Thông tư 03/2020/TT-BTNMT

CIRCULAR

TECHNICAL REGULATIONS ON NATIONAL SATELLITE NAVIGATION NETWORK

Pursuant to Law on Surveying and Mapping dated June 14, 2018;

Pursuant to Decree No. 27/2019/ND-CP dated March 13, 2019 of Government on elaborating to Law on Surveying and Mapping;

Pursuant to Decree No. 36/2017/ND-CP dated April 4, 2017 of the Government administering functions, tasks, powers, and organizational structure of Ministry of Natural Resources and Environment;

At the request of Director General of Mapping, Survey and Geographic information Agency, Director General of Department of Science and Technology and Director General of Department of Legal Affairs;

Minister of Natural Resources and Environment promulgates Circular on technical regulations on national satellite navigation network.

Chapter I

GENERAL PROVISIONS

Article 1. Scope

This Circular prescribes technical requirements for national satellite navigations in survey and mapping.

Article 2. Regulated entities

This Circular applies to regulatory authorities, organizations and individuals involved in developing national satellite navigation network; provision and use of national satellite navigation network in survey and mapping.

Article 3. Definitions and abbreviations

1. Term interpretation

a) Real-time kinematic (RTK) service provided by national satellite navigation network: refers to a service capable of providing data corrections processed by at least 3 national satellite navigation stations to serve survey and mapping with accuracy in cm in real time;

b) Data Sampling: refers to a period of time (in second) during which the measurement is recorded in memory of the reception apparatus;

c) Antenna mount: refers to an accessory to install the antenna fixed to the base section, capable of stabilizing and allowing adjustment of direction of the antenna, usually premade according to international standards;

d) ZAM sheet: refers to an alloy of steel with zinc – aluminum – magnesium developed to suit new line of products, with advanced anti-corrosion property and highly durable, primarily used as housing construction materials.

2. Abbreviations

a) GNSS: Global navigation satellite system;

b) GPS: Global positioning system developed by the US;

c) GLONASS: Global navigation satellite system developed by Russia;

d) GALILEO: Global navigation satellite system developed by the EU and operated by the European Space Agency;

dd) BDS (BeiDou Navigation Satellite System): Global navigation satellite system developed by China;

e) (Quasi-Zenith Satellite System): Navigation satellite system developed by Japan operating mainly in Asia – Australia;

g) IRNSS (Indian Regional Navigation Satellite System): Regional navigation satellite system developed by Indian Space Research Organisation;

h) IGS (International GNSS Service): International organizations providing services related to the GNSS system;

i) ITRF: International terrestrial reference frame;

k) RINEX (Receiver Independent Exchange forma): Standard GNSS data following ASCII data format to facilitate processing independent of reception apparatus or software;

l) VRS: Virtual reference station;

m) MAC: Master-Auxiliary concept;

n) MAX: Correction service utilizing MAC technology solution;

o) i-MAX: Correction service utilizing MAC technology solution corrections;

p) Single Base: Correction service utilizing single base technology solution;

q) RTCM (Radio Technical Commission for Maritime services): Standard data structure for correction transmission developed by the Radio technical commission for maritime services;

r) DVR (Digital video recorder): An electronic device capable of receiving signals from digital camera for processing and recording images in real time;

s) FTTH (Fiber to the Home): Simple cable connection solution transmitting directly from network providers to households or organizations;

t) Leased line: a form of direct connection between network nodes that use independently leased data transmission channel;

u) LAN (Local Area Network): refers to a network system for connecting computers in a small scale.

Article 4. General regulations on national satellite navigation network

1. The national satellite navigation network consists of national satellite navigation stations and central control and processing center connected via internet to ensure continuous and stable date receipt.

2. The central control and processing center consists of data center and operating rooms connected with each other via LAN capable of processing, calculating and providing services serving survey, mapping, highly accurate navigation and scientific research.

