comparative analysis of generated and available …comparative analysis of generated and available...

COMPARATIVE ANALYSIS OFGENERATED AND AVAILABLEDIGITAL ELEVATION MODELS(DEM) WITH DGPS SURVEY

Dr. R. Vijay Kumar1, D. Vijay Sai Devabhaktuni21Associate Professor, 2 UG StudentDepartment of Civil Engineering,

B V Raju Institute of Technology, [email protected],

[email protected]

July 18, 2018

Abstract

These Cartosat-I is a remote sensing satellite meant forcartographic applications like generation of Digital Eleva-tion Model (DEM) and was launched by Indian Space re-search organization (ISRO). In last few years we have expe-rienced exuberance of Digital Elevation Models in diverseapplications and utility in the fields of Terrain analyses,in geomorphology etc., The paper aims to show the com-parison between the generated DEM with openly availablesource like cartosat-v1 from bhuvan and DEM generatedwith established ground control points with DGPS survey.

Keywords: Digital elevation model, Differential GlobalPosition System (DGPS)

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International Journal of Pure and Applied MathematicsVolume 120 No. 6 2018, 7871-7881ISSN: 1314-3395 (on-line version)url: http://www.acadpubl.eu/hub/Special Issue http://www.acadpubl.eu/hub/

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1 INTRODUCTION

The Digital Elevation Model is a digital representation The DigitalElevation Model is a digital representation of terrain as a raster (agrid of squares) of the earth’s surface that stores Earths elevationinformation. A Digital Elevation Model (DEM) represents altitudeof Earth surface with latitude and longitude i.e. X, Y horizontalcoordinates and height Z [1]. The terms Digital Elevation Model(DEM), Digital Terrain Model (DTM) and Digital Surface Model(DSM) are synonymously used in scientific literature. However, theterm digital surface model represents the earth’s surface and in-cludes all objects like plants and buildings. But, DEMs represent aconvenient way of storing elevation information and of making suchinformation available to applications programs such as GIS. Mostfrequently the term is used to refer to a set of elevation data. Hencedue to its expanding utilization and importance many national car-tographic organizations are putting their efforts to generate DEMsof different characteristics. Remote sensing has the ability to covera large area in a short time which leads remote sensing to be a verydominant tool in the modern-day geosciences. There are many ap-plications of remote various fields, such as natural disasters, mineraland groundwater exploration, environmental studies, land use, for-est studies etc. DEMs are used often in geographic informationsystems. DEM can also be obtained from direct topographic sur-veys but now are being obtained through remote sensing (Sharmaet al., 2010).

National Remote Sensing Agency, has published a report onthe evaluation of Indian National DEM generated from Cartosat-1 Data. This report provides the overall quality of CartoDEMversion 1 in terms of absolute accuracy and a comparison withother globally available DEMs like ASTER and SRTM in terms ofaccuracy.

This assessment can give an indication of how accurate currentlyavailable DEM like CartoDEMs for general purposes. As indicatedearlier, it is essential to assess the accuracy of the DEM from stereodata without using ground control points because the collection ofcontrol points requires a lot of money and time.

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2 STUDY AREA

The B.V.Raju Institute of Technology, Narsapur, Medak District,Telangana, India. It is lying between the world coordinates of78.253031 decimal degrees west longitude and 78.260499decimaldegrees East longitude, 17.729559 decimal degree North latitude,17.722967 decimal degrees South latitude. The total area coveredby the study area is 0.353327 square kilometers.

Figure 1: Boundary of BVRIT,Narsapur Overlayed on GeorectifiedSatellite imagery taken from Google Earth pro

A. Georeferenced Satellite ImageryUse The imagery of the study area is taken from the Google

Earth Pro, then georectified with Control coordinates of DGPSSurvey using ArcGIS Software. DATA USEDB. Cartosat-1:DEM-version-1

CARTOSAT1 is the first Indian Remote Sensing Satellite capa-ble of providing in-orbit stereo images. The images were used forCartographic applications meeting the global requirements. Cam-eras of this satellite have a resolution of 2.5m (can distinguish asmall car).The Cartosat1 provided stereo pairs required for gener-ating Digital Elevation Models, Ortho Image products, and Valueadded products for various applications of Geographical Informa-tion System (GIS).C. Georeferenced Satellite Imagery

Use The imagery of the study area is taken from the GoogleEarth Pro, then georectified with Control coordinates of DGPSSurvey using ArcGIS Software.D. Control Data From DGBS Survey Of Study Area

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Differential GPS (DGPS), or indeed any differential global navi-gation satellite system GNSS2(DGNSS) in general, greatly increasesthe potential accuracy of either GPS or GLONASS. By determin-ing the major error sources at a base (or reference) station andapplying the corrections thus derived to any other station (whichmay be mobile), these errors can be largely eliminated

1. Static and Kinematic GPS surveying techniques: High pre-cision techniques based on post processing of carrier phasemeasurements

2. Differential GPS (DGPS): instantaneous low to moderate ac-curacy positioning and mapping technique based on pseudorange measurements.

3. Real Time Kinematic (RTK): versatile high precision tech-niques that use carrier phase measurements in an instanta-neous positioning mode.

