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					Three Essential Concepts
Layers
In Map Maker a map is made up of one or more layers. Each layer can be thought of as a sheet of tracing paper on which are drawn objects such as polygons, lines, symbols and text. Some of these objects are opaque and so hide objects in the layers below while others are transparent or translucent allowing detail in lower layers to be seen. A layer can either contain “vector” or “bitmap” data. Vector data is defined by co-ordinates (i.e. a straight line is defined by the co-ordinates of its two end points) while bitmap (or raster or scanned) data is composed of a rectangular area of coloured pixels (square dots). A layer of vector data can be linked to a database which enables the vector objects to be coloured according to data values and permits you to click on an object to display the database entry associated with the object. In Map Maker vector data is normally contained in a file type called DRA (for drawing). Other examples of vector data which can be read by Map Maker are ArcView shape files, Autocad DXF files, and MapInfo MIF files. Examples of bitmap data are Windows BMP files, TIF files, JPG file, and Idrisi RST files. Typically one layer contains data from one file but it can also contain several files of the same type. The layers which make up the map are known as “passive” layers since they cannot be edited they are simply viewed. To create, edit, or delete objects they must be in what, in Map Maker jargon, is called the “Live Layer” Continuing the analogy of a map as stack of tracing paper layers then the “live layer” is the top piece of tracing paper. It is the one you can draw on and on which you can amend and delete objects. There is only one live layer and the live layer is always there, even when it is empty. In other words, in Map Maker you do not select a layer to edit it. If you want to edit a particular file you copy it into the live layer. The contents of the live layer might be a copy of one file but it might also be an amalgam of several files or just objects which you have drawn using the various drawing tools. In almost all circumstances the live layer only contains vector data, the exception to this is when using the bitmap rubber sheet (see manual). Tip: Click the right-mouse button to display the “fast menu” which contains the tools and some of the most commonly used commands. All of the objects, or a group of objects, in the live layer can be selected either using the Select tool or a criteria such as “select all polygons larger than one hectare”. Using Map Maker Pro’s Selection Manager you can carry out a wide range of actions on the selected objects such as generating buffer zones, merging polygons, trimming objects to a boundary, and much more. Alternatively, these actions can also be carried out directly on vector files. Similarly actions are available for bitmap files such as clipping bitmaps to vector polygons and converting mono bitmaps to vectors.

Styles – or determining the appearance of objects
The commonest problems for new users of Map Maker concern the concept of “styles”. Styles are only applicable to vector objects. A vector object is simply a set of co-ordinates. This geometrical definition says nothing about the visual characteristics of the object, i.e. what colour is it? If it is a line is it dotted or dashed and how wide is the line? If it is a point object what symbol is used to indicate the point? All these elements go together to make a “style”. In Map Maker rather than store all this information with each object there is simply a single “style number” associated with an object. This number is used to select a style definition from a dictionary of style definitions. i.e. style definition 69 in a particular style set determines how to draw all objects that have the style number 69. The style definition includes fill colour and texture, line colour, width, and type, symbol size, colour and type, and text font attributes. The appearance of the finished object is determined by three things: The object’s geometry (its shape), the style number associated with the object, and the corresponding style definition in the selected style file. When you load a vector layer into Map Maker you can choose to associate a particular style set with that layer. Style 69 in one style set may look completely different to style 69 in another set. You can edit the style names and visual characteristics of all the style definitions and make as many new style sets as you like. In a DRA file a style number is stored with each object, but alternatively a style number might be generated from data in a database: if the database tells us that a given polygon represents a farmer’s field growing wheat then you might set up the layer to instruct Map Maker to draw that polygon with a style number which will select a style definition you have designed to indicate wheat. Style Set
In a style file e.g test.stl

+
Style Number

=

Style definition

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Object geometry

=

The appearance of the finished object

Map Maker has a default style set, which you can edit to suit your needs by going to File - System set up – Edit default style set. You can also create a library of other style sets designed to meet the needs of particular kinds of projects (i.e. rural and urban styles) by going to File – System set up – Styles library. If you like you can edit styles as you go along. When you draw a polygon, say, a dialogue box appears inviting you to enter a name and set other attributes. At this point you can select a style and edit it to make a blue polygon, or whatever. This ad hoc technique can be fine for simple maps but for most serious applications it is worth dedicating some time to developing one or more thematic style sets that can be used over and over again in different projects.

Projects – Finished maps
When you are drawing and editing files your main focus is the DRA files - the files which contain the vector data. When you come to start putting together a finished map your focus switches to the “Map Project”. A project is the whole assembly of information which goes together to produce a finished map. It includes layers, databases, the map projection, and those other bits and pieces which in Map Maker are called “Map Furniture”. Furniture covers all those visual elements which are not tied to a particular geographic location – i.e. are not contained in layers. These include scale bars, north points, borders, title panels, inset images, and the like. It does not include text objects which are tied to a place on the map, like the name of a mountain range or river. The elements of the project are encapsulated in a project file (*.geo). Note that the project file does not contain the actual data, it is simply a short text file which identifies the files which go together to make the map and which contains information about how the elements are arranged. When you open Map Maker or when you clear the screen (File – Clear) a new blank project is created, hence there is always a current project. Do not confuse saving the live layer with saving a project. When you save the live layer you are saving it to a DRA file. When you save a project to a GEO file you are saving a record of the elements that make up the map. Indeed, the one thing which is not saved to a project is the live layer. If you want to save the contents of the live layer to a project, first save the live layer to a DRA file and then save the project. When you create a new project (i.e. when you start Map Maker or clear the screen) a copy of the default style set is automatically made and this copy becomes the current project style set. You can edit this style set from the Project Manager (File – Project Manager). Changes that you make to this project style set will be confined to the project. Similarly changes which you make to the default style set (under File – System set up) will not be reflected in the current project. When you draw and edit objects in the live layer their appearance will be governed by the styles in the project style set. A map project describes the elements that come together on the screen to make the complete map: the layers, the styles, databases, gazetteers, map furniture, and the projection. It does not describe how the map is printed out. Map Maker offers a variety of default formats for placing the map on paper but in Map Maker Pro you can also create page templates to determine the page layout. The template is made using the Map Furniture tool to define one part of the page as the map frame and to place other visual elements.

Layers + Style files + Databases + Gazetteers + Map Furniture + Map projection

=

The map project

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Page template

=

The printed map

Tip: You can also display the Project Manager by pressing the space bar.


				
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posted:7/2/2009
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