Circular 39//tt-Btnmt By 2014: Technical Regulation Established Digital Elevation Model Using Scanning Lidar Flight Technology

Original Language Title: Thông tư 39/2014/TT-BTNMT: Quy định kỹ thuật thành lập mô hình số độ cao bằng công nghệ bay quét LiDAR

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Number: 39 /2014/TT-BTNMT
Hanoi, July 3, 2014


Technical regulation establishing a high degree model by

Lidar scan technology


Base of Protocol 12 /2013/ND-CP January 22, 2002 of the Government of the Measurement and Map Activity;

Base of Protocol 21 /2013/NĐ-CP March 4, 2013 of the Government regulates the function, mandate, jurisdiction and organizational structure of the Ministry of Natural Resources and Environment;

At the suggestion of the Office of the Bureau of Measurements and the Vietnam Map, the Chief of the Legal Affairs and the Chief of Science and Technology;

The Ministry of Natural Resources and Environment issued the specification of establishing a high-altitude model by LiDAR scanning technology.

Chapter I


What? 1. The adjustment range

This information provides technical requirements in establishing a high-altitude model with LiDAR scanning technology.

In case of a combination of digital imaging during LiDAR scan, the formation of the digital image will be done according to the technical regulation at this WDAR.

What? 2. Subject applies

It applies to state regulatory agencies of measurements and maps; organizations, individuals, and maps in the field of measuring and maps on the territory of the Socialist Republic of Vietnam.

What? 3. Explain words

In this Information, the words below are understood as follows:

1. Laser (Light Amplification by Stimulated Emission of Radiation): is the technology/light amplification device by excitation emission.

2. LiDAR (Light Detection And Ranging): is a laser-based measurement technology.

3. DEM (Digital Elevation Model): a high-degree model, showing the height of the terrain surface.

4. DSM (Digital Surface Model): is the surface number model, showing the top layer of the earth ' s surface visible from the top down.

5. The digital image: is the generic name of the digital image product that has been calibrated to the effect of the topographic difference, positioned in the coordinate system of the map to be established, resamed in line with the map ratio needed to be established, cut, grafted to the map and is named after the title of the corresponding piece of map.

6. EGM2008 (Earth Gravitational Model 2008) is a 2008 Earth-based gravity model published by the United States, commonly known as the global geoid model 2008.

7. IMU (Inertial Measurement Unit), which is a inertial gauge, consisting of a particle accelerator and a rotating angle in space.

8. GNSS (Global Navigation Satellite System) is a common name for global navigation systems using satellites such as GPS (US), the Galileo positioning system (European Union) and GLONASS (Russian Federation), Beidou (China) ...

9. PDOP (Position Dilution Of Precision), which represents an accurate decrease in the accuracy of the 3-dimensional positioning accuracy as a result of the relative position of the GPS/GNSS satellites relative to a GPS/GNSS.

10. WGS-84 (World Geodetic System 1984): World Geodetic System 1984, which includes data on Earth's reference frame, reference ellipsoid, the geoid face published by the U.S. Department of Defense in 1984.

11. GRID: A special format used to store high-degree model and surface number model in a square grid form, possibly in a binary code file (binary), or ASCII code file (American Standard Code for Information Interchange). Believe me.

12. GeoTIFF: A special format used to store image data attached to the location's geographical positioning information.

13. GNSS Base station: is the base GNSS station, a GNSS generator located at a point that knows the exact coordinates, used to distribute the reclamation information for mobile GNSS machines around with a certain range in the following GNSS measurements of the following processing. (Post Processing Differential GNSS) or measure GNSS fated by real-time (Real Time DGNSS).

14. Point cloud: a point cloud, which sets the points with coordinates, the altitude is determined through the process of processing the laser scan data.

15. Ground points: The ground layer, which includes points on the surface of the terrain that has been removed from surface-mantle objects such as: home, architectural works, food ...

16. Non-ground points: is the non-terrestrial class, consisting of points located on the surface of objects covering the ground when viewed from above.

17. Metadata: is metadata, including information that describes the properties of data such as content, format, quality, conditions, and other properties aimed at instructions on the approach, management body, access address, storage site, data preservation, data preservation, and data. Yeah.

18. LAS format: is the application format for storing and converting laser-point cloud data.

19. Intensity: The intensity of the feedback, defined as the ratio of the strength of the reflected light and the emission light, is strongly influenced by the reflectivity characteristic of the reflectiated objects.

