Re: [GRASS-user] how to get instantaneous heading of a line at a pt?
On Tue, Feb 17, 2009 at 5:05 AM, Hamish hamis...@yahoo.com wrote: Hi, I have used v.to.points to create a series of points that fall along a line. Now I want to upload to a DB column in the points map the instantaneous heading of the original line at that sample point. This functionality might be added to v.to.db - perhaps using Vect_get_node_line_angle(): http://download.osgeo.org/grass/grass6_progman/level__two_8c.html#a16 Markus ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] v.generalize for area boundaries?
On Tue, Feb 17, 2009 at 7:35 AM, Hamish hamis...@yahoo.com wrote: Hi, I am following the v.generalize tutorial at http://users.ox.ac.uk/~orie1848/tutorial.html (we should move that to the wiki before it disappears) Here are converters to Mediawiki syntax: http://www.jtidy.de/ http://diberri.dyndns.org/wikipedia/html2wiki/index.html Additionally, the screenshots need to be uploaded. Markus ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Thiessen Polygons
The Voronoi diagram is closely related to gravity models: every cell in the raster map gravitates towards the closest center point in the input point pattern. If you change the gravitational attraction of individual points, you get a weighted Voronoi diagram. If you change the measure of gravity by switching from straight-line distance to e.g. cost-based then you get something more complex and realistic than any Voronoi algorithm can provide. In Archaeology, a simple formula (called Xtent) has been used to calculate such gravity models for a long time: I = C^a - k*d With I being the influence of an input point. I gets calculated for every input point at every cell in the map. The input point with highest I wins and the cell gets assigned to that point's ID. (C^a) is the weight of a point. (k*d) is your (weighted) distance measure. Set (C^a) constant and use a straight-line distance measure and you get your basic Voronoi diagram. Assign different weights to C and you get a weighted diagram. Replace (k*d) with a more realistic, cost-based measure and you get something ... really cool. I am sure, there is a myriad of similar models/formulas in other disciplines. I have actually written a GRASS module called r.xtent based on this. It still has some known bugs, however, and I simply don't have the time to fix it right now. It's also pretty bloated and inefficient, so a clean, more minimalistic start might not be a bad idea. Ben Jan Hartmann wrote: Wouldn't this work with cost surfaces too? Starting from several points (the Thiessen centers) with a grid cell cost information raster containing only the value one, you get a raster representation of a classic Thiessen structure. Manipulating the cost information raster , you should get something like a weighted Thiessen structure. The last step would be to extract the boundaries between the polygons in vector format, with the methods above. Starting from each center point, the cost surface will rise, until it meets the rising surface from an adjacent point. At this location, slope becomes zero. These zero slope areas are effectively the Thiessen polygons, and can be vectorized. For normal Thiessen polygons, this should be no problem, but I am not sure what happens with really complex weighted cases. Does anyone have any experience with this? Jan ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user -- Benjamin Ducke Senior Applications Support and Development Officer Oxford Archaeology Ltd Janus House Osney Mead OX2 0ES Oxford, U.K. Tel: +44 (0)1865 263 800 (switchboard) Tel: +44 (0)1865 980 758 (direct) Fax :+44 (0)1865 793 496 benjamin.du...@oxfordarch.co.uk -- Files attached to this email may be in ISO 26300 format (OASIS Open Document Format). If you have difficulty opening them, please visit http://iso26300.info for more information. ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Thiessen Polygons
Hamish wrote: - use r.param.scale to create a feature map and extract all saddle-point boundaries between the bubbles as the voronoi boundaries, (or r.slope.aspect and find areas where slope1 deg then r.thin, r.to.vect) Wouldn't this work with cost surfaces too? Starting from several points (the Thiessen centers) with a grid cell cost information raster containing only the value one, you get a raster representation of a classic Thiessen structure. Manipulating the cost information raster , you should get something like a weighted Thiessen structure. The last step would be to extract the boundaries between the polygons in vector format, with the methods above. Starting from each center point, the cost surface will rise, until it meets the rising surface from an adjacent point. At this location, slope becomes zero. These zero slope areas are effectively the Thiessen polygons, and can be vectorized. For normal Thiessen polygons, this should be no problem, but I am not sure what happens with really complex weighted cases. Does anyone have any experience with this? Jan ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Thiessen Polygons
