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ORTHOGRAPHIC EARTH Version 9232 August 06, 1992 (C) Copyright David H. Ransom, Jr., 1992 All rights reserved. David H. Ransom, Jr. 7130 Avenida Altisima Rancho Palos Verdes, CA 90274 USA Computer Bulletin Boards ------------------------ RPV ASTRONOMY BBS (14400/9600/2400): (310) 541-7299 RPV HOTLINE BBS (2400/1200): (310) 544-8977 NASA SPACELINK BBS (2400/1200): (205) 895-0028 Program Description ------------------- ORTHOGRAPHIC EARTH is a demonstration of the orthographic projection method of displaying the Earth intended for use on EGA and VGA display monitors. The program is NOT compatible with other display types. The orthographic projection used here does not include perspective. It assumes you are at a great distance from the Earth and can therefore see a complete hemisphere. The zoom feature is roughly equivalent to what would be seen using a variable zoom lens on a camera. ORTHOGRAPHIC EARTH is copyrighted software; you are hereby granted a non- exclusive license for non-commercial or educational use only. Agencies of the U.S. Government are also hereby granted a non-exclusive license for internal use. Use ORTHOGRAPHIC EARTH if you like it, discard it if you don't. There are no warranties of any kind. If you wish to use ORTHOGRAPHIC EARTH commercially, write for license information. The only request I make of users is that they take the time to complete and return the confidential questionnaire in file README. The questionnaire gives users a chance to offer comments and suggestions, and lets me know that people use and appreciate ORTHOGRAPHIC EARTH . Registration of ORTHOGRAPHIC EARTH is inexpensive and optional -- but will be appreciated and will encourage me to continue supporting and enhancing the program. The initial orthographic rotation equations were implemented in Microsoft QuickBASIC by Matthew Merrill for possible inclusion in his fine Solar Eclipse program SOLAR, also available on my bulletin board systems, and he was kind enough to send his code to me for evaluation and for possible use in my own program STSORBIT PLUS. My thanks to Matthew for his assistance, and I have in turn supplied my rewritten code to him. Watch for a similar projection in SOLAR! Thanks also to Mike Gardner and Joel Runes for their testing efforts, comments, and suggestions. The purpose of writing ORTHOGRAPHIC EARTH is two-fold: first, to demonstrate and test the orthographic projection algorithms and performance for use in Matthew Merrill's program SOLAR and my own program STSORBIT PLUS; and second, to provide an interesting and entertaining view of the Earth on suitable personal computers. Subject the license information in the preceeding paragraph, the program may be freely used and distributed. The current version is always posted on my bulletin board systems (above) or may be obtained on disk for a donation of US$10.00 (please specify 5- 1/4" or 3-1/2" disks). The program is set up with default values set to display the Earth centered approximately on Rancho Palos Verdes, California, near Los Angeles. By responding "N" to the prompt asking if default values should be used, the user may enter any desired zoom factor from 10% to 2000%, set the map center coordinates (latitude and longitude), and select whether or not to display a map grid. The prompts are self-explanatory; values enclosed in square brackets [...] are the default values which will be used if ENTER is pressed. Math Coprocessor Chip --------------------- The drawing time for ORTHOGRAPHIC EARTH is a function of the part of the Earth being drawn, the selected Zoom Factor, the speed of the computer, and whether or not it has a math coprocessor chip. A math coprocessor is now relatively inexpensive and is STRONGLY RECOMMENDED! For example, the time using the default values is approximately 3.5 seconds on a 486DX and approximately 30 seconds on a 286/287. Times for computers without math coprocessor chips will be MUCH longer, on the order of several minutes even for 386 systems! Users are also cautioned to be certain that the math coprocessor chip which is selected will execute properly. One math coprocessor chip, not Intel, failed to execute ORTHOGRAPHIC EARTH without errors. I was unable to determine if the math coprocessor failure was a generic problem associated with that brand or speed, if the problem was the design of the laptop computer being evaluated, or only a problem associated with that particular chip. If errors are detected, error messages will appear on the right portion of the display. On the five computers I normally use for testing, NO ERRORS EVER APPEARED! Command Line Options -------------------- The program is started by switching to the directory which contains all of the program files and entering a command at the DOS prompt: EARTH [options] No options are required. However, the following command line options may be included: /D Force automatic demonstration mode. This option overrides all other options EXCEPT /M and bypasses operator prompts. Automatically enables the display of selected locations. /E Force a VGA monitor to use the EGA mode. /L Enables the display of selected location/city