20. Intensity image: A feedback intensity image, which shows the digital archive of the intensity of the feedback laser that is recovered and encoded in a grey scale scale.

21. First return: is the first feedback signal.

22. Last return: is the last response signal.

Chapter II


What? 4. The mathematical basis of the high number model

1. The high number model was established in accordance with the VN-2000 National System of Reference and System, the projection zone, the axis-based implementation line at the Digital Information 973 /2001/TT-TCC June 20, 2001, by the General Administration of the United States, guidelines for the application of the VN-2000 system and system.

2. The high system used in the construction of the high-altitude model is the current national system.

3. The geoid model used is the most accurate local geoid model available. The site of the unbuilt site is the local geoid model and the narrow range range (about 50km x 50km) is allowed to use the Global Geoid model EGM2008. The site of the site has not yet built a local geoid model but has a wide range or in the mountainous area that must build the local geoid model precisely for that area. The method of building the local geoid model must be specified in the Engineering Design-Proposition.

4. High-degree model (DEM) established by LiDAR technology is shown in the form of a square grid (GRID) or other formats according to requirements.

What? 5. The process of establishing a high degree model and digital image equality by LiDAR scanning technology

The process of establishing a high number of digital and digital pixels using LiDAR scanning technology includes the following main work steps:

Step one. Preparation work.

Step 2. Fly Sweep LiDAR and take the digital photo.

Step three. Data processing.

Step four. Set up the number of high numbers and digital pixels.

Step five. Check, collect the product.

Step six. Deliver the data, the product.

What? 6. Standard Job

1. Sweep design: executed by regulation at Article 7 of this.

2. Preparing full of resources that will be mobilized for mission execution, the project.

3. Check, check, install device system:

a) The device system must be flown by the manufacturer's regulations: the time cycle, the size of the flight area, the number of milestones, the milestones, the scale accuracy, the altitude accuracy, the altitude of the test points for flight testing;

b) A periodic test flight operation, a minimum of one time/year;

c) Check the ground device system before installing the aircraft;

d) Installation and test the device system before the aircraft took off.

4. Layout, measuring the GNSS Base station, the weather groups: executed by regulation at this Article 8.

5. Build the calibration deros: implement by regulation at Article 9 of this.

What? 7. Sweep design

1. The public area of the project to establish a high-altitude model (abbreviated as a measure) is divided into subsections to ensure the deployment of the GNSS Base station and for LiDAR scanning, digital photography.

2. The LiDAR scanning flight design and digital imaging of the basic principle is to cover the measure, ensure the most accurate and cost-saving accuracy.

3. The basic information needs to determine when the flight design includes: defining the demarcation boundary, flight altitude, flight direction, coverage for scanning routes, camera standards, vertical coverage, and horizontal coverage for photographic photography, installation parameters for the devices, and the design of the aircraft. It ' s been scanned and scanned.

4. Permission to use the dedicated software to design the flight route.

5. The design of the routes includes:

a) The main routes: the two adjacent LiDAR scanning (horizontal) is 30% on average. Digital imaging ensures an average of 60% vertical coverage, an average horizontal coverage of 30%. The flight range must be covered outside the minimum gauge boundary of 1/5 of the flight width. The flight direction is selected depending on the body of the gauge, the terrain condition, the unsaved conditions for the flight time being the shortest;

b) The intercepts are designed to cut through the main routes (preferable to the main flight route) to detect and reduce the system error, rough numbers; ensure that the maximum distance between the interception lines is 50km.

6. Other parameters such as altitude, flight speed, scan angle, scan frequency, scanner width, scan point density, depending on the type of LiDAR device, type of aircraft, the accuracy of the DEM needs to be established in Engineering Design-Proposition.

What? 8. Layout and measuring the GNSS Base station and weather nests

1. Each precinct must be deployed 2 GNSS Base station stations. The distance from the GNSS Base station to the scanning flight boundaries does not exceed 30 km, prioritits the location of the GNSS Base station station in the middle of the gauge. The choice points for the GNSS Base station must have a flat level accuracy and higher altitude than the accuracy of the DEM needs to be 1.4 times.

2. During the LiDAR scan process must conduct a 2-frequency GNSS receiver, recording continuous signal at the GNSS Base station with a frequency of 1-signal signal per second during the sweep. The GNSS receiver had to be turned on and recorded before the engine burst and was only off after the plane was stopped, following the order of the crew in charge of the crew.

3. The layout of the weather monitors during the duration of the construction site at the site or in the sub-districts to report information in time, with a high reliability of that area's weather for the person in charge of the flight, ensuring the effectiveness of each flight.