Interesting. I know something of these models (worked a few years for the archaeology department here in Amsterdam), and, like you, never had enough time to really code it. Apart from efficiency, I am wondering whether those really cool cost surfaces will degenerate into impossible vector polygons. Do you have any examples from archaeological practice, using this gravitation approach? How were they computed? Jan Benjamin Ducke wrote: The Voronoi diagram is closely related to gravity models: every cell in the raster map gravitates towards the closest center point in the input point pattern. If you change the gravitational attraction of individual points, you get a weighted Voronoi diagram. If you change the measure of gravity by switching from straight-line distance to e.g. cost-based then you get something more complex and realistic than any Voronoi algorithm can provide. In Archaeology, a simple formula (called Xtent) has been used to calculate such gravity models for a long time: I = C^a - k*d With I being the influence of an input point. I gets calculated for every input point at every cell in the map. The input point with highest I wins and the cell gets assigned to that point's ID. (C^a) is the weight of a point. (k*d) is your (weighted) distance measure. Set (C^a) constant and use a straight-line distance measure and you get your basic Voronoi diagram. Assign different weights to C and you get a weighted diagram. Replace (k*d) with a more realistic, cost-based measure and you get something ... really cool. I am sure, there is a myriad of similar models/formulas in other disciplines. I have actually written a GRASS module called r.xtent based on this. It still has some known bugs, however, and I simply don't have the time to fix it right now. It's also pretty bloated and inefficient, so a clean, more minimalistic start might not be a bad idea. Ben Jan Hartmann wrote: Wouldn't this work with cost surfaces too? Starting from several points (the Thiessen centers) with a grid cell cost information raster containing only the value one, you get a raster representation of a classic Thiessen structure. Manipulating the cost information raster , you should get something like a weighted Thiessen structure. The last step would be to extract the boundaries between the polygons in vector format, with the methods above. Starting from each center point, the cost surface will rise, until it meets the rising surface from an adjacent point. At this location, slope becomes zero. These zero slope areas are effectively the Thiessen polygons, and can be vectorized. For normal Thiessen polygons, this should be no problem, but I am not sure what happens with really complex weighted cases. Does anyone have any experience with this? Jan ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] shortest / less steep path in DEM
Hi, to calculate the shortest path from a mountain top into the valley, I ususally use r.flow, but what if I do not want the shortest but the less steepest path? thanks, Georg ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] Re: shortest / less steep path in DEM
On Tue, 17 Feb 2009 13:39:15 +, Georg Kaspar wrote: Hi, to calculate the shortest path from a mountain top into the valley, I ususally use r.flow [...] sorry, I meant r.drain... ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Re: shortest / less steep path in DEM
Forgot to post to the list as well, In short, combine both the length cost map and the steepness (r.slope output) cost map (according to your preference). Use this output as input for a final cost calculation. That should do the trick I think, Koen On Tue, 2009-02-17 at 14:15 +, Georg Kaspar wrote: On Tue, 17 Feb 2009 13:39:15 +, Georg Kaspar wrote: Hi, to calculate the shortest path from a mountain top into the valley, I ususally use r.flow [...] sorry, I meant r.drain... ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] v.generalize for area boundaries?
On 17.02.2009 08:35, Hamish wrote: Hi, I am following the v.generalize tutorial at http://users.ox.ac.uk/~orie1848/tutorial.html (we should move that to the wiki before it disappears) but it doesn't say much about working with areas beyond removing small ones. That page and the images exists in the svn too. How does one go about adding extra manual pages? Or perhaps we could integrate it into the manual page itself? I have a vector area which has a very steppy boundary, like from r.to.vect with a sawtooth pattern at the cell edges. I want to run a smoothing filter over it to get rid of the jaggy bits. No matter what method I try my output map is always the same as the input map, no vertices are created or destroyed. any ideas how to do this? I know about 'v.clean tool=prune' and Markus Metz's topology-preserving v.simplify (psst- add it to wiki addons) but I'd like to learn more about how to use v.generalize. How large is the cell you exported from? First you have to use a smoothing operator. When you are done with the smoothing you should use the douglas method to reduce the number of points. I'll see if I can whip up an example for you. --Wolf -- :3 ) Wolf Bergenheim ( 8: ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] v.generalize for area boundaries?
Hi, Is it possible with grass to replace missing values in a map by surrounding values by a sort of interpolation, knowing that sometimes many missing values are numerous one near another? If yes, how? Thank you very much Stéphanie ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] replacing missing data in a map
Sorry i forgot to change the subject. FAROUX STEPHANIE wrote: Hi, Is it possible with grass to replace missing values in a map by surrounding values by a sort of interpolation, knowing that sometimes many missing values are numerous one near another? If yes, how? Thank you very much Stéphanie ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] error saving workspace
Hello, currently working on grass64.svn (v.35911), I cannot save my workspace anymore under wxpython GUI. An error window pops up with the following message : Writing current settings to workspace file failed (global name 'val' is not defined). Am I doing something wrong ? Vincent ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] v.generalize for area boundaries?
