grass - SRTM NASA hillshade grainy appearance

I'm trying to create a hillshade surface from SRTM files downloaded form Earth Explorer, but the appearance is not the expected.

It has a grainy surface that I would like eliminate to have a smoothest surface. I'm running GRASS 6.4.3. to create this.

It happen mostly in coastal areas. I've tried to use r.denoise but the result is neither the expected, maybe isn't noise the cause of this.

Any idea?

If you need more info just ask.

Answer

I suppose that it is the result of r.shaded.relief.

Have you set the correct resolution of your region of work (resolution of the SRTM layer, Res: 59.74514451 here) ?

Resolution of the SRTM layer:

Resolution of the region:

Elevation;

r.shaded.relief without grainy surface with the correct resolution