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== GRASS GIS Integration ==
 
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<span id='sec:grass'></span>
 
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The GRASS plugin provides access to GRASS GIS {{Template:Cite|num=4|ref=GRASSweb}} databases and
 
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functionalities. This includes visualization of GRASS raster and vector
 
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layers, digitizing vector layers, editing vector attributes, creating new
 
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vector layers and analysing GRASS 2D and 3D data with more than 300 GRASS
 
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modules.
 
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In this Section we'll introduce the plugin functionalities and give some
 
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examples on managing and working with GRASS data. Following main features
 
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are provided with the toolbar menu, when you start the GRASS plugin, as
 
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described in Section [[#sec:starting_grass|9.1]]:
 
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<ul>
 
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<li>{{Template:ToolBtnTwo|grass_open_mapset|Open mapset}}
 
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<li>{{Template:ToolBtnTwo|grass_new_mapset|New mapset}}
 
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<li>{{Template:ToolBtnTwo|grass_close_mapset|Close mapset}}
 
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<li>{{Template:ToolBtnTwo|grass_add_vector|Add GRASS vector layer}}
 
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<li>{{Template:ToolBtnTwo|grass_add_raster|Add GRASS raster layer}}
 
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<li>{{Template:ToolBtnTwo|grass_new_vector_layer|Create new GRASS vector}}
 
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<li>{{Template:ToolBtnTwo|grass_edit|Edit GRASS vector layer}}
 
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<li>{{Template:ToolBtnTwo|grass_tools|Open GRASS tools}}
 
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<li>{{Template:ToolBtnTwo|grass_region|Display current GRASS region}}
 
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<li>{{Template:ToolBtnTwo|grass_region_edit|Edit current GRASS region}}
 
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</ul>
 
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=== Starting the GRASS plugin ===
 
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<span id='sec:starting_grass'></span>
 
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To use GRASS functionalities and/or visualize GRASS vector and raster layers
 
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in QGIS, you must select and load the GRASS plugin with the Plugin Manager.
 
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Therefore click the menu {{Template:MainMenuOpt|Plugins}} > {{Template:MainMenuOpt|Manage Plugins}},
 
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select {{Template:DropMenuOpt|GRASS}} and click {{Template:Button|OK}}.
 
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You can now start loading raster and vector layers from an existing GRASS
 
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{{Template:FileName|LOCATION}} (see Section [[#sec:load_grassdata|9.2]]). Or you create a
 
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new GRASS {{Template:FileName|LOCATION}} with QGIS (see Section [[#sec:create_loc|9.3.1]])
 
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and import some raster and vector data (see Section [[#sec:import_loc_data|9.4]])
 
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for further analysis with the GRASS Toolbox (see Section
 
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[[#subsec:grass_toolbox|9.9]]).
 
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=== Loading GRASS raster and vector layers ===
 
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<span id='sec:load_grassdata'></span>
 
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With the GRASS plugin, you can load vector or raster layers using the
 
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appropriate button on the toolbar menu. As an example we use the QGIS alaska
 
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dataset (see Section [[label_sampledata]]). It includes a small sample
 
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GRASS {{Template:FileName|LOCATION}} with 3 vector layers and 1 raster elevation map.
 
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<ol>
 
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  <li>Create a new folder {{Template:FileName|grassdata}}, download the QGIS alaska
 
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  dataset {{Template:FileName|qgis_sample_data.zip}} from
 
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  {{Template:URL|http://download.osgeo.org/qgis/data/}} and unzip the file into
 
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  {{Template:FileName|grassdata}}.
 
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  <li>Start QGIS.
 
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  <li>If not already done in a previous QGIS session, load the GRASS plugin
 
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  clicking on {{Template:MainMenuOpt|Plugins}} > {{Template:MainMenuOpt|Manage Plugins}} and
 
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  selecting {{Template:DropMenuOpt|GRASS}}. The GRASS toolbar appears on the toolbar menu.
 
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  <li>In the GRASS toolbar, click the {{Template:ToolBtnTwo|grass_open_mapset|Open
 
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  mapset}} icon to bring up the {{Template:FileName|MAPSET}} wizard.
 
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  <li>For {{Template:FileName|Gisdbase}} browse and select or enter the path to the
 
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  newly created folder {{Template:FileName|grassdata}}.
 
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  <li>You should now be able to select the {{Template:FileName|LOCATION alaska}}
 
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  and the MAPSET {{Template:FileName|demo}}.
 
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  <li>Click {{Template:Button|OK}}. Notice that some previously disabled tools in the
 
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  GRASS toolbar are now enabled.
 
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  <li>Click on {{Template:ToolBtnTwo|grass_add_raster|Add GRASS raster layer}},
 
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  choose the map name {{Template:FileName|gtopo30}} and click {{Template:Button|OK}}. The elevation
 
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  layer will be visualized.
 
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  <li>Click on {{Template:ToolBtnTwo|grass_add_vector|Add GRASS vector layer}},
 
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  choose the map name {{Template:FileName|alaska}} and click {{Template:Button|OK}}. The alaska
 
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  boundary vector layer will be overlayed on top of the gtopo30 map. You can
 
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  now adapt the layer properties as described in chapter [[sec:vectorprops]],
 
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  e.g. change opacity, fill and outline color.
 
