[QGIS Commit] r15793 - in docs/trunk/english_us/user_guide: . working_with_projections_screenies

svn_qgis at osgeo.org svn_qgis at osgeo.org
Thu Apr 21 08:12:11 EDT 2011


Author: custard
Date: 2011-04-21 05:12:11 -0700 (Thu, 21 Apr 2011)
New Revision: 15793

Modified:
   docs/trunk/english_us/user_guide/working_with_projections.tex
   docs/trunk/english_us/user_guide/working_with_projections_screenies/crsdialog.png
   docs/trunk/english_us/user_guide/working_with_projections_screenies/projectionDialog.png
Log:
updated projections

Modified: docs/trunk/english_us/user_guide/working_with_projections.tex
===================================================================
--- docs/trunk/english_us/user_guide/working_with_projections.tex	2011-04-21 10:48:37 UTC (rev 15792)
+++ docs/trunk/english_us/user_guide/working_with_projections.tex	2011-04-21 12:12:11 UTC (rev 15793)
@@ -5,13 +5,14 @@
 
 % when the revision of a section has been finalized,
 % comment out the following line:
-%\updatedisclaimer
+\updatedisclaimer
 
 QGIS allows users to define a global and project-wide CRS (Coordinate
-Reference System) for layers without a pre-defined CRS. It also allows the
-user to define custom coordinate reference systems and supports on-the-fly
-(OTF) projection of vector layers. All these features allow the user to
-display layers with different CRS and have them overlay properly.
+Reference System) for layers without a pre-defined CRS. It also allows
+the user to define custom coordinate reference systems and supports
+on-the-fly (OTF) projection of vector and raster layers. All these
+features allow the user to display layers with different CRS and have
+them overlay properly.
 
 \section{Overview of Projection Support}\label{label_projoverview}
 
@@ -22,18 +23,19 @@
 user database. See Section \ref{sec:customprojections} for
 information on managing your custom coordinate reference systems.
 
-The CRS available in QGIS are based on those defined by
-EPSG\index{EPSG} and are largely abstracted from the spatial\_references
-table in PostGIS\index{PostGIS} version 1.x. The EPSG identifiers are
-present in the database and can be used to specify a CRS in QGIS.
+The CRS available in QGIS are based on those defined by the European
+Petroleum Group (ESPG)\index{ESPG} and the Institut Geographique
+National of France (IGNF)\index{IGNF} and are largely abstracted 
+from the spatial reference tables used in GDAL\index{GDAL}. EPSG identifiers are present in the database and can be used
+to specify a CRS in QGIS.
 
 In order to use OTF projection, your data must contain information about its
 coordinate reference system or you have to define a global, layer or
 project-wide CRS. For PostGIS layers QGIS uses the spatial reference
 identifier that was specified when the layer was created. For data supported
-by OGR, QGIS relies on the presence of a format specific means of specifying
+by OGR, QGIS relies on the presence of a recognised means of specifying
 the CRS. In the case of shapefiles, this means a file containing the Well
-Known Text (WKT)\index{WKT} specification of the CRS. The projection file
+Known Text (WKT)\index{WKT} specification of the CRS. This projection file
 has the same base name as the shapefile and a prj extension. For example, a
 shapefile named \filename{alaska.shp} would have a corresponding projection
 file named \filename{alaska.prj}.
@@ -48,58 +50,78 @@
 \index{Projections!specifying}
 \label{sec:projection-specifying}
 
-QGIS no longer sets the map CRS to the coordinate reference system of the
-first layer loaded. When you start a QGIS session with layers that do not
-have a CRS, you need to control and define the CRS definition for these
-layers. This can be done globally or project-wide in the \tab{CRS} tab under
-\mainmenuopt{Edit} \arrow \dropmenuopttwo{mActionOptions}{Options} (Gnome, OSX)
-or \mainmenuopt{Settings} \arrow \dropmenuopttwo{mActionOptions}{Options} (KDE, Windows).
-See Figure~\ref{fig:crsdialog}.
+\begin{figure}[bt]
+   \centering
+   \includegraphics[clip=true, width=12cm]{crsdialog}
+   \caption{CRS tab in the QGIS Options Dialog \osxcaption}\label{fig:crsdialog}
+\end{figure}
 
+QGIS starts each new project using the global default projection.The
+global default CRS is EPSG:4326 - WGS 84 (\texttt{proj=longlat
+  +ellps=WGS84 +datum=WGS84 +no\_defs}) and comes predefined in
+QGIS. This default can be changed using the \button{Select Global
+  Default} button shown in Figure~\ref{fig:crsdialog}. This choice
+will be saved for use in subsequent QGIS sessions.
+
+When you use layers that do not have a CRS, you need to define how
+QGIS responds to these layers. This can be done globally or
+project-wide in the \tab{CRS} tab under \mainmenuopt{Edit} \arrow
+\dropmenuopttwo{mActionOptions}{Options} (Gnome, OSX) or
+\mainmenuopt{Settings} \arrow \dropmenuopttwo{mActionOptions}{Options}
+(KDE, Windows).
+
+The options shown in Figure~\ref{fig:crsdialog} are:
 \begin{itemize}[label=--]
 \item \checkbox{Prompt for CRS}
 \item \checkbox{Project wide default CRS will be used}
 \item \checkbox{Global default CRS displayed below will be used}
 \end{itemize}
 
-The global default CRS \texttt{proj=longlat +ellps=WGS84 +datum=WGS84
-+no\_defs} comes predefined in QGIS but can of course be changed, and the new
-definition will be saved for subsequent QGIS sessions.
+If you want to define the coordinate reference system for a certain
+layer without CRS information, you can also do that in the
+\tab{General} tab of the raster (Section \ref{label_generaltab}) and
+vector (Section \ref{vectorgeneraltab}) properties dialog. If your
+layer already has a CRS defined, it will be displayed as shown in
+Figure~\ref{fig:vector_symbology}.
 
