[GRASSLIST:14] Re: New GIS Manager adds transparency to layers

Sat Mar 11 12:24:52 EST 2006

I¹m co-teaching an interdisciplinary Remote Sensing and Quaternary
Landscapes class with a couple of colleagues in other schools. We decided to
show students how to do some basic GIS-related tasks like import a DEM,
reproject it from latlon to UTM, do a shaded relief map, drape it with
color, create basic slope and aspect maps, and do profile analysis‹and do it
on 2 systems ArcGIS 9 and GRASS 6.1.

My colleague (who is eager to learn more about GRASS) did this in ArcGIS
this week and I will do the same in GRASS after Spring Break. Having barely
touched Arc in a couple years now, I was feeling bad about showing students
the complications in getting GRASS started and some of the esoteric aspects
of this complex program. Then I watched the ArcGIS presentation. Easy to
start and then the difficulties started. Sure you can open any map in an
projection, but... Getting the projection right so that the maps actually
overlay correctly is more difficult than in GRASS. Hill shading/shaded
relief is about the same in both. Draping is definitely more versatile in
GRASS‹especially with the new transparency. Slope and aspect are marginally
easier to do in GRASS and much easier to find in the menus. Profiling is a
LOT easier in GRASS, even though it is still tied to the x11 displays.
Several times my colleague mentioned, if only we could... And I said, you
can do that in GRASS. For example, after finally getting profiling to work
in ArcGIS (He needed to restart...so I don¹t feel quite so embarrassed about
occasional lockups in the GIS Manager, though a want it to be bug free), he
said, if only we could output the profile points in some way. GRASS has a
couple ways to do this‹via d.profile and r.profile.

Since I¹ll be following the ArcGIS demo, I¹ll be able to feel pretty good
about the GRASS demo when I do it.

Michael

On 3/10/06 5:01 PM, "Ian MacMillan" <Ian.MacMillan at pomona.edu> wrote:

> Michael, I haven't tried this out yet, but it sounds excellent.  Cheers to all
> of your efforts to make GRASS more user-friendly for newbies.  I am going to
> feel less guilty about making my students use GRASS in their classes instead
> of Arc. 
> 
> -Ian 
> 
> On Mar 10, 2006, at 12:59 PM, Michael Barton wrote:
> 
>> I¹ve just finished phase 2 of the GIS Manager update and it¹s pretty
>> exciting. At first glance, it looks a lot like the one I¹ve been working on
>> and have in the CVS now, but with a couple of important exceptions. One is
>> that transparency is now supported for all GRASS layers.
>> 
>>  The second will probably generate the most discussion, so I¹m ready to duck
>> and run for cover.  Now GRASS is consistent with other GIS programs and more
>> intuitive (as much as I am skeptical about that term) in that the uppermost
>> layer in the layer tree is also the top map in the display. Related to this,
>> new layers insert directly above the currently selected layer instead of at
>> the bottom of the layer tree.
>> 
>>  The main changes come Œunder the hood¹ of this version of the GIS Manager.
>> It uses g.pnmcomp to composite a set of maps (each rendered as *.PPM files)
>> into a visual display. One of the results is that now GRASS is significantly
>> faster in adding new layers, turning layers on and off, and changing layer
>> attributes‹only the new or changed layer needs to be rendered; the others
>> will just be re-composited into a display from existing PPM files. This all
>> happens in a GRASS .tmp directory, so that it doesn¹t clutter up your home
>> directories. The other important thing about this new architecture is that it
>> makes GRASS even less dependent on the xdriver and PNGdriver for
>> visualization. GRASS can become more easily portable to different OS¹s and
>> GUI frameworks. It is also more scriptable. You can write a script that will
>> create a complete, multilayered map, and output it to a graphics file.
>> 
>>  One consequencer of this new architecture is that the GIS Manager does not
>> currently support display output to PNG files. With GDAL (required for many
>> GRASS features) and ghostscript installed, it does support output to PPM/PNM,
>> TIF, JPG, BMP, EPS, and PDF.
>> 
>>  Command line usage is still supported  in several ways‹the old xterminal is
>> still there, there is the new command console, and you can add command layers
>> to the layer tree and display them.
>> 
>>  You can see a screen shot of semi-transparent soil vector areas overlaying a
>> raster shaded relief map at
>> 
>> http://www.public.asu.edu/~cmbarton/files/grass_screenshots/gism2-2.jpg
>> 
>>  I¹ve committed all changes to the CVS. For those of you with binary versions
>> of GRASS who would like to try it, I¹ve posted packages you can use to
>> replace your current GIS Manager on my website. For full functionality, you
>> need a version of grass that is dated 21-February-2006 or later. For those of
>> you with a slightly earlier version, I made a second package with all
>> functionality minus transparency. Here are the links.
>> 
>>  New GIS Manager files
>> 
>>  
>> <http://www.public.asu.edu/~cmbarton/files/grass_gismgr/gism_rc4_20060307.tgz
>> > 
>> 
>>  New GIS Manager files for people with recent, but pre-21 February 2006
>> binaries. 
>> 
>> <http://www.public.asu.edu/~cmbarton/files/grass_gismgr/gism_rc4_20060307pre_
>> 02-21.tgz> 
>> 
>>  Enjoy 
>>  Michael 
>> 
>>  ______________________________
>>  Michael Barton, Professor of Anthropology
>>  School of Human Evolution and Social Change
>>  Arizona State University
>>  Tempe, AZ  85287-2402
>>  USA 
>> 
>>  voice: 480-965-6262; fax: 480-965-7671
>>  www: http://www.public.asu.edu/~cmbarton
>>   
>> > 
>> > 
> What happens if a big asteroid hits Earth? Judging from realistic simulations
> involving a sledge hammer and a common laboratory frog, we can assume it will
> be pretty bad. 
>  - Dave Barry 
> 

___________________________
Michael Barton, Professor of Anthropology
School of Human Evolution & Social Change
Arizona State University
Tempe, AZ  85287

WWW - http://www.public.asu.edu/~cmbarton
Phone: 480-965-6262
Fax: 480-965-7671

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