3. The national satellite navigation network is developed simultaneously and nationwide in VN-2000 national coordinate system, national altitude system; calculated by determining coordinate regularly and continuously on a daily basis in the ITRF; with gravity value and fluctuation of gravity value determined once every 10 years.

4. Geoid model serving determination of orthometric height is the Geoid model developed conforming to Vietnam territory and publicized by Ministry of Natural Resources and Environment at the same time as providing services of the national satellite navigation network.  Orthometric height (h) = H – N (in which H refers to ellipsoid height, N refers Geoid deducted from the aforementioned Geoid model).

5. Some coastal national satellite navigation stations must be connected with the nearest oceanography stations to monitor sea level to service establishment of national altitude systems, improve the Geoid model and monitor rise of sea level.

6. The national satellite navigation network must be able to be expanded and upgraded to satisfy use demand and compatibility with technical and technology infrastructure of currently active satellite navigation systems around the world.

Chapter II

NATIONAL SATELLITE NAVIGATION STATIONS

Article 5. Overall design of national satellite navigation station

1. National satellite navigation station consisting of 2 types designed according to use purposes as follows:

a) Continuous operating reference stations: distributed evenly nationwide, with average distance between stations of 150 km – 200 km, used as the national coordinate reference, scientific research and serving survey and mapping.   Positions of 24 constructed continuous operating reference stations 999re displayed under Annex 1 of this Circular, from 1 to 3 stations among which participate in the IGS network;

b) Continuous operating stations: positioned in between continuous operating reference stations with average distance between stations of 50 km – 70 km, this distance may be increased up to 100 km.  Continuous operating stations combine with the continuous operating reference stations to create national satellite navigation network capable of providing navigation services in real time with accuracy in cm and meeting most of accuracy requirements in survey and mapping.

2. The design process must prioritize installation in areas already equipped with infrastructure such as natural resource and environment monitor facilities, local agencies specialized in natural resource and environment and People’s Committees of all levels to reduce expenditure on investment and operation while ensuring data stability and security. 

3. At the end of the preliminary design process, display general positions of all national satellite navigation stations on a 1:1,000,000 nation topographic map. Specific position of each station must be displayed on a 1:50,000 national topographic map or larger to serve as the basis for survey and choosing station location.

Article 6. Naming and numbering national satellite navigation stations

1. Name of a national satellite navigation stations must include a full name and an abbreviated name. The full name shall be the location of the station. The abbreviated name consists of 4 letters abbreviated from the full name satisfactory to following requirements:

a) Distinguishable from the full name; and

b) Not repeating other names in the national satellite navigation network; and

c) Not repeating names of connection points in the IGS network (with respect to connection points within satellite navigation network of the IGS).

2. Number of a national satellite navigation station consists of: the first 2 letters are country code, the next 4 letters are abbreviated name of the station, the next 3 letters are order of the station within the national satellite navigation network in which the continuous operating reference stations shall be numbered from 001 to 039 and continuous operating stations shall be number from 040. Number of each national satellite navigation station must be idiosyncratic within the national satellite navigation network.

Article 7. Survey and selection of location of national satellite navigation station

1. On the basis of results of preliminary design of national satellite navigation stations performed as specified in Article 5 of this Circular, conduct physical survey at estimated station location. The survey aims to collect following information:

a) Criteria regarding basic information, including information on natural geography, characteristics, climate, traffic, socio-economic conditions, local security, etc.;

b) Criteria regarding environment and scenery including information on whether surroundings of the estimation station location influence satellite signal receipt quality;

c) Criteria regarding infrastructure including available information on local infrastructure as well as other information serving installation and placement of equipment;

d) Criteria regarding GNSS satellite: collect data directly by GNSS reception apparatus in at least 24 hours at estimated calibrating gauge with specifications established on the reception apparatus similar to official operation to analyze and assess satellite signal receipt quality on monitored frequency; assess interference, obstruction and reduction of signal of each satellite in a day; assess impact of other radio signals in the area;

dd) Criteria regarding measurement and survey of current conditions: directly me33sure the premises of the areas, pay special attention to objects with great height that potentially affects ability to receive signals of the reception apparatus;

e) Criteria regarding national coordinate and national altitude, including examining presence and usability of coordinates, altitude and gravity in the areas to serve measurement and connection;

g) Criteria regarding geological information: provide general assessment regarding geological, geomorphologic and pedological characters in construction location for base section ò the continuous operating reference stations;

h) Details for each criteria specified in Points a, b, c, d, dd, e and g of this Clause are specified in Annex 2 of this Circular. At the end of the survey, entities conducting the survey must produce survey final reports with confirmation of participating parties.

