[GRASSLIST:2467] native resolution of raster maps

GRASS GRASS user
1

Is there a way to find out the native resolution of a raster map and _set_it_ using g.region?

I'm concerned about making sure that raster operations (such as r.patch) occur at the native resolution of the maps involved, not the resolution of the region. The reason that this concerns me is that I noticed that the grid resolution setting of g.region only goes down to 1 sec (in a lat-lon location). If I calculate correctly, that's about 30m. What if I have data that have, say, a 10m resolution? Can I not perform operations on those data at their native resolution because g.region won't let me set the resolution low enough? For maps that have a resolution higher than 30m, how do I set the resolution in g.region to exactly match the native resolution of the map. Right now, I'm guessing and I'm afraid that I'm loosing data.

As always, thanks ahead of time,

Jason
Jason Horn
Boston University Department of Biology
5 Cumington Street Boston, MA 02891

jhorn@bu.edu
617 353 6975

2

Presuming I'm understanding the question right, what you're looking for is just:
g.region rast=nameofexistingmap

to make the current region match that of the existing map.

But that's only part of the question, because it sounds like you're mixing things with different spatial units? Or maybe you mean that the resolution _corresponds_ to 10m resolution but is actually in lat/long coordinates/units?

Scott Mitchell

On Wednesday, Feb 4, 2004, at 21:24 Canada/Eastern, Jason Horn wrote:

Is there a way to find out the native resolution of a raster map and _set_it_ using g.region?

I'm concerned about making sure that raster operations (such as r.patch) occur at the native resolution of the maps involved, not the resolution of the region. The reason that this concerns me is that I noticed that the grid resolution setting of g.region only goes down to 1 sec (in a lat-lon location). If I calculate correctly, that's about 30m. What if I have data that have, say, a 10m resolution? Can I not perform operations on those data at their native resolution because g.region won't let me set the resolution low enough? For maps that have a resolution higher than 30m, how do I set the resolution in g.region to exactly match the native resolution of the map. Right now, I'm guessing and I'm afraid that I'm loosing data.

As always, thanks ahead of time,

Jason
Jason Horn
Boston University Department of Biology
5 Cumington Street Boston, MA 02891

jhorn@bu.edu
617 353 6975

------
Scott W. Mitchell Scott_Mitchell@carleton.ca
Department of Geography and Environmental Studies
Carleton University, B349 Loeb Building
Ottawa, ON Canada
+1-613-520-2600 ext 2695

3

In addition you can actually get a smaller resolution in a lat-long location,
just use decimal degrees.

For example you can do

g.region nsres=0.00013889 ewres=0.00013889
(this corresponds to ~15m resolution)

or you can set a region to the boundary of a raster, and a different resolution
at the same time.

g.region raster=your_rast nsres=0.000833 ewres=0.00083

Good luck, ian

Presuming I'm understanding the question right, what you're looking for
is just:
g.region rast=nameofexistingmap

to make the current region match that of the existing map.

But that's only part of the question, because it sounds like you're
mixing things with different spatial units? Or maybe you mean that the
resolution _corresponds_ to 10m resolution but is actually in lat/long
coordinates/units?

Scott Mitchell

> Is there a way to find out the native resolution of a raster map and
> _set_it_ using g.region?
>
> I'm concerned about making sure that raster operations (such as
> r.patch) occur at the native resolution of the maps involved, not the
> resolution of the region. The reason that this concerns me is that I
> noticed that the grid resolution setting of g.region only goes down to
> 1 sec (in a lat-lon location). If I calculate correctly, that's about
> 30m. What if I have data that have, say, a 10m resolution? Can I not
> perform operations on those data at their native resolution because
> g.region won't let me set the resolution low enough? For maps that
> have a resolution higher than 30m, how do I set the resolution in
> g.region to exactly match the native resolution of the map. Right
> now, I'm guessing and I'm afraid that I'm loosing data.
>
> As always, thanks ahead of time,

4

> > The reason that this concerns me is that I noticed that the grid
> > resolution setting of g.region only goes down to 1 sec (in a
> > lat-lon location).

...

In addition you can actually get a smaller resolution in a lat-long
location, just use decimal degrees.

...

g.region nsres=0.00013889 ewres=0.00013889
(this corresponds to ~15m resolution)

or you can set a region to the boundary of a raster, and a different
resolution at the same time.

g.region raster=your_rast nsres=0.000833 ewres=0.00083

.. you can also just do

g.region res=0:0:0.001

H

5

Hello dear list,
I have some problems in 5.7, I wish you help me...

