Subset Map Area

Icon on the map toolbar: Move to the NW corner of the area you want, hold down the left mouse button, and drag to the SE corner.  The area selected will be redrawn, keeping the aspect ratio you selected on screen and one of the dimensions from the original map.  If you do not select a map region with the same aspect ratio as the original map, the new map will be smaller in one of the dimensions.

If the map becomes too small, Zoom in (blow up; same coverage area on a larger scale).  If you use the zoom in indiscriminately, the map will become very large, and you can run out of memory, or it becomes to difficult to navigate with the scroll bars.

This enables you to blow up the map, but cannot change the underlying resolution of the map data. You may begin to clearly see stair-stepping of the individual data points with raster data, or the straight line segments with vector data.

If you want to blow up a very small area of the screen, it is often best to do it in several steps. This will allow you to select the corners more closely. Graphical selection limits the coordinates you can select, and at smaller scales this limitation becomes more severe.


Last revised  11/2/2017