and Mapping Technology Co. Ltd. The four satellites operate from an altitude of 530 km and are phased 90° from each other on the same orbit, providing 0.5m panchromatic resolution and 2m multispectral resolution on a swath of 12 km. Disadvantages Because the total area of the land on Earth is so large and because resolution is relatively high, satellite databases are huge and image processing (creating useful images from the raw data) is time-consuming. Preprocessing, such as image destriping, is often required. Depending on the sensor used, weather conditions can affect image quality: for example, it is difficult to obtain images for areas of frequent cloud cover such as mountaintops. For such reasons, publicly available satellite image datasets are typically processed for visual or scientific commercial use by third parties. Commercial satellite companies do not place their imagery into the public domain and do not sell their imagery; instead, one must acquire a license to use their imagery. Thus, the ability to legally make derivative works from commercial satellite imagery is diminished. Privacy concerns have been brought up by some who wish not to have their property shown from above. Google Maps responds to such concerns in their FAQ with the following statement: "We understand your privacy concerns... The images that Google Maps displays are no different from what can be seen by anyone who flies over or drives by a specific geographic location." See also Aerial photography Earth observation satellite Moderate-resolution imaging spectroradiometer Reconnaissance satellite Remote sensing Shuttle Radar Topography Mission Stratellite Timeline of first images of Earth from space Virtual globe NASA World Wind Weather satellite References External links ESA Envisat Meris – 300m – the most detailed image of the entire Earth to date, made by the European Space Agency's Envisat Meris. Blue Marble: Next Generation – a detailed true-color image of the entire Earth. World Wind – an open source 3D Earth-viewing software developed by NASA that accesses NASA JPL database Earth observation satellites Geographic data and information Photography by genre