[GRASS-user] [GRASSLIST:1120] Arc vs grass coming soon (unless someone wants to get it started)

[Jonathan Greenberg]

Grassers:

	I'll get the table started ASAP, but I'm busy over the next few
weeks -- if someone wants to get it going on the wiki feel free, otherwise
I'll get to it when can.  I was thinking a table at the top of the page with
the headings "Software (ARCINFO/ArcMap/ArcView)","ESRI command/feature",
"GRASS command(s)", and an anchor-link to a set of headers below the table
that have a discussion of the similarities/differences, and how to replicate
the arc process "perfectly" if possible.  The table and subsequent
discussion should be alphabetized by the ARC software and then by the arc
command.  Here's an example/possible entry that could be included:

***

Table entries:
Software: ARC/INFO (ARC)
ESRI command/feature: LATTICESPOT 
GRASS command(s): v.what.rast 

Discussion entry:
LATTICESPOT
LATTICESPOT has a nearly perfect translation to v.what.rast as follows:
LATTICESPOT <in_lattice> <in_cover> {spot_item} {z_factor}
	translates to:
v.what.rast vector=<in_cover> raster=<in_lattice> layer=layer
column={spot_item}

Discrepancies:
	-{spot_item} defaults to "SPOT" for LATTICESPOT, but must be
explicitly defined for v.what.rast
	-{z_factor} must be applied the GRASS vector database
after-the-fact.
	-LATTICESPOT performs a bilinear interpolation to assign raster
values to the output vector, whereas v.what.rast uses nearest neighbor.

***

One of the goals of this wiki page, I think, would be to minimize or remove
all discrepancies.  This is where the use of a wiki really helps: power
users of GRASS can offer ways that people like me (who are basically
newbies) can't figure out.  For instance, how can we solve the z_factor
discrepancy -- how do I multiply a GRASS vector column by a fixed value?
This would remove that discrepancy between the ARC and GRASS.  

--j

--

Jonathan A. Greenberg, PhD
NRC Research Associate
NASA Ames Research Center
MS 242-4
Moffett Field, CA 94035-1000
Phone: 415-794-5043
AIM: jgrn3007
MSN: jgrn3007 at hotmail.com