Drawings

Drawings in Manifold are similar to drawings in a CAD system used to create blueprints. They are made up of points, lines or areas and are often referred to as vector drawings in other mapping programs or CAD systems.

 

images\panama.gif images\palo_sm_drawing.gif images\athinai.gif

 

Existing drawings may be imported into a Manifold project using the File - Import - Drawing command. New drawings may be created in Manifold and then exported into common drawing file formats using File - Export. See the Import and Export topic for more information on specific import dialogs used to import drawings from various GIS formats.

 

Creating a New Drawing

 

1. Open a project or create a new project with File - New.

2. Choose File - Create - Drawing to create a new drawing.

 

The File - Create - Drawing dialog takes the projection parameters for the new drawing from whatever window is active at the time the new drawing is created. If the project pane is active, the drawing will be created using the system default projection of Orthographic centered at the 0,0 world latitude/longitude origin. If a map window or other drawing window is active when the new drawing is created, the new drawing will be created using whatever projection is used by that active window. This context-sensitive setting of default projection parameters makes it much easier to create new drawings using projection parameters that are hassle-free by default.

 

Every drawing has a table associated with that drawing. Creating a drawing will automatically create the table for it.

 

Drawing Fundamentals

 

Drawings are fundamentally different from images in several ways:

 

·      Drawings are made up of objects drawn using points, lines and areas that are defined by specific coordinates. In contrast, images have no objects, only a sea of pixels. The "objects" we see in an image appear to be there because our eyes and brains automatically match up pixels of similar colors to interpret that part of the image as being an object.

·      The appearance of objects in a drawing is determined by the format of each object and not by the zoom level. A point in a drawing that is formatted to appear as a small circular dot will have the same size and appearance regardless of zoom level. Areas that are formatted so that they appear with a contrasting color on their border will have the same thickness of border line no matter how far one zooms in. Changes in zoom will simply show more or less of the object. In contrast, the appearance of images varies dramatically as one zooms in past the point where individual pixels become visible.

·      Drawings use a coordinate system that specifies the precise geometric relationship between different parts of different objects. Drawings intended for use as geographic maps will use a geographic coordinate system so they automatically may be located on the surface of the Earth. In contrast, images have no intrinsic coordinate system except that which is implied by the row and column arrangement of pixels. Images that might be imported into Manifold are rarely bound to geographic coordinates and thus will usually require a quick georegistration before they can be used in geographic maps in a sensible way.

·      Because drawings have distinct objects, a drawing can be linked with database information by attaching database records to objects in the drawing. In contrast, because there are no objects in images, databases cannot be attached to images. The only data in images are the color values of the pixels.

·      Every drawing has a table associated with that drawing. Each row in the table corresponds to an object in the drawing. A drawing with three points in it will have three rows in its table, for example. The table will have at least one field, an object ID field, that is used to link each row in the table to an object in the drawing.

 

Points, Lines and Areas

 

Drawings are created from only three types of objects:

 

·      Points

·      Lines

·      Areas

 

No matter how detailed or cleverly formatted a drawing may be, it is ultimately made up of only these three types of objects. Drawings do not have to contain all three types of objects. Many drawings contain only points, only lines or only areas.

 

images\points.gif

 

Points are simply dots at a particular location. Points are formatted by default as small, round dots. Points can be shown as anything from a single pixel to a multicolored icon. In the illustration above, the three points to the left are shown as single pixels whereas the four points to the right are dots formatted with bright green background color.

 

images\palo_z1.gif images\palo_z3.gif

 

Lines may appear to be straight lines or smooth curves. However, all lines are ultimately made up of straight-line segments drawn between the sequence of coordinates that define the line. Zooming far into even the most smoothly curved line will show that it is made up of straight-line segments. Some CAD and GIS systems call such lines "polylines." In Manifold, we simply say "lines."

 

images\w_solid.gif images\w_solid_apart.gif

 

Areas are like shapes cut out of cardboard. They are objects that actually have some "substance" in their inner region and are often used to show regions such as states or provinces in a map. The illustrations above show a few western states drawn using areas. At left we see the areas drawn in their normal position, and at right drawn separate from each other. The illustration at right has had "shadows" added in a simple way to provide a greater impression of substance, to promote the analogy with shapes cut out of cardboard.

 

Historical Note: Areas were called "polygons" and lines were called "arcs" in some older GIS systems. This terminology may still be used in some organizations that are still using legacy systems. See the Terminology in GIS essay for notes on the difference between older words and modern usage.