1. Sometimes that I use of d.what.vect, it shows me:
     Buttons
     Left: what's here
     Middle: toggle flash color
     Right: quit
   But when I click left key of the mouse on the map
   nothing happens and if I do it again it shows:
     Broken pipe
   and quit from d.what.vect

2. When I am successful on use of d.what.vect, I have
   these values on my street map:
     ...
     Type: Point
     field: 1
     category: 6
     ...
     -----------------------
     ...
     Type: Point
     field: 1
     category: 160
     ...
    
    Now I want to find the best path between two
points
    so I use:
      v.net.path input=Teh_Vect output=t2 type=line
afield=1 nfield=1
    It shows:
      Vector 't2' already exists and will be
overwritten.
      Building graph:
      Registering arcs ... 100%
      Flattening the graph ... done.
      Graph was built.

    Now I write :
      6 160 (Is it correct?)
    But nothing happens.
    
Would you please tell me my wrong and explain me more
about v.net.path?

Thanks a lot

Maliheh

__________________________________
Do you Yahoo!?
Yahoo! Finance: Get your refund fast by filing online.
http://taxes.yahoo.com/filing.html

6

Sorry again me,
I changed my command like this:

v.net.path input=Teh_Vect output=t4 afield=1 nfield=2

Now it shows:

Building graph:
Registering arcs ... 100%
Flattening the graph ... done.
Graph was built.
WARNING: 61 points without category.
6 160
WARNING: No point with category 6
WARNING: No point with category 160

What should I do?

__________________________________
Do you Yahoo!?
Yahoo! Finance: Get your refund fast by filing online.
http://taxes.yahoo.com/filing.html

7

Hello All,

I’m wondering if anybody of the grass-community has used Grass for Vehicle-Navigation or Routing till now?

Regards

Do you Yahoo!?
Yahoo! Finance: Get your refund fast by filing online

8

Hello to all!

I'm wondering if anybody of the grass-community has used Grass for Vehicle-Navigation or Routing till now?

...and, generally, where could I find information on GRASS utilization history?

Thanks in advance,

Alex

9

I'm wondering if anybody of the grass-community has used Grass for
Vehicle-Navigation or Routing till now?

I've done something for real-time shipboard positioning, it would work
pretty well for aerial as well after adjustments for speed. It would need
to be reworked by someone to be used for real-time land-vehicle use on a
road network, using GRASS 5.7's v.net.path et al. That would include both
updating it to work with 5.7 vectors and intergrating v.net.*.

"NOT FOR NAVIGATION, USE AT OWN RISK"
(It's a hack, but it works fairly well)

Screenshots:
  http://bambi.otago.ac.nz/hamish/grass/realtime_gps_4.png
  http://bambi.otago.ac.nz/hamish/grass/realtime_gps5.png
  http://bambi.otago.ac.nz/hamish/grass/realtime_gps6.png

You can underlay GIS layers & do real-time display of say soil type
or whatever at current postion.. (broken lines are from previous tracks)

see
http://article.gmane.org/gmane.comp.gis.grass.user/3148
http://article.gmane.org/gmane.comp.gis.grass.user/3125

slightly older version:
http://article.gmane.org/gmane.comp.gis.grass.user/2361

To do non-realtime vehicle routing over road networks, use GRASS 5.7
and d.path, v.net.*

http://grass.ibiblio.org/grass51/tutorial/network.html
http://grass.ibiblio.org/grass51/manuals/html57_user/vector.html

Hamish

10

...and, generally, where could I find information on GRASS utilization
history?

Search the full mailing list or just ask, maybe someone will remember..

the 1996-today searchable mailing list archive:
http://www.ecosconsult.com.br/grass-list/

or download the full archive and search through it with 'grepmail':
http://grass.itc.it/pipermail/grassuser/
http://grepmail.sourceforge.net/

see also the users' survey from last year:
http://www.ecosconsult.com.br/grass-list/arq/6525.html

Hamish

11

On Mon, Feb 16, 2004 at 04:25:27PM +1300, Hamish wrote:

> ...and, generally, where could I find information on GRASS utilization
> history?

Search the full mailing list or just ask, maybe someone will remember..

the 1996-today searchable mailing list archive:
http://www.ecosconsult.com.br/grass-list/

or download the full archive and search through it with 'grepmail':
http://grass.itc.it/pipermail/grassuser/

This archive is complete (1991-today).

Note that you can also search that archive:
http://grass.itc.it/searchgrass.html
-> Restrict to: "GRASS Users mailing list"
-> or the "google" search on that page

Markus