Geography Reference
In-Depth Information
map canvas. Zooming out works the same way but with one nuance.
When you drag a rectangle to zoom out, the current view will be scaled
to fit in the rectangle.
You can also use the mouse wheel to zoom in and out on the map.
First, make sure the mouse cursor is over the map canvas. To zoom in,
roll the mouse away from you (think of it as flying toward the map). To
zoom out, roll it toward you (flying away from the map). The focal point
of the zoom is the location of the mouse cursor. After a mouse zoom,
the map will be centered at the cursor location. You can change this
behavior on the Map Tools tab of the Options dialog box. If you like,
you can set it to just zoom in and not re-center the map. You can also
set the zoom factor used with each “roll” of the wheel. Using the mouse
wheel to zoom can be very useful when digitizing data.
We need to mention a several other zoom tools here:
Zoom Full
This tool zooms to the full extent of the layers on the map canvas.
This means you will see all the features in all the layers on the
map. This is a quick way to reset the view after you have zoomed
in and panned around.
Zoom to Layer
This zooms to the extent of the currently selected a layer. The
selected layer is the one highlighted in the legend. You can invoke
this by using the tool button or by right-clicking the legend and
choosing
Zoom to layer extent
from the pop-up menu.
Zoom to Selection
In QGIS (as in most GIS applications), you can select features in a
layer either interactively on the map using a selection tool or from
the attribute table. If you have a selection set, you can zoom to
just the area it covers using this tool.
Zoom Previous
This is like a back button. It zooms to the previous view extent. If
you hit the button again, it will take you to where you were before.
In other words, it's a one-shot deal. There is no zoom history that
you can navigate forward and back through. But it's still a quick
way to back out of a zoom or pan operation.
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