1. A method of matching interest points between images comprising: from a dataset of interest points in a first image, the dataset comprising information identifying the position, scale and orientation of each interest point, calculating a first dataset of objects that each relate a base interest point to a satellite interest point, the calculated dataset comprising information identifying the normalized position of the satellite interest point relative to the base interest point and the normalized scale and orientation of the satellite interest point, wherein normalized means expressed relative to the scale and orientation of the base interest point; from a dataset of interest points in a second image, the dataset comprising information identifying the position, scale and orientation of each interest point, calculating a second dataset of objects that each relate a base interest point to a satellite interest point, the calculated dataset comprising information identifying the normalized position of the satellite interest point relative to the base interest point and the normalized scale and orientation of the satellite interest point, wherein normalized means expressed relative to the scale and orientation of the base interest point; generating matched pairs of objects by matching objects from the first calculated dataset to objects in the second calculated dataset; from the matched pairs of objects, determining the interest points in the first dataset that are to be matched with interest points in the second dataset; and matching the interest points accordingly.