[GRASS-user] Reprojecting and resampling raster map

[stephen sefick]

When you reproject a raster map to a new location does it
automatically re-sample it to the regions resolution.  I have a 10x10
meter grid in albers equal area projection.  I have reprojected it
into UTM zone 17 res=50.  This is a base flow index map bfi.  Does
grass resample the map to 50x50m?

The problem is this:
I have an average runoff value (arv) in m/s (converted from mm/day
into m/s by dividing by 86,400s*1000mm).
flow accumulation grid produced by r.terraflow (which was 30x30m
resampled to 50x50m).
flow accumulation * 250 (to get square meters (50x50))

bfi*arv*flow accumulation (sqm)

to get discharge in cms

I converted this to cfs (multiplied by 35.314454)

the resulting map is discharge in cfs

The estimate for discharge is ~3x what the long term average is at
usgs gauging stations along the rivers of interest (point layer to
identify where they are located).  The only thing that I have been
able to think of at this point is that there is a resampling step I am
missing because 10x10=100 and 50x50=250.  which would account for
almost the 3x discrepancy.

If you need anymore information please don't hesitate to ask.  I
appreciate any and all help.

-- 
Stephen Sefick

Let's not spend our time and resources thinking about things that are
so little or so large that all they really do for us is puff us up and
make us feel like gods.  We are mammals, and have not exhausted the
annoying little problems of being mammals.

								-K. Mullis