[GRASS-user] Georrectify and nearest neighbor
My name is Jenny Turner and I've been using georrectify graphical module in WxpyTHon GRASS6.4. I saw a video of the proceeding but I would like to know if there is a description or a tutorial of what to do and how. I have understand what I have to do but I need to explain to other persons (non-grass users :) ). Just one more thing: Is it used any resampling to the data or only nearest neighbor? Thanks Jenny ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] calculating road density
Thanks! I'm trying this route. On Wed, May 26, 2010 at 11:18 PM, Dylan Beaudette dylan.beaude...@gmail.com wrote: v.rast.stats, So far its running for 5 days on my whole region! No segfault error so far. :) -- cheers, maning -- Freedom is still the most radical idea of all -N.Branden wiki: http://esambale.wikispaces.com/ blog: http://epsg4253.wordpress.com/ -- ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] Using v.distance between two identical layers...
Hi, do you know if it's possible to use v.distance command when for and to layers are the same layer ? I have a layer describing ecological areas of interest and I want to qualify spatial relation between all patches. I want to identify and calculate shortest relation between all my patches boundaries. How can I do as v.distance command doesn't have any option like : eliminate identical objects from the from and to layer ? I'd like to use this particular command because of the option that create lines between nearest objects. Thanks Nicolas This message was sent using IMP, the Internet Messaging Program. ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] modis data
On 06/01/2010 09:10 PM, Hamish wrote: bharath s wrote: iam working on modis data (mydo9q1 250 m) using grass (gis) software. i want to overlay google earth boundary for southindia.. after geocorrection on modis data... but the boundaries are not matching. please help me to solve this problem. is the projecton playing any role in it ? actually iam using lat/long and datum as wgs84. I would try to use the natural earth vector boundary instead of Google's one. Yes, indeed. Since Google's shiny 3D toy is getting dangerously close to being accepted into mainstream science and research now, one should be aware that there are differences between Google's private way of handling lat/lon projections and international geodetic systems: http://www.sharpgis.net/post/2008/05/SphericalWeb-Mercator-EPSG-code-3785.aspx This will lead to inaccuracies when trying to overlay Google data and EPSG 4326 data. The same problem exists for Microsoft's clone of Google Earth (they do seem to take the copying business serious at MS). The magnitude of error will vary with your region's scale and location. NASA's 3D Earth tool is, as may be expected, more competent, so perhaps the better choice for 3D GIS visualization: http://worldwindcentral.com/wiki/Map_projection_Plug-in Best, Ben see 1:10 million, 1:50 million and 1:110million scale maps from http://grass.osgeo.org/wiki/Global_datasets#Natural_Earth_imagery if 1:10m is too crude for you, there NOAA's coastline extractor + v.in.mapgen, or v.in.gshhs from wiki addons; or others listed on the above wiki page. see also http://grass.osgeo.org/wiki/MODIS Hamish ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user -- 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
[GRASS-user] Using Vector Digitizer in Windows
Hi I'm using Vector Digitizer in MS-Windows (Tcltk since WxGUI is not available) and I wanted to know How can I put an image as a background? I am at v.digit form and I cannot see any field regarding that Thanks Kim ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] get coords from a raster
Hi List, I'm trying to make a script to calculate the slope along a path. I want to calculate the slope as the average of cell per cell slope. For my purpose I found r.profile to produce the input file for my script, but I have to give it the coordinates of the points. As I have a raster and not a vector, I was wondering if is there a non interactive way like a d.where or something like that, that i can use for my purpose. I mean, i have a raster in which there is the path i'm interested in, and the other cells are null. Thank you in advance Margherita ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] get coords from a raster
Christian, thank you for answering. My problem is that I don't want to use the slope map to get slope, bu i want to calculate it as the ratio between the difference of the elevation and the distance between two given points (pixels). To do that, I need to get the coordinates of the points as a input file for r.profile. Margherita 2010/6/2 Christian Schwartze christian.schwar...@uni-jena.de Why are you not using r.statistics, since it takes one base map (your path as a raster) and another map containing data you want to analyze (your slope). With the average option/method you will get the desired result, if I understand you correctly... Christian. *From:* Margherita Di Leo direg...@gmail.com *Sent:* Wednesday, June 02, 2010 6:17 PM *To:* grass-user@lists.osgeo.org *Subject:* [GRASS-user] get coords from a raster Hi List, I'm trying to make a script to calculate the slope along a path. I want to calculate the slope as the average of cell per cell slope. For my purpose I found r.profile to produce the input file for my script, but I have to give it the coordinates of the points. As I have a raster and not a vector, I was wondering if is there a non interactive way like a d.where or something like that, that i can use for my purpose. I mean, i have a raster in which there is the path i'm interested in, and the other cells are null. Thank you in advance Margherita -- ___ 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] huff model
hello all, saw some of you to know if there is any implementation of huff model for grass gis or failing that a script on it in Open Source software arcgis but I do not want to work with such libraries. thanks for your answers Ricardo Rodríguez Univalle ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] surface cost