 

Don’t Confuse Lines with Areas

 

Areas are a new concept to users of simple drawing packages. Many graphics arts packages that allow the creation of vector drawings allow use of lines and points, but not areas. Other graphics packages, such as the drawing toolbar in Microsoft Word, uses "shapes" in a manner that is part way between line drawings and the use of areas in more sophisticated packages.

 

An important difference between areas and lines is that areas have inner substance, like a cardboard cutout, whereas even when lines are drawn in a way that makes a closed figure there is no "substance" inside the white space of the figure. A closed figure drawn using lines is like a figure made up of wire twisted into the desired shape. There’s nothing "inside" the figure.

 

images\w_wires.gif images\w_wires_apart.gif

If we redraw the Western states using lines instead of areas, we can see that when we pull apart the constituent lines there is nothing "inside" the states. It is as if we made a wireframe figure out of pieces of stiff wire twisted into the shape of the state boundaries. When we take the figure apart we see it is just bits and pieces of wire.

 

The distinction between drawings made up of lines and those made up of areas is important because the appearance of the objects depends on how they are formatted. Only the "substance" of the objects can be formatted. If we wish to draw Western states with different, smooth colors within their interior regions we should use areas to draw the states. We can’t color the interiors of a drawing of Western states made up of lines because there is no "interior" to color.

 

images\paint_wire.gif

 

Imagine, for a moment, the drawing of states using lines as though it were made up of wires and seen in perspective. If we tried to paint the inside of the states with a paint bucket the paint would flow right through the empty spaces between the wires.

 

images\paint_area.gif

 

If we imagine the drawing made up of areas as though they were shapes cut out of cardboard we can pour paint onto the shape and have it color the interior of the area.

 

Advantages of Lines

 

It’s a good thing that figures drawn of lines have no interior substance. That makes it easy to use lines to draw linear features like roads in a layer that overlays other objects. One can then see the objects below through the nothingness between the lines.

 

images\line_layers.gif

 

The image above uses three line drawings stacked up above an image layer. One layer uses lines formatted as thick black lines, while the others use thinner lines. The illustration shows Palo Alto, California, with Highway 101 cutting across from left to right and San Francisquito Creek (the border between Santa Clara and San Mateo counties), shown in blue.

 

Don’t Confuse Area Boundaries with Lines

 

In a drawing created entirely from areas it could be difficult to see the "joints" between areas if they fit together perfectly.

images\w_faint_apart.gif

Suppose we cut out the shapes of Western states from fine paper and fitted them together so carefully the seams between them could not be seen:

 

images\w_faint.gif

That’s a less useful drawing than one that clearly shows the seams between the areas so that it’s obvious where each area begins and ends:

 

images\w_solid.gif

By default, Manifold will use an area style to draw areas that draws the last pixel at their edges in a contrasting color. This makes it possible to see the seams between areas even when they are perfectly fitted together. When looking at areas drawn using this default area style, we might be tempted to think that we are looking at a map that includes a set of lines drawn in the shape of the areas; however, this is just a different area style. See the Areas and Boundary Lines topic for more discussion on this.

 

Using Lines to Duplicate Area Boundaries

 

Sometimes we will want to use both areas and lines to show the same thing, in order to take advantage of greater formatting flexibility.

 

images\line_area.gif

 

It’s easy in Manifold to create a set of lines that follow the boundaries of area objects using Transform - Boundaries . If we like, we can use this command to create lines that exactly follow the borders of our Western state areas. We can then stack these lines in a layer above the area layer. This gives us greater formatting flexibility than is possible using area styles alone. For example, we can make the lines layer using extra-thick lines in some boundaries to emphasize certain states.

 

Another reason to create a layer of lines that follow the borders of our state areas is to create a layer of lines that can be overlaid upon an image. Consider the following example:

 

images\sc_drawing_arealines01.gif

 

Suppose we have an image of the US and a drawing that shows US states as areas.

 

images\sc_drawing_arealines02.gif

 

If we stack the areas drawing in a layer above the image the substance of the areas will obscure the image. Although we might use a transparent area effect so that the image could show through the areas in this case we will use lines to get exactly the right visual effect desired.

 

images\sc_drawing_arealines03.gif

 

To create the lines, we use Boundaries to create lines in the shape of the area boundaries.

 

images\sc_drawing_arealines04.gif

 

We can create the new lines in a new drawing layer in our map. We can then stack the lines above the image to show boundaries in the image.

