Geospatial services

Geospatial data analysis services

GIS Feature Extraction

GIS Feature Extraction

Any kind of developmental projects involves collection of certain amount of spatial and non-spatial data. Collection, analysis and deriving of useful inferences from these data sets are collectively called Geospatial data analysis. That being said Geospatial data analysis involved collection of spatial data, its digitization, and attributization, analysis and report generation. Geospatial data play a vital role from the pre-feasibility stage to the completion stage of the project and much beyond completion like long term environmental impact assessment.
GIS data processing starts with collection of geo spatial data set. Geospatial data can be any information or data having a spatial relation with it in the form of geographic coordinates. These can be satellite data, aerial data, LiDAR data, Unmanned Aerial Vehicle (UAV) data or paper maps. Once the data is acquired, it requires some amount of processing to bring it to the intended usage. Geo-referencing and other preprocessing is the activity involved at this stage of geospatial data processing. Data collected through remote sensing technique such as satellite images need satellite image processing expertise and knowledge.
Once the geospatial data is acquired and undergone all the preprocessing, the GIS data is ready for further analysis and processing. The spatial data analysis is generally included digitization and interpretation of useful information from the acquired geospatial data sets. Here need based thematic and subjective information is collected. This will be later taken for further refined interpretation. In the spatial domain vector data will be in the form of point, line and polygons. These data can be attributed with any kind of information in the form of tables and spread sheets. All the raster as well as vector data can be assembled in a spatial database, then predefined analyses such as over lay analysis, suitability analysis, analysis based Boolean logic etc can be performed on the data. Also in case of spatial data, analysis is possible in 2D as well as 3D environment.
SBL offers a wide range of Geospatial data analysis services. It ranges from simple geo-referencing to digitization to complex 2D and 3D model creation. SBL’s skilled technical staff is able to do all the pre-processing of the satellite images and other geospatial data analysis. SBL possess long term experience in processes and procedures involved with geospatial data acquisition services and is associated with international organizations who acquire geospatial data.

GeoSpatial Scientific back up to Vastu Shastra

In a recent study, SBL has provided scientific back up to Vastu Shastra. Vastu shastra deals with the ancient Hindu beliefs in architecture. According to this school of thought prosperity of the house hold depends on its slope of the land and directional alignment of that location on the surface of the earth.In a similar way prosperity of the country also depends on its elevation orientation and position on the surface of the earth. In this context SBL has assisted a research study by Vastuvidya Gurukulam by analyzing elevation data of 50 countries.The digital terrain model generated through Shuttle Radar Topographical Mapping (SRTM) were analyzed for all these 50 countries and presented in the form of ready to print maps. Care has taken to see a true representation of the rich and poor counties and countries lies north and south of equator. In a similar way population density and per capita income of these 50 counties analyzed for establishing a correlation between these three entities and finally to related with other vastu vidya practices. So a geospatial data base has created for these 50 countries along with cartographic representations whereby spatial variation of elevation, population density and per capita income of all these countries were established.

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Geo referencing Service

SBL through its varied geospatial services is in forefront to full fill the requirements of all of its clients. Georeferencing is one such service SBL provides. Georeferencing means bringing maps and images in to a real world coordinate system. Satellite and other kinds of images and scanned maps are devoid of any coordinate information in its raw form and hence cannot used for any of the geospatial purpose. Some of the satellite images are loosely georeferenced when it is procured. Here also positional accuracy is a big issue. So georeferencing is the primary pre requisite for the creation of any kind of geospatial data base creation. For scanned maps georeferencing means bringing to the geospatial frame work. For satellite images georeferencing means applying geometric correction to the images. Assigning a suitable project is always an associated activity in georeferencing. So georeferencing is not only bringing the maps and images to the coordinate framework, it also involves with assigning a suitable projection so that maps and images will be of real world coordinates. A georeferenced map or image will open in its correct spatial location and can be used with similar other georeferenced maps for various overlay analysis. Hence georeferencing is a positional correction applied in x, y direction of the maps and images. Orthorectification is a refined form of georeferencing where relief displacement will also be taken care so that images will be correct with respect to x, y and z planes.