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  <li>Also load the other two vector layers {{Template:FileName|rivers}} and
 
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  {{Template:FileName|airports}} and adapt their properties.
 
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</ol>
 
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As you see, it is very simple to load GRASS raster and vector layers in QGIS.
 
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See following Sections for editing GRASS data and creating a new
 
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{{Template:FileName|LOCATION}}. More sample GRASS {{Template:FileName|LOCATIONs}} are available at
 
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the GRASS website at {{Template:URL|http://grass.osgeo.org/download/data.php}}.
 
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{{Template:Tip
 
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|num=34
 
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|caption=GRASS Data Loading
 
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|qgistip=If you have problems loading data or QGIS terminates abnormally,
 
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check to make sure you have loaded the GRASS plugin properly as described in
 
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Section [[#sec:starting_grass|9.1]].
 
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}}
 
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=== GRASS LOCATION and MAPSET ===
 
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<span id='sec:about_loc'></span>
 
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GRASS data are stored in a directory referred to as GISDBASE. This directory
 
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often called {{Template:FileName|grassdata}}, must be created before you start working
 
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with the GRASS plugin in QGIS. Within this directory, the GRASS GIS data
 
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are organized by projects stored in subdirectories called {{Template:FileName|LOCATION}}.
 
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Each {{Template:FileName|LOCATION}} is defined by its coordinate system, map projection
 
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and geographical boundaries. Each {{Template:FileName|LOCATION}} can have several
 
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{{Template:FileName|MAPSETs}} (subdirectories of the {{Template:FileName|LOCATION}}) that are used
 
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to subdivide the project into different topics, subregions, or as workspaces
 
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for individual team members (Neteler & Mitasova 2008
 
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{{Template:Cite|num=2|ref=neteler_mitasova08}}). In order to analyze vector and raster layers with
 
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GRASS modules, you must import them into a GRASS {{Template:FileName|LOCATION}}.
 
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<ref>This is not strictly true - with the GRASS modules
 
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{{Template:FileName|r.external}} and {{Template:FileName|v.external}} you can create read-only links
 
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to external GDAL/OGR-supported data sets without importing them. But because
 
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this is not the usual way for beginners to work with GRASS, this functionality
 
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will not be described here.</ref>
 
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<table align='center'>
 
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<caption>'''図 25:''' GRASS data in the alaska LOCATION (adapted from Neteler &
 
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Mitasova 2008 {{Template:Cite|num=2|ref=neteler_mitasova08)}}</caption>
 
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<tr><td><span id='fig:grass_location'></span>
 
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[[File:grass_location.png]]</td></tr></table>
 
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==== Creating a new GRASS LOCATION ====
 
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<span id='sec:create_loc'></span>
 
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As an an example you find the instructions how the sample GRASS
 
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{{Template:FileName|LOCATION alaska}}, which is projected in Albers Equal Area
 
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projection with unit feet was created for the QGIS sample dataset. This
 
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sample GRASS {{Template:FileName|LOCATION alaska}} will be used for all examples and
 
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exercises in the following GRASS GIS related chapters. It is useful to
 
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download and install the dataset on your computer [[label_sampledata]]).
 
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<table align='center'>
 
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<caption>'''図 26:''' Creating a new GRASS LOCATION or a new MAPSET in QGIS {{Template:Nix}}</caption>
 
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<tr><td>
 
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<span id='fig:create_grass_location'></span>
 
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[[File:create_grass_location.png|378px]]</td></tr></table>
 
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<ol>
 
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  <li>Start QGIS and make sure the GRASS plugin is loaded
 
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  <li>Visualize the {{Template:FileName|alaska.shp}} Shapefile (see Section
 
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  [[sec:load_shapefile]]) from the QGIS alaska dataset~[[label_sampledata]].
 
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  <li>In the GRASS toolbar, click on the {{Template:ToolBtnTwo|grass_open_mapset|Open
 
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    mapset}} icon to bring up the {{Template:FileName|MAPSET}} wizard.
 
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  <li>Select an existing GRASS database (GISDBASE) folder
 
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  {{Template:FileName|grassdata}} or create one for the new {{Template:FileName|LOCATION}} using a
 
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  file manager on your computer. Then click {{Template:Button|Next}}.
 
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  <li>We can use this wizard to create a new {{Template:FileName|MAPSET}} within an
 
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  existing {{Template:FileName|LOCATION}} (see Section~[[sec:add_mapset]]) or to create
 
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  a new {{Template:FileName|LOCATION}} altogether. Click on the radio button
 
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  {{Template:RadioButtonOn|Create new location}} (see Figure [[#fig:create_grass_location|26]]).
 
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  <li>Enter a name for the {{Template:FileName|LOCATION}} - we used alaska and click
 
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  {{Template:Button|Next}}
 
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  <li>Define the projection by clicking on the radio button
 
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  {{Template:RadioButtonOn|Projection}} to enable the projection list
 
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  <li>We are using Albers Equal Area Alaska (feet) projection. Since we
 
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  happen to know that it is represented by the EPSG ID 2964, we enter it in
 
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  the search box. (Note: If you want to repeat this process for another
 
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  {{Template:FileName|LOCATION}} and projection and haven't memorized the EPSG ID,
 
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  click on the
 
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  {{Template:ToolBtnTwo|mIconProjectionEnabled|projector}} icon in the lower right-hand
 
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  corner of the status bar (see Section [[label_projstart]])).
 
