[GRASS-user] getting started (stuck) with GRASS 2.

Hi

I need to present early this week landscape analysis of a site and thought it may be an opportunity for me to leave microstation (my cad program) and “get my feet wet” in GIS. Read as much as I could find about free gis, downloaded and installed the files needed for Grass 6.4, created the needed directories and started it. unfortunately all I have managed to get oen is the terminal box and the first wizard screens. In it I have tried several ways to create a localization to Israel and my site (including use of georeferenced dwg file and prj files but nothing was added to the directory or to the list and there no way to turn on the MapSet preparation button.

I am just a landscape architect - no programer, no knowledge of compiling or script work which may tell you I shouldn’t even dare trying but I am curious and see some potential in it for landscape evaluation.

I intend to buy the book but need to find out first if GRASS 6.4 is something I am able to use at work… If at all possible I would like to be able preferably also to be able to load/import GIS drawings and DB from ArcInfo, microstation geography etc. For this initial trying I have a 3d CAD survey of a mountain in .dwg format. Based on it I want to produce slope analysis, viewshed analysis and land use analysis. I also have a folder sent to me from an ArcInfo user with the following file types: .dbf .sbn .sbx shp .shp.xml .shx .prj. I trust that unlike me they will mean something to you.

I am running it on an imac 24

Best regards
Ruvy

___________________________________________________
ראובן (רובי) עמיר - אדריכל נוף מתכנן סביבה
Reuven (Ruvy) Amir Landscape Architect

ֿruvy@ruvyamir.co.il
www.ruvyamir.co.il


TelFax: 972-9-9580440
Mobile: 972-54-6656511

Hi Ruvy,

GRASS can definitely do all the stuff that you listed. I've never worked
with the DWG format, but I believe there's a module that lets you import it
called v.in.dwg. As far as importing the Arc data, it sounds like you're
wanting v.in.ogr. That's the module used to import shapefiles, which are the
formats you're talking about.

Buying the book is definitely a good idea, because getting started with
GRASS isn't necessarily as easy as with other GI-Systems. However, you'll
find that you can do a whole lot more with GRASS than with many other
systems. As it sounds like you've already set the location of your GRASS
database, you need a location and a mapset to get started. For the location,
you need a coordinate system - try using one of your georeferenced files to
create that, like your .shp from the Arc user's data. As soon as that's done
you can create mapsets that are geographically or thematically sorted - as a
practice you might want to just open up your "PERMANENT" mapset and import
some data into it, set the region settings to match your data and play
around.

Anyway, those are just some fast starter tips, but I would definitely
suggest getting the book. All your data should be compatible, the functions
you're looking for are there - I hope this helps you a bit further :slight_smile:

Best,
Daniel
--
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Hi Ruvy,

Don't worry, setting up the location is something that can even be difficult
for geographers that aren't familiar with GRASS. The concept is:

1. Geodata (data connected with locational information) consists of
descriptive information as well as data describing the object's position,
normally on the Earth's surface. That means coordinates. But because there
are multiple ways to describe positions on the Earth's surface, meaning
various coordinate systems, GRASS has to know what coordinate system your
data uses in order to be able to analyze your data in a spatial context.
2. In order to be more organized once a coordinate system has been defined
GRASS analyzes the data you import into various sub-categories that you can
organize as you like.

Practically, that means that you need to first define the coordinate system
you're working with. That's what you do in the "Location" GUI. In the first
GUI that pops up when you start GRASS, you tell GRASS where it should put
its database (the GIS Data Directory, field at the top) - that's a directory
that GRASS works with, where it will put all its data - including any data
you import and any data you produce. It sounds like you've already done
this.

After that you need to define a location that you'll be working in.
Locations can hold your data. All the data in a single location needs to use
the same coordinate system. If you have data with different coordinate
systems and want to be able to analyze or view them together in GRASS, it's
no problem, but you'll need to transform the data so that it all has a
single coordinate system. We won't worry about that. Let's worry about
getting you a working location first.

