Re: [GRASS-user] Best format for exporting raster data

2010-09-02 Thread Rainer M Krug 
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Hash: SHA1

On 01/09/10 19:45, Glynn Clements wrote:
> 
> Rainer M Krug wrote:
> 
>> It would be nice, if grass would be able to deal with on-the-fly
>> decompression - not from a .tar.gz file, but from gz compressed files.
> 
> GRASS rasters are already compressed by default, either using RLE or
> zlib compression (OTOH, the null bitmap isn't compressed; that will
> cease to be an issue if we embed nulls into the raster data).

That is good to know - as mentioned in an earlier email, I will then
leave as it is. I actually compared the size of the compresses grass
folder with the non-compressed one, and the difference did not justify
the effort.

> 
> But GRASS doesn't generally read data from files per se, but from
> either the GRASS "database" or from GDAL (and the former might
> eventually go away if we can get "native" GRASS support into GDAL).

I don't understand that statement - I am the database is ultimately a
file, so grass is requesting the data from the database which then reads
it from the mapset which consists of files. And gdal is used when data
is read which is not in the mapset - right?

> 
> The main issue with on-the-fly decompression using general-purpose
> formats is that rasters aren't guaranteed to be read sequentially,
> while compression algorithms require sequential access.

Makes sense - thanks for the clarification.

> 
> Similarly, while there exist filesystems which can mount archives, tar
> files (and especially compressed tar files) are a poor choice, as they
> are designed for sequential access. ZIP/RAR are more suited to such
> tasks.

but they can actually be mounted as was pointed out by Markus Neteler
(http://www.linux.com/archive/feature/132196).

> 
> Ultimately, I don't think that this situation is common enough to be
> worth doing anything about. If you want to access archived data, you
> just unpack the archives first (or use an archive format which can be
> mounted).

I'll folow the following approach: I'll leave the data uncompressed,
until the analysis are completed (I have a new 2TB hdd now) and will
compress them into tar.gz files as soon as the project is finished. If I
need them again, I will use archivemount to access the data.

Thanks everybody for your help,

Rainer

> 


- -- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
Biology, UCT), Dipl. Phys. (Germany)

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Re: [GRASS-user] Land use/cover change detection with GRASS GIS

2010-09-02 Thread Nikos Alexandris 
fatih:

> I plan to determine land use/cover changes using different Landsat images
> in GRASS GIS. Is there anybody who has tried this before? I am not
> familiar with the GRASS GIS. So, a document/manual which includes step by
> step description of image processing may help.

GRASS provides the tools to do it :-). What you really need is to decide which 
methods to try and finally use (worth reading [1][2][3]).

 A few more words

Among the most common change detection techniques are:

1. post-classification comparison (of a pre and a post data set): classify the 
pre and the post data separately (check the wiki-page that Daniel posted in 
the other reply to your post), then subtract to produce a change map.

2. PCA-based method(s) where PCA is utilised in order to "isolate" the changes 
in less dimensions than the original (given we talk about multi-dimensional 
data sets, e.g. multi-spectral bands of a satellite image acquisition). [4][5]

One PCA-based example is to treat all (pre and post) bands as one data set and 
perform PCA. Changes are expected to appear "isolated" in a few (lower order) 
components. You can use the "enhanced" components to classify the changes.

However, it is required to carefully check the numbers in order to best 
identify the changes of your interest. Visually controlling the outcomes is 
not enough! The eigen-vectors which "compose" the outcomes and the eigen-
values which describe how much of the original variance holds each component.

Have (also) a look here: 
.

Cheers, Nikos

---
[1] Lu, D and Mausel, P and Brondizio, E and Moran, E, "Change detection 
techniques", International Journal of Remote Sensing, vol. 25, no. 12, pp. 
2365, 2003.

--%<--- PCA-based
[2] Deng, JS and Wang, K and Deng, YH and Qi, GJ, "PCA-based land-use change 
detection and analysis using multitemporal and multisensor satellite data", 
International Journal of Remote Sensing, vol. 29, no. 16, pp. 4823, 2008.