2. On the basis of preliminary design combining with survey for selecting location for nation satellite navigation stations, produce official design. The official design must display all basic information of the station namely: name, number, approximate coordinate, distance to neighboring stations; symbols used in design must be clear and consistent. Official design must be submitted in physical form and digital form.

Article 8. Construction of base section of national satellite navigation stations

1. Base section of a national satellite navigation station must be constructed on stable and spacious ground with 170^o view to the sky from the antenna position.  Do not place metal plating, trees with broad canopy, metal fences, etc. within 2 meters of the base section to minimize multipath interference.

2. The base section shall be made of reinforced concrete with grade M25 concrete (according to 39 TCVN 6025:1995) or higher. The base section shall be in form of a cylinder, 0.3 m in radius, height from the base to antenna placement position is 4 meters. Special cases are prescribed as follows:

a) In case of surrounding structures affecting signal receipt, may raise height of the base section by no more than 8 meters;

b) In case a base section is positioned on other structures, may lower height of the base section to no lower than 2 meters compared to roof of said structures.

3. An antenna mount shall be attached to the top of the base section. The antenna mount must be installed fixed to base section, processed with stainless steel and capable of performing following functions: tightening the antenna, returning the antenna to flat surface and adjusting the antenna orientation (consult Annex 3 of this Circular).

4. Mark 2 altitude marks at the bottom of the base section, one of which is above the base section and the other is below ground level. In case of base sections installed on other structures, place only 1 altitude mark. Determine vertical distance between the altitude mark and antenna reference point (ARP) with accuracy of less than 2mm. Display of altitude mark shall comply with Annex 4 of this Circular.

5. Base sections of base continuous operating reference stations shall only be constructed on ground surface, drilled down and filled with reinforced concrete up to stable level. Regulations on base continuous operating reference stations shall comply with Annex 5 of this Circular.

6. Base sections of continuous operating reference stations shall be constructed above the ground or on ancient architectural structures. Regulations on continuous operating stations shall comply with Annex 6 of this Circular.

Article 9. Satellite signal receptor of national satellite navigation stations

1. antenna receiving satellite signals shall be installed on top of the base section via the antenna mount, returned to flat surface; the antenna must face true north with deviation no more than ±5^o, if exceeding 5o, record the specific value in diary. antennas must meet following basic requirements:

a) Use antennas with choke rings, capable of receiving all signals (frequencies) available from satellite navigation systems at the time of installation such as: GPS, GLONASS, GALILEO, BDS, QZSS; encourage using antennas capable of receiving signals that are not transmitted by only planed to be transmitted from aforementioned satellite navigation systems or new satellite navigation systems such as the IRNSS;

b) Antenna’s name must be included in list of antenna whose phase center receives absolute calibration by the IGS;

c) Antennas must endure humidity up to 100 %; dust and water resistance standards must be at least IP67 according to stanrd3s of the International Electrotechnichal Committee (IEC);

d) Antennas must be able to operate in temperature ranging from -10^oC +70^oC;

dd) Base continuous operating reference stations must use antennas with choke rings made from Dorne-Margolin materials which are recommended for other stations;

e) Only use hemispherical protective covering for antennas, do not use conical protective covering;

g) Do not disassemble the antennas when the stations have initiated operation unless repair is required due to hardware damage.

