This paper proposes a new procedure to erase noises on raster map. Basing taxon and clustering of color map pixels

and by establishing a polar coordinate system with its origin on any noisy pixel and searching along all eight directions till road pixel or area pixel is found

of course

sometimes neither road pixel nor area pixel is found because pixels from origin to edge of map along some direction are all noisy pixels

the number of road pixels

the number of area pixels and the number of edges at all eight directions can be abtained. Letr denotes the number of road pixels

adenotes the number of area pixels andedenotes the number of edges.r

a andeare called the character parameters of noisy pixels. Then by comparingrwitha

the character of any noisy pixel can be extracted. With“equity”clustering rule

most of noisy pixels can be clustered and grouped into either road or area. Then with“partial”clustering rule

the limitrophe noisy pixels

which can not be grouped into either road or area

can also be grouped into either road or area. At last

all noisey pixels can be grouped into either road or area. This new method can completely erase the noises on raster map

so as to obtain more effective identifying with all roads and areas on a map.