representing geology with rasters?

[Andreas Holz]

Hello,
	as I mailed to You yesterday, there have been several effords
	to connect a groundwater-model to a GIS, esp. GRASS. E.g.
	look at:

		J. Fuerst: Decision Support Systeme fuer die Grund-
		wasserwirtschaft unter Verwendung geographischer 
		Informationssysteme. - Wiener Mitteilungen Wasser,
		Abwasser, Gewaesser, Band 93, 1990.

	Here some Informations from this paper (excuse me, there are
	sometimes Informations of value in GERMAN!) about the representation
	of in- and outputdata for the groundwater-model MODFLOW:

	Daten				Representation in GRASS	
	(data for GW-model)
	-----------------------------------------------------------
	Fluesse Geometrie		Grundriss als GRASS Vektorkarte
	Hoehe (Laengsschnitt)		Folge von (x,y,z) als 3D Ergaenzung
					zur Vektorkarte
	Fluesse Hydrologie		Pegelganglinien in Zeitreihendatenbank
	Extreme Spiegellinien		Grundriss + Folge von (x,y,z)
	
	Aquiferparameter		GRASS Punktkarte (x,y,par)
	Oberflaechenmodell		GRASS Rasterkarte

	Grundwasserneubildung		GRASS Polygonkarte oder Rasterkarte
	
	Landnutzung			GRASS Polygonkarte oder Rasterkarte

	Rdnder				GRASS Vektorkarte

	Lage von Grundwasser-		GRASS Punktekarte (x,y,id)
	messstellen

	Entnahmebrunnen			wie Messstellen

	Draenagen			wie Fluesse

	FD Grundwassermodell		
	  Geometrie			Ausschnitt u. Aufloesung als GRASS Fenster
	  Aquiferparameter		GRASS Rasterkarte
	  Anfangsspiegel		GRASS Rasterkarte
	  Optionen			Liste als Textdatei
	  Berechnete Spiegellagen	GRASS Rasterkarte


	In this article a connection of GRASS 3.0 to MODFLOW using XGEN-scripts
	is presented.


	If You think about a connection of GRASS with groundwater-models
	think about the following:

		1) GRASS raster layers are rectangular, so You can
		   use them only for finite-difference models.

		2) GRASS has no real 3D capabilities. You can simulate
		   different layers of a groundwater-model with
		   several connected raster-layers.

		3) I think, via voronoi- or delaunay-triangulation modules
		   in GRASS You can prepare  a mesh for a FEA-groundwater-
                   model, but You can generate 2D-meshes only. There are
		   no volume-meshing routines.

	
	I4m currently developing routines for 2D and 3D mesh generation
	with triangular and rectangular elements for FE-modelling, primary
	not for the use with groundwater-models, but for FE-modelling in
	Geology. But I4m also interested in gw-models and their connection 
	to GRASS, so I will implement this mesh-generator in GRASS soon.

	
	P.s.: 	To all users of GRASS or GIS and groundater-models:

			- wich groundwater-model are You using?
			- wich pre- and postprocessor are You using?
			- is You gw-model connected to Your GIS?
			- do You want to share Your experiences?
			- do You want to develop a standard interface from
			  GRASS to Your favourite gw-model?
			- 

=========================================================================================
Dipl. Geol. Andreas Holz		e-mail: asholz at cip.informatik.uni-erlangen.de
Institut fuer Geologie und Mineralogie
Universitaet Erlangen-Nuernberg
Schlossgarten 5
91054 Erlangen
GERMANY

currently to get my doctors degree at
SIEMENS AG				e-mail: holz at oi32.kwu.siemens.de
KWU NDA 2
PO BOX 3220
91050 Erlangen
GERMANY