Georeferencing is a basic function available in almost all geospatial software platforms. The major activities involved are incorporation of ground control points, re projection and re sampling. Ground control points are those points whose coordinate information (latitude and longitude values) were known prior hand and is identifiable in maps and images. Ground control points can be taken from printed graticule values on maps, or can be surveyed using precision instruments such as DGPS and can be taken from a pre geo referenced map or image. A minimum number of 5 GCP values are required for georeferencing. Based on the accuracy requirement number of GCPs and type of GCPs can be determined. Once the ground control points are placed, using the software algorithms we can re project and re sample the maps or images. Various complex statistical methods and transformational equations were used for the re sampling the images to its real world coordinates. During the process each and every pixel of the maps and images will be re positioned with respect to the GCP and methods used for the purpose and finally a georeferenced maps or image can be generated. Accuracy of the georeferencing can always be obtained through RMSE error for the GCPs used in the process. Hence it is very much a quality controlled activity where very high positional accuracy can be obtained. SBL is capable of handling images and maps in huge numbers for geo referencing and allied acidities.

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Georeferencing services

Georeferencing services

Ground water pollution modeling through time series 3D modeling

Ground water during its conduit through soil leaches pollutants and getting itself contaminated in the process. Regional scale treatment is required to contain such spreading of contamination. Present study is one such study conducted by SBL geospatial team for an environmental management firm at Ohio area of United States of America. Ground water samples were collected from 1998 to 2012 and analyzed for ethane content. It was for an environmental management exercise to demonstrate that ethane content can be contained by time duration of 14 to 15 years. All the well locations were plotted initially in a 2D environment and later converted to 3D environment by implying well screen height with respect to mean sea level and treated as z element in the analysis. Then the spread of ethane horizontally and vertically is established by a complex 3D model plotting of the ethane concentration in µgm/liter derived through analysis of collected water samples. Later 3D contours of the ethane concentration were derived from the created 3D surface model.This analysis was iterated for monthly data of ethane concentration for a period of 1998 to 2012. Later time series analysis of the ethane concentration has done and found that as duration increases ethane concentration was reducing and is fully contained by 2012.

Click to view the case study : http://www.sblcorp.com/GIS_Case_Studies_pdf4.php

Geospatial 3D model creation

Remote sensing and GIS in Hydrogeological Mapping and Water Quality Modeling

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SBL has trained officers from soil conservation, agriculture, and ground water departments and scholars from cochin University of Science and Technology on hydro geological mapping and water quality modeling through remote sensing and GIS techniques. SBL’s has developed this capability in house and can model water quality and hydro geological set up in 2D as well as in 3D environment.

Venugopalan Nair, Senior Manager, SBL has delivered a lecture on “Remote sensing and GIS in hydrogeological mapping and water quality modeling” for a training course on sustainable development and management of ground water resources, conducted by Central Ground Water Board, Rajiv Gandhi National Ground Water Training and Research Institute, River Development and Ganga Rejuvenation, Ministry of water Resources, Government of India

In the lecture, Mr.Nair has explained the basics of remote sensing technology to participants from agricultural, soil conservation, Cochin University of Science and Technology, and many other departments constantly works for sustainable development. The presentation explained how this useful technology and implement in agriculture, land resource utilization, water conservation and ground water quality modeling. The enthusiastic participants made many queries in their respective domain and updated themselves about this technology.

We invite you to the presentation by Mr.Nair on Slide share www.slideshare.net/sblgraphics1/geospatial-services-44862290e

Orthorectification for Precision Mapping

orthorectification

orthorectification

Planimetrically accurate images are a necessary pre requisite for any mapping projects.  Accurate maps are a basic necessity of the developmental projects like, infrastructure development, mining, master planning, precision agriculture etc. Orthorectification is a process by which a raw image is transformed into a planimetrically accurate image.  Often georeferencing is used in synonym with the orthorectification.  But in true sense, through georeferencing only x, y corrections and transformation is dealt with while ortho rectification will do a correction on relief displacement caused due to elevations of the objects within the map.  So orthorectification is considered as most accurate process by which an image is brought to the real world coordinates by considering correction in all three directions of x, y and z.

