Introduction to the software of gdds

In this paper, a geomagnetic drawing digitization system, "Geomagnetic Drawing Digitalization System", was introduced. In this system, we provided some functions, such as scanning, rotating, image clipping, geometric proportion scaling, cleaning horizontal and vertical lines, wave tracking, etc. based on some algorithms of image processing. The key techniques in this system includes wavelet analysis, image thinning, pixel tracing. With this system, it is possible to analyze historical geomagnetic drawing recorded in paper by using computer. Application of this system will be of help to the progress in earthquake prediction and seismological researches.