2. Satellite signal receivers must be placed in dry and spacious areas and ensured regarding continuous operation. Receivers must meet following basic requirements:

a) Capable of receiving all available signals from satellite navigation systems at the time of installation such as: GPS, GLONASS, GALILEO, BDS, QZSS;

b) Have no less than 555 channels, at least 12 of which must be assigned to each frequency from ach aforementioned satellite navigation systems;

c) Capable of searching and receiving signals from satellites in mask angle of <10^o and eliminating multipath interference;

d) Capable of receiving signals with data sampling of 1 second or less, extracting data via current versions of RTCM such as 2.x/3.x, extracting data via CRM, CMR+, NMEA-0183, etc. and supporting Ntrip, TCP/IP and FTP;

dd) Have at least 2 power supply, support connecting directly with meteorology sensors and inclinometer;

e) Have all basic ports such as RJ-45, USB, 3G/4G/5G, RS-232;

g) Dust and water resistance standards must be at least IP67 according to stanrd3s of the International Electrotechnichal Committee (IEC);

h) Capable of operating in temperature ranging from -10^oC +65^oC;

i) Internal memory can store data for at least 60 days; support attachment of extended memory;

k) Signal cable from receivers to antennas must not exceed 70 meters. If necessary, measure and assess signal quality prior to official installation. With respect to areas with high lightning density, set the distance from the receivers to antennas as short as possible;

l) Connection between antennas and receivers must be placed in industrial PVC or HDPE pipes and buried underground level, if necessary, may design exposed transmission with firm shelves and do not leave the lines too tensed. Whichever end connects to the antenn3 must be watertight, especially when installed in coastal areas to prevent corrosion and rust;

m) Receivers are installed to receive signal 24 hours continuously from all visible satellite with data sampling of 1 second; mask angle in receivers is 0^o;

3. Receivers of satellite navigation signal and other auxiliary equipment must be placed in equipment cabinet with ventilation fans that are automatically turned on/off via thermo sensor relays to reduce temperature in cabinet (design of the cabinet is illustrated under Annex 7 of this Circular).

4. The equipment cabinet must be placed in indoors, in special cases in which distance from rooms to base section of the antennas is too great or no more space for placement in the rooms, the cabinet may be placed outdoors. With respect to areas with unfavorable weather conditions namely high temperature, high annual precipitation or poor security, when placing equipment cabinet outdoors, construct buildings to ensure safety of the cabinet (design of buildings is illustrated under Annex 8 of this Circular).

Article 10. Meteorological sensors

1. In case meteorological sensors are integrated in national satellite navigation stations to serve scientific research, improve calculation and research weather model, the installed sensors must be specialized equipment; all meteorological sensors must be inspected in terms of technical requirement satisfaction prior to installation.

2. Meteorological sensors must be installed near antennas receiving satellite navigation signals but must not interfere signal receipt or cause any interference; must determine vertical distance from antenna reference point (ARP) to atmospheric pressure sensors of meteorological sensors with less than 1 cm in accuracy.

3. Basic requirements of meteorological sensors:

a) Accuracy when measuring atmospheric pressure ≤ ±0.1 hPa;

b) Accuracy when measuring relative humidity: ≤ ±2%;

c) Accuracy when measuring temperature: ≤ ±0.1^oC;

d) Antennas must be able to operate in temperature ranging from -10^oC +60^oC;

4. During operation, regularly examine all sensors, especially temperature sensors and take immediate measures to repair or replace. Examination, maintenance, repair and replacement shall comply with Article 7, Article 8 and Article 9 of Circular No. 70/2015/TT-BTNMT dated December 23, 2015 of Ministry of Natural Resources and Environment on technical regulations for automatic meteorology and hydrology stations.

Article 11. Power supply

1. Each satellite navigation station must have 2 power supplies: a main power supply and a backup power supply. In which, the main power supply shall be powered by the national power grid while the backup power supply is powered by UPS system, rechargeable battery, etc. to maintain continuous operation of equipment of the station for at least 48 hours. In areas with high annual daytime hours, the backup power supply can be the solar panel system.