Hi.. please try r.neighbors cheers.. Ivan Il giorno mar, 17/02/2009 alle 18.00 +0100, FAROUX STEPHANIE ha scritto: Hi, Is it possible with grass to replace missing values in a map by surrounding values by a sort of interpolation, knowing that sometimes many missing values are numerous one near another? If yes, how? Thank you very much Stéphanie ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user -- Ti prego di cercare di non inviarmi files .dwg, .doc, .xls, .ppt. Preferisco formati liberi. Please try to avoid to send me .dwg, .doc, .xls, .ppt files. I prefer free formats. http://it.wikipedia.org/wiki/Formato_aperto http://en.wikipedia.org/wiki/Open_format Ivan Marchesini Department of Civil and Environmental Engineering University of Perugia Via G. Duranti 93/a 06125 Perugia (Italy) Socio fondatore GFOSS Geospatial Free and Open Source Software http://www.gfoss.it e-mail: marches...@unipg.it ivan.marches...@gmail.com tel: +39(0)755853760 fax (university): +39(0)755853756 fax (home): +39(0)5782830887 jabber: geoiva...@jabber.org ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] v.generalize for area boundaries?
On Tue, Feb 17, 2009 at 7:03 PM, ivan marchesini marches...@unipg.it wrote: Hi.. please try r.neighbors r.fillnulls is another option: http://grass.osgeo.org/grass64/manuals/html64_user/r.fillnulls.html Markus cheers.. Ivan Il giorno mar, 17/02/2009 alle 18.00 +0100, FAROUX STEPHANIE ha scritto: Hi, Is it possible with grass to replace missing values in a map by surrounding values by a sort of interpolation, knowing that sometimes many missing values are numerous one near another? If yes, how? Thank you very much Stéphanie ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] error saving workspace
Hi, 2009/2/17 Vincent Bain b...@toraval.fr: currently working on grass64.svn (v.35911), I cannot save my workspace anymore under wxpython GUI. An error window pops up with the following message : Writing current settings to workspace file failed (global name 'val' is not defined). fixed in r35912. Martin -- Martin Landa landa.martin gmail.com * http://gama.fsv.cvut.cz/~landa ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] error saving workspace
Indeed,:-) Thank you. Vincent Le mardi 17 février 2009 à 20:39 +0100, Martin Landa a écrit : Hi, 2009/2/17 Vincent Bain b...@toraval.fr: currently working on grass64.svn (v.35911), I cannot save my workspace anymore under wxpython GUI. An error window pops up with the following message : Writing current settings to workspace file failed (global name 'val' is not defined). fixed in r35912. Martin ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] Interpolation on a Grid
List, I'd like to do an interpolation of xyz data points that I have, and put the interpolated data on 100' x 100' grid. So that each 100' x 100' square has an associated elevation value. Any suggestions as to how best to do this? -- Frank Aragona ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] ERROR geonames_features
On Sun, Feb 15, 2009 at 8:13 PM, Zahid Parvez
grassgisbanglad...@gmail.com wrote:
Dear grass user,
It may be a silly error but it is confusing me. I will be very glad if you
could help.
I am learning GRASS GIS from Open source gis a grass gis approach book.
This a an excellent book for the beginners.
I am using winGRASS 6.3.0.4 native version and running nc_spm 0...@permanent.
I have executed the following comand:
r.contour elevation out=elev_contour_m step=3 min=55 max=154
it is giving following error:
BMI-DBF driver error:
SQL parser error: syntax error, unexpected NAME, expecting '(' processing
'geonames_features'
in statement:
create table database geonames_features.elev_contour_m ( cat integer,
level double precision )
Error in db_execute_immediate()
Unable to create table: create table database
geonames_features.elev_contour_m ( cat integer, level double precision )
then I have run the following steps:
- db.connect
- db.connect driver=dbf
{database=$GISDBASE/$LOCATION_NAME/$MAPSET/dbf/} {schema=database
geonames_features}
- I want to remove the schema=database geonames_features ; because i think
it is creating problem
- I have deleted from txtbox and execute db.connect driver=dbf
{database=$GISDBASE/$LOCATION_NAME/$MAPSET/dbf/}
- but when again I open db.connect window it shows schema=database
geonames_features
- How can I remove it.
The easiest way is to go into the PERMANENT directory and
exit the VAR file and remove the offending schema line using
Wordpad or another ASCII editor.
DBF does not support schema.