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  <li>Click {{Template:Button|Find}} to select the projection
 
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  <li>Click {{Template:Button|Next}}
 
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  <li>To define the default region, we have to enter the {{Template:FileName|LOCATION}}
 
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  bounds in north, south, east, and west direction. Here we simply click on
 
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  the button {{Template:Button|Set current QGIS extent}}, to apply the extend of the
 
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  loaded layer {{Template:FileName|alaska.shp}} as the GRASS default region extend.
 
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  <li>Click {{Template:Button|Next}}
 
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  <li>We also need to define a {{Template:FileName|MAPSET}} within our new
 
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  {{Template:FileName|LOCATION}}. You can name it whatever you like - we used demo.
 
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  <ref>{When creating a new {{Template:FileName|LOCATION}}, GRASS automatically
 
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  creates a special {{Template:FileName|MAPSET}} called {{Template:FileName|PERMANENT}} designed to
 
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  store the core data for the project, its default spatial extend and
 
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  coordinate system definitions (Neteler & Mitasova 2008
 
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  {{Template:Cite|num=2|ref=neteler_mitasova08}}).</ref>
 
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  <li>Check out the summary to make sure it's correct and click
 
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  {{Template:Button|Finish}}
 
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  <li>The new {{Template:FileName|LOCATION alaska}} and two {{Template:FileName|MAPSETs demo}}
 
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  and {{Template:FileName|PERMANENT}} are created. The currently opened working set is
 
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  {{Template:FileName|MAPSET demo}}, as you defined.
 
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  <li>Notice that some of the tools in the GRASS toolbar that were
 
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  disabled are now enabled.
 
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</ol>
 
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If that seemed like a lot of steps, it's really not all that bad and a very
 
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quick way to create a {{Template:FileName|LOCATION}}. The {{Template:FileName|LOCATION alaska}} is
 
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now ready for data import (see Section [[#sec:import_loc_data|9.4]]).
 
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You can also use the already existing vector and raster data in the sample
 
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GRASS {{Template:FileName|LOCATION alaska}} included in the QGIS alaska dataset
 
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[[label_sampledata]] and move on to Section [[#label_vectmodel|9.5]].
 
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==== Adding a new MAPSET ====
 
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<span id='sec:add_mapset'></span>
 
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A user has only write access to a GRASS {{Template:FileName|MAPSET}} he created. This
 
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means, besides access to his own {{Template:FileName|MAPSET}}, each user can also read
 
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maps in other user's {{Template:FileName|MAPSETs}}, but he can modify or remove only
 
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the maps in his own {{Template:FileName|MAPSET}}. All {{Template:FileName|MAPSETs}} include a
 
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{{Template:FileName|WIND}} file that stores the current boundary coordinate values and
 
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the currently selected raster resolution (Neteler & Mitasova 2008
 
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{{Template:Cite|num=2|ref=neteler_mitasova08}}, see Section [[#sec:grass_region|9.8]]).
 
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<ol>
 
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  <li>Start QGIS and make sure the GRASS plugin is loaded
 
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  <li>In the GRASS toolbar, click on the
 
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  {{Template:ToolBtnTwo|grass_new_mapset|New mapset}} icon to bring up the
 
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  {{Template:FileName|MAPSET}} wizard.
 
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  <li>Select the GRASS database (GISDBASE) folder {{Template:FileName|grassdata}}
 
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  with the {{Template:FileName|LOCATION alaska}}, where we want to add a further
 
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  {{Template:FileName|MAPSET}}, called test.
 
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  <li>Click {{Template:Button|Next}}.
 
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  <li>We can use this wizard to create a new {{Template:FileName|MAPSET}} within an
 
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  existing {{Template:FileName|LOCATION}} or to create a new {{Template:FileName|LOCATION}}
 
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  altogether. Click on the radio button {{Template:RadioButtonOn|Select location}}
 
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  (see Figure [[#fig:create_grass_location|26]]) and click {{Template:Button|Next}}.
 
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  <li>Enter the name {{Template:FileName|text}} for the new {{Template:FileName|MAPSET}}. Below
 
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  in the wizard you see a list of existing {{Template:FileName|MAPSETs}} and its owners.
 
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  <li>Click {{Template:Button|Next}}, check out the summary to make sure it's all
 
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  correct and click {{Template:Button|Finish}}
 
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</ol>
 
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=== Importing data into a GRASS LOCATION ===
 
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<span id='sec:import_loc_data'></span>
 
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This Section gives an example how to import raster and vector data into the
 
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{{Template:FileName|alaska}} GRASS {{Template:FileName|LOCATION}} provided by the QGIS alaska
 
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dataset. Therefore we use a landcover raster map {{Template:FileName|landcover.img}}
 
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and a vector GML File {{Template:FileName|lakes.gml}} from the QGIS alaska
 
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dataset [[label_sampledata]].
 
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<ol>
 
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  <li>Start QGIS and make sure the GRASS plugin is loaded.
 
