We would often like to create a map where different layers turn on and off as we zoom in and out. This allows us to hide dense layers when zoomed far out and to make them visible when zooming in. This example creates a simple map of Mexico with different layers.
Important: If you have installed 64-bit Manifold, do this example in 32-bit mode by launching Manifold System using the Manifold System (32-bit) shortcut. See the note on 64-bit Manifold at the end of this topic.
We would like to create a map of Mexico that has boundaries, highways and railroads layers plus a drawing layer showing data points and a labels layer.
Without the use of zoom ranges, the map looks very busy when zoomed out.
If you do not have an analogous map of your own to use and wish to follow along in this example, do the following to create a map like the one illustrated in this example:
Step 1: Import the drawings to be used in the map
Drawings used in this example are in the Examples directory of the Manifold CD. Use File - Import - Drawing with file type set to MFD Files to import Mex boundaries.mfd, Mex highways.mfd and Mex railroads.mdb.
This creates three drawing components in the project pane, as seen above.
Step 2: Create a Labels Component
Create a new labels component by clicking on the Create button in the project pane toolbar and choosing a new Labels component (or, by choosing File - Create - Labels from the main menu).
In the Create Labels dialog, click on the Mex boundaries drawing component. This will make its fields appear in the dialog's Columns pane. [For the sake of brevity in this topic henceforth we will refer to the Mex boundaries drawing as simply the "boundaries drawing" and likewise for the other drawings used.]
In the Create Labels dialog, double-click on the Place name field to add it to the labels text and press OK.
A labels component appears in the project pane, indented under its parent boundaries drawing.
Step 3: Create a Map
To create a map, we use File - Create - Map and in the Create Map dialog check the boxes for the components we wish to appear in the map.
In the illustration above we named the new map Mexico. We also changed the default order of the layers using the Move Up and Move Down buttons so the map will be created with the order of layers seen above.
The result is a new map component in the project pane. We can double click the map to open it in a map window. Use Zoom commands to zoom as desired into the map.
Step 4: Apply a projection to the components
Zoom ranges only work with projected components. They do not work with components in Latitude / Longitude that have not yet been projected. The fastest way to project the components in the map is to first apply a projection to the map using the Edit - Assign Projection dialog. Choose the Orthographic projection centered on Latitude 24 and Longitude -102 (about the center of Mexico, the defaults suggested by the Suggest button). There will be little change in the appearance of the map since the Orthographic projection so close to the Equator is visually very similar to Latitude / Longitude coordinates.
To apply the projection to all of the components in the map, first confirm the original projection of each component by using the Assign Projection dialog, and then project each component to the projection of the map by right clicking its layer tab and choosing Project to Map. This will re-project the component into the same Orthographic projection used by the map. Alternately (and more slowly) in the project pane double click open each of the components in turn, choose Edit - Change Projection and set the projection to Orthographic with a Latitude center of 24 and a Longitude center of -102.
Step 5: Format the Map Layers
Seen in default formatting, the map is somewhat confusing.
We will make it more comprehensible in two steps: first, we will apply formatting to distinguish different layers by color and second, we will use zoom ranges to turn layers on and off as needed as we zoom. Apply formatting using the format toolbar using the methods described in the Formatting Drawings topic.
Using the format toolbar change the foreground color for lines of the railroads layer to a dotted style using dark blue foreground and white background colors. Leave the highways layer in the default colors. Change the background color for areas in the boundaries layer to your choice of color (we used a beige color in this example).
The illustration above shows a cluster of green points in the center of Mexico. This example uses a points layer for illustrative purposes. To create such a layer, right-click on the highways layer tab in the map and choose Add - New Drawing. This will add a new drawing layer (and create the drawing in the project pane) as a layer just above the highways layer. Use the Insert Point tool to add some points in the center of Mexico and then use the format toolbar to change those points to a bright green background color.
Note: The Mexico drawings provided in the Examples folder on the Manifold CD don't have any points in the line drawings such as the highways or railroads drawings. This is unusual, since most drawings created for transportation analysis have points at the ends of each line to enable them to be used for network analysis. If you use different drawings in the examples, you may find that line drawings are imported with numerous points. These may be easily deleted. See Point Styles and Sizes for examples.
