appendix)
Schematic diagram of the relationship between camera and image space coordinate system, schematic diagram of camera installation orientation Common calculation formulas for low-altitude digital aerial photography
GB/T39612—2020
GB/T39612—2020
Appendix C ( Appendix D (Informative Appendix)
Appendix E (Informative Appendix)
Appendix F (Informative Appendix)
Appendix G (Informative Appendix)
Aerial Flight Record Table
Spin Angle Calculation Diagram
Aerial Division Diagram and Route Diagram
Photographing Area Completion Map
Photograph Control Point Result Table and Point Record Sample 18
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/T39612—2020
The drafting units of this standard are: China Surveying and Mapping (Beijing) Remote Sensing Technology Co., Ltd., China Surveying and Mapping (Beijing) Low-altitude Digital Surveying and Mapping Technology Co., Ltd., Wuhan China Surveying and Mapping Remote Sensing Technology Co., Ltd., and Zhejiang China Surveying and Mapping Geographic Information Technology Co., Ltd. The main drafters of this standard are: Li Yingcheng, Xue Yanli, Ding Xiaobo, Zhu Xiange, Li Xilin, Dai Fang, Ren Yafeng, Chen Beiping, Cao Hualong, Liu Pei, Liao Ming, Zheng Anwu, and Kuang Xiumei.
1 Scope
Specification for low-altitude digital aerial photography and data processing
GB/T39612—2020
This standard specifies the basic requirements for low-altitude digital aerial photography and data processing, including the technical requirements for low-altitude digital aerial photography, photo control measurement, aerial triangulation, and production of basic geographic information products. This standard applies to the production of 1:500, 1:1000 and 1:2000 digital orthophotos (DOM), digital elevation models (DEM), digital surface models (DSM) and digital line graphs (DLG) using unmanned aerial vehicle low-altitude digital aerial photography systems. 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. GB/T13989 National basic scale topographic map division and numbering GB/T18314—2009 Global Positioning System (GPS Measurement Specification GB/T18316
GB/T24356
Quality inspection and acceptance of digital surveying and mapping results
Quality inspection and acceptance of surveying and mapping results
2011 Technical Specification for IMU/GPS Assisted Aerial Photography GB/T27919—2
GB35650 Basic Technical Regulations for National Basic Scale Map Surveying and Mapping CH/T1007
CH/T1024
Metadata of Basic Geographic Information Digital Products
Technical Regulations for Quality Inspection of Image Control Surveying Results CH/T20092010 Full
Global Positioning System Real-time Kinematic Measurement (RTK) Technical Specifications CH/T3006—2011
Digital Aerial Photogrammetry Control Measurement Specifications CH/T3007.1
Digital Aerial Photogrammetry Mapping Specifications Part 1: 1:5001:10001:2000 Digital Elevation Model Digital Orthophoto Map Digital Line Map CH/T3012
CH/T9022
Surface Model
Terms and Definitions
Digital Surface Model Aerial Photogrammetry Production Technical Specifications Basic Geographic Information Digital Achievements 1:5001:10001:20001:50001:10000 Digital Table The following terms and definitions apply to this document. 3.1
unmanned aerial vehicle
Unmanned aerial vehicle
An aircraft controlled by a remote control device or a self-contained program control device, with no pilot on board. 3.2
low-altitudedigitalaerial photography
Digital aerial photography with a relative altitude below 2000m using an unmanned aerial vehicle. 3.3
2000 National Geodetic Coordinate System
ChinaGeodeticCoordinateSystem2000; CGCS2000 adopts the 2000 reference ellipsoid and a right-handed earth-fixed rectangular coordinate system with the origin at the center of the earth. The B axis is the reference pole direction of the International Bureau of Earth Rotation, and the X1
GB/T39612—2020bzxz.net
axis is the reference pole direction of the International Bureau of Earth Rotation. The intersection of the reference meridian plane and the equatorial plane perpendicular to the Z axis, the Y axis, Z axis and X axis form a right-handed orthogonal coordinate system.
[GB/T14911—2008.Definition 2.32]
1985 National Vertical Datum
NationalVerticalDatum1985
Promulgated and named in 1987, the elevation datum 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/T149112008.Definition 2.24
4 Basic requirements
Framing and numbering
The framing and numbering of basic geographic information products shall be carried out in accordance with the provisions of GB/T13989. When necessary, free framing and numbering may also be used.