[3] Koutsias, N and Mallinis, G and Karteris, M, "A forward/backward principal 
component analysis of Landsat-7 ETM+ data to enhance the spectral signal of 
burnt surfaces", ISPRS Journal of Photogrammetry and Remote Sensing, vol. 64, 
no. 1, pp. 37, 2009.
--->%--

[4] 

[5] an attempt to collect details on using PCA (in GRASS, R): 

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[GRASS-user] v.surf.rst does not get past 0% from cli, throws error from python gui but not tcltk

2010-09-02 Thread Eric Hardin 

Hi,
I recently tried to interpolate some data using v.surf.rst but ran into
trouble. I'm pretty sure I've interpolated since my last fresh install, so
maybe it is an update that's causing the trouble. I'm using Ubuntu 10.04
64bit. 
I have GRASS70 compiled from source and GRASS6.4 from the package manager. 
When I try to run v.surf.rst from the command line, it starts and maxes the
cpu but never gets past 0% in both GRASS versions. When I run it from tcltk
gui it does the same thing. When I run it from python gui I sometimes get:
The program 'python' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadValue (integer parameter out of range for operation)'.
  (Details: serial 7354 error_code 2 request_code 18 minor_code 0)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the --sync command line
   option to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)
Does this sound familiar to anyone?
Thanks,
Eric

-
Eric Hardin
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View this message in context: 
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Sent from the Grass - Users mailing list archive at Nabble.com.
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Re: [GRASS-user] Finding the value of a point in a raster map

2010-09-02 Thread Glynn Clements 

vbkhp wrote:

> I am writing a r.mapcalc instruction, and I would like to find the
> value of a point in the map (other than the point that the window is
> currently at).
> More precisely, in a raster dem I would like to calculate the
> difference between the height of one point and the rest of the map. 

Use r.what to query the value at specific point, then insert ther
result into the r.mapcalc expression as a constant.

-- 
Glynn Clements 
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[GRASS-user] bug in v.net

2010-09-02 Thread Ricardo Rodríguez 
hello all, I found a bug in the script v.net creates more nodes to be
created, for example using the Gisdemo_ncspm mapaset creating a network
between the layer of streets and schools in this mapaset schools are 169,
but the resulting network appears with 49 746 nodes this is a mistake
recording advised me to correct it or what version of GRASS GIS is in good
condition and has the scripts of centrality and short cuts for all couples

thanks for the support and help

Ricardo Rodríguez

Univalle
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Re: [GRASS-user] g.extension not working

2010-09-02 Thread Glynn Clements 

Hamish wrote:

> > > Otherwise, if you installed grass as root (make install as root), you
> > > most probably also have to install addons as root.
> Markus Neteler wrote:
> > Perhaps we need to add some sudo magic...?
> 
> will that work with MSys? (does g.extension work at all with standalone
> WinGrass?)
> 
> addons should really be installed to $GRASS_ADDON_PATH, right? not $GISBASE
> (typically that will be read-only if GRASS came from a package; GISBASE is
> the default for prefix= currently).

On a system where GRASS itself has been installed from a "package"
(RPM or similar), the installation probably shouldn't be modified
other than via the OS' own administration tools.

-- 
Glynn Clements 
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Re: [GRASS-user] Best format for exporting raster data

2010-09-02 Thread Glynn Clements 

Rainer M Krug wrote:

> > But GRASS doesn't generally read data from files per se, but from
> > either the GRASS "database" or from GDAL (and the former might
> > eventually go away if we can get "native" GRASS support into GDAL).
> 
> I don't understand that statement - I am the database is ultimately a
> file, so grass is requesting the data from the database which then reads
> it from the mapset which consists of files.

Ultimately, it's files, but only at the lowest level of the core
libraries. Modules get their data from the "GRASS database", but the
nature of that database is an implementation detail.

> And gdal is used when data is read which is not in the mapset -
> right?

GDAL is used if you create a "linked" map using r.external or
r.external.out. 

> > Similarly, while there exist filesystems which can mount archives, tar
> > files (and especially compressed tar files) are a poor choice, as they
> > are designed for sequential access. ZIP/RAR are more suited to such
> > tasks.
> 
> but they can actually be mounted as was pointed out by Markus Neteler
> (http://www.linux.com/archive/feature/132196).

They can, but the filesystem will have to decompress a substantial
part of the archive just to access one file. If you use zip/rar, it
only has to decompress files which are accessed.

