Photogrammetry
Our core competency lies in our ability to provide geospatial solutions to a varied customer base, operating in diverse parts of the world. We integrate knowledge, technology, people, and business within a geographic context, to develop innovative solutions for local as well as global clients. Our high-precision photogrammetry services play a significant role in this.
The photogrammetry team is multi-disciplinary and well-manned, but it is above else highly professional, which is crucial in an environment that requires patience, concentration and unswerving attention to detail. The team has a long-standing reputation for offering a consistently efficient and accurate service, at very competitive rates, even by local standards.
The photogrammetry Services are extensive and comprehensive, and include: aerial triangulation; DEM / DTM generation, photogrammetry mapping, stereo compilation, topographic and planimetric feature extraction, orthophoto production, colour balancing, mosaicking and tile generation, pan sharpening, contour generation, 3D terrain visualisation, orthophotography services, LiDAR data processing. To compliment the photogrammetry we also offer ancillary services to remote sensing capture such as classification, image correction, image enhancement, image processing, and change detection services.
As a whole, SBL's Aerial Photogrammetric Services act as an excellent tool within GIS projects: for instance in the correction of topographic or radial distortions in the earth's environment. Using the aerial photographs provided, we plan, design and generate raster or vector GIS layers that best meet the project objectives.
Image Geo-rectification / Geo-referencing
Geo-referencing is the process that defines an object's existence in physical space and its location in terms of a coordinate system. Geo-referencing is used to establish the relationship between raster or vector images, by determining the spatial location of the geographical features. This procedure is mandatory for data modelling within Geographic Information Systems (GIS). For instance when data from different sources or time periods need to be combined and then used in a GIS application (for change detection or damage assessment following a natural disaster) it is essential to have a common referencing system. It is possible to geo-reference a set of points, lines, polygons, images, or 3D structures (e.g. shape file geo-referencing). This is achieved through various geo-referencing techniques and SBL are expert in them all.
Most Geo-referencing tasks are undertaken for one of the following reasons: to produce a new map, to link two or more different data sets to the same geographic locations, to map new features or updates in an existing dataset. To ensure effective delivery a geo-referencing/ geo-rectification service needs to a) establish control points, b) input the known geographic coordinates of these control points, c) choose the coordinate system and other projection parameters and d) minimise residuals. Residuals are the difference between the actual coordinates of the control points and the coordinates predicted by the geographic model created using those control points. The residuals help to determine the level of accuracy of the process. In the case of images, or Raster geo-referencing, in the established position the image may be re-sampled to special GIS file formats (like GeoTiff, MrSID) or, when stored in graphic formats like tif, jpg or png, be accompanied by a world file which contains geo-referenced information including rotation.
For aerial images and satellite images, if the orthorectification is not possible, due either to unforeseen circumstances or inadequate supporting datasets, as an alternative, direct geo-referencing can be used to a certain extent. For example time series satellite images need coregistration and subpixel correlation among the layers to achieve certain analytical tasks, especially when analysing vegetation status using CIR (Colour Infra Red) or NIR (Near Infra Red) imagery.
Colour Infrared (CIR) enhances vegetation aerial images by colouring the green vegetation red. This red colour feature of the vegetation is due to the infrared ray being emitted back to the atmosphere by the leaf pigments after receiving the sunlight. CIR orthophotos are generally used to determine the area of vegetation.