So the first step is to open the location wizard to create a new location.
If you click on that button it'll ask you what your new location should be
called - you can name it as you like - and after clicking "Next" you'll be
asked how you'd like to create your new location. As you're a landscape
architect I'm assuming you don't have too much experience with coordinate
systems and etc., which could make the next menu somewhat confusing. If you
know more information about the coordinate system you're working with, you
can enter that info. I'll assume you want to just take the coordinate system
of the data you've been given. Your first post sounded like you might have
already tried it, but I'll go through that quickly by describing two methods
that both work just as well:
- Select "Read projection and datum terms from a georeferenced data file"
and click next. Then enter one of your shapefiles (that's an Arc file with
the extension .shp). You could probably just as easily use the DWG file, but
since I've never tried that before we'll stick with the shapefile.
Alternatively, you can
- Select "Read projection and datum terms from a WKT or PRJ file" and click
next. Then take one of your *.prj files from the Arc data.

Now you should see a summary of the info you've entered. Click Finish and
you've got your location. In the interest of simplicity, don't set the
default region extents and resolution yet.

That's just step one, now you need a mapset to work in. Mapsets are inside
locations and contain data. You can have several datasets inside one mapset.
Mapsets can also interact with each other, as long as all the data's inside
the same location. Most users find it helpful to put data in mapsets that
either covers the same geographic area or is thematically related, but it's
really a matter of taste and effectiveness and must be decided from project
to project.

Normally I would always suggest making a new mapset to hold your data, but
since you don't have experience with GRASS and need your stuff quickly, we
can skip that and you can start working more "cleanly" later, after you've
gotten the GRASS book :slight_smile: Once your location is made, you've got a mapset
automatically. It's called PERMANENT. Every location has a permanent mapset;
all other mapsets are added manually by the user. Let's use that one, so go
ahead and open it by clicking "Start GRASS".

Now you're in GRASS, and this is where I was talking about as I mentioned
"v.in.ogr" and "v.in.dwg". You'll have two windows, one is your layer
manager and the other is the map display, and if you type in "v.in.ogr"
without quotation marks in the "Cmd" field at the bottom of the layer
manager, you'll get the GUI for that module. It should let you import almost
any vector data format you want. I mentioned "v.in.dwg" after seeing your
data format and glancing over the results of a Google search, but I can't
find it either and in the documentation it seems to perhaps not exist any
more. I'm not sure what other options you have for that kind of data since I
don't know that format - it's for CAD data, right? There's probably a way of
importing it into GRASS, or of converting it into a format that can be
imported to GRASS, but I unfortunately can't help you much further in that
area.

Entering the commands in the command field is a great way to access them if
you know what commands you're looking for. But if you don't know them, you
can explore the menus in the layer manager - you'll find just about
everything you need there, plus descriptions. About your slope analysis:

GRASS does slope and viewshed analyses using rasters. For land use analyses
it depends a lot on what you want to do. If you've only got vector data, you
should import it into GRASS (v.in.ogr is the command), then convert it to a
raster (v.to.rast), then perform the analyses you need - you'll find the
commands you need in the "Raster" menu at the top of the layer manager.
Terrain analysis will be interesting for you (particularly r.slope.aspect),
as well as r.los for viewshed analyses.

Hope that helps! I know it's a lot of info at once, but I wanted to give you
something of a jump start if you need to have the analysis done within a few
days :slight_smile:

Best regards,
Daniel
--
View this message in context: http://osgeo-org.1803224.n2.nabble.com/getting-started-stuck-with-GRASS-2-tp5620514p5621385.html
Sent from the Grass - Users mailing list archive at Nabble.com.

LeeDaniel wrote:

GRASS can definitely do all the stuff that you listed. I've never worked
with the DWG format, but I believe there's a module that lets you import it
called v.in.dwg.

v.in.dwg isn't included in binary releases because it relies upon the
OpenDWG library, whose licence is incompatible with the licence used
by GRASS itself (the GNU GPL).

If you want v.in.dwg, you have to build it from source, and you also
have to obtain the OpenDWG library yourself.

--
Glynn Clements <glynn@gclements.plus.com>

Glynn wrote:

v.in.dwg isn't included in binary releases because it relies upon the
OpenDWG library, whose licence is incompatible with the licence used
by GRASS itself (the GNU GPL).

If you want v.in.dwg, you have to build it from source, and you also
have to obtain the OpenDWG library yourself.

also of note is the new v.in.dwg2 in GRASS addons svn, I'm not sure if it's
operational yet or not though. It'll get around needing OpenDWG's stuff
once ready.

also, v.in.dxf works great if DXF is an option for you.

Hamish