Symbol separation is a key step of the automatic input of topographic map. A great deal of important information can be acquired through the pick up of symbols. Although there has been a lot of algorithms aiming at this question

they were all obsessed by the conglutination problem. In this paper we define a new kind of morphological erosion operation and propose a new symbol separation algorithm based on it. Experiment result shows that this algorithm provides high resolution and rapid speed

and it can get over the familiar conglutination problem between symbols and lines that is inextricable to the general symbol separation algorithms. Its performance has met the requisition of actual automatic input system of topographical map. Further more

with a few modifications of the program

it can be extended to the recognition of other analogous line drawing such as engineering blueprint. We could also combine it with traditional algorithms to achieve better proformance.