4. The DGPS RTK techniques, because they are able to de-liver results in real time, are very powerful GPS positioningtechnologies.

5. There are essentially two types of conventional static GPSsurveying techniques.

3 METHODOLOGY

The DGPS survey is carried out establishing Ground Control Pointsevenly spreaded through the study area. The altitude data fromthe DGPS survey of our study area is imported to ArcGIS software.The elevation point data of our study area is then converted toraster using Topo to Raster tool in spatial analyst tools in ArcGIS.The generated DEM from Cartosat-1:Version-1 of our study area isimported to ArcGIS then the raster is converted to point data ,byusing From raster to point Tool in ArcGIS. The points obtained areagain converted by highlighting gridcode/elevation field using topoto raster tool in ArcGIS software.

The data obtained by DGPS survey and the Data by cartosat-1:DEM-Version1 are Superimposed using a georectified image of the

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study area in ArcGIS software. Where georectification of imagerywhich is taken from Google Earth Pro is done using DGPS controlpoints in ArcGIS Software.

Figure 2: Super imposition of DGPS survey control points on gen-erated points from cartosat-1:DEM-Version-1, the image is georec-tified satellite imagery taken from Google Earth Pro

4 RESULTS AND CONCLUSION

A. Comparison of DEMIn this study 112 Ground control points are established using

DGPS survey where the elevations are collected. Elevations of thesame points are extracted using Cartosat-1: DEM-Version-1 dataprovided by Bhuvan (A NRSC website). Elevation values of Car-toDEMs including the one generated using DGPS survey show that,CartoDEMs have have higher values of elevation because of the el-lipsoid pattern adopted in their study. The change in elevation hasoccurred due to the change in datum. CartoDEM uses the datumbased on geoid and for data for GCP are taken using DGPS, whichuses datum based on spheroid and hence in the processing, the da-tum is taken as spheroid based. Hence, for the sake of comparison,all the values are to be reduced to the same datum.

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Figure 3: DEM of the study area created using DGPS control pointson ArcGIS Software

Figure 4: DEM of the study area taken from BHUVAN an opensource NRSC web site. Cartosat-1:DEM-Version-1 of 78.253031decimal degrees west longitude 17.729559 decimal degree North lat-itude, 17.722967 decimal degrees South latitude

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B. Comparing TIN Generated using ArcGIS

Figure 5: TIN model of study area created using Cartosat-1;DEM-Version-1 elevation data on ArcGIS Software

Figure 6: TIN model of study area created using DGPS Surveyelevation data on ArcGIS Software

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Table 1: ELEVATION DATA OF CARTOSAT-1:DEM-VERSION-1 AND DGPS SURVEY OF STUDY AREA

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5 CONCLUSION

• DGPS is effectively used to find out the elevations and com-pute the Digital Elevation Models (DEM).

• The maximum and minimum elevations of the 112 points fromDGPS Survey are 538.895 m and 531.435 m.

• The maximum and minimum elevations from the CartosatData are 463 m and 473 m.

• The highest difference in elevation in comparison with bothDGPS Survey and Cartosat Data is 62.063.

• The lowest difference in elevation in comparison with bothDGPS Survey and Cartosat Data is 73.751 m.

• In comparison between the generated DEM with DGPS sur-vey with openly available source like cartosat-v1 from bhuvanit is found that the DEM with DGPS Survey is higher andthe average elevation difference between them is about 67m.

• The elevations from the DGPS Survey are found to be moreaccurate in comparison.

References

[1] Pandey, P., Venkataraman, G. Generation and evaluation ofCartosat-I DEM for ChhotaShigri glacier, Himalaya. Interna-tional Journal of Geomatics and Geosciences; 2012. 3 (2). p.704-711.

[2] Malinverni, E. S. DEM automatic extraction on Rio deJaneiro from WV2 stereo pair images. 8th International Sym-posium of the Digital Earth; 2014. Online Available HTTP:http://iopscience.iop.org/1755-1315/18/1/012022

[3] National Remote Sensing Center, Indian Space ResearchOrganisation: Evaluation of Indian National DEM fromCartosat-I data, Summary Report, (Ver. 1); 2011.

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[4] Sooraj Krishnana , N Sajikumarb *, Sumam K Sb Interna-tional Conference on Emerging Trends in Engineering, Scienceand Technology (ICETEST - 2015)

[5] Baral, S. S.1*, Das, J.2, Saraf, A. K.1, Borgohain, S.1 andSingh, G.1, comparision of cartosat Aster, SRTM DEMS ofdifferent terrains.

[6] Eckert, S., Kellenberger, T., and itten, K. (2005), Accuracyassessment of automatically derived digital elevation modelsfrom ASTER data in mountainous terrain. International Jour-nal of Remote Sensing, 26(9), 1943 1957.

[7] Foni, A., and Seal, D. (2004), Shuttle Radar Topography Mis-sion: an innovative approach to shuttle orbital control. ActaAstronautica, 54, 565570.

[8] Jacobson, K. (2006), SRTM height models, GEOconnexion In-ternational Magazine, 20-21.

[9] U. Duncombe, Infrared navigationPart I: An assessment

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comparative analysis of generated and available …comparative analysis of generated and available...

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