[QGIS Commit] r11057 - docs/trunk/english_us/gis_introduction

[svn_qgis at osgeo.org]

Author: dassau
Date: 2009-07-13 11:34:58 -0400 (Mon, 13 Jul 2009)
New Revision: 11057

Modified:
   docs/trunk/english_us/gis_introduction/mapproduction.tex
Log:
finished section 8


Modified: docs/trunk/english_us/gis_introduction/mapproduction.tex
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--- docs/trunk/english_us/gis_introduction/mapproduction.tex	2009-07-13 14:17:50 UTC (rev 11056)
+++ docs/trunk/english_us/gis_introduction/mapproduction.tex	2009-07-13 15:34:58 UTC (rev 11057)
@@ -17,5 +17,311 @@
 
 \subsection{Overview}\label{subsec:overview}
 
+\textbf{Map production} is the process of arranging map elements on a sheet of paper
+in a way that, even without many words, the average person can understand
+what it is all about. Maps are usually produced for presentations and reports
+where the audience or reader is a politician, citizen or a learner with no
+professional background in GIS. Because of this, a map has to be effective in
+communicating spatial information. Common elements of a map are the \textbf{title,
+map body, legend, north arrow, scale bar, acknowledgement}, and \textbf{map
+border} (see Figure \ref{fig:mapelements}).
 
+\begin{figure}[ht]
+   \begin{center}
+   \caption{Common map elements (labelled in red) are the title, map body,
+legend, north arrow, scale bar, acknowledgement and map border.}
+\label{fig:mapelements}\smallskip
+   \includegraphics[clip=true, width=0.8\textwidth]{common_map_elements}
+\end{center}
+\end{figure}
 
