[Qgis-user] Re: [GRASS-user] Re: Perimeter of lakes
On 04/12/2010 23:18, Emma wrote: Hello, Thanks for your answer. I think this is exactly what I want to achieve (sorry I don't have much experience in GRASS). However I tried: r.param.scale in=dem out=terrain param=feature s_tol=0.01 and get the error "Lat/Long location is not supported". I don't really understand why this occurs and what I need to do to solve the issue. Any idea? This module runs only in a projected (planar) coordinate system. This is because in Lat/Lon - with angular coordinates around the ellipsoid - the concepts of slope and curvature are not really applicable. So the module can't calculate these basic terrain parameters. If you decide that this is the way to go, you'll have to project your DEM into some other coordinate system, i.e. UTM or whatever is suitable to your area. In GRASS, thuis means making a new *projected* LOCATION and a new MAPSET in that LOCATION. Then start GRASS in that LOCATION and use r.proj to reproject the DEM from your Lat/Lon LOCATION into the new LOCATION. Regards, Micha Thanks a lot for your help! Emma On 12/04/2010 11:37 AM, Emma wrote: > Dear all, > > Is there a way to calculate from the DEM the total perimeter of all > lakes (+reservoirs, etc.)? In other words, I need to calculate the > total length of lake banks and so far could only determine the total > lakes area, which is of no use in this case. > From a DEM directly? No, not that I know. How would you determine what is a lake, and what is a flat land area? How did you get the area?? Furthermore, sometimes lakes have a slight slope... Maybe have a look at r.param.scale: r.param.scale in=dem out=terrain param=feature s_tol=0.01 (or some other very small value) This creates terrain features: peaks, channels, saddles and flat areas. The s_tol (slope tolerance) sets how flat an area needs to be before it's classified as flat. Once you have devised a method to identify the lakes, then convert those raster areas to a vector, and the v.to.db module will give you the perimeter. It would go something like: v.db.addcol lakes col="perim double percision" v.to.db lakes opt=perimeter col=perim units=hectares This mail was received via Mail-SeCure System. ___ grass-user mailing list grass-u...@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user This mail was received via Mail-SeCure System. -- Micha Silver http://www.surfaces.co.il/ Arava Development Co. +972-52-3665918 ___ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-user
[Qgis-user] Re: [GRASS-user] Re: Perimeter of lakes
Emma wrote: > Is there a way to calculate from the DEM the total perimeter of > all lakes (+reservoirs, etc.)? In other words, I need to > calculate the total length of lake banks and so far could only > determine the total lakes area, which is of no use in this > case. It's a fractal problem and so an impossible task to get the right answer to. The best you can do is compare the relative perimeter distances within the dataset (eg lake x has twice the shoreline of lake y), but even then only if you can verify that the original dataset is entirely consistent in its level of detail & digitization. see http://en.wikipedia.org/wiki/How_Long_Is_the_Coast_of_Britain%3F_Statistical_Self-Similarity_and_Fractional_Dimension which is to say, you're probably going to have to consider your problem in another way. maybe you could calculate the plan-area of the littoral strip in a 5m(?) buffer around each one of the lakes and reservoirs? Hamish ___ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-user
Re: [Qgis-user] mapserver
On Sat, 2010-12-04 at 14:12 +0100, Lionel Roubeyrie wrote: > shp2img isn't shp2img a mapserver only utility? cheers -- Giovanni -- ___ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-user
Re: [Qgis-user] mapserver
Hi Jean Roc, sorry I'm talking about qgis_mapserver. I have already followed the two links you give but they speak about dev version of qgis. Trying to mix these docs with the 1.6 stable version, I get a blank image with shp2img from a simple qgis project containing one layer from a postgis database. I use the maserver export plugin by changing "mapserv" by "qgis_mapserv.fcgi", but maybe is it wrong... 2010/12/4 MORREALE Jean Roc : > Le 03/12/2010 21:45, Lionel Roubeyrie a écrit : >> >> Hi, >> is there a simple example/tutorial of how to set up a mapserver with >> the latest qgis version on ubuntu, I can't get a correct result (blank >> image)? >> thanks >> > > Are you talking about qgis-mapserver or mapserver umn ? > > If this is about Q-MS there is a few pages to read : > - official tutorial > http://karlinapp.ethz.ch/qgis_wms/documentation/index.html > - http://linfiniti.com/2010/08/qgis-mapserver-a-wms-server-for-the-masses/ > - ubuntu package at > https://launchpad.net/~ubuntugis/+archive/ubuntugis-unstable/+packages > ___ > Qgis-user mailing list > Qgis-user@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/qgis-user > -- Lionel Roubeyrie lionel.roubey...@gmail.com http://youarealegend.blogspot.com ___ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-user
[Qgis-user] AutoGCP plugin
I am trying to get the AutoGCP plugin to work correctly. I am running Debian squeeze I build the latest subversion development source regularly following these instructions: http://www.qgis.org/wiki/Building_QGIS_from_Source#Building_on_GNU.2FLinux I installed the AutoGCp plugin a while back and it seemed to work ok. At some point the functionality all seemed to fail. That is none of the buttons or commands have any effect. I cannot load images. Also the upgrade from 0.4 -> 0.5 seems to fail. That is, despite doing the upgrade and receiving the messagebox that the upgrade was successful it still indicates daily that it is upgradeable. I've tried to uninstall but to no avail. Any clues? ___ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-user
[Qgis-user] Re: [GRASS-user] Perimeter of lakes
On 12/04/2010 11:37 AM, Emma wrote: Dear all, Is there a way to calculate from the DEM the total perimeter of all lakes (+reservoirs, etc.)? In other words, I need to calculate the total length of lake banks and so far could only determine the total lakes area, which is of no use in this case. From a DEM directly? No, not that I know. How would you determine what is a lake, and what is a flat land area? How did you get the area?? Furthermore, sometimes lakes have a slight slope... Maybe have a look at r.param.scale: r.param.scale in=dem out=terrain param=feature s_tol=0.01 (or some other very small value) This creates terrain features: peaks, channels, saddles and flat areas. The s_tol (slope tolerance) sets how flat an area needs to be before it's classified as flat. Once you have devised a method to identify the lakes, then convert those raster areas to a vector, and the v.to.db module will give you the perimeter. It would go something like: v.db.addcol lakes col="perim double percision" v.to.db lakes opt=perimeter col=perim units=hectares Thanks a lot for your help! Sincerely yours, Emma ___ grass-user mailing list grass-u...@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user This mail was received via Mail-SeCure System. -- Micha Silver Arava Development Co. +972-52-3665918 http://www.surfaces.co.il ___ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-user
Re: [Qgis-user] mapserver
Le 03/12/2010 21:45, Lionel Roubeyrie a écrit : Hi, is there a simple example/tutorial of how to set up a mapserver with the latest qgis version on ubuntu, I can't get a correct result (blank image)? thanks Are you talking about qgis-mapserver or mapserver umn ? If this is about Q-MS there is a few pages to read : - official tutorial http://karlinapp.ethz.ch/qgis_wms/documentation/index.html - http://linfiniti.com/2010/08/qgis-mapserver-a-wms-server-for-the-masses/ - ubuntu package at https://launchpad.net/~ubuntugis/+archive/ubuntugis-unstable/+packages ___ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-user
