A primary purpose of this weeks lab is to teach both some computer mapping and air photo interpretation skills. The advantages of computers in producing maps is now so great that hand drafted maps are increasingly rare. You will also be introduced into some basic principles involved in constructing maps. These principles are very helpful in some of the subsequent exercises, especially those related to GIS.

There isn't a reading for this week, except you are urged to read through the Help portions of Adobe Illustrator, the software we will use to construct the maps. It is a good idea to get used to using the internal documentation that comes with many programs. This week won't involve a lot of lecture. This is something you learn best by doing.

The most important thing to consider when constructing a map is to consider - what is the maps purpose? What information is the map to convey? What needs to be shown in order to provide meaningful context for that information? Who is your audience? The more multi-purpose a map, the more complicated and detailed it often is. Yet, such complicated maps can be hard read and understand. There is an essential tension between map simplicity providing readability, and map complexity, providing more information. A simple guide is that providing more information than is needed simply produces clutter.

Many maps are now dynamic, they evolve as more information is collected. This is a key aspect to GIS, which we will consider later. This means that you might also consider what uses the map be put to in the future - how might it grow? The map becomes more than a static depiction, but is instead linked to an evolving database.

These are basic elements that all maps need to have.

• Scale indicator: a bar scale is best in that it doesn't change if the image is scaled to a different size. Providing UTM coordinates provides both location and scale. Latitude and longitude provide location, but only a general sense of scale (unless the reader takes all the trouble to translate lat-long into distances).
• North arrow (magnetic declination can be useful in many cases).
• Clear and complete map legend, that explains what the map elements (symbols, lines, colors, patterns) mean.
• Map location: by marking latitude or longitude, UTM coordinates, or with an inset map with these, or at a minimum some locatable feature such as roads or USGS markers. If you include UTM coordinates you should also include information at to the UTM zone and the map projection.
• Referencing of base map and other information used to construct the map (just as you would for text).

The conventions of language help us communicate, and there are conventions associated with different types of maps that help us read them. Blue squiggly lines are easily recognized as rivers. There are conventions for geologic and geoscience maps.

• The aesthetics are very dependent on the purpose of map and the audience.
• Yes, color scheme can be important. Look at many geologic maps and you will begin to sense some conventions as to color schemes. Here is a link about geologic maps.
• We can only address some basic thoughts on the 'art' of map making in this course.
• Get feedback. Show your map to others. Quiz them to see if they are 'reading' the map as you intended it should be read.
• We want our maps to be as truthful as possible. Some have discussed at length how maps are not truthful in the absolute. Roads have exaggerated thickness, giving them prominence. Contacts between different features (e.g. grassland vs. woodlands) are often smoothed out, or in reality are a transition instead of a sharp line. In some cases it is interesting to think on what is not being plotted on a given map, what is not being 'privileged'. Some of these 'inaccuracies' are necessities of communication, and are implicitly understood. One consideration of truthfulness needs particular attention in drawing maps in geoscience. Information is almost always incomplete, and a certain degree of certainty can be attached to an interpretation, interpolation or extrapolation. For example, where a geologic boundary exists is often not directly exposed, but is constrained by outcrops of the opposing units. A convention exists to deal with this. Where it is well constrained a continuous line might be drawn. Where it is poorly constrained a dashed line is drawn. Where it is buried, a dotted line is drawn. It is also helpful to show on your map the distribution of data upon which the map interpretation is based. When contouring data you did this by posting the control points.
• U.S. Geological Survey Open-File Report 99-430 Online version 1.0
  Public Review Draft ­ Digital Cartographic Standard for Geologic Map Symbolization (PostScript Implementation) Prepared in cooperation with the Geologic Data Subcommittee of the Federal Geographic Data Committee By the U.S. Geological Survey. Has PDF documents showing standard symbols for an array of geologic features.

