  Filaments are clearly visible in galaxy distributions, but they are hardly
detected by computer algorithms. Most methods of filament detection can be used
only with numerical simulations of a large-scale structure. New simple and
effective methods for the real filament detection should be developed. The
method of a smoothed galaxy density field was applied in this work to SDSS data
of galaxy positions. Five concentric radial layers of 100 Mpc are appropriate
for filaments detection. Two methods were tested for the first layer and one
more method is proposed.
