The term "zoom" refers to the enlargement or reduction of a map or chart image on your computer monitor. A 100% zoom level means that the map or chart is being displayed at full resolution: one pixel in the digital image is being displayed as one pixel on your computer monitor. (In other words, the on-screen image contains all the pixels of the original digital image created by Maptech.)

At a 50% zoom level, the original map or chart image is reduced by a factor of 2, meaning that only half the original pixels are displayed. This enables the MapServer window to display twice the image width and height (compared to 100% zoom). Twice the width and height means four times the area.

At a 200% zoom level, the original map or chart image is enlarged by a factor of 2. The MapServer window displays half the width and height (compared to 100%). Therefore, a 200% zoom shows one quarter of the total area that a 100% zoom shows.

The zoom level and the scale of a map or chart display are related. If you view a 1:10,000 scale chart at a 50% zoom level, the apparent scale of the chart on your computer monitor will be 1:20,000 (1:10,000 x 2). If you view a 1:10,000 scale chart at a 200% zoom level, the apparent scale of the chart on your computer monitor will be 1:5,000 (1:10,000 x ½). (While enlarging a map or chart image by 200% will let you examine an area more closely, it will not increase the precision or detail of the map image.)

Related pages:
More about Scale
 More about the maps and charts available from the MapServer