Circular No. 12/2023/TT-BTNMT on technical regulations for flood inundation monitoring using remote sensing technology

CIRCULAR

Technical regulations for flood inundation monitoring using remote sensing technology

WHEREAS, Decree No. 03/2019/ND-CP dated January 4, 2019 of the Government on remote sensing activities;

Pursuant to Decree No. 68/2022/NĐ-CP dated September 22, 2022 of the Government stipulating the functions, tasks, powers, and organizational structure of the Ministry of Natural Resources and Environment;

AT THE REQUEST OF THE DIRECTOR OF THE NATIONAL REMOTE SENSING CENTER, THE HEAD OF THE SCIENCE AND TECHNOLOGY DEPARTMENT, AND THE HEAD OF THE LEGAL AFFAIRS DEPARTMENT;

The Minister of Natural Resources and Environment issues this Circular to stipulate technical regulations for flood inundation monitoring using remote sensing technology.

PART I

GENERAL PROVISIONS

Article 1. Scope of Regulation

This Circular stipulates technical regulations for flood inundation monitoring using remote sensing technology.

Article 2. Applicability

This Circular applies to agencies, organizations, and individuals participating in flood inundation monitoring activities using remote sensing technology.

Article 3. Definitions and Abbreviations

In this Circular, the following terms are understood as follows:

1. Radar remote sensing imagery is information and images of geographic objects obtained from satellites using microwave radiation with wavelengths ranging from 1 mm to 1 m.

2. Remote sensing flood inundation monitoring map is a thematic map established using remote sensing imagery data to monitor areas affected by floods at different times before, during, and after flooding occurs.

3. Noise filtering is the process of removing all or part of the information that affects image quality.

4. HH polarization is the type of horizontal transmission and reception of electromagnetic waves.

5. VH polarization is the type of vertical transmission and horizontal reception of electromagnetic waves.

6. HV polarization is the type of horizontal transmission and vertical reception of electromagnetic waves.

7. VV polarization is the type of vertical transmission and reception of electromagnetic waves.

8. Image quality enhancement is the adjustment of image radiation to improve the information capacity of the image.

Article 4. Mathematical basis for remote sensing flood inundation monitoring maps

1. Coordinate system and reference frame shall be implemented according to Decision No. 83/2000/QĐ-TTg dated July 12, 2000 of the Prime Minister on the use of the National Reference Frame and Coordinate System of Vietnam. Specifically:

The National Reference Frame and Coordinate System VN-2000 shall be used to represent the Flood Inundation Monitoring Map. Parameters include: UTM projection grid, WGS84 ellipsoid, 6° zone, scale factor k0 = 0.9996.

2. Other components: legend table (if applicable), map key, map scale, and scale bar.

The frame of the remote sensing flood inundation monitoring map is specified in Model No. 01 attached as an appendix to this Circular.

Article 5. Contents of work

1. Preparation work.

2. Processing remote sensing imagery.

3. Extracting background monitoring data from the national geographic database.

4. Extracting flood inundation information.

5. Editing the flood inundation information layer.

6. Establishing the flood inundation monitoring map.

7. Checking and evaluating the reliability of the flood inundation monitoring map.

8. Preparing the flood inundation monitoring report.

9. Submitting products.

Chapter II

TECHNICAL REGULATIONS FOR FLOOD INUNDATION MONITORING USING REMOTE SENSING TECHNOLOGY

Article 6. Preparation Work

1. Collecting and compiling disaster information, including:

a) Information on rainfall forecasts, including duration and location of rainfall;

b) Typhoon forecast information, including typhoon intensity, direction of movement, time, and affected area;

c) Collecting and compiling other meteorological and hydrological forecast and warning information within the national meteorological and hydrological forecasting and warning system.

2. Collecting information from remote sensing satellites passing over Vietnam, including:

a) Information on satellite management agencies;

b) Information on imaging time and coverage;

c) Technical parameters of the required imagery types.

3. Scheduling remote sensing imagery for flood inundation monitoring:

a) Determining the location and coverage of the imagery;

b) Timing of imagery acquisition;

c) Frequency of imagery acquisition;

d) Sending requests for imagery acquisition to the data provider agency.

