PRIMEWIN: Processing of Images on Windows

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## Regional Remote Sensing Centre-Central, NAGPUR

# GEOCOR: Geometric Corrections

GEOCOR is a module for geometric corrections. It facilitates GCP collection, image-to-image registration using the collected GCPs, Image rectification using GCP library chips (for LISS-3, AWiFS only), tools for deriving state level projection parameters for UTM and LCC projections, coordinate conversion etc.

GCP Collection Interface |

Image Registration | Projection Parameters|

· GCP Collection Interface: This module provides a user-friendly interface for collection of ground control points. Following figure shows brief description of icons.

Following figures depicts complete sequence of procedure for collection of ground control points (GCPs).

· Procedure for GCP collection and saving the file

o Place the cursor in uncorrected overview window on desired area. Press to load desired area in uncorrected full resolution window.

o Place the cursor in corrected overview window around same area. Press to load desired area in corrected full resolution window.

o Place cursor on identified GCP in uncorrected image (uncorrected full resolution window) and on same GCP in corrected image (corrected full resolution window). Press Accept as GCP button.

o For deleting a GCP, select the GCP in the GCP list and press Delete button.

o Depending upon the number of GCPs acquired, order of polynomial can be selected.

o GCP list can be sorted by ID or by worst.

o After required number of GCPs have been taken, SAVE the GCPs in the file. Go to File -> Save GCP data -> Select directory, enter filename and Press Save.

· Drawing mosaic area (subset for registration)

· Registration Preview

· Image Registration: Follow sequence of steps shown in the following figure to perform registration to disk.

· Projection Parameters: This module enables the computation of state level projection parameters for LCC projection viz. standard parallel-I, standard parallel-II, longitude of origin, latitude of origin, central scale factor and for UTM projection viz. longitude of origin, latitude of origin, central scale factor. Geographical extents have been fixed for each state and the user cannot change these. However, projection parameters can also be computed for user-defined extents by selecting custom option. Once the projection parameters are computed, coordinate conversion to geodetic and to projection can also be done. Following interface depicts the step-by step procedure-

· Coordinate Conversion: Once the projection parameters are computed for a given geographic extent & projection; coordinate conversion from Geodetic to selected projection or from selected projection to Geodetic coordinates can be done.