IMAGE ANALYSIS / INTERPRETATION

With increasing resolution, lower cost and easy availability, high-resolution satellite data is becoming a popular choice for large scale mapping projects. High-resolution satellites like Cartosat-1 make it easier and more cost effective to create or update landbase features like buildings, street network, vegetation, water etc. Bisag has substantial technical resources with extensive knowledge and experience to handle such digital remote sensing data. Bisag has carried out many projects handling high-resolution satellite images for mapping.

HIGH - END DIGITAL PHOTOGRAMMETRY SERVICES

Bisag has been providing solutions in digital photogrammetry for over a year. With extensive experience at the management level, highly trained staff and the latest equipment/software, Bisag is well equipped to provide the full range of services in digital photogrammetry.

Bisag's approach in designing the workflow for a project ranging from Satellite photography and ground signalization to stereo compilation and orthophoto generation.

Before commencing any stereo compilation project, an initial project review is conducted to analyze the needs and expectations of the client. All standards and specifications are documented in compliance with ISO 9001:2000 & ISO 27001:2005 certified process, to ensure a smooth production flow.

DIGITAL TERRAIN / ELEVATION MODELS (DTM/DEM)

For Digital Terrain / Elevation Modeling, Breakline features with supplemental random mass points are collected to maintain mapping accuracy. In order to assure that contours meet the required accuracy stipulations; we prepare a Digital Terrain Model (DTM) that well exceeds these standards. Each breakline and mass point is directly measured from the aerial photographs, in stereo, to assure the accuracy and integrity of the final surface.

Our optional automatic procedure extracts DTM points from digital satellite stereo pair images. This yields high overall accuracy because it generates a large number of DTM by going through a pyramidal data structure and robust terrain modeling.

DIGITAL ORTHOPHOTOGRAPHY

Orthorectification is a process of removing the effects of tilt, relief, and many of the lens aberrations from standard perspective photographs. An orthophoto serves as a visual depiction of a tract of land while simultaneously providing the viewer with details about the land.

To create a digital orthophoto that most closely achieves the resolution of the continuous tone original aerial image, we employ a variety of image enhancement and edge sharpening routines using special Image Processing techniques.

The study area or area of interest (AOI) may span several orthopthoto images. In this case, it is necessary to combine / mosaic several ortho images into one final deliverable ortho image file. The process includes contrast matching and edge feathering to ensure a virtually seamless mosaic. Many images can be mosaicked together and resampled to produce an overview image file to supplement the original orthoimages. Accuracy is measured by comparing the rectified position of ground control point to the true coordinates of the point.