Result accuracy
Result accuracy requirements are as follows:
Digital line drawing, digital elevation model, digital orthophoto results should meet the requirements of GB35650; a)
Digital surface model results should meet the requirements of CH/T9022. b))
5 Aerial photography
Aerial photography preparation
Before aerial photography, the following preparations should be made: Collect terrain data and meteorological data in the shooting area: a)
b) Survey and investigate the ground information in the shooting area, such as tall buildings, high-voltage lines, radio interference sources, etc. that may affect flight safety. 2 Requirements for aerial photography equipment
5.2.1 Requirements for unmanned aerial vehicles
When using unmanned aerial vehicles for low-altitude aerial photography, the following basic requirements should be met: a) They should be able to fly safely under normal meteorological conditions, and their wind resistance should generally be no less than level 4; b)
The autopilot should have the function of fixed-point exposure or equidistant exposure control; and the function of recording the camera's position and attitude information at the time of exposure c)
5.2.2 Requirements for cameras
5.2.2.1 Basic requirements
The basic requirements for cameras are as follows:
The camera lens should be a fixed-focus lens with infinity focus;a
The lens and camera body, and the body and imaging detector should be firmly connected;b)
The maximum shutter speed of the camera should not be slower than 1/800s;The camera should have the function of signal feedback at the exposure time:d)
The field of view of the camera should not be less than 27 in the flight direction;f)
The dynamic range of grayscale recording should not be less than 8 bits per channel;GB/T39612—2020
The original image should be stored in an uncompressed format. When stored in a compressed format, the compression ratio should not be greater than 10 times. g)
Calibration requirements
The camera should be geometrically calibrated and meet the following requirements:a) Calibration error: the coordinates of the principal point should not be greater than 10μm, the principal distance should not be greater than 5uμm, and the residual distortion should not be greater than 0.3 pixels;b)
Calibration parameters and calibration mathematical model should be provided for each calibration:d)
When the camera is overhauled, key components are replaced, or it is subjected to severe vibration and impact, it should be recalibrated. 5.2.2.3
Installation requirements
The camera should meet the following requirements when installed on an unmanned aerial vehicle: The connection between the camera and the aircraft should be firm and reliable;a)
b) There should be a shock-absorbing device between the camera and the aircraft;c) A schematic diagram of the camera installation orientation should be provided, see Appendix A. 5.3 Aerial photography plan and design
5.3.1 Mathematical basis
The mathematical basis is stipulated as follows:
a) The coordinate system shall adopt the 2000 National Geodetic Coordinate System, and an independent coordinate system approved by law may also be adopted; b) The elevation datum shall adopt the 1985 National Elevation Datum, and other elevation datums approved by law may also be adopted; c) The map projection adopts the Gauss-Krüger projection, with a 3° zone according to the longitude difference, and a 1.5° zone may also be adopted. 5.3.2
Aerial photography plan
An aerial photography plan shall be formulated according to the needs of mapping. The aerial photography plan shall include the following contents: the scope of the photography area and its landform features;
mapping scale and photography ground resolution; c)
route laying method, film heading and lateral overlap; d)
type, parameters of aircraft and aerial photography camera and other auxiliary equipment parameters; e)
name and quantity of aerial photography results to be provided; season and period for carrying out aerial photography tasks;
other technical requirements.
5.3.3 Aerial photography design
5.3.3.1 Selection of basic geographic data for design The basic geographic data for design should be the latest topographic map, image map or digital elevation model of the photography area. The scale of topographic map and image map should not be less than 1:10000, and the scale of digital elevation model should not be less than 1:50000. 2 Selection of ground resolution of datum
The ground resolution of the datum of each aerial photography sub-area should be based on the requirements of aerial photography mapping of different scales, combined with the terrain conditions of the sub-area, mapping contour distance, aerial photography base height ratio and image use, etc., on the premise of ensuring the mapping accuracy, in the spirit of shortening the mapping cycle, reducing costs and improving 3
GB/T396 12—2020
The principle of comprehensive benefits of surveying and mapping is to be selected within the range of Table 1. Table 1 Ground resolution of aerial photography datum Design range Mapping scale
1:1000
1:2000
5.3.3.3 Division of aerial photography zones and determination of datum The division of aerial photography zones and determination of datum should follow the following principles Ground resolution/cm
≤10. 8
≤20 is preferred, 16 is preferred
Division should take into account factors such as mapping scale, flight efficiency, flight direction, and flight safety. The calculation of aerial photography datum should generally take the weighted average of the proportion of elevation within the zone. For the calculation method, see Appendix B B.6. b)
The terrain height difference within the zones of flat land, hilly land and mountainous land should not be greater than 1/4 of the relative flight height; the terrain height difference within the zone of high mountainous land should not be greater than 1/3 of the relative flight height.