What? 9. Build a flat face correction standard and height

1. The number of calibrated dermers: depending on the LiDAR scan range, the characteristic subsection shape and feature terrain features in the subsection to build the calibrated standard. A minimum construction requirement of two (02) is calibrated to serve the smooth, high-level, and inspection calibration.

2. The layout of the calibration stations: the calibrated deros need to be arranged in accordance with the feature, the site of the measurement, not the layout of the close calibration, but rather the relative positions in the area.

3. Selection of the calibrated field measure: calibrated deros must be selected in areas with flat, recognizable terrain, optimal for the ability to only respond to a single laser pulse. When the survey was selected to select the calibration standard for selection in empty beach areas, stadiums, squares, large roads.

4. Edit calibration standard:

a) Must build a grid that controls the drawing measure at the calibration site in the event that cannot be used directly with the flat surface control points, the altitude for measuring the points of detail;

b) At each calibration standard, using precision measuring devices such as electronic integrity machines, standard machine machines, GNSS machines that define coordinates, minimum height of 50 points of detail on the ground and a minimum of 5 sharp terrain objects with different contrast. They ' re large with all the surrounding things like: home, yard, lawn.

5. The error specified coordinates, the height of the detail points specified in table 1.

Table 1

The accuracy of the DEM needs to be established

Error number (m)



0.2 m-0.3 m



0.4 m-0.5 m



1.0 m



6. The case of not measuring the sharp geophysical item must proceed to build the prescribed mark as follows:

a) The mark must be made in the area with relatively flat terrain, with no surrounding food. The mark shape can be circular, the cross-shaped form depends on the laser pulse point density with the wings of the wings of the cross (or the diameter of the circle) not less than two (2) times the distance between the surrounding reflective points. Laser. The surface coating material of the marker must ensure that there is good reflective with laser pulses and the color must have high contrast with the surrounding terrain;

b) The landmark case is a circle, the coordinates and altitude of the mold must be accurately defined in the field. The case is a cross-shaped which has to measure the position of the eight angles of the four cross-shaped wings. The error determines the coordinates, the altitude of the specified points at table 1.

What? 10. Fly Sweep LiDAR and take a digital photo

1. The GNSS Server installed on the aircraft is a 2-frequency GNSS generator with the same parameters set similar to the GNSS Base station. The selection of the time in addition to the weather dependence, the flight command was also dependent on the GNSS satellite imagery at the time of the flight. Only flight sweeps of the GNSS have a PDP value of < 4.0 and GNSS aircraft on the aircraft, as well as the GNSS Base station, which obtained a minimum simultaneously signal from five health satellites.

2. When installing the devices on the aircraft needed to notice the scanning angle of the laser collection and the camera angle of the digital camera was not hampered by the fuselage and floor of the aircraft. After an accurate measurement of offset offset (dX, dY, dZ) between the center of the devices: GNSS antennas, digital cameras, laser detectors and IMU derivative equipment with precision to cm.

3. During LiDAR scanning and digital imaging must always monitor the activity of the devices, the performance of the scanning and photography process, which specifically noted the operation of the LiDAR scanner, the coverage between the flight paths, the areas with no data scanning data. Or there &apos; s data, but intensity, flooding areas ... to decide whether to fly directly or not.

4. When completing the main routes and the interception routes must proceed to test results, take out data, backup to serve and calculate. The format of data depends on each type of specific scanning device.

5. When the end of the measure must proceed immediately to check out the LiDAR scanning quality and scan the number in the sweep area including the flight quality test work, the calculation of the open area, the fault for having a compensated flight plan.

What? 11. Data processing

1. The LiDAR scanning flight data processing process incorporates the number of key segments as follows:

Step one. Calculating flight trajectory.

Step 2. Create a cluster of points in the range and join the cube.

Step three. Calculating cloud-point cloud data on the coordinate system, the altitude of VN-2000 through the calculation parameters and the geoid model.

Step four. Check and clear the cloud points according to the calibration standard.

Step five. Sort and filter points.

2. The flight path trajectory is determined through the handling of the GNSS measurement between the generator at the GNSS Base station and the aircraft installed on the aircraft using the device attached to the device to determine coordinates, antenna height, laser emission center, camera mind set up. on the plane at the time of the GNSS signal capture. The central error is the point where the plane is flat and the average height after processing for the entire measuring area must be less than 0.1m.

3. The coordinates and altitude in the WGS-84 system of data cloud points are determined through: coordinates, laser capture height, laser measurement data, and IMU measurement data applied to Kalman filtering.

