Using Signs To Improve The Accuracy About Measure The Ground Points In IKONOS Image

During digital photogrammetry, the aerial triangulation is the one which based on the phantom space position, the image plane coordinates of the tie points, the image plane coordinates and the ground coordinates of control points, solves the ground coordinates of tie points. The accuracy of the measurement point and the coordinates of control points and directly determine the connection point for solving the precision of coordinates.The distinctive pixel structure of the digital images makes it difficult to measure the point position in the couple of images the same, that means the same point will not necessarily falling on the same central of the pixel. And the mixed pixel makes it different between the control points in the images and on the ground, so these mistakes will make the coordinates of the tie points wrong. It's because of the differences between the film carrier and the digital carrier, it's a fundamental problem of measuring based on the images. Only when the location precision of control points fixes with pixel scale in the same order of magnitude, the matter will be diluted.By analyzing the advantages and disadvantages of existing methods, we found layouting signs outside before doing aerial triangulation may deal these difficulties, so we design a special sign and a method solving the offset.Comparing traditional images with digital images to analyze the shortcomings of existing technology.Comparing the existing signs using in photogrammetry and remote sensing technology, design a special sign, including the kind of sign size, shape, material, color and layout orientation and so on. Using a solid color pixels with different gray levels of gray around the pixel through the up and down, left and right gray pixel, solve the offset of horizontal and vertical direction.Using the same images, the same image plane coordinates of ground control points,the same image plane coordinates of tie points, compare one tie point coordinates meaning the same pixel with different ground coordinates of control points.The experiments show that after the offset location of the connection point calculated by the coordinates is closer to its coordinates in the field, that means, the images represent the connection point of the pixel with the pixel coordinates of the representative of surface features closer to the coordinate value. So, this method improves the accuracy of aerial triangulation, the encrypted connection point coordinates out more reflect the true situation of surface features.