Methodology |
First Base Solutions created a digital 12cm resolution colour orthophoto mosaic of every 60% FOL photograph using the adjusted digital images, ground control data and a digital elevation model.
Correcting the distortion found in the original imagery creates the orthophoto. There are three distortions, camera lens distortion, changes in aircraft altitude and changing ground elevation.
Processing of the orthoimagery is done by using a combination of PCI and Intergraph software. Once the adjusted image orientation data is imported, the remaining data required to produce the orthophoto is input. This includes the camera calibration data, control data and the digital elevation model. The number of times the imagery is subject to re-sampling is minimized. The re-sampling algorithms used employs cubic convolution strategies for deriving the output pixel intensity value. Once the individual images have been orthorecified they are imported into the Intergraph OrthoPro mosaicing environment. Intergraph produces remarkable mosaics with virtually invisible seams and remarkably even tone. Initial tiles are clipped from within Intergraph and then mosaiced together using MrSID for QC evaluation. Visual QC checks are done to look for wobbles along road/railways and bridges, even colour tones, poor cutline location and incorrect elevations. Once corrections are complete the final tiles are clipped using PCI and final delivery tiles are processed. |