Tripathy PK, Sanabada MK, Parida PK and Mahapatra AK
Orissa Space Applications Centre, Bhubaneswar, Orissa, India
Orissa holds a prominent place amongst the states of India in mineral resources with large deposits of minerals. Also, the receipts from mines constitute the largest source of revenue for the state. There are a total of 605 mining leases covering an area of 99,932 hectares in the state, thus making it one of the most profitable sectors. To cater to the demand of industries, illegal mining activities are being practised in Orissa as in rest of the country. In the process, the state has lost a lot of revenue. The mining department has thus begun verification of the mining lease boundary by resurveying the lease area, and then comparing the same with the earlier approved lease map. The process requires a lot of time and manpower if carried out by conventional verification method. The modern technology using differential GPS (DGPS)/ Electronic Total Station (ETS), remote sensing technique (interpretation of high resolution satellite image) in a GIS environment can be a suitable method to solve the above problem in a cost and time effective manner.
Study area
Thakurani Iron Ore mines having a lease area of 947 ha.(Fig-1) is situated in Joda-Barbil mining circle of Keonjhar district of Orissa which is well connected by roads and railways from Jamshedpur (150 km), Rourkela (140 km), and can be approached by National highway from the district headquarter Keonjhar (80 km). The area presents a highly rugged landform and can best be described as ridge. The valley topography belonging to the Koida-Noamundi group of rocks, is a part of the famous horse-shoe shape (U shape) synclinorium (Iron Ore Super Group). The iron ore deposits are associated with the banded iron formation (BIF) and are structurally deformed with the parent rocks.
Methodology
Ortho-image preparation
The study area falls in a hilly terrain. Ortho-image is required to maintain the planimetric accuracy. For this purpose, high resolution satellite stereo pair image of Worldview II with a spatial resolution of 0.5 m, has been obtained along with 1.8 m multi-spectral image. Coordinates of ground control points have been collected from the established and network adjusted points of SOI as well as control point network (4km x 4km) obtained under NLRMP project (Cadastral Resurvey Project) using dual frequency DGPS for Keonjhar district. Leica photogrammetry suite is used for generation of DEM and ortho-image. This software uses bloc triangulation procedure taking the internal and external orientation using both sensor recorded DGPS observations from the header files of digital stereo pairs as well as GCPs taken from the study area.
The RMS for the triangulation was .300 pixels. DEM of spatial resolution of 2 m was created which was then edited properly to create a good surface image. The ortho-image was created using the raster DEM as well as digital stereo pair images of spatial resolution of .5 meter. The multi spectral data of WV-II was ortho rectified using DEM, created using PAN WV-II stereo data and resolution merge of both MX and PAN created having 0.5 meter spatial resolution for this study.
Geo-referencing of maps
Taking the help of ortho-image, the approved mining lease map is geo-referenced after digitisation. The interior angle, distance and bearing from the reference point used during the initial survey for preparation and pillar demarcation of the mining lease map is also considered at the time of geo-referencing (Fig-3).
Revenue cadastral maps of the area are digitised and geo-referenced with the ortho-image taking the bijunctions, trijunctions, roads, ponds and the habitation area of the cadastral map with the corresponding features of the image.
DGPS/ ETS survey of lease boundary
To assess the present situation (actual possession) of the lease pillars and lease boundary, the survey has been carried out by dual frequency DGPS to first transfer the established GCP to temporary GCPs within the mining lease area by way of extension from nearest GCP, through RTK mode of observation. Subsequent observations on each boundary pillar of the mining lease area have been undertaken taking reference from the temporary GCPs so established.
Precise geo-coordinates of the pillars in the mining lease area are recorded to carry out the exact survey of all the pillars of the mining lease area using dual frequency DGPS in RTK mode/ ETS from the temporary GCP. The lease boundary vector in the form of shape file is then prepared using the coordinates of the pillars in latitude/longitude as well as UTM projection with WGS 84 spheroid and datum (Fig-2).
GIS analysis
The surveyed boundary shape file from DGPS/ETS survey, geo-referenced cadastral village boundary, geo-referenced mining lease boundary are then superimposed on the ortho-image in ARCGIS (Fig-5). The perimeter and area of different layers are analysed in Fig-4.
The area from different sources are shown below
Lease area as per record – 947.00 ha
Lease area from DGPS/ ETS survey – 937.00 ha.
Lease area from existing lease map – 938.35 ha.
Lease area from angle & distance calculation – 939.65 ha.
Result/ Conclusion
Results obtained from the present study show that there is a slight difference in area allotted to the lessee and actual area found from the survey. The difference may be due to the survey technique used during allotment time and the present high precision survey. However, any difference in allotment area and possessed area can be differentiated by this method. It is also observed that the different methods of lease boundary extraction are fitting to the ortho-image where the lease boundary is clearly visible on the image.
The study highlights the possibilities that all the mining lease area can be geo-referenced into a single coordinate system. This will work as the base line data in future to have a solution to the administrator, surveyors and most importantly to the lessee during any boundary discrepancies. This will lead to a proper mine plan preparation as each and every point within the lease are referenced. Further this gives the advantage of linking any other geo-referenced information related to mining activity to design individual mineral information system as well as a single database system for the mining belt. The mine plans can also be attached to this information system.
This type of database will help to assess and monitor the mining area in terms of revenue, environment and development.
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