Summary Journal of Geodesy and Cartography Vol 41 (9) year 2019

Cập nhật : 20/10/2019
Lượt xem: 37

NATIONAL SPATIAL REFERENCE SYSTEM CLOSED WITH TECTONIC PLATE – TENDENCY OF CONSTRUCTION OF  MODERN NATIONAL REFERENCE SYSTEM INTHE WORLD

 Ha Minh Hoa, Vietnam Institute of Geodesy and Cartography 

                                                               

In process of construction of national spatial reference system, aninterested problem is stability of the national height system for building ofhigh accurate quasigeoid model. Because the national height system had beenexploited a long time, many fist and second orders benchmarks had beendisplaced from social – economical and tectonical  activities, repeat measurement of first andsecond orders networks requires many cost and time, then many countries onlyhad selected stable fist and second orders benchmarks to fit to the nationalquasigeoid model constructed by gravimetric data. In Vietnam, quasigeoid model VIGAC2017 had been constructed by this approach. Apart from that at present thenational spatial reference system is reference system closed with tectonicplate. This scientific article will consider above mentioned problems.


EVALUATION GLOBALGEOPOTENTIAL MODELS USING TERRECTRIAL GRAVITY ON THE SEA OF VIETNAM


Le Minh, Vietnam Association of Geodesy Cartography and Remote Sensing

Nguyen Tuan Anh, Department of Survey, Mapping and Geographic information Vietnam


Using Global Gravity Models Data ismost important method for establised unified gravity data base covering holdcountry of Vietnam. For this job need determination of the GGMs with highaccuracy and better resolution of the gravity anormalies for combinated  with terrectrial gravity observation on thesea of Vietnam. Gravity anormalies from Four selected GGMs: EGM2008 (n=2159),GECO (n=2190), EIGEN 6C4 (2190) and SGG-UGM-1 are  using for analized andcompared with gravityanomalies derived from terrectrial gravity observation on the two site of thesea Vietnam. The Comparison and the results of analized gravity anomalies  between GGMs and terrectrial gravity wasshown Global gravity model GECO is most accurated model with residual 4,3 mGalfor the northern site and 3,0 for Southern site of sea Vietnam. From theresults show that global gravity model GECO with the spherical hamonic coefficients up to 2190 is the most suitable model can be use for combination with terrectrial gravity for establised unified gravity data base corveringover sea of Vietnam.


APPLICATION OF STUMPT ALGORITHM AND MACHINE LEARNING METHODS IN DETERMINING DEPTH OF SEA FLOOR IN THE OFFSHORE ISLANDS OF VIETNAM

Pham Minh Hai, Instituteof Geodesy and Cartography

Phan Quoc Yen, Military TechnicalAcademy

The depth map is a thermatic map showing information aboutdepth of seafloor. Currently, Vietnam has been applying a new technologies to generate thedepth map by using multiple or single-beam detectors. However, this methodrequires a an expensive investment in both technology and technicians. Thedepth measurement using satellite images was published by Stumpf in 2013. Thedepth measurement method of this research group uses the ratio between Blueband and Green band, and the rate reduction from these two channels willgenerate a reflex ratio model. With increasing depth, the spectral reflectiondecreases faster in the high absorption band (green) than the lower absorptionband (blue), so the variables in the corresponding channel ratio change withdepth. The research objective of this paper is to introduce a new and improvedmethod based on the combination of Stumpf algorithm and machine learning methodin determining the depth of seafloor in offshore islands by remote sensing. Theresults of the study have shown that the methodology of the topic together withthe Sentinel - 2A image can meet the depth mapping of 1 / 10,000 and theability to perform up to a depth of 10 m underwater.