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  <li>In the GRASS toolbar, click the {{Template:ToolBtnTwo|grass_open_mapset|Open
 
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  MAPSET}} icon to bring up the {{Template:FileName|MAPSET}} wizard.
 
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  <li>Select as GRASS database the folder {{Template:FileName|grassdata}} in the QGIS
 
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  alaska dataset, as {{Template:FileName|LOCATION alaska}}, as {{Template:FileName|MAPSET}}
 
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  {{Template:FileName|demo}} and click {{Template:Button|OK}}.
 
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  <li>Now click the {{Template:ToolBtnTwo|grass_tools|Open GRASS tools}} icon. The
 
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  GRASS Toolbox (see Section [[#subsec:grass_toolbox|9.9]]) dialog appears.
 
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  <li>To import the raster map {{Template:FileName|landcover.img}}, click the module
 
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  {{Template:FileName|r.in.gdal}} in the {{Template:Tab|Modules Tree}} tab. This GRASS module
 
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  allows to import GDAL supported raster files into a GRASS
 
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  {{Template:FileName|LOCATION}}. The module dialog for {{Template:FileName|r.in.gdal}} appears.
 
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  <li>Browse to the folder {{Template:FileName|raster}} in the QGIS alaska dataset
 
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  and select the file {{Template:FileName|landcover.img}}.
 
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  <li>As raster output name define {{Template:FileName|landcover_grass}} and click
 
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  {{Template:Button|Run}}. In the {{Template:Tab|Output}} tab you see the currently running GRASS
 
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  command {{Template:FileName|1=r.in.gdal -o input=/path/to/landcover.img
 
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  output=landcover_grass}}.
 
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  <li>When it says '''Succesfully finished''' click {{Template:Button|View output}}.
 
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  The {{Template:FileName|landcover_grass}} raster layer is now imported into GRASS and
 
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  will be visualized in the QGIS canvas.
 
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  <li>To import the vector GML file {{Template:FileName|lakes.gml}}, click the module
 
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  {{Template:FileName|v.in.ogr}} in the {{Template:Tab|Modules Tree}} tab. This GRASS module allows
 
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  to import OGR supported vector files into a GRASS {{Template:FileName|LOCATION}}. The
 
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  module dialog for {{Template:FileName|v.in.ogr}} appears.
 
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  <li>Browse to the folder {{Template:FileName|gml}} in the QGIS alaska
 
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  dataset and select the file {{Template:FileName|lakes.gml}} as OGR file.
 
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  <li>As vector output name define {{Template:FileName|lakes_grass}} and click
 
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  {{Template:Button|Run}}. You don't have to care about the other options in this
 
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  example. In the {{Template:Tab|Output}} tab you see the currently running GRASS
 
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  command {{Template:FileName|1=v.in.ogr -o dsn=/path/to/lakes.gml output=lakes_grass}}.
 
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  <li>When it says '''Succesfully finished''' click {{Template:Button|View output}}.
 
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  The {{Template:FileName|lakes_grass}} vector layer is now imported into GRASS and will
 
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  be visualized in the QGIS canvas.
 
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</ol>
 
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=== The GRASS vector data model ===
 
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<span id='label_vectmodel'></span>
 
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It is important to understand the GRASS vector data model prior to
 
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digitizing. In general, GRASS uses a topological
 
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vector model. This means that areas are not represented
 
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as closed polygons, but by one or more boundaries. A boundary between two
 
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adjacent areas is digitized only once, and it is shared by both areas.
 
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Boundaries must be connected without gaps. An area is identified (labeled)
 
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by the centroid of the area.
 
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Besides boundaries and centroids, a vector map can also contain
 
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points and lines. All these geometry elements can be mixed
 
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in one vector and will be represented in different so called 'layers' inside
 
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one GRASS vector map. So in GRASS a layer is not a vector or raster map but a
 
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level inside a vector layer. This is important to distinguish carefully.
 
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<ref>Although it
 
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is possible to mix geometry elements, it is unusual and even in GRASS only
 
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used in special cases such as vector network analysis. Normally you should
 
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prefere to store different geometry elements in different layers.</ref>
 
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It is possible to store more 'layers' in one vector dataset. For example,
 
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fields, forests and lakes can be stored in one vector. Adjacent
 
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forest and lake can share the same boundary, but they have separate attribute
 
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tables. It is also possible to attach attributes to boundaries. For example,
 
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the boundary between lake and forest is a road, so it can have a different
 
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attribute table.
 
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The 'layer' of the feature is defined by 'layer' inside GRASS. 'Layer' is the
 
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number which defines if there are more than one layer inside the dataset, e.g.
 
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if the geometry is forest or lake. For now, it can be only a number, in the
 
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future GRASS will also support names as fields in the user interface.
 
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Attributes can be stored inside the GRASS {{Template:FileName|LOCATION}} as DBase or
 
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SQLITE3 or in external database tables, for example PostgreSQL, MySQL,
 
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Oracle, etc.
 
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Attributes in database tables are linked to geometry elements using
 
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a 'category' value. 'Category' (key, ID) is an
 
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integer attached to geometry primitives, and it is used as the link to one
 
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key column in the database table.
 