-\begin{figure}[ht]
-   \centering
-   \includegraphics[clip=true, width=12cm]{crsdialog}
-   \caption{CRS tab in the QGIS Options Dialog \nixcaption}\label{fig:crsdialog}
-\end{figure}
+\begin{Tip}
+\caption{\textsc{CRS in the Map Legend}} Right clicking on a layer in
+the Map Legend (Section \ref{label_legend}) provides two CRS short cuts.
+\begin{itemize}
+\item \dropmenuopt{Set layer CRS} takes you directly to the Coordinate
+  Reference System Selector dialog. Which you also get to by the
+  \button{Select} button on the \button{General} tab of the layer
+  properties dialog.
+\item \dropmenuopt{Set project CRS from Layer} redefines the project
+  CRS using the layer's CRS
+\end{itemize}
+\end{Tip}
 
-If you want to define the coordinate reference system for a certain layer
-without CRS information, you can also do that in the \tab{General} tab of the
-raster (\ref{label_generaltab}) and vector (\ref{vectorgeneraltab}) properties
-dialog. If your layer already has a CRS defined, it
-will be displayed as shown in Figure~\ref{fig:vector_symbology}.
-
 \section{Define On The Fly (OTF) Projection}\label{label_projstart}
 
-QGIS does not have OTF projection enabled by default, and this function is
-currently only supported for vector layers. To use OTF projection, you must
-open the \dropmenuopttwo{mActionOptions}{Project Properties} dialog, select a
-CRS and activate the \checkbox{Enable on the fly projection} checkbox.
-There are two ways to open the dialog:
+QGIS now supports OTF projection for both raster and vector
+data. However, OTF is not activated by default. To use OTF projection,
+you must activate the \checkbox{Enable on the fly projection} checkbox
+in the \tab{CRS} tab of the \dropmenuopttwo{mActionProjectProperties}{Project
+  Properties} dialog.
 
+There are three ways to achieve this end:
 \begin{enumerate}
 \item Select \dropmenuopttwo{mActionOptions}{Project Properties} from the
 \mainmenuopt{Edit} (Gnome, OSX) or \mainmenuopt{Settings} (KDE, Windows) menu.
-\item Click on the \toolbtntwo{mIconProjectionDisabled}{projector} icon in the
+\item Click on the \toolbtntwo{geographic}{CRS status} icon in the
 lower right-hand corner of the statusbar.
+\item Turn OTF on by default, by selecting the \tab{CRS} tab of the 
+  \dialog{Options} dialog and selecting \checkbox{Enable 'on the fly'
+    reprojection by default}
 \end{enumerate}
 
 If you have already loaded a layer, and want to enable OTF projection, the
 best practice is to open the \tab{Coordinate Reference System} tab of the
-\dialog{Project Properties} dialog, select the CRS of the currently loaded
-layer, and activate the \checkbox{Enable on the fly projection} checkbox. The
-\toolbtntwo{mIconProjectionEnabled}{projector} icon will show a green hook
-and all subsequently loaded vector layers will be OTF projected to the
-defined CRS.
+\dialog{Project Properties} dialog, select the a CRS, and activate the
+\checkbox{Enable on the fly projection} checkbox. The
+\toolbtntwo{geographic}{CRS status} icon will no longer be greyed-out
+and all layers will be OTF projected to the CRS shown next to the icon.
 
 The \tab{Coordinate Reference System} tab of the \dialog{Project Properties}
 dialog contains five important components as shown in Figure
@@ -108,7 +130,7 @@
 \begin{figure}[ht]
    \centering
    \includegraphics[clip=true, width=10cm]{projectionDialog}
-   \caption{Projection Dialog \nixcaption}\label{fig:projections}
+   \caption{Projection Dialog \wincaption}\label{fig:projections}
 \end{figure}
 
 \begin{enumerate}
@@ -140,7 +162,7 @@
 \mainmenuopt{Edit} (Gnome, OSX) or \mainmenuopt{Settings}
 (KDE, Windows) menu, you must click on the \tab{Coordinate Reference
 System} tab to view the CRS settings. Opening the dialog from the
-\toolbtntwo{mIconProjectionEnabled}{projector} icon will automatically bring
+\toolbtntwo{geographic}{CRS status} icon will automatically bring
 the \tab{Coordinate Reference System} tab to the front.
 \end{Tip}
 

Modified: docs/trunk/english_us/user_guide/working_with_projections_screenies/crsdialog.png
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Modified: docs/trunk/english_us/user_guide/working_with_projections_screenies/projectionDialog.png
===================================================================
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