 

images\sc_drawing_arealines05.gif

 

Note: this is a small image to fit into the Help documentation and so a very bright color has been used for the boundary lines. In "real life" it is often cooler to use more subdued colors to achieve a more modern look in one's maps.

 

Areas Can be Drawn in Opaque or Transparent Styles

 

By default, areas are drawn using an opaque style in gray color. Objects below areas drawn in such style will not be visible. If you can’t see objects that you expect to be in your drawing, make sure that they are not on a layer that is below an opaque area. Move them above the area and they will become visible.

 

images\trans_solid.gif

 

Areas may also be drawn using a variety of transparent hatch patterns or even in a translucent style (by changing the Layer Opacity of the layer they are in). In this case, they are like shapes cut out of transparent plastic or translucent paper.

 

images\trans_trans.gif

 

Areas that overlap each other within the same layer will overlap above or below each other depending on the order in which they were created. When working with areas that overlap, it’s often helpful to use transparent area styles so that the region of overlap is clearly visible in all cases. See the Overlapping Objects and Transparent Area Styles topics for more information.

 

When drawings are used as layers in a map , the layers can be shown with different Layer Opacity so that different layers can be seen through those that are partially transparent. This is a fine way to show overlapping areas.

 

Suggestions

 

·      Use lines to draw linear features like roads and streams.

·      Use areas to draw regional features such as provinces or lakes.

·      When formatting objects, keep in mind the visual analogy that lines are like wires hovering above the drawing and areas are like shapes cut out of cardboard.

 

Drawings and Maps

 

Drawings by themselves can only show points, lines or areas. To show other visual elements, such as labels or images, we use other Manifold components such as Images or Labels components. By combining drawings with images and labels layers in a map we can achieve exactly the visual effect desired.

 

Using the Layers Pane with Drawings

 

The Layers pane is used to control the appearance of drawings within drawing windows. The layers pane includes checkboxes for two system "layers" - a background color layer and a border layer that shows an enclosing box about the widest extents of objects in the drawing.

 

images\sc_layers_dwg_01.gif

Drawings are shown using the checkerboard background Manifold uses to provide a backdrop for any transparent regions. The layers pane is shown to the right of the drawing window.

 

images\sc_layers_dwg_02.gif

Checking the Background box in the layers pane will replace the checkerboard background with whatever is the default background color. The default setting for drawings is to show a white background.

 

images\sc_layers_dwg_03.gif

Checking the Border box will draw a one-pixel border that represents the minimum enclosing box for all objects in the drawing. When working with drawings that include points, using the Border is a handy way to see if any very small objects exist far away and unnoticed from other objects, since the border will expand to include all objects.

 

Note that only maps can have true "layers" in Manifold in the sense that they can layer more than one component within the same map window. The border and background "layers" in the Layers pane for are not true layers even though they appear in the Layers pane in the same manner as do layers in maps. These are simply system controls that take advantage of the Layers pane as a conceptually convenient user interface.

 

images\sc_layers_dwg_04.gif images\sc_layers_dwg_05.gif

 

Clicking off the Background in the layers pane can resolve visual ambiguities between areas that are white in color and regions that are bordered by lines. With Background on as in the illustration at left above it is not possible to immediately see solid areas that are colored in the same color as the background color. With Background off, white areas will stand out against the default checkerboard pattern.

 

We can change the background color in Tools - Options . See the Layers topic for an example of how changing background color can radically change the appearance of a drawing or map.

 

Layouts and the Layers Pane

 

If a drawing has any Layouts created they will appear as "layers" in the layers pane for that drawing. Checking the box for one of these print layout layers will cause a layout rectangle to appear in the drawing that shows the region covered by the layout.

 

images\sc_dwg_layout_layers.gif

 

In the illustration above the drawing has four layouts that show different parts of Mexico. Three of the layouts have been checked in the layers pane causing three layout preview rectangles to appear in the drawing.

 

Right clicking onto the hatched border of one of the layout rectangles in the drawing will cause a context menu to appear with controls based on that layout rectangle. For example, we can Zoom to a given layout rectangle, Print it or change its Properties. If a layout is empty (for example, if the layout scope is set to selection and nothing is selected in the parent component) zooming to the layout will do nothing.

 

Use Tools - Options - Colors - Layout Rectangle to change the color in which layout rectangles are shown. The default color is black.

 

See Also

 

Format Toolbar

View - Properties - Zooms