| Description:The GEO_Transformation describes the relationship between raster positions (in pixel/line coordinates) and georeferenced coordinates. This is defined by an affine transform. The affine transform consists of six coefficients which map pixel/line coordinates into georeferenced space using the following relationship: Xgeo = GT(0) + Xpixel*GT(1) + Yline*GT(2) Ygeo = GT(3) + Xpixel*GT(4) + Yline*GT(5) or also defined as: GT[0] = Xmin; // upperleft_corner_y GT[1] = CellSize in X; // W-E pixel size, pixel_resolution_x GT[2] = 0; // rotation term, 0 if 'North Up' GT[3] = Ymax; // upperleft_corner_y GT[4] = 0; // shear term, 0 if 'North Up' GT[5] = CellSize in Y; // N-S pixel size, pixel_resolution_y In case of north up images, the GT(2) and GT(4) coefficients are zero, and the GT(1) is pixel width (pixel_resolution_x), and GT(5) is pixel height (pixel_resolution_y). The (GT(0),GT(3)) position is the top left corner of the top left pixel of the raster. Note that the pixel/line coordinates in the above are from (0.5,0.5) at the top left corner of the top left pixel to (width_in_pixels,height_in_pixels) at the bottom right corner of the bottom right pixel. The pixel/line location of the center of the top left pixel would therefore be (1.0,1.0). |