Module 4:Geometric Correction: Image to Map Rectification

Usefulness of Rectification process: Image rectification is a preprocessing operation that intent to correct the distorted or degraded image data hence creating a more reliable representation of the original scene. It involves geo referencing. The random distortions and residual unknown systematic distortions are corrected by analyzing the Ground Control Points (GCP) in an image and then accurately locating the known ground locations in the map. The image with unknown coordinate system can be projected into a known coordinate system. The transformation equations involved, inter-relate the geometrically correct coordinates and distorted image coordinates. Hence once this process is done, the distorted image coordinates for any map position can be precisely estimated.
Pitfalls in Rectification process: Locating GCPs identifiable in both the images and pinpointing the exact location can be difficult sometimes if the image is not very clear, making the entire process of rectification challenging and difficult.
For the lab in particular, it was somehow difficult to place the checkpoints initially, error was quite high but finally I got to place the check points and got an error of 3.1.