[GRASS-user] .e00 to DEM

[Nikos Alexandris]

On Wed, 2009-07-08 at 09:51 -0700, Dylan Beaudette wrote:
> On Wednesday 08 July 2009, Nikos Alexandris wrote:
> > There is something strange with the values though (they expand from min
> > = -32687  max = 32645). Don't have the time to dig further, maybe there
> > are details in the meta-data about it (!?).
> 
> This looks like an overflow problem. Could it be that this file contains 
> unsigned 16 / 32 bit integers, but is being read in as signed 16 bit 
> integers?

Probably you are right Dylan. In the meta-data it is written:

<< Level 2 DEM: Level 2 DEMs may contain void areas due to interruptions
to contours in the source graphic or DLG. Void area elevation grid posts
are assigned the value of -32,767. >>

* This means that original data are for sure Signed (probably
Int16-bit... ?).

* gdal reads the data correctly (look previous post of mine) as:
  Band 1 Block=20x4 Type=Int16, ColorInterp=Undefined
  Min=0.000 Max=1371.000 
  NoData Value=-32768

* grass reports the range of the imported data as:
r.info dem250 -tr
min=-32687
max=32645
datatype=CELL

* The data show up correctly in GRASS:

g.region rast=dem250 && r.colors dem250 color=terrain && d.mon x0 &&
d.rast dem250


If we accept min=-32687 that was assigned to be nodata, what is this
max=32645?

Nikos