Earth Screen Saver for Windows Version 3.1 Release Notes by John Walker http://www.fourmilab.ch/ INTRODUCTION ============ The Earth screen saver displays an image of the Earth as currently illuminated by the Sun, from a variety of viewpoints. You can view the Earth from the Sun (day side), the night side, from the Moon, or from an arbitrary altitude above any point on the globe specified by latitude and longitude. Day and night regions of the globe are shown based on the current date and time. The image of the Earth shifts location on the screen every 10 minutes to avoid burning in the phosphor in one location. The Earth Screen Saver is in the public domain. You can do anything you like with it. The images are generated based on imagery prepared by the NASA Goddard Space Flight Center from the MODIS instrument onboard the Terra satellite. The image of the Earth by night is based on nine months of observation by the Defense Meterological Satellite Program. For further information and additional images, visit the NASA Earth Observatory site: http://earthobservatory.nasa.gov/ If you obtained this file from a site other than www.fourmilab.ch, you may want to check: http://www.fourmilab.ch/earthscr/ to see if there has been an update subsequent to this release. INSTALLATION ============ The Earth Screen Saver works only on 32-bit Windows systems such as Windows 95 and Windows NT; it cannot be used on Windows 3.x. To install the Earth Screen Saver, download the archive EARTHSCR.ZIP and extract the files from it with PKUNZIP. You will obtain: EARTH.SCR - Screen saver module README.TXT - This document Copy EARTH.SCR to your Windows directory (usually C:\WINDOWS), then from the Desktop option of the Control Panel, choose "Earth" as your screen saver and use "Settings.." to select the view you prefer. CONFIGURATION ============= The "Settings..." button in the Control Panel/Display/Screen Saver panel displays a dialogue which allows you to select the view of the Earth and the size of the image. The image size defaults to "Auto", which fills 2/3 of your screen, but you can enter any size from 64 pixels to the entire height of your monitor. You can view the Earth from the following vantage points: Sun (day side) This is the default. The illuminated hemisphere of the Earth is shown, rotating as the day progresses. Moon The Earth is shown as it currently appears from the Moon. The phase of the Earth is inverse to that of the Moon: at new Moon the Earth is full and vice versa. Night side The night hemisphere is shown. This can be handy for shortwave listeners interested in bands on which propagation is best at night. Above location The Earth is viewed from the given latitude, longitude, and altitude. The default altitude is that of geosynchronous Earth satellites. The finite resolution of the map image limits the detail you can see by entering low altitudes. Enter the latitude and longitude of the location you want to look down upon, in degrees, minutes, and seconds in the boxes, and don't forget to click the buttons to specify whether the latitude is North or South and the longitude East or West. Don't worry about getting the longitude and latitude absolutely precise--a couple of minutes of error don't make much difference in the appearance of the earth rendered at this scale. If you enter your own latitude and longitude, you'll see the Earth centred upon your location and be able to watch the progression of day and night. HOME PLANET =========== The Earth Screen Saver was developed based on Home Planet, a comprehensive Earth and sky simulator for Windows which displays the Earth, tracks satellites, asteroids, and comets, includes an extensible multimedia object catalogue, a simulated telescope for viewing the sky at any magnification or location, a database of more than a quarter million stars, and a complete hypertext help file and introduction to astronomy linked to the components of the program. Displays include the illuminated portion of the Earth, the Sky, the Telescope, the Earth as viewed from a satellite, the Moon, or the Sun, an orrery, panels displaying current information about the Moon and planets, and more. Real-time astronomical information can be exported to other applications via DDE. There's even a cuckoo clock (you can turn it off). Home Planet is in the public domain. For more information about Home Planet, visit the World-Wide Web page: http://www.fourmilab.ch/homeplanet/ UPDATE LOG ========== Version 2.0 (19 Apr 1996): Initial release. The first release is numbered 2.0 to keep it in sync with the related Sky screen saver. Version 2.0a (28 Apr 1996): Workaround for inane and undocumented misbehaviour in the Microsoft screen saver library. See the development log in the source release for the ugly details. This fixes the problem where the image would cease to be updated but the caption would continue to move around on the screen, cluttering it up. Version 3.0 (12 Aug 2002): Integrated "Scream Saver" library for easier testing. Fixed anachronisms in code dating from 16-bit days. Changed year format to display full four digit year number. Replaced topographic map with NASA cloudless Earth image. Fixed screen saver logic to be restartable for debugging under Scream Saver (this isn't necessary when run as an actual system screen saver). Version 3.1 (19 Jul 2006): Ported to Visual Studio .NET and linked with its libraries in order to support dual-monitor configurations on Windows XP and later.