Changeset 4871

Timestamp:

Dec 3, 2007, 3:00:01 PM (16 years ago)

Author:

sexton

Message:

including more FAQs in usermanual

Location:

anuga_core/documentation/user_manual

Files:

• anuga_user_manual.tex (modified) (2 diffs)
• graphics/polyanddata.jpg (added)
• graphics/polyanddata2.jpg (added)

anuga_core/documentation/user_manual/anuga_user_manual.tex

@@ -1305 +1305 @@
 the gauges shown in Figure \ref{fig:cairnsgauges} is \file{gauges.csv}
 
-\verbatiminput{demos/cairns/gauges.csv}.
+\verbatiminput{demos/cairns/gauges.csv}
 
 Header information has been included to identify the location in terms of eastings and
@@ -3971 +3971 @@
 (as for the \file{run\_sydney\_smf.py} example).
 
+\subsubsection{How can I set the friction in different areas in the domain?}
+The model area will typically be estimating the water height and momentum over varying
+topographies which will have different friction values. One way of assigning 
+different friction values is to create polygons (say \code{poly1, poly2 and poly3}) describing each 
+area and then set the corresponding friction values in the following way
+
+\code{domain.set_quantity('friction',Polygon_function([(poly1,f1),(poly2,f2),
+(poly3,f3))]))}
+
+The values of \code{f1,f2} and \code{f3} could be constant or functions 
+as determined by the user.
+
+\subsubsection{How can I combine data sets?}
+
+A user may have access to a range of different resolution DEMs and raw data points (such 
+as beach profiles, spot heights, single or multi-beam data etc) and will need
+to combine them to create an overall elevation data set. 
+
+If there are multiple DEMs, say of 10m and 25m resolution, then the technique is similar to 
+that defined in the Cairns example described earlier, that is
+
+{\small \begin{verbatim}
+convert_dem_from_ascii2netcdf(10m_dem_name, use_cache=True, verbose=True)
+convert_dem_from_ascii2netcdf(25m_dem_name, use_cache=True, verbose=True)
+\end{verbatim}}
+followed by  
+{\small \begin{verbatim}
+dem2pts(10m_dem_name, use_cache=True, verbose=True)
+dem2pts(25m_dem_name, use_cache=True, verbose=True) 
+\end{verbatim}}
+These data sets can now be combined by
+{\small \begin{verbatim}
+from anuga.geospatial_data.geospatial_data import *
+G1 = Geospatial_data(file_name = 10m_dem_name + '.pts')
+G2 = Geospatial_data(file_name = 25m_dem_name + '.pts') 
+G = G1 + G2
+G.export_points_file(combined_dem_name + ‘.pts’)
+\end{verbatim}}
+this is the basic way of combining data sets, however, the user will need to
+assess the boundaries of each data set and whether they overlap. For example, consider
+if the 10m DEM is describing by \code{poly1} and the 25m DEM is described by \code{poly2} 
+with \code{poly1} completely enclosed in \code{poly2} as shown in Figure \ref{fig:polydata}
+\begin{figure}[hbt]
+  \centerline{\includegraphics{graphics/polyanddata.jpg}}
+  \caption{Polygons describing the extent of the 10m and 25m DEM.}
+  \label{fig:polydata}
+\end{figure}
+To combine the data sets, the geospatial addition is updated to
+{\small \begin{verbatim}
+G = G1 + G2.clip_outside(Geospatial_data(poly1)) 
+\end{verbatim}}
+For this example, we assume that \code{poly2} is the domain, otherwise an additional dataset
+would be required for the remainder of the domain. 
+
+This technique can be expanded to handle point data sets as well. In the case
+of a bathymetry data set available in text format in an \code{.xya} file, then
+the geospatial addition is updated to
+{\small \begin{verbatim}
+G3 = Geospatial_data(file_name = bathy_data_name + '.xya')
+G = G1 + G2.clip_outside(Geospatial_data(poly1)) 
+\end{verbatim}}
+The \code{.xya} file has the data stored as \code{x,y,elevation} with the text \code{elevation}
+on the first line. 
+
+The coastline could be included
+as part of the clipping polygon to separate the offshore and onshore datasets if required.
+Assume that \code{poly1} crosses the coastline 
+In this case, two new polygons could be created out of \code{poly1} which uses the coastline
+as the divider. As shown in Figure \ref{fig:polycoast}, \code{poly3} describes the 
+onshore data and \code{poly4} describes the offshore data. 
+\begin{figure}[hbt]
+  \centerline{\includegraphics{graphics/polyanddata2.jpg}}
+  \caption{Inclusion of new polygons separating the 10m DEM area into an
+  onshore (poly3) and offshore (poly4) data set.}
+  \label{fig:polycoast}
+\end{figure}
+Let's include the bathymetry 
+data described above, so to combine the datasets in this case, 
+{\small \begin{verbatim}
+G = G1.clip(Geospatial_data(poly3)) + G2.clip_outside(Geospatial_data(poly1)) + G3
+\end{verbatim}}
+
+Finally, to fit the elevation data to the mesh, the script is adjusted in this way
+{\small \begin{verbatim}
+    domain.set_quantity('elevation',
+                        filename = combined_dem_name + '.pts',
+                        use_cache = True,
+                        verbose = True)
+\end{verbatim}}
 \subsection{Boundary Conditions}