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{{Template:Tip
 
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|num=35
 
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|caption=Learning the GRASS Vector Model
 
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|qgistip=
 
−
The best way to learn the GRASS vector model and its capabilities is to
 
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download one of the many GRASS tutorials where the vector model is described
 
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more deeply. See {{Template:URL|http://grass.osgeo.org/gdp/manuals.php}} for more
 
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information, books and tutorials in several languages.
 
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}}
 
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=== Creating a new GRASS vector layer ===
 
−
<span id='sec:creating_new_grass_vectors'></span>
 
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To create a new GRASS vector layer with the GRASS plugin click the
 
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{{Template:ToolBtnTwo|grass_new_vector_layer|Create new GRASS vector}} toolbar icon.
 
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Enter a name in the text box and you can start digitizing point, line or
 
−
polygone geometries, following the procedure described in Section
 
−
[[#grass_digitising|9.7]].
 
−
 
−
In GRASS it is possible to organize all sort of geometry types (point, line
 
−
and area) in one layer, because GRASS uses a topological vector model, so you
 
−
don't need to select the geometry type when creating a new GRASS vector. This
 
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is different from Shapefile creation with QGIS, because Shapefiles use the
 
−
Simple Feature vector model (see Section [[sec:create shape]]).
 
−
 
−
{{Template:Tip
 
−
|num=36
 
−
|caption=Creating an attribute table for a new GRASS vector layer
 
−
|qgistip=
 
−
If you want to assign attributes to your digitized geometry features, make sure to create an attribute table with columns before you start digitizing (see Figure [[#fig:grass_digitizing_table|31]]).
 
−
}}
 
−
 
−
=== Digitizing and editing a GRASS vector layer ===
 
−
<span id='grass_digitising'></span>
 
−
The digitizing tools for GRASS vector layers are accessed using the
 
−
{{Template:ToolBtnTwo|grass_edit|Edit GRASS vector layer}} icon on the toolbar. Make
 
−
sure you have loaded a GRASS vector and it is the selected layer in the legend
 
−
before clicking on the edit tool. Figure [[#fig:grass_digitizing_category|28]]
 
−
shows the GRASS edit dialog that is displayed when you click on the edit tool.
 
−
The tools and settings are discussed in the following sections.
 
−
 
−
{{Template:Tip
 
−
|num=37
 
−
|caption=Digitizing polygones in GRASS
 
−
|qgistip=
 
−
If you want to create a polygone in GRASS, you first digitize the boundary of
 
−
the polygone, setting the mode to {{Template:UserText|No category}}. Then you add a
 
−
centroid (label point) into the closed boundary, setting the mode to
 
−
{{Template:UserText|Next not used}}. The reason is, that a topological vector model links
 
−
attribute information of a polygon always to the centroid and not to the
 
−
boundary.
 
−
}}
 
−
 
−
===== Toolbar =====
 
−
<span id='label_grasstoolbar'></span>
 
−
In Figure [[#fig:grass_digitizing_toolbar|27]] you see the GRASS digitizing
 
−
toolbar icons provided by the GRASS plugin. Table [[tab:grass_tools]]
 
−
explains the available functionalities.
 
−
 
−
<table align='center'>
 
−
<caption>'''図 27:''' GRASS Digitizing Toolbar {{Template:Nix}}</caption>
 
−
<tr><td><span id='fig:grass_digitizing_toolbar'></span>
 
−
  [[File:grass_digitizing_toolbar.png|454px]]</td></tr></table>
 
−
 
−
<table border='1' aligh='center'><caption>'''表 3:''' GRASS Digitizing Tools</caption><span id='tab:grass_tools'></span>
 
−
<!-- {|l|l|p{5in}|} -->
 
−
<tr><td> '''Icon''' <td> '''Tool''' <td width='480'> '''Purpose''' </tr>
 
−
<tr><td> [[File:grass_new_point.png|26px]] <td> New Point <td> Digitize
 
−
new point </tr>
 
−
<tr><td> [[File:grass_new_line.png|26px]] <td> New Line <td> Digitize
 
−
new line (finish by selecting new tool) </tr>
 
−
<tr><td> [[File:grass_new_boundary.png|26px]] <td> New Boundary <td>
 
−
Digitize new boundary (finish by selecting new tool)</tr>
 
−
<tr><td> [[File:grass_new_centroid.png|26px]] <td> New Centroid <td>
 
−
Digitize new centroid (label existing area)</tr>
 
−
<tr><td> [[File:grass_move_vertex.png|26px]] <td> Move vertex <td> Move
 
−
one vertex of existing line or boundary and identify new position</tr>
 
−
<tr><td> [[File:grass_add_vertex.png|26px]] <td> Add vertex <td> Add a
 
−
new vertex to existing line</tr>
 
−
<tr><td> [[File:grass_delete_vertex.png|26px]] <td> Delete vertex <td>
 
−
Delete vertex from existing line (confirm selected vertex by another click)</tr>
 
−
<tr><td> [[File:grass_move_line.png|26px]] <td> Move element <td> Move
 
−
selected boundary, line, point or centroid and click on new position</tr>
 
−
<tr><td> [[File:grass_split_line.png|26px]] <td> Split line <td> Split
 
−
an existing line to 2 parts</tr>
 
−
<tr><td> [[File:grass_delete_line.png|26px]] <td> Delete element <td>
 
−
Delete existing boundary, line, point or centroid (confirm selected element by
 
−
another click)</tr>
 
−
<tr><td> [[File:grass_edit_attributes.png|26px]] <td> Edit attributes
 
−
<td> Edit attributes of selected element (note that one element can represent
 
−
more features, see above)</tr>
 
−
<tr><td> [[File:grass_close_edit.png|26px]] <td> Close <td> Close
 
−
session and save current status (rebuilds topology afterwards)</tr>
 
−
</table>
 
−
 
−
===== Category Tab =====
 
−
 
−
The {{Template:Tab|Category}} tab allows you to define the way in which the category
 
−
values will be assigned to a new geometry element.
 