2. Powering equipment of the national satellite navigation station must be managed by distributor capable of automatically switching between the main power supply and the backup power supply.

3. all electrical components must be equipped with surge protectors to ensure safety for the whole system.

Article 12. Data transmission solution

1. all national satellite navigation stations must have stable internet connection to serve transmitting data to central control and processing stations. Internet connection must be design specifically for data transmission of the station and not for any other purposes to ensure data security and safety and transmission bandwidth.

2. In addition to primary internet connection which is FTTH cable (or Leased line), each national satellite navigation station must have a backup internet connection which is FTTH cable of an internet service provider other than the internet service provider providing the primary internet connection or use 3G/4G/5G connection solution in areas with stable 3G/4G/5G signal. Each FTTH connection must be provide with a static IP address to ensure stable data transmission.

3. Central control and processing stations must be equipped with 2 internet connections which are FTTH cable (or Leased Line) provided by 2 different internet service providers. Each internet connection shall be provided with at least 1 static IP address. Both connections must have adequate bandwidth to receive data transmitted from satellite navigation stations and provide services for users continuous and uninterrupted.

4. In order to guarantee quality of providing re33l-time kinematic services, average permissible latency for transmitting data from satellite navigation stations to central control and processing stations is <50ms for FTTH (or Leased Line) connection and <100ms for 3G/4G/5G connection.

Article 13. Lightning protection

1. Direct lightning protection system is designed to ensure safety for equipment in the national satellite navigation stations. Install earth electrodes satisfactory to Circular No. 26/2016/TT-BTTTT dated December 7, 2016 of Ministry of Information and Communications attached to National Technical Regulation on earthing of telecommunication stations.

2. Equipment potentially struck by lightning must be equipped with lightning dissipators and surge protection devices consisting of: power supply, conductor connecting antennas with satellite signal receivers, conductor connecting meteorological sensors with satellite signal receivers (if any).

Chapter III

CALIBRATION IN NATIONAL SATELLITE NAVIGATION NETWORK

Article 14. Calibrating and determining VN-2000 coordinates of national satellite navigation network

1. Use level 0 national coordinates in the area as the starting points for calibration network; in case of expanding or intensifying national satellite navigation stations, may use satellite navigation stations active in the areas to use as the starting points for calibration network. Starting points must be distributed evenly within the calibration network; number of starting points shall rely on number of national satellite navigation stations that require to be calibrated but must not be lower than 5 points.

2. GNSS receivers positioned in level 0 national coordinates must be multifrequency receivers which must be able to receive at least L1/L2 signals from GPS and GLONASS systems; period of simultaneous and continuous monitor must not be less than 24 hours, starting from 7 a.m (Vietnam time); data sampling is 15 seconds; utilizing static measurement method with mask angle of 10^o. Receivers installed in national satellite navigation stations must be configured as specified in Point m Clause 2 Article 9 of this Circular.

3. Calculation and processing shall be performed by common GNSS processing software; during calculation and processing of baselines, must use final orbit to calculate. Variance of point positions after adjustment calculation must not exceed 2cm.  Calculation process shall comply with Circular No. 06/2009/TT-BTNMT dated June 18, 2009 of Ministry of Natural Resources and Environment attaching Technical Regulations on developing national coordinate network.

Article 15. Calibrating and determining altitude of national satellite navigation stations

1. Establish independent altitude grids to determine altitude of points in national navigation network. Design single grid, each of which must utilize at least 2 points in high-level national leveling network in the areas as starting points. Designing, calibrating and calculating altitude shall comply with Decision No. 11/2008/QD-BTNMT dated December 18, 2008 of Ministry of Natural Resources and Environment attached to National Technical Regulations on development of leveling grid.

2. For points affiliated to base continuous operating reference stations: designing, calibrating and calculating shall be performed 999ccording to second-degree elevation measurement procedures. National altitude points serving as starting points must be second-degree and third-degree altitude points. Closure between 2 measurements and between 2 high category points must not exceed ±4√L for plains and ±5√L for mountainous regions (L refers to length of the measured space in km).