When the zoning is performed according to the provisions of c), and the zoning area is small, scattered, and fragmented, which makes it difficult to implement the flight mission, the zoning can be re-divided according to the principle that the ground resolution of the lowest d)
point is not less than 1.5 times the reference surface resolution: or multiple small zoning areas with an area exceeding the resolution limit of no more than 10% in the shooting area can be merged into adjacent larger zoning areas. e) When the terrain height difference meets the conditions specified in c) and d), the span of the zoning area should be as large as possible and completely cover the shooting area. 5.3.3.4 Overlap design
The overlap should be designed on the aerial photography zoning reference surface, and the design indicators are as follows: a
The heading overlap should generally be 65% to 75%; the lateral overlap should generally be 30% to 45%; b)
When aerial photography is performed in steep mountainous areas, urban areas with dense tall buildings, islands, roads, pipelines, rivers and other shooting areas, the overlap design should be appropriately increased.
5.3.3.5 Camera shutter speed design
The flight speed of the UAV should match the camera shutter speed setting to ensure that the displacement of the image point on the aerial photography reference surface does not exceed 0.5 pixels. For the image point displacement calculation formula, see B.1.5.3.3.6
Route laying
Route laying should follow the following principles:
The route is generally laid parallel to the long side of the survey area shape, and can also be laid in an east-west or north-south direction, or fly along the direction of lines, rivers, islands, coasts, borders, etc.;
The exposure point should be based on the digital elevation model and designed using fixed-point exposure or equidistant exposure control methods; b)
c) When laying out the framework route, it should be as perpendicular to the normal route in the photography area as possible, and the flight altitude should be consistent. 5.3.3.7 Selection of season and time for aerial photography
The selection of season and time for aerial photography should follow the following principles: a) Aerial photography should be avoided as much as possible in conditions of snow accumulation, floods, blowing sand, smog, etc.; b) When aerial photography is conducted in deserts, Gobi, rivers, lakes, oceans, large areas of salt marshes, saline-alkali land, tidal flats, etc., photography should be conducted 1 to 2 hours before and after noon to reduce the loss of image details caused by strong reflections from the ground; 4
GB/T39612—2020
c) In steep mountainous areas and urban areas with dense high-rise buildings, photography should be conducted within 2 hours before and after noon to reduce the impact of shadows on the details of the objects.
5.3.3.8 Laying aerial photography ground signs
For areas lacking characteristic features (such as forests, Gobi, deserts, tidal flats, etc.) or requiring high-precision aerial photography measurement, artificial points should be made, signs should be laid, and coordinates should be measured before aerial photography is implemented. The requirements are as follows: a) The shape and specifications of artificial ground signs should ensure that they can be accurately identified and measured in the image; b) The color of artificial ground signs should ensure that they have good contrast with the surrounding ground and are clearly visible in the image. 5.4 Aerial photography implementation
During the implementation of aerial photography, the following principles should be followed: When using an airport for takeoff and landing, the flight should be carried out in accordance with the relevant regulations of the airport; when not using an airport for takeoff and landing, the takeoff and landing site and backup site should be selected according to the performance requirements of the unmanned aerial vehicle. A detailed flight plan should be made before aerial photography is implemented, and an emergency plan should be made for possible emergencies b)
On the premise of ensuring flight safety and when the lighting and visibility conditions permit, cloud photography can be carried out. c
When using GNSS or IMU/GNSS-assisted aerial photography, follow GB/T27919-2011. d)
Before takeoff, the difference between the barometric altimeter, GNSS geodetic height, and topographic map altitude should be calibrated to ensure that the real-time flight altitude does not have a large systematic deviation from the designed altitude. f) The aerial photography flight record form should be filled in, see Appendix C5.5 Flight quality and image quality requirements
5.5.1 Flight quality
Flight quality should meet the following requirements:
The heading overlap of the image is generally 60% to 90%, and the minimum should not be less than 53%; the lateral overlap is generally 15% to 60%, and the minimum should not be less than 8%.