−
 
−
<table align='center'>
 
−
<caption>'''図 28:''' GRASS Digitizing Category Tab {{Template:Nix}}</caption>
 
−
<tr><td><span id='fig:grass_digitizing_category'></span>
 
−
  [[File:grass_digitizing_category.png|378px]]</td></tr></table>
 
−
 
−
<ul>
 
−
<li>'''Mode''': what category value shall be applied to new geometry
 
−
elements.
 
−
<ul>
 
−
<li>Next not used - apply next not yet used category value to geometry
 
−
element.
 
−
<li>Manual entry - manually define the category value for the geometry
 
−
element in the 'Category'-entry field.
 
−
<li>No category - Do not apply a category value to the geometry element.
 
−
This is e.g. used for area boundaries, because the category values are
 
−
connected via the centroid.
 
−
</ul>
 
−
<li>'''Category''' - A number (ID) is attached to each digitized geometry
 
−
element. It is used to connect each geometry element with its attributes.
 
−
<li>'''Field (layer)''' - Each geometry element can be connected with
 
−
several attribute tables using different GRASS geometry layers. Default layer
 
−
number is 1.
 
−
</ul>
 
−
 
−
{{Template:Tip
 
−
|num=38
 
−
|caption=Creating an additional GRASS 'layer' with QGIS
 
−
|qgistip=If you would like to add more layers to your dataset, just add a new
 
−
number in the 'Field (layer)' entry box and press return. In the Table tab
 
−
you can create your new table connected to your new layer.
 
−
}}
 
−
 
−
===== Settings Tab =====
 
−
<span id='label_settingtab'></span>
 
−
 
−
The {{Template:Tab|Settings}} tab allows you to set the snapping in screen pixels. The
 
−
threshold defines at what distance new points or line ends are snapped to
 
−
existing nodes. This helps to prevent gaps or dangles between boundaries. The
 
−
default is set to 10 pixels.
 
−
 
−
<table align='center'>
 
−
<caption>'''図 29:''' GRASS Digitizing Settings Tab {{Template:Nix}}</caption>
 
−
<tr><td><span id='fig:grass_digitizing_settings'></span>
 
−
[[File:grass_digitizing_settings.png|302px]]</td></tr></table>
 
−
 
−
===== Symbology Tab =====
 
−
 
−
The {{Template:Tab|Symbology}} tab allows you to view and set symbology and color
 
−
settings for various geometry types and their topological status (e.g. closed
 
−
/ opened boundary).
 
−
 
−
<table align='center'>
 
−
<caption>'''図 30:''' GRASS Digitizing Symbolog Tab {{Template:Nix}}</caption>
 
−
<tr><td><span id='fig:grass_digitizing_symbology'></span>
 
−
[[File:grass_digitizing_symbology.png|302px]]</td></tr></table>
 
−
 
−
===== Table Tab =====
 
−
 
−
The {{Template:Tab|Table}} tab provides information about the database table for
 
−
a given 'layer'. Here you can add new columns to an existing attribute table,
 
−
or create a new database table for a new GRASS vector layer (see Section
 
−
[[#sec:creating_new_grass_vectors|9.6]]).
 
−
 
−
<table align='center'>
 
−
<caption>'''図 31:''' GRASS Digitizing Table Tab {{Template:Nix}}</caption>
 
−
<tr><td><span id='fig:grass_digitizing_table'></span>
 
−
[[File:grass_digitizing_table.png|378px]]</td></tr></table>
 
−
 
−
{{Template:Tip
 
−
|num=39
 
−
|caption=GRASS Edit Permissions
 
−
|qgistip=You must be the owner of the GRASS {{Template:FileName|MAPSET}} you want to
 
−
edit. It is impossible to edit data layers in a {{Template:FileName|MAPSET}} that is not
 
−
yours, even if you have write permissions.
 
−
}}
 
−
 
−
=== The GRASS region tool ===
 
−
<span id='sec:grass_region'></span>
 
−
The region definition (setting a spatial working window) in GRASS is important
 
−
for working with raster layers. Vector analysis is per default not limited
 
−
to any defined region definitions. All newly-created rasters will have the
 
−
spatial extension and resolution of the currently defined GRASS region,
 
−
regardless of their original extension and resolution. The current GRASS
 
−
region is stored in the {{Template:FileName|$LOCATION/$MAPSET/WIND}} file, and it
 
−
defines north, south, east and west bounds, number of columns and rows,
 
−
horizontal and vertical spatial resolution.
 
−
 
−
It is possible to switch on/off the visualization of the GRASS region in the
 
−
QGIS canvas using the {{Template:ToolBtnTwo|grass_region|Display current GRASS region}}
 
−
button. .
 