3. For points affiliated to continuous operating reference stations: designing, calibrating and calculating shall be performed 999ccording to third-degree elevation measurement procedures. National altitude points serving as starting points must be first-degree, second-degree and third-degree altitude points. Closure between 2 measurements and between 2 high category points must not exceed ±10√L for plains and ±12√L for mountainous regions (L refers to length of the measured space in km).

4. Calibrating and determining altitude of national navigation stations must be performed for all points as specified in Clause 4 Article 8 of this Circular. Vertical difference in the middle of altitude mark and ARP is determined by specialized steel rule or measuring instruments with equivalent accuracy and separately recorded from orthometric readings.

Article 16. Calibrating and determining gravitational value of national satellite navigation stations

1. On the basis of base gravitational points and first-degree gravitational points in measured areas, design measuring grids connected to national satellite navigation network with accuracy of second-degree gravity according to relative gravity measurement method. Each grid must utilize at least 2 points in high-level national gravity network in the areas as starting points.

2. Position for determining gravitational value on national satellite navigation stations is the altitude mark embossed on the base section. Reference variation of gravitational acceleration after having been adjusted must not exceed 0.05mGal.

3. Use gravity measuring devices with accuracy of at least 0.03 mGal to determine gravitational value for national satellite navigation network.

Article 17. Connecting national satellite navigation network with the ITRF

1. The national satellite navigation network shall be connected with the ITRF via stations affiliated to network of international GNSS service providers, IGS in the area. All points in the national navigation network shall be processed and calculated on a regular and daily basis in ITRF with accuracy of ≤ 2mm.

2. Use GNSS data from at least 5 stations within the IGS network, prioritize stations with stable data and stations that have been constructed not recently and other figures relating to stations according to recommendation of the IGS.

3. Use software with high accuracy namely Bernese, GAMIT/GLOBK, etc. to do the calculation. During the calculation process, in addition to GNSS value, use other related data to increase accuracy such as: figures regarding post-inspected antennas of IGS, accurate satellite schedules, rotation of the Earth’s poles, updated models of tidal impact, model of troposphere, model of ionosphere, etc.

4. Calculation shall be performed on a daily basis, starting from 12 a.m (UTC time); use GNSS data with data sampling of 30 seconds for calculation. The generated results shall serve as the basis for determining platform displacement, vertical displacement, developing frame of reference and national dynamic coordinate systems and determining transformation parameter for transforming between VN-2000 national coordinate system and ITRF.

Chapter IV

CENTRAL CONTROL AND PROCESSING STATION

Article 18. Central control and processing station

1. Central control and processing station calculates, processes and provides services of the national satellite navigation network. Central control and processing station must be placed in area with secured technical infrastructure, stable national grid, fast internet speed and guaranteed in terms of security, order, data safety and security.

2. Central control and processing station must be capable of receiving data continuously from national satellit3 navigation stations; calculate, process and provide services for users promptly 24 hours/7 days.

3. Central control and processing station must be capable of processing and calculating coordinates of points of national satellite navigation network within the ITRF with accuracy in mm.

4. Central control and processing station must be capable of providing real-time kinematic services with high accuracy for users rapidly, precisely and promptly via the internet.

5. Central control and processing station must b3 capable of conducting post-processing with respect to GNSS values offline.

6. Central control and processing station must be capable of controlling, establishing configuration and monitoring oper33tion of national satellite navigation stations regularly, continuously and remotely via the internet.

7. Central control and processing station must be capable of monitoring operation of GNSS measuring instruments utilizing real-time kinematic service.

8. Central control and processing station must be capable of managing accounts that have and are using services provided by the national satellite navigation network.

9. Central control and processing station must assist calculating figures related to atmospheric layers based on GNSS data combining with data from meteorological sensors at national satellite navigation stations.

