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[Peter Hraber]

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Date: Wed, 26 Jan 94 09:11:35 MST
From: tkeitt (Timothy Keitt)
Posted-Date: Wed, 26 Jan 94 09:11:35 MST
Received-Date: Wed, 26 Jan 94 09:11:35 MST
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To: bmilne, gchong, lfitzg, phraber, rtaylor, starbox, tduran, tkeitt
Status: R

GRASS is a Geographic Information System (GIS) for displaying, analyzing, and
entering spatial data such as maps or sattelite images.  In the following
you will run grass and access an existing database containing a digital
elevation model (DEM).

1. First run grass by typing "grass".  There are three fields in the
startup screen.  Read what it says about each field and the instructions
for what to do next.  Depending on your certain settings in your environment,
there may be text already in some of the fields.  Fill in the fields as
follows:

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
------------------------------------------------------------------------------
                            GRASS 4.1

LOCATION: This is the name of an available geographic location.  -spearfish-
          is the sample data base for which all tutorials are written.

MAPSET:   Every GRASS session runs under the name of a MAPSET.  Associated
          with each MAPSET is a rectangular COORDINATE REGION and a list
          of any new maps created.

DATABASE: This is the unix directory containing the geographic databases

         The REGION defaults to the entire area of the chosen LOCATION.
         You may change it later with the command: g.region
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

LOCATION:   list__________             (enter list for a list of locations)
MAPSET:     (login name)               (or mapsets within a location)

DATABASE:   /landscape/projects/pj/work/gisdbase______________



              AFTER COMPLETING ALL ANSWERS, HIT <ESC> TO CONTINUE
                            (OR <Ctrl-C> TO CANCEL)
------------------------------------------------------------------------------
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Where it says (login name), put your account name, i.e. what you type
to login.  Be sure to get the full DATABASE path name correct (HINT: you can
use the mouse to cut and paste from this tutorial).

2. Now hit <ESC> and you will see a list of available locations:

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
------------------------------------------------------------------------------
Available locations:
----------------------
arabela         el_paso_gap_ne  mummy_cave_rui  rancho_de_taos  taos
arroyo_hondo    gardner_peak    oscura          red_butte       taos_sw
arroyo_seco     global          oscura_peak     red_butte_sw    temp
bullis_spring   guadalupe_mtn   osha_mtn        red_river       toothpick_ridg
canon_colorado  high_rolls      palo_flechado   robertson_cany  tres_ritos
canteen_canyon  lobo_springs    pine_canyon     rowe            turkey_canyon
carracas_canyo  magdalena       point_lookout   sandiapark      water_canyon
circle_mesa     milan           pueble_park     southwest       wheeler_pk
datil           mt_sedgwick     purcell_canyon  spider_rock
desert_view     mule_canyon     questa          table_mtn
----------------------

Hit RETURN -->
------------------------------------------------------------------------------
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

3. Hit RETURN and in the location field enter wheeler_pk:

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
------------------------------------------------------------------------------
                            GRASS 4.1

LOCATION: This is the name of an available geographic location.  -spearfish-
          is the sample data base for which all tutorials are written.

MAPSET:   Every GRASS session runs under the name of a MAPSET.  Associated
          with each MAPSET is a rectangular COORDINATE REGION and a list
          of any new maps created.

DATABASE: This is the unix directory containing the geographic databases

         The REGION defaults to the entire area of the chosen LOCATION.
         You may change it later with the command: g.region
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

LOCATION:   wheeler_pk____             (enter list for a list of locations)
MAPSET:     tkeitt________             (or mapsets within a location)

DATABASE:   /landscape/projects/pj/work/gisdbase______________



              AFTER COMPLETING ALL ANSWERS, HIT <ESC> TO CONTINUE
                            (OR <Ctrl-C> TO CANCEL)
------------------------------------------------------------------------------
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

4. Now type "d.mon x0".  A window will popup which you can then place anywhere
on the screen (click the first mouse button).

5. Type "d.rast wheeler_pk.dem" and you will see a 2D display of the data
points where the color correspond to different elevations.

6. Now type "d.3d" followed by "wheeler_pk.dem" at the first two prompts,
then hit <RETURN>.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
------------------------------------------------------------------------------
        3-D Landscape display

First enter the names of the maps to be used to
for color and for elevation:


Enter raster file to be displayed: 
Enter 'list' for a list of existing raster files
Enter 'list -f' for a list with titles
Hit RETURN to cancel request
> wheeler_pk.dem
<wheeler_pk.dem>

Enter raster file to used for elevation: 
Enter 'list' for a list of existing raster files


Enter 'list -f' for a list with titles
Hit RETURN to cancel request
> wheeler_pk.dem
<wheeler_pk.dem>


If you have previously saved 3-D viewing options in this mapset
you may recover them by entering the name under which they were saved.

Enter nothing and hit <RETURN> to have default values calculated.


Enter name of saved 3-d viewing options to be used: 
Enter 'list' for a list of existing 3d.view files
Hit RETURN to cancel request
> 
------------------------------------------------------------------------------
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

7. Hit <RETURN> and then <ESC> and you should get a rather rough 3d display
of Wheeler Peak in the Sangre de Cristo Mts.

8. Edit the fields as follows:

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
------------------------------------------------------------------------------

--------------------------------------------------------------------------
            VIEWING REGION              | RUN? Y/N              Y_
            N: 4053202                  | Erase Color           black___
   W: 455206    ---|--- E: 466426       | Vertical Exaggerat.   1______
            S: 4039282                  | Field of View (deg)   20.00__
                                        | Lines Only? Y/N       n_
           VIEW COORDINATES:            | Line Color            color___
Eye Position              Center of view| Line Frequency        1____
 4025362.00<- Northing (y) -> 4046242.00| Resolution            50.00_____
 443986.00_<- Easting  (x) -> 460816.00_| Plot zero elev? Y/N   N_
 14733.37__<- Height   (z) -> 1324.20___| Box color             none____
                                        | Average elevs? Y/N    N_
--------------------------------------------------------------------------
Eye -----                          | Colors: red orange yellow green blue
 \                    N            |   indigo violet brown gray white black
  \     /MAP----------/            |
   \   /      X      /             | Special 'colors':
     W/_____________/E             |   'None' available for 'Erase Color'
                   S               |   'color' available for 'Line Color'
--------------------------------------------------------------------------


              AFTER COMPLETING ALL ANSWERS, HIT <ESC> TO CONTINUE
------------------------------------------------------------------------------
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

9. You should get a much better display.  Experiment with other settings
(you'll find that setting your resolution much higher will speed things
up).

10. The DEM is georeferenced, i.e. each pixel corresponds to a particular
place on the earth +/- some error.  The coordinates are in the Universal
Trans-Mercador (UTM) system.  Elevation values are in meters and each pixel
is 30 meters wide.  Wheeler Peak is the highest point in New Mexico.  Can
you get GRASS to give you the approximate UTM coordinates of Wheeler Peak?
How high is Wheeler Peak? How accurate are your estimates?  

HINT: take a look at r.stats and possibly r.mapcalc.  When you're running
GRASS you're still using the UNIX shell so you can use pipes to other
programs like awk.

11. Take a look at some of the images in the sandiapark location.  There
are several quite large scanned aerial photographs and a DEM file.  The
scanned images represent different years 1935, 1951, etc.  You might
try using r.mapcalc to display differences between the images.  This
will be very slow on large images, but you can change the region using
g.region and set the resolution to a higher number.  Remember if you
get stuck to read the instructions on the screen and use g.manual or
g.help to get help.

T. Keitt -- Tue Jan 25 17:06:51 MST 1994
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