hello all, I have a question that can be evaluated as sustainable urban accessibility of a zone map go through friction, but the only difference to the examples in the book that the analysis I want to do is not over in many respects an attractive location but several points of interest between themselves, to facilitate the compression of what I want to analyze the connection (and accessibility) among various warehouses or schools, both topologically (factor map distance matrix) as the gravitational level ( huff model), which commands do you recommend for this type of process. code more than I would like to hear experiences and suggestions on this topic thanks for your attention, time and answers ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Using Vector Digitizer in Windows
On Wed, Jun 2, 2010 at 6:10 PM, Kim Besson kimbesson1...@gmail.com wrote: Hi I'm using Vector Digitizer in MS-Windows (Tcltk since WxGUI is not available) and I wanted to know How can I put an image as a background? I am at v.digit form and I cannot see any field regarding that There should be, when starting, the option to select a background display *command* http://grass.osgeo.org/grass64/manuals/html64_user/v.digit.html which could be set to d.rast map=name_of_raster Markus ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] get coords from a raster
On Wed, Jun 2, 2010 at 6:50 PM, Margherita Di Leo direg...@gmail.com wrote: Christian, thank you for answering. My problem is that I don't want to use the slope map to get slope, bu i want to calculate it as the ratio between the difference of the elevation and the distance between two given points (pixels). If you treat them as vectors, perhaps this could help? v.to.db ... slope: slope steepness of vector line or boundary ? Markus ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] calculating road density
On Wed, Jun 2, 2010 at 1:24 PM, maning sambale emmanuel.samb...@gmail.com wrote: Thanks! I'm trying this route. On Wed, May 26, 2010 at 11:18 PM, Dylan Beaudette dylan.beaude...@gmail.com wrote: v.rast.stats, So far its running for 5 days on my whole region! No segfault error so far. :) Perhaps this could be a fast alternative: http://grass.osgeo.org/wiki/GRASS_AddOns#r.univar.zonal Markus ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] huff model
On Wed, Jun 2, 2010 at 7:21 PM, Ricardo Rodríguez ricardorodo...@gmail.com wrote: hello all, saw some of you to know if there is any implementation of huff model for grass gis or failing that a script on it in Open Source software arcgis but I do not want to work with such libraries. Do you mean something like this? http://www.directionsmag.com/article.php?article_id=896 Markus ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] get coords from a raster
Markus, Thank you. I'm pretty sure this is the way. So I run: r.to.vect input=mainchannel output=points feature=point --o v.to.db map=points option=coor col=x,y (like the man page suggests) but I get a number of errors like: Column 'x' not found Error in db_execute_immediate() where am I wrong now? 2010/6/2 Markus Neteler nete...@osgeo.org If you treat them as vectors, perhaps this could help? v.to.db ... slope: slope steepness of vector line or boundary I calculate slope as S = (z2-z1)/(sqrt((x2-x1)^2+(y2-y1)^2))*100 where x1,y1 are the coords of point 1, x2,y2 are the coords of point 2, and z1, z2 are the elevations in the raster map associate at the points 1 and 2 respectively. Margherita ? Markus ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] get coords from a raster
On Wed, Jun 2, 2010 at 10:07 PM, Margherita Di Leo direg...@gmail.com wrote: Markus, Thank you. I'm pretty sure this is the way. So I run: r.to.vect input=mainchannel output=points feature=point --o v.to.db map=points option=coor col=x,y (like the man page suggests) but I get a number of errors like: Column 'x' not found Error in db_execute_immediate() where am I wrong now? Two times v.db.addcol is missing for the x and y columns (before v.to.db). Markus ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Using v.distance between two identical layers...
devaux wrote: do you know if it's possible to use v.distance command when for and to layers are the same layer ? I have a layer describing ecological areas of interest and I want to qualify spatial relation between all patches. I want to identify and calculate shortest relation between all my patches boundaries. How can I do as v.distance command doesn't have any option like : eliminate identical objects from the from and to layer ? I'd like to use this particular command because of the option that create lines between nearest objects. use g.copy or v.extract as a first step to separate/duplicate the features? Hamish ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Select random cells from map
António wrote: I need to randomly select non-null cells from a given map. I tried r.random.cells but I cannot define a maximum number random cells and some selected random cells are not valid values in my map. is there any other function to randomly select cells from a raster? Hamish: r.to.vect to get a vector area coverage of your raster (do not use the -s flag), then v.random.cover from wiki addons then v.to.rast, and finally r.mapcalc to transfer values from source map to random cell map? (probably we/I should make a new wrapper script to do that automatically) or you might skip the last steps and just use v.random.cover's raster= option to sample the raster map directly. probably the best idea is to fix r.random's cover= option to loop until it has enough points. also if you will be doing a lot of geostats it is probably worth your while to learn about the GRASS-R interface: http://grass.osgeo.org/wiki/R_statistics ... then the world is open to you. António wrote: Thanks for your answer. I tried r.random with my input data and the number of cells and it worked but I do have one question: I didn't understand the objective of cover_map. I used the map from I want to extract random cells as input but what is the objective of cover_map? r.random creates random points all over the current rectangular region block. Adding a cover map makes those random points only occur within the irregular area covered by the cover map. (but r.random cover= is a bit buggy right now; see new ticket in the bug trac'er) Hamish ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] In Which OS should I develop: Linux or Windows
Greetings I'm GRASS user in Linux and in MS-Windows and Now I need to start developing a few things. In which one should I start? In which GRASS is more stable and robust? Thanks best regards Katrin ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
