OK, I thought that might be your issue; it is an arbitrary value because the surface is not sloping in ANY direction -- a flat surface! Consequently, the aspect is assigned the value 0.5*pi radians (or 90 degrees if unit =âdegreesâ)
You possibly could assign a different value, such as null or a missing value, e.g., -999 On Tuesday, May 6, 2014, Beatriz González DomÃnguez < aguitatie...@hotmail.com> wrote: > Hi Thomas, > > Thanks a lot for your answer! However, I still do not have clear why in > the raster package vignette it says: > > 'If slope = 0, aspect is set to 0.5*pi radians (or 90 degrees if > unit=âdegreesâ) > > Cheers > > > I think this is what you want: > > "The *aspect* output raster map indicates the direction that slopes are > facing. The aspect categories represent the number degrees of east. > Category and color table files are also generated for the aspect map layer. > The aspect categories represent the number degrees of east and they > increase counterclockwise: 90deg is North, 180 is West, 270 is South 360 is > East. The aspect value 0 is used to indicate undefined aspect in flat areas > with slope=0." > > On Tuesday, May 6, 2014, Bea GD > <aguitatie...@hotmail.com<javascript:_e(%7B%7D,'cvml','aguitatie...@hotmail.com');>> > wrote: > > Hi all, > > This is a bit general question. I've searched the web but I haven't gotten > a consistent answer. > > I've used a digital elevation model to produce another raster with aspect > data by using 'terrain{rater}'. > Aspect data ranges from 0 to 360 degrees. In the vignette of the raster > package it also says: > 'If slope = 0, aspect is set to 0.5*pi radians (or 90 degrees if > unit=âdegreesâ)' > > Could anyone help me to interpret the aspect data? > > Many thanks for your help. > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > > > > -- > Thomas E Adams, III > 718 McBurney Drive > Lebanon, OH 45036 > > 1 (513) 739-9512 (cell) > > > -- Thomas E Adams, III 718 McBurney Drive Lebanon, OH 45036 1 (513) 739-9512 (cell) [[alternative HTML version deleted]]
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