+Other elements that might be added are e.g. a \textbf{graticule}, or
+\textbf{name of the map projection} (CRS). Together, these elements help the
+map reader to interpret
+the information shown on the map. The map body is, of course, the most
+important part of the map because it contains the map information. The other
+elements support the communication process and help the map reader to
+orientate himself and understand the map topic. For example, the title
+describes the subject matter and the legend relates map symbols to the mapped
+data.  
+
+\subsection{Map Title in detail}
+
+The map title is very important because it is usually the first thing a
+reader will look at on a map. It can be compared with a title in a newspaper.
+It should be short but give the reader a first idea of what the map is about.
+
+\subsection{Map Border in detail}
+
+The map border is a line that defines exactly the edges of the area shown on
+the map. When printing a map with a graticule (which we describe further
+down), you often find the coordinate information of the graticule lines along
+the border lines, as you can see in Figure \ref{fig:maplegends}.
+  
+\subsection{Map Legend in detail}
+
+A map is a simplified representation of the real world and map
+\textbf{symbols} are
+used to represent real objects. Without symbols, we wouldn't understand maps.
+To ensure that a person can correctly read a map, a map legend is used to
+provide a key to all the symbols used on the map. 
+
+\begin{figure}[ht]
+   \begin{center}
+   \caption{Two maps from the same area, both with a water body in the
+background but with different themes, map symbols and colours in the legend.}
+\label{fig:maplegends}\smallskip
+   \includegraphics[clip=true, width=0.8\textwidth]{legend-maps}
+\end{center}
+\end{figure}
+
+It is like a dictionary
+that allows you to understand the meaning of what the map shows. A map legend
+is usually shown as a little box in a corner of the map. It contains icons,
+each of which will represent a type of feature. For example, a house icon
+will show you how to identify houses on the map (see Figure
+\ref{fig:maplegends}). 
+
+You can also use different symbols and icons in your legend to show different
+themes. In Figure \ref{fig:maplegends} you can see a map with a lake in light
+blue
+overlaid with contour lines and spot heights to show information about the
+terrain in that area. On the right side you see the same area with the lake
+in the background but this map is designed to show tourists the location of
+houses they can rent for their holidays. It uses brighter colours, a house
+icon and more descriptive and inviting words in the legend. 
+
+\subsection{North arrow in detail}
+
+A north arrow (sometimes also called a compass rose) is a figure displaying
+the main directions, \textbf{North, South, East} and \textbf{West}. On a map
+it is used to
+indicate the direction of North. 
+For example, in GIS this means that a house that is located north from a lake
+can be found on top of the lake on a map. The road in the east will then be
+to the right of the water body on the map, a river in the south will be below
+the water body and if you are searching for a train station to the west of
+the lake you will find it on the left side on the map. 
+
+\subsection{Scale in detail}
+
+The scale of a map, is the value of a single unit of distance on the map,
+representing distance in the real world. The values are shown in map units
+(meters, feet or degrees). The scale can be expressed in several ways, for
+example, in words, as a ratio or as a graphical scale bar (see Figure
+\ref{fig:scales}).
+
+\textbf{Expressing a scale} in words is a commonly used method and has the
+advantage
+of being easily understood by most map users. You can see an example of a
+word based scale in Figure \ref{}a below. Another option is the
+\textbf{representative fraction (RF)} method, where both the map distance and the
+ground distance in the real world are given in the same map units, as a
+ratio. For example, a RF value 1:25,000 means that any distance on the map is
+1/25,000th of the real distance on the ground (see Figure \ref{fig:scales}b below).
+The value 25,000 in the ratio is called the \textbf{scale denominator}. More
+experienced users often prefer the representative fraction method, because it
+reduces confusion. 
+
+When a representative fraction expresses a very small ratio, for example
+1:1000 000, it is called a \textbf{small scale map}. On the other hand if the
+ratio is
+very large, for example a 1:50 000 map, it is called a \textbf{large scale
+map}. It is
+handy to remember that a small scale map covers a \textbf{large area}, and a
+large scale map covers a \textbf{small area}!
+
+A \textbf{scale expression as a graphic or bar scale} is another basic method of
+expressing a scale. A bar scale shows measured distances on the map. The
+equivalent distance in the real world is placed above as you can see in
+Figure \ref{fig:scales}c below. 
+
+\begin{figure}[ht]
+   \begin{center}
+   \caption{A map scale can be expressed in words (a), as a ratio (b), or as
+graphic or bar scale (c).}
+\label{fig:scales}\smallskip
+   \includegraphics[clip=true, width=0.7\textwidth]{mapscale}
+\end{center}
+\end{figure}
+
+Maps are usually produced at standard scales of, for example, 1:10 000, 1:25
+000, 1:50 000, 1:100 000, 1:250 000, 1:500 000. What does this mean to the
+map reader? It means that if you multiply the distance measured on the
+\textbf{map} by the \textbf{scale denominator}, you will know the distance in
+the \textbf{real world}.
+
+For example, if we want to measure a distance of 100mm on a map with a scale
+of 1:25,000 we calculate the real world distance like this:
+
+\begin{table}[ht]
+\centering
+ \begin{tabular}{|p{6cm}|}
+ \hline
+ 100mm x 25,000 = 2,500,000 mm \\
+ \hline
+\end{tabular}
+\end{table}
+
+This means that 100mm on the map is equivalent to 2,500,000mm (250m) in the
+real word. 
+
+\begin{figure}[ht]
+   \begin{center}
+   \caption{Maps showing an area in two different scales. The map scale on
+the left is 1:25,000. The map scale on the right is 1:50,000.}
+\label{fig:diffscales}\smallskip
+   \includegraphics[clip=true, width=\textwidth]{different_scales}
+\end{center}
+\end{figure}
+
+Another interesting aspect of a map scale, is that the lower the map scale,
+the more detailed the feature information in the map will be. In Figure
+\ref{fig:diffscales}, you can see an example of this. Both maps are the same
+size but have
+a different scale. The image on the left side shows more details, for example
+the houses south-west of the water body can be clearly identified as separate