The inclination angle of the image is generally not more than 12° and the maximum is not more than 15°; the rotation angle of the image is generally not more than 15 and the maximum is not more than 25°; the inclination angle and the rotation angle of the image should not reach the maximum value at the same time. For the calculation method of the rotation angle of the image, please refer to Appendix D. The heading coverage beyond the partition boundary line should be no less than two baselines; the lateral coverage beyond the entire shooting area and the partition boundary line should generally be no less than 50% of the image frame
The flight altitude difference between two adjacent images on the same route should not be greater than 30m, and the difference between the highest and lowest altitudes on the same route should not be greater than 50m.
Relative loopholes and absolute loopholes that appear during the implementation of aerial photography should be supplemented in time. The same type of camera should be used for supplementary photography, and the two ends of the supplementary photography route should exceed the two baselines outside the hole. f)
The image data should correspond to the positioning and attitude data records one by one, and ensure integrity. 5.5.2 Image quality
The image quality should meet the following requirements:
a) The image should be clear, rich in layers, moderate in contrast, and soft in color: there should be no defects such as clouds, snow, large areas of smoke, reflections, stains, etc. on the image that affect the connection and mapping of the stereo model; b)
The image point displacement should generally not be greater than 0.5 pixels, and the maximum should not be greater than 1 pixel; c)
d) There should be no image blur caused by vibration on the aircraft, lens contamination, camera shutter failure, etc. 5
GB/T39612—2020
5.5.3 Quality of attitude and positioning data
When using GNSS or IMU/GNSS to assist aerial photography, the data quality shall meet the requirements of 8.1.1 of GB/T27919-2011.
Quality inspection and collation of aerial photography results
5.6.1 Quality inspection of aerial photography results
After the aerial photography is completed, the quality of the results shall be inspected according to the requirements of 5.5, and the results shall be delivered to the next process for use after the inspection is qualified. 5.6.2 Collation of aerial photography results
5.6.2.1 Aerial film numbering
The method of aerial film numbering is as follows:
The aerial film number consists of 12 Arabic numerals, and the serial numbering is based on the route. From left to right, the 1st to 4th digit of the film number is the code of the shooting area, the 5th to 6th digit is the partition number, the 7th to 9th digit is the route number, and the 10th to 12th digit is the film serial number. b) Generally, the number increases in the direction of flight. c)
The film numbers within the same route are not allowed to be repeated. d)
When there is a supplementary flight route, the film serial number of the supplementary flight route is based on the original serial number of the route plus 500. Aerial film storage
Create a directory according to the shooting area, partition, and route, and store them separately. Hard disks or optical disks should be used for storage. See Appendix E for the schematic diagram of aerial photography partitions and routes.
Aerial photography results data
Aerial photography results data include the following contents:
Image data;
Image position and attitude data;
Aerial photography division diagram, route diagram; aerial photography flight record form;
Photography area completion status map, see Appendix F;
Camera calibration report, calibration model and calibration parameters; aerial photography approval document;
Aerial photography data review report;
Aerial photography technical design book;
Aerial photography technology summary report:
Aerial photography results inspection report and acceptance report; Aerial photography results list;
Other relevant materials.