4. Acquiring remote sensing imagery data before, during, and after flooding.

5. Collecting maps and related information about the monitored area, including:

a) Flood inundation monitoring data from domestic and international organizations;

b) Background geographic data;

c) Digital elevation models.

Article 7. Remote sensing image processing

1. Input data entry

a) Remote sensing images, after quality inspection, are entered into the remote sensing image processing software;

b) Convert the gray value of the image (DN) to the radiometric value of the image (dB).

2. Enhance image quality

a) Process for radar remote sensing image model reconstruction (SAR Simulation);

b) Adjust the impact of terrain on image quality;

c) Noise filtering: Remove high-frequency noise while preserving the characteristics of the image; the size of the filter is 5x5 pixels or 7x7 pixels to ensure the best results.

3. Conversion to National Coordinate System VN-2000.

4. Image stitching, cutting, and exporting maps according to the monitored area.

Article 8. Extraction of flood monitoring base data from the national geographic database

1. National land borders, administrative boundary lines.

2. Provincial People's Committee headquarters, district People's Committee headquarters, commune People's Committee headquarters.

3. National railways, expressways, national highways, provincial roads, district roads, airports.

4. Hydrographic objects with areas larger than 15 mm² according to the scale required for establishment; linear hydrographic objects with lengths greater than 2 cm according to the scale required for establishment.

Article 9. Flood information extraction

1. Select image polarization in the following priority order: HH polarization, VH polarization, HV polarization, VV polarization.

2. Determine the radiation value threshold of water bodies in the image.

3. Separate flooded areas.

4. Export the boundaries of flooded areas in vector format.

Article 10. Editing of flood information layer

1. Adjust flood information results:

a) Adjust the impact of terrain on the separation of flooded areas;

b) Remove or consolidate flooded areas with areas smaller than 15 mm² on the map.

2. Smooth the edges of flooded areas: smoothing parameter is 0.1 mm on the map.

3. Remove frequently flooded areas.

4. Calculate the area of flooded regions by administrative province, district, and commune units.

The flood area statistics table is specified in Model No. 02 attached as an appendix to this Circular.

Article 11. Establishing flood monitoring maps

1. Flood monitoring maps using remote sensing technology are determined by the scale according to the scope of influence and resolution of the image data used.

2. Edit flood monitoring maps according to the specifications of thematic maps.

3. Design additional symbols.

4. Present flood monitoring maps.

Article 12. Checking and evaluating the reliability of flood monitoring maps

1. Take a minimum of 10 samples from remote sensing image data in areas affected by floods for verification purposes.

2. Compare flood monitoring maps with samples.

3. The reliability of flood monitoring maps must be over 90%.

4. Correct flood monitoring maps after verification (if necessary).

Article 13. Preparing flood monitoring reports

1. Prepare flood monitoring reports using remote sensing technology according to Model No. 03 attached as an appendix to this Circular.

2. Prepare annual comprehensive reports on flood monitoring results using remote sensing technology according to Model No. 04 attached as an appendix to this Circular.

Article 14. Submission of products

1. Submit flood monitoring maps and flood reports to the managing authority and data users within no more than five days after the end of the disaster period.

2. Submit annual comprehensive reports on flood monitoring results using remote sensing technology before December 25 each year.

Chapter III

IMPLEMENTING PROVISIONS

Article 15. Effective Date

This Circular takes effect from December 1, 2023.

Article 16. Implementation Organization

1. Ministries, ministerial-level agencies, agencies under the Government, People's Committees of provinces and centrally governed cities, and relevant organizations and individuals are responsible for implementing this Circular.

2. The Director of the National Remote Sensing Center shall be responsible for organizing the dissemination and inspection of the implementation of this Circular.

3. IN CASE OF ANY DIFFICULTIES OR OBSTACLES DURING IMPLEMENTATION, THE CONCERNED AUTHORITIES, ORGANIZATIONS, AND INDIVIDUALS SHALL PROMPTLY REPORT TO THE MINISTRY OF NATURAL RESOURCES AND ENVIRONMENT FOR REVIEW AND DECISION./.