10. Central control and processing station must b3 capable of storing GNSS data collected from national satellite navigation stations in RINEX V2.x,V3.x format. Storage period is prescribed as follows:

a) Permanent storage for data with data sampling of 30 second;

b) At least 20 years for data with data sampling of 15 seconds (except for special request);

c) At least 10 years for data with data sampling of 1 seconds;

d) Permanent for calculation results related to developing national frame of reference and coordinate system.

11. Central control and processing station must have multi-layer security to ensure safety and assurance for data of national satellite navigation network and users.

12. Central control and processing station must be capable of backing up data automatically on a periodic basis to ensure data safety.

Article 19. Data center

1. Data centers must be powered by stable and quality national electrical grid with 3 phases and backup power generator to provide adequate power in case of power shortage.

2. High capacity uninterruptible power supply (UPS) to sustain the entire equipment system of the center including servers, air conditioners, auxiliary devices, etc. in at least 30 minutes, backup power generators and UPS are recommended to be set 1+1.

3. Data centers must be cooled by air conditioning systems which operate in turns, continuously and are capable of controlling temperature with accuracy of ±1^oC and humidity with accuracy of ±5%. 

4. Data centers must have mechanical floors or electrical insulating layers. Power system and equipment must be installed with lightning dissipators and surge protection devices.

5. Data centers must be installed with fire alarm systems capable of detecting smoke early, warning automatically and suppressing fire automatically.

6. Data centers must have surveillance camera system connected with the DVR to monitor situations inside and outside of the data centers regularly and continuously.

7. Data centers must have server systems powerful enough taking into account backup element, switching system operating parallel with optimal backup mechanism.  Cable systems must be organized, flexible and reusable. All cabins, racks, panels and cables must be labeled in a memorable and expandable fashion.

Chapter V

PROVISION AND USE OF SERVICES OF NATIONAL SATELLITE NAVIGATION NETWORK

Article 20. Services provided by national satellite navigation network

1. Providing GNSS data with respect to data type with data sampling of 30 seconds, 15 seconds and 1 second in RINEX format serving post-processing in period specified in Clause 10 Article 18 of this Circular.

2. Providing GNSS network calculation and processing services with accuracy of mm in the ITRF.

3. Providing GNSS value processing and calculation services for users online on personal request.

4. Providing real-time kinematic services within the VN-2000 national coordinate system and national altitude system via applying network solution (Network RTK) such as: VRS, MAX, iMAX or Singe Base, etc. for users.

5. Services provided by the national satellite navigation network used in survey and creation of topographic maps; development and update of national geological database; survey and creation of cadastral maps; scientific research and other survey, mapping activities. 

Article 21. Using real-time kinematic services

1. Mobile GNSS measuring instruments utilizing real-time kinematic services must satisfy following basic requirements:

a) Mobile multiband GNSS measuring instruments, capable of receiving all signals from popular satellite navigation systems such as: GPS, GLONASS, GALILEO, BDS;

b) Capable3 of establishing connection via Ntrip protocol and receiving RTCM v3.x data corrections with message packets from 1021 – 1027;

c) Receiving signals from satellite navigation systems in clear weather condition.

3. Accuracy of real-time kinematic services provided by the national satellite navigation network is specified in schedule below:

In which:

- “k” refers to distance between processing satellite navigation stations within the network to provide real-time kinematic services.  Specific ra3nge of areas until December 31, 2019 is specified under Annex 09 attached hereto.

- “S” refers to distance from mobile satellite signal receivers to fixed satellite navigation stations used for corrections.

- Area covering Geoid model of Ministry of Natural Resources and Environment is specified under Annex 10 attached hereto.

Chapter VI

IMPLEMENTATION

Article 22. Entry into force

This Circular comes into force from July 15, 2020.

Article 23. Implementation

1. Ministries, ministerial agencies, Governmental agencies, People’s Committees of provinces and central-affiliated cities and relevant organizations, individuals are responsible for the implementation of this Circular./.

2. Difficulties that arise during implementation should be reported promptly to Ministry of Natural Resources and Environment./.