24 Part I — Basics
FIGURE2-9: Closest zoom on the National Maritime Museum.Just as Google Maps and Google Earth images are not always available at all zoom levels
(within maps, sparsely populated areas are rarely shown below 500 feet, and sometimes 1,000
feet), satellite information is not always available, either. Much of the United States has been
photographed at a resolution of 1 meter, making 200-foot images readily available but, as with
map information, some sparsely populated areas or extremities are not available at such a high
resolution. But a lot of the United Kingdom is unavailable for satellite imagery below the
2,000-foot zoom level, although heavily populated areas such as London, Birmingham, and
Manchester areavailable at the highest zoom level. Other parts of the world are similarly split
into different levels of higher and lower resolution according to their population density or the
amount of interest in the location. Satellite imagery is constantly being updated and improved,
and this process is likely to increase as more people begin to use the information.Resolution quality has no defined boundaries, and it is possible to find a location on the map
that shows satellite for only a portion of the area viewed. At certain zoom levels, you can deter-
mine where the higher-resolution images are available; for example, these areas of unavailability
showed up in Figure 2-9 as differently shaded patches on a map of the United Kingdom.You, therefore, need to take care to ensure that when you display a map or satellite image, you
choose a zoom level appropriate to the area you are viewing.