4. False deviation of the height of each laser pulse response point that forms the following point cloud handling must be less than or equal to two-thirds of the allowed error of the DEM model to be established.

5. Use measurements from the interception routes for the wrong side between the main routes and the interception routes.

6. Processing the flat face and the altitude between the point cloud data and the measuring points at the calibrated dermages performed according to the dedicated software based on the deviation values defined as follows:

a) The plane ' s deviation values are determined through the measurements at the corrector and corresponding points in the cloud of points or on the image;

b) The deviation values of the altitude are determined through the measurements at the calibrated dermables and the similarities in the point cloud.

7. Progress categorisates the cloud of points into ground points and non-ground points using specialized software on the basis of a feedback intensity image and snapshot image simultaneously served the formation of the DEM and DSM models.

What? 12. Set up the high number model and digital image jar

1. The process of establishing a high degree model and the digital image chart consists of the main segments as follows:

Step one. Create a DSM surface number model, high number model, feedback intensity image according to the map piece.

Step 2. Calculate the external orientation elements of the image.

Step three. Convert the format and enhance image quality.

Step four. Reshape the image, establish a digital image.

Step five. Standardization of DEM high-altitude model.

2. High-degree model (DEM) built from the Last return data (Last return). The surface number model (DSM) is built from the First return data.

3. The intensity image is created in the VN-2000 coordinate system on the basis of the intensity of the optical feedback intensity data (the integrity) of the laser beam and is used in the classification of point data. The value of the GRID grid is interpolated from the intensity value at discrete LiDAR points. The resolution of the feedback intensity image is determined on the average distance basis between the laser pulse response points.

4. Define the external orientation parameter for the image made using the device attached to the device based on the external orientation parameters as GNSS, IMU, and the time of the photo shoot.

5. Transfer of Image Format (on GeoTIFF format) and enhance image quality from the original image capture by dedicated software.

6. The digital image is set up on the basis of the digital image data that has been converted from the original snapshot during LiDAR scanning and is used as the basis for standardization of the DEM model and serves the formation of the terrain map. The resolution of the image jar is determined on the average distance between the laser pulses feedback points.

7. Degrade the DEM model to use survey results and other sources, specifically noted areas with weak LiDAR intensity, flooded areas at the time of the flight. In the event it is necessary to conduct additional measurements in the field.

8. Requiem the accuracy of the DEM model to be established as follows:

a) The number of marketing errors between the other DEM fragments of the scanning area failed to exceed 1.5 times the DEM's license number under the Engineering Design-Proposition;

b) The absolute number of DEM errors are evaluated through field test scores. The central error on the altitude of the test point set between the altitude measured over the endothisine high from the DEM does not exceed the accuracy of the DEM according to the Engineering Design-Proposition. The limit error is not exceeded 2 times the local error. The deviation of the test measurements is not exceeding the limit margin, the number of measured values lying in the range (70%-100%) of the limited number not exceeding 10%.

What? 13. Check out the product collection

Test work, the current implementation of the specified income in the Digital Information 02 /2007/TT-BTNMT February 12, 2007 by the Minister of Natural Resources and Environmental Protection, appraisal and testing of works, product measurements and maps.

What? 14. Data delivery, product

The data, the delivery product is:

1. All the original data from laser scanning equipment, IMU, GNSS, digital screenshots and intermediate calculation results.

2. The DEM high number model is stored in 2 binary GRID formats and ASCII accompanied by metadata (Metadata).

3. File cloud data point in LAS format (LAS format).

4. Digital image data files in GeoTIFF format.

5. The DSM surface number model is stored in 2 binary GRID formats and ASCII with metadata (Metadata) or in other formats if required.

6. Career measurement: construction of calibrated standard, additional measurement (if available), which connects the GNSS Base station, which builds the local geoid model (if any).

7. Technical sump Report: detailing the information about the used equipment, the processing software, LiDAR scanning parameters, data-based gends based on data from the interception and calibration lines, the result of the point classification filter, the error assessment. of the processing steps, the technical specifications of DEM.

Chapter III


What? 15.

It has been in effect since August 18, 2014.

What? 16.

1. Ministry, peer agency, government agency, People's Committee of the provinces, Central City, and organizations, individuals who are involved in the responsibility of this private practice.

2. In the course of the execution, if there is an entanging, the agency, the organization, the individual reflects in time to the Ministry of Natural Resources and the Environment for consideration, decision ./.



Nguyen Ling Yu