−
 
−
With the {{Template:ToolBtnTwo|grass_region_edit|Edit current GRASS region}} icon you
 
−
can open a dialog to change the current region and the symbology of the GRASS
 
−
region rectangle in the QGIS canvas. Type in the new region bounds and
 
−
resolution and click {{Template:Button|OK}}. It also allows to select a new region
 
−
interactively with your mouse on the QGIS canvas. Therefore click with the
 
−
left mouse button in the QGIS canvas, open a rectangle, close it using the
 
−
left mouse button again and click {{Template:Button|OK}}.
 
−
The GRASS module {{Template:FileName|g.region}} provide a lot more parameters to define
 
−
an appropriate region extend and resolution for your raster analysis. You can
 
−
use these parameters with the GRASS Toolbox, described in Section
 
−
[[#subsec:grass_toolbox|9.9]].
 
−
 
−
=== The GRASS toolbox ===
 
−
<span id='subsec:grass_toolbox'></span>
 
−
The {{Template:ToolBtnTwo|grass_tools|Open GRASS Tools}} box provides GRASS module
 
−
functionalities to work with data inside a selected GRASS {{Template:FileName|LOCATION}}
 
−
and {{Template:FileName|MAPSET}}. To use the GRASS toolbox you need to open a
 
−
{{Template:FileName|LOCATION}} and {{Template:FileName|MAPSET}} where you have write-permission
 
−
(usually granted, if you created the {{Template:FileName|MAPSET}}). This is necessary,
 
−
because new raster or vector layers created during analysis need to be written
 
−
to the currently selected {{Template:FileName|LOCATION}} and {{Template:FileName|MAPSET}}.
 
−
 
−
==== Working with GRASS modules ====
 
−
 
−
<table align='center'>
 
−
<caption>'''図 32:''' GRASS Toolbox and searchable Modules List {{Template:Nix}}</caption>
 
−
<tr><td><span id='fig:grass_modules'></span>
 
−
  <table align='center'><caption align='bottom'>(a) Modules Tree</caption><tr><td><span id='subfig:grass_module_tree'></span>[[File:grass_toolbox_moduletree.png|296px]]</td></tr></table>
 
−
  <table align='center'><caption align='bottom'>(b) Searchable Modules List</caption><tr><td><span id='subfig:grass_module_list'></span>[[File:grass_toolbox_modulelist.png|296px]]</td></tr></table>
 
−
</td></tr></table>
 
−
 
−
The GRASS Shell inside the GRASS Toolbox provides access to almost all (more
 
−
than 300) GRASS modules in command line modus. To offer a more user
 
−
friendly working environment, about 200 of the available GRASS modules and
 
−
functionalities are also provided by graphical dialogs. These dialogs are
 
−
grouped in thematic blocks, but are searchable as well. You find a complete
 
−
list of GRASS modules available in QGIS version \CURRENT
 
−
in appendix [[appdx_grass_toolbox_modules]]. It is also possible to
 
−
customize the GRASS Toolbox content. It is described in Section
 
−
[[sec:toolbox-customizing]].
 
−
 
−
As shown in Figure [[#fig:grass_modules|32]], you can look for the appropriate
 
−
GRASS module using the thematically grouped {{Template:Tab|Modules Tree}} or the
 
−
searchable {{Template:Tab|Modules List}} tab.
 
−
 
−
Clicking on a grapical module icon a new tab will be added to the toolbox
 
−
dialog providing three new sub-tabs {{Template:Tab|Options}}, {{Template:Tab|Output}} and
 
−
{{Template:Tab|Manual}}. In Figure [[#fig:grass_module_dialog|33]] you see an example
 
−
for the GRASS module {{Template:FileName|v.buffer}}.
 
−
 
−
<table align='center'>
 
−
<caption>'''図 33:''' GRASS Toolbox Module Dialogs {{Template:Nix}}</caption>
 
−
<tr><td><span id='fig:grass_module_dialog'></span>
 
−
  <table align='center'><caption align='bottom'>(a) Module Options</caption><tr><td><span id='subfig:grass_module_option'></span>[[File:grass_module_option.png|222px]]</td></tr></table>
 
−
  <table align='center'><caption align='bottom'>(b) Modules Output</caption><tr><td><span id='subfig:grass_module_output'></span>[[File:grass_module_output.png|222px]]</td></tr></table>
 
−
  <table align='center'><caption align='bottom'>(c) Module Manual</caption><tr><td><span id='subfig:grass_module_manual'></span>[[File:grass_module_manual.png|222px]]</td></tr></table>
 
−
</td></tr></table>
 
−
 
−
===== Options =====
 
−
 
−
The {{Template:Tab|Options}} tab provides a simplified module dialog where you can
 
−
usually select a raster or vector layer visualized in the QGIS canvas and
 
−
enter further module specific parameters to run the module. The provided
 
−
module parameters are often not complete to keep the dialog clear. If you want
 
−
to use further module parameters and flags, you need to start the GRASS Shell
 
−
and run the module in the command line.
 