BUILDING A SUPPLYING AND RECEIVING SYSTEM FOR INFORMATION SOURCES CAUSING ENVIRONMENTAL POLLUTION WITH WEBGIS TECHNOLOGY

Hoang Thi Tam, Nguyen Thi Chi, Nguyen Thi Thao, Institute of Geodesy and Cartography

To provide an effectivesolution to manage the source of soil environment pollution and to create adirect interactive channel for the Web-based community - WebGIS provides and receives information about the source ofsoil environment pollution was developed. WebGIS  system is built on the basis of Java Scriptand C # APS.Net programmed languages, the base of data is put into SQL Servermanagement system and ArcGIS API for Javascript library in querying anddisplaying version information


GENERAL REQUIREMENTS INUPDATE VIETNAM INLAND STANDARDIZEDGEOGRAPHICAL NAMES FOR NATIONAL FUNDAMENTAL GEOGRAPHICAL DATABASE 1/50,000SCALE

Tran Minh Hang, Departmentof Survey, Mapping and Geographic information Vietnam

This articlestates the necessary of updated standardized geographical names to nationalfundamental geographical database in Vietnamthrough analyses examples from other countries and current status of Vietnam. Generalrequirements are pointed out according todetermining used informative columns of standardized geographical namesdatabases, as well as geographical names correlation exploration betweenstandardized geographical names and national fundamental geographical database1/50 000 scale.



DEVELOPMENT OF WEBGIS SYSTEM TOEXPLOIT DRAINAGE-NETWORK DATA VIA THE INTERNET


Tran Trong Duc, Ho Chi Minh city University of Technology, VNU – HCM

To manage drainage-networksystem of Hochiminh city, the city’s Urban Drainage Company has been developinga desktop GIS based on ArcGIS software, and ArcEngine library of ESRI. In thissystem, drainage database is organized into Geodatabase model and is stored ina server placed at the company headquarter. In order to allow staffes from thecompany’s satellite offices get access to the server’s database, it isnecessary to build a WebGIS system. With this webGIS, the staff with permissioncan access to drainage database from everywhere through the Internet by usingjust a normal web browser. To reduce investment cost, a WebGIS system has beendeveloped based on open source products Geoserver, and OpenLayerscombined usingprogramming language Javascript and Jquery library. The system allows toimplement basic functionssuch as i) display drainage-network data on base mapof Open Street Map ii) retrieve attributes by direct interact with drainagefeatures on map iii) search for features based on their attributes iv) searchfor features in spatial relationship with other features, … The system has beentested and proved to work effectively in exploiting the drainage-networkdatabase through the internet.


RESEARCH OF DESIGNING THE DATA COLLECTION MODULE WHICH IS USED IN URBAN NOISE MONITORING SYSTEM

Nguyen Thi Hue, Nguyen Thanh Thuy, Vietnam Intitude of Geodesy and Cartography

Lương Quang Hai, Military Technical Academy

Pham Thi Thuy, Northern Center of Environmental Monitoring

The paper presents thesolution of designing the data collection module which is used in urban noisemonitoring system. The sound signal (noise level) is digitized using a soundsensor in combination with an analog - digital converter. The received data isthen processed by the average filter and calculated in dB by a microcontroller.Noise data is transmitted wirelessly to the data integration center using 4G transmission technology. The data integration center will process and provideonline noise level distribution map on the WebGIS environment. The obtainedtest results are compared with a noise level measuring device. This confirmedthe success of the proposed solution in this study.


COMBINED USE OF SENTINEL-1 AND RCR FOR DEFORESTATION  DETECTION: A CASE STUDY IN QUANG SON COMMUNE, DAK GLONG DISTRICT, DAK NONG PROVINCE

Ngo Duc Anh, Vu Anh Tuan Vietnam National Space Center (VNSC) – Vietnam Academy of Science andTechnology (VAST)

Nguyen Thu Hang Vietnam Institute of Geodesy and Cartography

Nguyen Thanh Binh The International Center for Tropical Agriculture (CIAT)

 In recent years, deforestation in Dak Nong hashad a complicated situation. It is essential to conduct forest monitoringfrequently and continuously. Frequent forest monitoring using optical data haslow efficiency due to the impacts of tropical climate conditions and cloudcover. In order to address the need for timely update on deforestation, usingSAR (Synthetic Aperture Radar) time series can monitor the forest monthly.Sentinel -1 with a 12-day repeat cycle in both ascending and descending pass(one day) meets the requirement for data continuity as well as not beingdependent on the weather. In this study, the authors analyzed theback-scattering from Sentinel-1time series, using the ratio of RCR (radarchange ratio) to detect unusual changes in forest cover, the results arerecorded from both ascending and descending orbit that increased the accuracy,thereby making the monthly hot-spot deforestation mapping.