Project with GRASS. Help!!

[Carlos Martinez]

Hi.

First of all, sorry for my english. I don't speak english very well, but I
need some help about GRASS and I don't find spanish people that develop
applications with it.

I'm working in a project to manage archeologic excavations. In this
project I have to manage the objects found on the ground when the
excavation is done. I have some problems because I'm beginning in GRASS
and GIS world.

There are three type of objects that can be found in the excavation. The 
first and more important are the geological layers. The second are the
objects builded by the humans like walls or houses. The third are the
rests of dead people. The last two types of objects are less important
because I think its imposible to handle them in a GIS in other way that
with sites.

The problem is the firs type. In the project that I'm developing the
objects corresponds to the space of the same material, not to the
limit of this material. I have done a DEM introducing points with x, y and
z coordinates. But the problem is that this DEM corresponds to one of
the two limits of one object. I have done this because one of the work of
the archeolegs is to give points from the ground to make a map after.

Despite of this the problem is that is posible to find an object of one
material inside an object of another material. I don't know how to do
this. To do this I need to develop a system in wich the limit between two
objects is had to be clear. Two layers can be considered two surfaces
interpolated from sites, wich z value is the height from an horizontal
plane, but the object between them...

I have seen that there is a type of data in GRASS called G3D from wich a
good aproaching can be done. Do you know something about it? Can I use it
to do the application? Do you know where can I find some information?

In http://www2.gis.uiuc.edu:2280/modviz/gsoils/ccsoil2.html I have seen
some pictures like the thing I want to do. The difference is that I want
to do that with ground. 

Other thing is that in an excavation can be found a lot of ground layers.
If one ground layer of one material corresponds to two raster layers and I
can find a lot of them, is it posible to have problems because a lot of
layers are needed?

Another problem is that I want to assign some attributes to
each object of the excavation. It's easy if the objects are of the two
last types because they are sites. The problem is if the object is a
ground layer. How can I do it? How can I add fields to the object? How can
I link it with the database table, with cathegory or with coordinates? I
don't know how Postgress/GRASS interface does it. I need to develop the
system without any data, introducing points of the ground, so I can't use
an ArcView shapefile. How can I do it with the Postgres/GRASS interface?

The archeolegs need to work at really small scales, perhaps to 1:10 or
1:5, because they need to manage small objects with good precission. Is it
possible to have problems because of that? Is a good idea to use a GIS to
develop the project?

Thanks and sorry for my english again. If I could explain myself in
spanish I think this letter could be better.

Thank you again.