Orthorectification is the process of eliminating the relief displacement due to sensor mal functioning, height of the terrain, earth rotation, panoramic distortions etc.  The outcome of the orthorectification is a planimetrically true image.  It also brings uniformity in scale throughout the image.    SBL has the capability to do the orthorectification to a wide variety of images such as satellite images, aerial photographs and UAV images.

The main input for the orthorectification process is as follows

  • Near Nadir image
  • Rational Polynomial Coefficient (RPC) file or camera calibration certificates
  • Digital Elevation Model (DEM)
  • GCPs

Orthorectification can be done in a variety of software.  SBL uses ortho master module of Inpho for the aerial photographs and satellite images and PIX4D for UAV images.  The process involves importing of the image, DEM, external and internal parameterization files in to the model.  Parametric approach can be followed in the model where internal and external correction files in the form of GCP files and RPC files are involved.  At this step desired projection can also applied in the model.  Back ward projection can be applied in the process.  The object space X, Y coordinates related to every pixel of the final ortho image is determined. The height Z at a specific X, Y point will be calculated from the DEM or the 3D model and then the X, Y, Z object space coordinates are projected in the original image in order to acquire the gray level value for the ortho image pixel. Interpolation or re-sampling process in the original image is also essential because of the fact that the projected coordinates will not fit accurately at the original image pixel centers.  Output cell size and extent will be defined at this step.  Output file type can also be specified at this step.  Error calculation is generally derived in the form of RMSE report.

Quality assessment of the orthorectified images is one of the activities which SBL perform to ensure highest standard of the output images.  Pan sharpening, mosaicking, color balancing, and tiling are the associated activities once the generalized orthorectified output images were generated.    Quality assessment will be majorly done through visual inspection of the images.  Major checks on the orthorectified images include spatial resolution, edge matching, double feature checking, tonal balance, and pixel dropouts.

Satellite Image Interpretation for Land Cover Classification

SBL’s Geospatial wing recently won a project from Canada for the delineation of Land cover in Northwest Territory. This is again a reaffirmation of the varied skills of the Geospatial team wherein our pool of experts were able to provide a better solution to the forest department based on our quality of interpretation of the sample data and competitive pricing.

Land cover basically refers to the interpretation of land features that are visible on the surface of the earth. It does not cover the land usage which comes under Land use. 

Land cover classification includes land features like trees, water bodies, bare earth and rock outcrops. In the present study our task was to interpret Land cover in forested regions of Northwest Territories, Canada. The input image provided by the client was mono satellite image and each image covered an area of 4 sq.km.

SBL’s experienced interpreters delineated the treed and non treed areas and created polygons out of it. The client had specified a minimum area for forest polygons and the area specified was 4 hectare and for non forested area polygon it was 0.5 hectare. The classification was done based on the tone and texture of the features(Fig.1).

Forest delineation based on tone and texture

The tree heights, texture and tree density were taken into account for the delineation. Trees situated in the high land regions will have a different tone, texture, height and density with respect to the trees in the high land and mid land regions(Fig.2, Fig.3).

Landcover classification in highland region

Landcover classification based on density of vegetation

Various tree species occurring in the forest areas display unique textural and tonal characteristics which were used as guide for the interpretation.

The water bodies consisted of rivers, major streams and also the closed water bodies like lakes which fall within the area stipulation of 0.5 hectares were also captured (Fig.4).

Flood plain delineation

Rivers were captured at the edge of water and flood plains were delineated wherever the width is greater than 20m. The digitization was to be done in a scale level of 1:2000 and 1:2500 and the final output was viewed in a scale of 1:10000 in order to find out any dangle polygons, large polygon and also to merge adjacent polygons if necessary. The entire digitization was carried out in ArcGIS environment and the final output was delivered as shape files to the client.