+squares. In the image on the right you can only see a black clump of
+rectangles and you are not able to see each house clearly.
+
+\subsection{Acknowledgment in detail}
+
+In the acknowledgment area of a map it is possible to add text with important
+information. For example information about the quality of the used data can
+be useful to give the reader an idea about details such as how, by whom and
+when a map was created. If you look at a topographical map of your town, it
+would be useful to know when the map was created and who did it. If the map
+is already 50 years old, you will probably find a lot of houses and roads
+that no longer exist or maybe never even existed. If you know that the map
+was created by an official institution, you could contact them and ask if
+they have a more current version of that map with updated information. 
+
+\subsection{Graticule in detail}
+
+A graticule is a network of lines overlain on a map to make spatial
+orientation easier for the reader. The lines can be used as a reference. As
+an example, the lines of a graticule can represent the earth's parallels of
+latitude and meridians of longitude. When you want to refer to a special area
+on a map during your presentation or in a report you could say: 'the houses
+close to latitude 26.04 / longitude -32.11 are often exposed to flooding
+during January and February' (see Figure \ref{fig:graticule}).
+
+\begin{figure}[ht]
+   \begin{center}
+   \caption{Graticules (red lines) representing the Earth's parallels of
+latitude and meridians of longitude. The latitude and longitude values on the
+map border can be used for better orientation on the map.}
+\label{fig:graticule}\smallskip
+   \includegraphics[clip=true, width=0.7\textwidth]{kommandodrif_graticule}
+\end{center}
+\end{figure}
+
+\subsection{Name of the map projection in detail}
+
+A map projection tries to represent the 3-dimensional Earth with all its
+features like houses, roads or lakes on a flat sheet of paper. This is very
+difficult as you can imagine, and even after hundreds of years there is no
+single projection that is able to represent the Earth perfectly for any area
+in the world. Every projection has advantages and disadvantages. 
+To be able to create maps as precisely as possible, people have studied,
+modified, and produced many different kinds of projections. In the end almost
+every country has developed its own map projection with the goal of improving
+the map accuracy for their territorial area (see Figure \ref{fig:diffprojs}).
+
+\begin{figure}[ht]
+   \begin{center}
+   \caption{The world in different projections. A Mollweide Equal Area
+projection left, a Plate Carree Equidistant Cylindrical projection on the
+right.}
+\label{fig:diffprojs}\smallskip
+   \includegraphics[clip=true, width=\textwidth]{different-projections}
+\end{center}
+\end{figure}
+
+With this in mind, we can now understand why it makes sense to add the name
+of the projection on a map. It allows the reader to see quickly, if one map
+can be compared with another. For example, features on a map in a so-called
+Equal Area projection appear very different to features projected in a
+Cylindrical Equidistant projection (see Figure \ref{fig:diffprojs}). 
+    
+Map projection is a very complex topic and we cannot cover it completely
+here. You may want to take a look at our previous topic: Coordinate Reference
+Systems if you want to know more about it.
+
+\subsection{Common problems / things to be aware of}
+
+It is sometimes difficult to create a map that is easy to understand and well
+laid out whilst still showing and explaining all the information that the
+reader needs to know. To achieve this, you need to create an ideal
+arrangement and composition of all the map elements. You should concentrate
+on what story you want to tell with your map and how the elements, such as
+the legend, scale bar and acknowledgements should be ordered. By doing this,
+you will have a well designed and educational map, that people would like to
+look at and be able to understand.  
+
+\subsection{What have we learned?}
+
+Let's wrap up what we covered in this worksheet:
+
+\begin{itemize}
+\item \textbf{Map production} means arranging map elements on a sheet of paper.
+\item \textbf{Map elements} are the title, map body, map border, legend,
+scale, north arrow and the acknowledgement.
+\item \textbf{Scale} represents the ratio of a distance on the map to the
+actual distance in the real world.
+\item Scale is displayed in \textbf{map units} (meters, feet or degrees)
+\item A \textbf{legend} explains all the symbols on a map.
+\item A map should \textbf{explain complex information as simply as possible}. 
+\item Maps are usually always displayed \textbf{'North up'}.
+\end{itemize}
+
+\subsection{Now you try!}
+
+Here are some ideas for you to try with your learners:
+
+\begin{itemize}
+\item Load some vector layers in your GIS for your local area. See if your learners
+can identify examples of different types of legend elements such as road
+types or buildings. Create a list of legend elements and define what the
+icons should look like, so a reader can most easily figure out their meaning
+in the map.
+\item Create a map layout with your learners on a sheet of paper. Decide on the
+title of the map, what GIS layers you want to show and what colours and icons
+to have on the map. Use the techniques you learned in Topics 2 and 3 to
+adjust the symbology accordingly. When you have a template,  open the QGIS
+Map Composer and try to arrange a map layout as planned.
+\end{itemize}
+
+\subsection{Something to think about}
+
+If you don't have a computer available, you can use any topographical map and
+discuss the map design with your learners. Figure out if they understand what
+the map wants to tell. What can be improved? How accurately does the map
+represent the history of the area? How would a map from 100 years ago differ
+from the same map today?
+
+\subsection{Further reading}
+
+\textbf{Books}: 
+
+\begin{itemize}
+\item Chang, Kang-Tsung (2006): Introduction to Geographic Information Systems. 3rd
+Edition.  McGraw Hill. (ISBN 0070658986)
+\item DeMers, Michael N. (2005): Fundamentals of Geographic Information Systems.
+3rd Edition. Wiley. (ISBN 9814126195)
+\end{itemize}
+
+\textbf{Websites}:
+
+\url{http://en.wikipedia.org/wiki/Scale\_(map)} \\
+\url{http://www.colorado.edu/geography/gcraft/notes/mapproj/mapproj.html}
+
+The QGIS User Guide also has more detailed information on map production
+provided in QGIS.
+
+\subsection{What's next?}
+
+In the section that follows we will take a closer look at \textbf{vector
+analysis} to see how we can use a GIS for more than just making good looking
+maps!
+