Photographic control measurement
Photographic control point layout
Basic requirements
Photographic control point layout should meet the following basic requirements:6
GB/T39612—2020
Various instruments and equipment used in photographic control measurement operations should be inspected and calibrated, and the calibration certificate should be valid: Before field photographic control measurement, a site survey should be conducted to select the working road, characteristic objects, and the location of the markers, and reasonably allocate personnel and b)
Instruments;
Photographic control points should be laid out according to regional networks or routes. The distribution of control points should be able to control the entire survey area and meet the accuracy requirements of the results. The control points between adjacent image pairs and adjacent routes should be shared. Layout requirements
Point selection requirements
The selection of photo control points should meet the following requirements:a)
The self-marked image of the photo control point should be clear, easy to read the puncture point and stereo measurement, and should be a place with small elevation fluctuations, relatively fixed all year round, and easy to accurately locate and measure. Arc-shaped objects, shadows, tall buildings, and places near tall trees, and places that are difficult to distinguish from the surrounding areas should not be selected as point targets.b)
Photo control points should be selected near the overlapping midline of the photo, as far away from the edge of the photo as possible. 6.1.2.2
Regional network layout plan
6.1.2.2.1 Basic requirements
The regional network layout should meet the following requirements:
The division of the regional network should be based on the mapping scale, ground resolution, terrain characteristics of the survey area, division of aerial photography areas, shape of the survey area, etc., and the best implementation plan should be selected according to the specific situation. b)
The regional network shape should be rectangular. The size of the regional network and the span between the image control points should be based on the principle of meeting the accuracy requirements of aerial triangulation, and are mainly determined by multiple factors such as mapping accuracy, relevant parameters of aerial photography data, and processing of system errors. 6.1.2.2.2 Regional network point layout plan without GNSS or IMU/GNSS assisted aerial photography When there is no GNSS or IMU/GNSS assisted aerial photography, when regional network point layout is adopted for two or more parallel routes, the requirements are as follows:
a) The baseline span of adjacent control points in the heading should generally not exceed the provisions of Table 2. When it is only used for DOM measurement, the baseline span can be relaxed to 2 times;
Table 2 Baseline span of adjacent control points in the heading
Scale
1:1000
1:2000
Baseline span
Lateral The route span of adjacent control points should generally not exceed the provisions of Table 3. When it is only used for measuring DOM, the route span can be relaxed b)
to 2 times;
Table 3 Route span of lateral adjacent control points
Scale
1:1000
1:2000
Route span
GB/T39612—2020
The baseline span and route span in the point layout requirements for special difficult areas (large areas of deserts, Gobi, swamps, forests, etc.) shall be relaxed c
to 1 to 2 times accordingly, and shall be clearly specified in the technical design book. 6.1.2.2.3GNSS, IMU/GNSS assisted aerial photography regional network point layout plan When using GNSS, IMU/GNSS assisted aerial photography, in addition to meeting the requirements of GB/T27919-2011, the following requirements shall also be met: the line connecting the image control points shall completely cover the mapping area, and all level points shall be arranged; a
control points shall adopt the corner point and inflection point layout method, that is, level points shall be arranged at the turning points of convex corners and concave corners of the regional network, and b)
at least one level point shall be arranged in the regional network. During actual layout, the baseline span of the control points shall not exceed the provisions of Table 4, and the route span shall not exceed the provisions of Table 5.
Table 4 Baseline span of adjacent control points in heading
Scale
1:1000
1:2000
Note: When only DOM is measured, the baseline span can be relaxed to twice the route span of the adjacent control points in the lateral direction
Scale
1:1000
1:2000
6.1.2.3 Single route point layout plan
Baseline span
Route span
When single route point layout is adopted, the heading baseline span between adjacent control points can be designed in accordance with 6.1.2.2, and control points need to be laid at the upper and lower standard points of the images where points need to be laid.
6.1.2.4 Full field point layout plan
The full field point layout plan shall be implemented in accordance with the requirements of CH/T3006-2011. Point arrangement plan for special situations
When encountering special situations such as the main point or standard point falling into the water, or the absolute loophole of aerial photography in the bay island area, it is impossible to arrange the image control points according to the normal situation. The control points shall be arranged according to the specific situation in principle to meet the requirements of aerial triangulation and stereo mapping. The specific method shall be in accordance with 6.3.2 of CH/T3006-2011.3. Basic control point measurement
Basic control point measurement should meet the following requirements: for basic control point measurement used for plane control, when using GNSS static relative orientation method, its layout principle, point selection, observation, recording, data processing, results inspection and delivery materials should comply with the provisions of GB/T18314-2009 E-level network; b) for basic control point measurement used for elevation control, the measurement should be carried out according to the standard leveling measurement or the method with equivalent accuracy.
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