Hope this helps,
Markus
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Re: [GRASS-user] Export specific shapes from a vector file
Λεωνίδα, you might be interested in this tutorial: Αναπαραγωγή του χάρτη CORINE με το GRASS-GIS (http://users.hol.gr/~dzach/tilaphos/corine_grass-gis_el.pdf) published at http://tilaphos.blogspot.com/2009/02/gis-corine.html Χαιρετίσματα, Νίκος ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] replacing missing data in a map
On Feb 17, 2009, at 6:08 PM, grass-user-requ...@lists.osgeo.org wrote: Date: Tue, 17 Feb 2009 18:11:23 +0100 From: FAROUX STEPHANIE stephanie.far...@meteo.fr Subject: [GRASS-user] replacing missing data in a map To: GRASS Users grass-user@lists.osgeo.org Message-ID: 499aefbb.1060...@meteo.fr Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sorry i forgot to change the subject. FAROUX STEPHANIE wrote: Hi, Is it possible with grass to replace missing values in a map by surrounding values by a sort of interpolation, knowing that sometimes many missing values are numerous one near another? If yes, how? Thank you very much Stéphanie ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user r.fill.nulls Michael___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Thiessen Polygons
Jan wrote: Wouldn't this work with cost surfaces too? Starting from several points (the Thiessen centers) with a grid cell cost information raster containing only the value one, you get a raster representation of a classic Thiessen structure. Manipulating the cost information raster , you should get something like a weighted Thiessen structure. The last step would be to extract the boundaries between the polygons in vector format, with the methods above. Starting from each center point, the cost surface will rise, until it meets the rising surface from an adjacent point. At this location, slope becomes zero. These zero slope areas are effectively the Thiessen polygons, and can be vectorized. For normal Thiessen polygons, this should be no problem, but I am not sure what happens with really complex weighted cases. Does anyone have any experience with this? right, the idea is to apply the wealth of landscape analysis modules to the cost surface (or whatever) instead of a real DEM. Lots of power there just waiting to be harnessed. Hamish ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] Re: v.generalize for area boundaries?
Wolf wrote: I'll see if I can whip up an example for you. Okay here is what I did: r.to.vect input=geology output=test v.generalize method=snakes input=test output=snakes It produces nice straight lines and with method=douglas threshold=30 you can get it even better (note that the cell size was 30m) Also note that the method=snakes I used simply the default values for alpha and beta. same here. [added feature=area for r.to.vect] proposed example for the help pages based on that: # spearfish g.region rast=geology r.reclass in=geology out=geology.claysand EOF 8 = 8 claysand EOF r.to.vect in=geology.claysand out=geology_claysand feature=area v.generalize in=geology_claysand out=geology_claysand_smooth method=snakes ah, I see the problem now, I need to run v.build.polylines first, then it works ok. Problematic vector attached. Hamish: http://users.ox.ac.uk/~orie1848/tutorial.html (we should move that to the wiki before it disappears) Wolf: That page and the images exists in the svn too. where in svn? How does one go about adding extra manual pages? what kind of man page did you have in mind? Or perhaps we could integrate it into the manual page itself? the module man page is already quite large. There are so many options, I'd prefer a wiki page with an explanation example (incl screenshots) of each method. The tutorial at users.ox.ac.uk is a great start for that. It is extensive enough that I think retaining a separate tutorial is justified. Helena: I would strongly suggest to integrate at least the most important info into the man page. Nobody maintains tutorials and other extra docs and they become quickly obsolete. Also many people use man pages so there is a better change of fixing / enhancing explanations if necessary, 2c: I believe the wiki is alive enough that it gets maintained. It is not as integrated strictly updated, but not collecting dust like the GDP in the web pages either. Also images are not seen by `man`, add significantly to the bulk of the source distribution, and integrate nicely in MediaWiki. for v.generalize the bare description.html file is already 250 lines long, so presumably already contains most important info. (although no examples) thanks, Hamish blocky.vasc.gz Description: GNU Zip compressed data ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] unable to install Grass
Dear all, I m trying to install Grass on my PC. I recieived a Cygwin Setup window which says: Unable to get setup.ini from http://geni.ath.cx/grass Please Help. Ta, jimmy ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] unable to install Grass
Jimmy wrote: I m trying to install Grass on my PC. I recieived a Cygwin Setup window which says: Unable to get setup.ini from http://geni.ath.cx/grass in the instructions at http://grass.osgeo.org/grass62/binary/mswindows/ you will see setup.ini at the top of that page, and it says: At step #3 use http://grass.ibiblio.org/grass62/binary/mswindows/ (or a local mirror) instead of http://geni.ath.cx/grass.; good luck, Hamish ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] how to get instantaneous heading of a line at a pt?
Hamish: I have used v.to.points to create a series of points that fall along a line. Now I want to upload to a DB column in the points map the instantaneous heading of the original line at that sample point. Markus: This functionality might be added to v.to.db - perhaps using Vect_get_node_line_angle(): http://download.osgeo.org/grass/grass6_progman/level__two_8c.html#a16 hmmm. at a node there are two lines, the fn wants to know which one. I have a point somewhere along the line (between two vertices) and want to #1 find the polyline, #2 extract the current linear feature (between two nearest connected vertices), and #3 calc the angle of that line. I see now the corner case of if the point falls exactly on a vertex or a node you will have to average to angles of the lines on either side. I don't think v.to.db could help other than the overall bearing from the polyline's start node to end node. Remember a single line cat can only hold a single value. 'v.distance upload=to_angle' might be something... Hamish ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