Step 6: Open individual components and assign zoom ranges
In the following section we will open each drawing in its own drawing window. Do this by double clicking on the component in the project pane. It will open in a drawing window (or, a labels window for the labels component). Note that we can have a component window open at the same time we see that component as a layer in the map window.
Let's begin by adjusting the zoom range on the railroads drawing layer. To do this, we double click open the railroads drawing in its own window and then choose View - Properties and click the […] button to the far right of the Zooms caption.
This opens the Zooms dialog. By default the zoom range displays the drawing from the Minimum zoom (lowest value) to the Maximum zoom (highest value). The Current Zoom number shows the current zoom in the opened railroads drawing window. It will vary as we zoom in or out of the window. It has no effect in setting zoom ranges except to provide a guide that may be used to estimate which zoom values to enter in the Minimum zoom or Maximum zoom boxes based on the current appearance of the component window.
In the Maximum zoom list box, we will choose the 1:10000000 preset and then press OK to apply this new zoom range to the drawing. This means that the railroads drawing will be visible in the map from any lowest zoom level up to a highest zoom level of one to ten million. At higher (further out) zoom levels the drawing will not be displayed.
If the map is zoomed out farther than one to ten million the railroads layer will disappear. There will be no change visible in the drawing window for railroads since zoom range only affects the visibility of drawings in maps.
We can repeat this process with the other drawings in the map. For example, we can alter the zoom ranges for the highways drawing.
We double-click open the highways drawing in a window. We can then choose View - Properties and click the […] Zooms button to set zoom range for the highways.
By default the Minimum zoom and Maximum zoom boxes offer preset zoom ranges as factors of ten. We can also enter a zoom range that is not an even factor of ten.
For the Minimum zoom range we can choose 1:1000000. For the Maximum zoom range we can enter 3000000 to specify a zoom range of 1:3000000. These values mean that the highways layer will be displayed in maps at zoom levels between 1:1000000 and 1:3000000. At zoom levels below 1:1000000 or zoom levels above 1:3000000 the highways layer will not be displayed in maps. Applying this zoom range to the drawing instantly causes the highways to disappear from the map if the map window is zoomed farther out than one to three million.
Next we can click open the points drawing layer and set the zoom range for the points.
We will set it from any lowest zoom up to a highest Maximum zoom value of 1:1000000. In the map window, the data points layer immediately disappears if the map window is zoomed higher than 1:1000000.
Finally, we can click open the labels component and set the zoom range for the labels.
We will leave the zoom range for Minimum zoom blank so there is no minimum zoom value and we will set the Maximum zoom to 1:5000000.
Within the map window we can now zoom in and out and the drawing layers will appear as directed by the zoom ranges we have specified.
Suppose we begin with the zoomed out view seen above. The view is zoomed out farther than 1:10000000 so no layers except the boundaries appear. As we zoom in, the different layers will appear. We will zoom in to the central part of the illustration in each case.
As we zoom in closer than a scale of 1:10000000 the railroads appear in dotted lines.
As we zoom closer than 1:5000000 the labels layer appears. Labels, surfaces and image components can have zoom ranges specified as well as drawings. Assigning different zoom ranges to different labels layers is an essential method to keep maps from becoming cluttered with labels that are too close together.
As we zoom to below 1:3000000 the highways layer appears.
Finally, as we zoom to below 1:1000000 the highways disappear, leaving only the railroads, labels and data points layers.
Notes
What does a scale of 1:1000000 (one to one million) really mean? It means that what is shown in one unit of measure on the computer screen is one million of those units on the surface of the Earth. If we measured a feature on the screen that was five centimeters wide it would be five million centimeters (50 kilometers) wide on Earth.
Important Note when Using 64-bit Manifold Editions
Due to a lack of required Microsoft facilities in 64-bit Windows systems, Manifold in 64-bit mode cannot export, import, export or link to DB, HTML, MDB, XLS or WKx format files. This includes no access to the MDB parts of Manifold MFD and MapInfo TAB imports. The workaround for importing or exporting such files is to launch Manifold in 32-bit mode by using the Manifold System (32-bit) shortcut, perform the export from or import into a .map project file and then re-launch Manifold in 64-bit mode using the Manifold System (64-bit) shortcut. Linking is more complex: the data must be in some format usable in 64-bit mode within 64-bit Windows systems, such as a SQL Server database. Alternatively, the data can be kept within a Manifold .map project file and linked using the Manifold ODBC driver.