> > Ultimately, I don't think that this situation is common enough to be
> > worth doing anything about. If you want to access archived data, you
> > just unpack the archives first (or use an archive format which can be
> > mounted).
> 
> I'll folow the following approach: I'll leave the data uncompressed,
> until the analysis are completed (I have a new 2TB hdd now) and will
> compress them into tar.gz files as soon as the project is finished. If I
> need them again, I will use archivemount to access the data.

If you're planning on using archivemount, use zip/rar rather than
.tar.gz (and don't use "solid" rar archives, which have the same
problems with random access as tar files).

-- 
Glynn Clements 
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Re: [GRASS-user] g.extension not working

2010-09-02 Thread Markus Neteler 
On Thu, Sep 2, 2010 at 8:44 AM, Hamish  wrote:
...
> ps- I suspect 'svn commit' uploaded a bit more than you planned in this one:
>  https://trac.osgeo.org/grass/changeset/43379

Yes, but reverted that immediately
https://trac.osgeo.org/grass/changeset/43385

Please double check...

Markus
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Re: [GRASS-user] g.extension not working

2010-09-02 Thread Markus Neteler 
On Thu, Sep 2, 2010 at 9:08 PM, Glynn Clements  wrote:
> Hamish wrote:...
>> (does g.extension work at all with standalone WinGrass?)

To my knowledge only the Python version in GRASS 7.

>> addons should really be installed to $GRASS_ADDON_PATH, right? not $GISBASE
>> (typically that will be read-only if GRASS came from a package; GISBASE is
>> the default for prefix= currently).
>
> On a system where GRASS itself has been installed from a "package"
> (RPM or similar), the installation probably shouldn't be modified
> other than via the OS' own administration tools.

Right - I replace my sudo suggestion with $GRASS_ADDON_PATH magic :)

Markus
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Re: [GRASS-user] v.surf.rst does not get past 0% from cli, throws error from python gui but not tcltk

2010-09-02 Thread Markus Neteler 
On Thu, Sep 2, 2010 at 3:06 PM, Eric Hardin  wrote:
>
> Hi,
> I recently tried to interpolate some data using v.surf.rst but ran into
> trouble. I'm pretty sure I've interpolated since my last fresh install, so
> maybe it is an update that's causing the trouble. I'm using Ubuntu 10.04
> 64bit.
> I have GRASS70 compiled from source and GRASS6.4 from the package manager.
> When I try to run v.surf.rst from the command line, it starts and maxes the
> cpu but never gets past 0% in both GRASS versions. When I run it from tcltk
> gui it does the same thing.

Please post the output of

g.region -p

Perhaps too many rows/cols?

Markus

> When I run it from python gui I sometimes get:
> The program 'python' received an X Window System error.
> This probably reflects a bug in the program.
> The error was 'BadValue (integer parameter out of range for operation)'.
>  (Details: serial 7354 error_code 2 request_code 18 minor_code 0)
>  (Note to programmers: normally, X errors are reported asynchronously;
>   that is, you will receive the error a while after causing it.
>   To debug your program, run it with the --sync command line
>   option to change this behavior. You can then get a meaningful
>   backtrace from your debugger if you break on the gdk_x_error() function.)
> Does this sound familiar to anyone?
> Thanks,
> Eric
>
> -
> Eric Hardin
> --
> View this message in context: 
> http://osgeo-org.1803224.n2.nabble.com/v-surf-rst-does-not-get-past-0-from-cli-throws-error-from-python-gui-but-not-tcltk-tp5491018p5491018.html
> Sent from the Grass - Users mailing list archive at Nabble.com.
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Re: [GRASS-user] bug in v.net

2010-09-02 Thread Maris Nartiss 
Hello,
please provide exact commands to execute in Spearfish or NC datasets
to reproduce Your issues.

IMHO You are just mixing up things - when You use v.net
operation=connect, You will get node_count = School_nodes + Road_nodes
as it connect's every school with road segment to nearest road and
thus creates one or two extra nodes per school on a road network.

Maris.


2010/9/2, Ricardo Rodríguez :
> hello all, I found a bug in the script v.net creates more nodes to be
> created, for example using the Gisdemo_ncspm mapaset creating a network
> between the layer of streets and schools in this mapaset schools are 169,
> but the resulting network appears with 49 746 nodes this is a mistake
> recording advised me to correct it or what version of GRASS GIS is in good
> condition and has the scripts of centrality and short cuts for all couples
>
> thanks for the support and help
>
> Ricardo Rodríguez
>
> Univalle
>
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