This is fundamental distinction that is important to recognize. Raster format is akin to a simple x,y,z image where x and y are position on the page and z is the color value of that position (or on a computer screen of that pixel). Think of the art style of pontillism where images were created with small colored dots. A raster format is attractive in its simplicity, but has some severe shortcomings. If you draw a straight line the pixel values that were there before are usually lost. More importantly once drawn it loses its identity as any sort of distinct object. The computer doesn't know which pixels belong to the line and which don't. If you want to make it longer, change its orientation or width, the original line needs to be erased pixel by pixel, then the new line drawn. Redrafting soon becomes tedious and a mess. Still some information, such as a satellite or air photo images, comes in a basic raster form.

Vector formats are where objects are defined mathematically via a suite of attributes and drawn from those. Change the objects attributes and you change its appearance without affecting anything else. These objects can be points, lines, shapes and can have all sorts of characteristics such as position, width, and color. The computer keeps track of all this information and draws the appropriate object. For geometric shapes, including polygons, this is a much more efficient and versatile way to keep track of graphic elements. Compare the amount of information it takes to specify a black square one inch on a side, with 333 dpi, in a raster versus a vector format. What is more, one information is easily retrievable for other uses in both cases. Overlapping objects can exist in vector format and so information is not lost by superimposition and the operator can decide which element should be in front of the other. A next natural step is to be able to store information about each object as hidden object attributes. You could then plot all objects with attributes in a certain range. This is a fundamental concept behind GIS. Adobe Illustrator can deal with both types of formats but uses vector format primarily. Adobe Photoshop is basically limited to a raster format.

Many other map drafting programs exist. Autocad is probably the best known, and is in some ways the most powerful. It is geared toward engineering and architecture. Canvas is another package that has some strong adherents. Learning one of these will help somewhat with the others. We will use Illustrator because it has some advantages. It is one of the more widely used packages, we have experience with it, and the resources are here.

Important concepts in Illustrator: We will explore these in the Geography and Geology Department Cartographic Lab. Marv is in charge.

Layers: One of the strengths of Illustrator is the easy ability to work in layers and then utilize whatever layers you need. These can be considered as overlays. A base map can be put in one layer, geologic features can be put in another, geographic in another, data points in another, and so on. Custom maps can then be made from the combination of layers. Elements can easily be transferred from one layer to another. We will see the importance of this layering concept in future labs. You can turn off a layer so it can't be seen, or lock a layer so it can't be modified, or set a layer so that it won't be printed.

Objects: What you 'draw' in iIlustrator are a great variety of objects. These can be lines, polygons, raster images, text, graphs and combinations of the above. Objects are editable after you have created them.

Drawing lines and polygons with fill: Lines and polygons as objects have two parts to them, an outline (border) and a fill. Either one can be transparent so that you have only a border or a fill. In addition, the border can be of different line thicknesses (referred to as weights), and they can be dashed. The fills can be colors or patterns. Again, at any time you can change the character of the outline or fill.

Handles and redrawing lines and shapes: The small box ornaments along the length of the outline of an object can be used to reshape it. You can also use the endpoint ornaments to link to another object or to continue extending the existing line.

Multiple windows: There are multiple small windows to create and manipulate the layers and objects you create. Often, if you can't find something, it is because that window was inadvertently closed or is hidden behind another window. There are windows to choose your drawing and editing tools, a window to manage your layers, a window to choose your fills (swatches), a window to alter line or border attributes, and more.

The Help part of the software can actually be helpful.

One way to learn methods of abstraction and depiction involved in making maps is to see how others have approached this challenge. We are going to look at a very diverse suite of geoscience maps and explore some of the conventions used. You will work in groups of two. For your map complete the following

• List specific types of information/data are being displayed.
• Why do you think this combination information/data was chosen? In other words, what might be the connections between the different types of data?
• What 'devices' are used for showing the information? Possibilities include: contour lines, shaded or colored areas, boundary lines, orientation lines/vectors, unclassified or classified symbols, graphs or charts, other.
• Critique the map. Is there unnecessary information or clutter? Is there missing information that should be shown? Could a different method of depiction be used? Is the map 'truthful' in terms of information quality?

Copyright by Harmon D. Maher Jr.. This material may be used for non-profit educational purposes if proper attribution is given. Otherwise please contact Harmon D. Maher Jr.