−
 
−
===== Output =====
 
−
 
−
The {{Template:Tab|Output}} tab provides information about the output status of the
 
−
module. When you click the {{Template:Button|Run}} button, the module switches to the
 
−
{{Template:Tab|Output}} tab and you see information about the analysis process. If all
 
−
works well, you will finally see a {{Template:UserText|Successfully finished}} message.
 
−
 
−
===== Manual =====
 
−
 
−
The {{Template:Tab|Manual}} tab shows the HTML help page of the GRASS module. You can
 
−
use it to check further module parameters and flags or to get a deeper
 
−
knowledge about the purpose of the module. At the end of each module
 
−
manual page you see further links to the {{Template:FileName|Main Help index}}, the
 
−
{{Template:FileName|Thematic index}} and the {{Template:FileName|Full index}}. These links provide
 
−
the same information as if you use the module {{Template:FileName|g.manual}}
 
−
 
−
{{Template:Tip
 
−
|num=40
 
−
|caption=Display results immediately
 
−
|qgistip=If you want to display your calculation results immediately in your
 
−
map canvas, you can use the 'View Output' button at the bottom of the
 
−
module tab.
 
−
 
−
}}
 
−
 
 
==== Working with the GRASS LOCATION browser ====
 
==== Working with the GRASS LOCATION browser ====
 
   
 
   
 
Another useful feature inside the GRASS Toolbox is the GRASS  
 
Another useful feature inside the GRASS Toolbox is the GRASS  
−
{{Template:FileName|LOCATION}} browser. In Figure~[[fig:grass_mapset_browser]] you  
+
{{Template:FileName|LOCATION}} browser. In Figure [[#fig:grass_mapset_browser|34]] you  
 
can see the current working {{Template:FileName|LOCATION}} with its {{Template:FileName|MAPSETs}}.
 
can see the current working {{Template:FileName|LOCATION}} with its {{Template:FileName|MAPSETs}}.
  
行595: 行12:
  
 
<table align='center'>
 
<table align='center'>
−
<caption>'''Figure xx:''' GRASS LOCATION browser {{Template:Nix</caption>
+
<caption>'''図 34:''' GRASS LOCATION browser {{Template:Nix}}</caption>
−
<tr><td>}caption}<span id='fig:grass_mapset_browser'></span>
+
<tr><td><span id='fig:grass_mapset_browser'></span>
 
  [[File:grass_mapset_browser.png|378px]]</td></tr></table>
 
  [[File:grass_mapset_browser.png|378px]]</td></tr></table>
  
行615: 行32:
 
your currently selected {{Template:FileName|MAPSET}}. All other tools also work with  
 
your currently selected {{Template:FileName|MAPSET}}. All other tools also work with  
 
raster and vector layers in another {{Template:FileName|MAPSET}}.
 
raster and vector layers in another {{Template:FileName|MAPSET}}.
−
 
−
==== Customizing the GRASS Toolbox ====
 
−
<span id='sec:toolbox-customizing'></span>
 
−
 
−
Nearly all GRASS modules can be added to the GRASS toolbox. A XML
 
−
interface is provided to parse the pretty simple XML files which configures
 
−
the modules appearance and parameters inside the toolbox.
 
−
 
−
A sample XML file for generating the module {{Template:UserText|v.buffer}} (v.buffer.qgm)
 
−
looks like this:
 
−
<pre>
 
−
<?xml version="1.0" encoding="UTF-8"?>
 
−
<!DOCTYPE qgisgrassmodule SYSTEM "http://mrcc.com/qgisgrassmodule.dtd">
 
−
 
−
<qgisgrassmodule label="Vector buffer" module="v.buffer">
 
−
        <option key="input" typeoption="type" layeroption="layer" />
 
−
        <option key="buffer"/>
 
−
        <option key="output" />
 
−
</qgisgrassmodule>
 
−
</pre>
 
−
 
−
The parser reads this definition and creates a new tab inside the toolbox
 
−
when you select the module. A more detailed description for adding new
 
−
modules, changing the modules group, etc. can be found on the QGIS wiki at <br>
 
−
{{Template:URL|http://wiki.qgis.org/qgiswiki/Adding_New_Tools_to_the_GRASS_Toolbox}}.
 

2009年10月5日 (月) 00:51時点における版

Working with the GRASS LOCATION browser

Another useful feature inside the GRASS Toolbox is the GRASS LOCATION browser. In Figure 34 you can see the current working LOCATION with its MAPSETs.

In the left browser windows you can browse through all MAPSETs inside the current LOCATION. The right browser window shows some meta information for selected raster or vector layers, e.g. resolution, bounding box, data source, connected attribute table for vector data and a command history.

図 34: GRASS LOCATION browser Nix.png
Grass mapset browser.png

The toolbar inside the Browser tab offers following tools to manage the selected LOCATION:

  • Grass add map.png Add selected map to canvas
  • Grass copy map.png Copy selected map
  • Grass rename map.png Rename selected map
  • Grass delete map.png Delete selected map
  • Grass set region.png Set current region to selected map
  • Grass refresh.png Refresh browser window

The Grass rename map.png Rename selected map and Grass delete map.png Delete selected map only work with maps inside your currently selected MAPSET. All other tools also work with raster and vector layers in another MAPSET.

「http://wiki.osgeo.jp./index.php?title=Grass_integration&oldid=827」から取得