names when Zoom Factor is equal to or greater than 100%. /M Force monochrome operation. Note that this command line option uses WHITE and LIGHT WHITE, usually available on monochrome monitors. /R Display the Earth in motion, using five degrees (if the drawing time is 10 seconds or greater) or two and a half degrees (otherwise) rotation per display. This option is ONLY available in EGA resolution and forces EGA emulation on VGA monitors. During the demonstration mode or if automatic rotation is enabled with the "/R" command line option AND the zoom factor is less than 100%, the zoom factor will be increased by 5% for each drawing cycle until it reaches 100%. For a demonstration of the rotation and zoom features, enter: EARTH /D at the DOS prompt. Press ESC to stop the automatic rotation and press ESC again to quit the program. Initial Menu ------------ Except when the program is started with the "/D" command line option (in which case map drawing begins immediately), the initial menu is presented to the user: ORTHOGRAPHIC EARTH VIEW Version 9233 by David H. Ransom, Jr. Accept default values? (Y/N) [Y]: Type in Zoom Factor (10-2000) [100]: Origin Longitude (-180 to +180) [-118]: Origin Latitude (+90 to -90) [34]: Display the grid? (Y/N) [Y]: Display locations? (Y/N) [Y]: In each case, the available choices or the acceptable range of numeric values are shown in parentheses and the default value (used when ENTER is pressed alone in response to the prompt) is shown in square brackets. Stopping EARTH -------------- When automatic rotation has been requested ("/D" or "/R" command line options), the message "Press ESC to stop" will be displayed. Pressing the key marked "ESC" will cause map drawing to stop, a "beep" will be heard, and the message will change to "Press ESC to quit". There may be a slight delay, as long as the current map drawing time, before the ESC key takes effect. When the message "Press ESC to quit" is displayed, pressing the key marked "ESC" will return you to the DOS prompt. Moving the Map Center and other options --------------------------------------- The map center is set initially by either selecting the default values (for Rancho Palos Verdes, California) or by entering latitude and longitude coordinates for a selected location. The initial map will always be drawn using these coordinates. The center of the map is marked by a small yellow circle in the center of the map area. When the message "Press ESC to quit" is displayed, you may press the "C" key (upper or lower case) and you will be prompted to enter new coordinates (latitude and longitude) for the map center. Any time the messages "PgUp/PgDn to ZOOM" and "Arrow Key to MOVE" are displayed, those keys are active. There is a built-in 0.5 second delay from the time one of these keys is pressed until the action is taken; this allows for multiple keypresses (to save intermediate map drawing time). The following keys are active: PgUp Increases the ZOOM to a maximum of 2000%. The size of the increment changes depending upon the current Zoom Factor. PgDn Decreases the ZOOM to a minimum of 20%. The size of the increment changes depending upon the current Zoom Factor. Home Returns the Zoom Factor to 100%. End Steps the Zoom Factor from 50% to 100% to 300% to 1000% to 2000% and then back to 50%. Up Arrow Moves the center of the map UP on the map. The size of the increment changes depending upon the current Zoom Factor. Dn Arrow Moves the center of the map DOWN on the map. The size of the increment changes depending upon the current Zoom Factor. Rt Arrow Moves the center of the map RIGHT on the map. The size of the increment changes depending upon the current Zoom Factor. Lt Arrow Moves the center of the map LEFT on the map. The size of the increment changes depending upon the current Zoom Factor. C Prompts the user to enter new map center coordinates. D Executes the demonstration sequence; identical to using the "/D" command line option. L Toggles the display of selected locations. R Enable automatic rotation. Note that on VGA displays, the display will switch to EGA mode for rotation. Location Data File ------------------ ORTHOGRAPHIC EARTH expects the geographic location data to be in file EARTH.LOC and it must be in the same directory from which the program is run. The file includes 350+ locations (cities), their coordinates, and certain information required by the program. The file is normal ASCII comma-delimited data. The following is a typical data line in the file: "London",-.1167,51.5,7,100 ---+-- ---+-- --+- + -+- | | | | | | | | | +--- Minimum zoom factor to display | | | | | | | +------ Color to display name (1 to 15) | | | | | +--------- Latitude in degrees | | | +--------------- Longitude in degrees | +----------------------- Location name The minimum zoom factors in file EARTH.LOC have been carefully selected so that the display is not too "cluttered" at a given zoom factor and so that location names near to each other do not overlap upon each other. Some care is required when adding new locations to avoid this problem! Note that location data is NOT displayed if the zoom factor is less than 100%. Acceptable zoom factors range from 100 to 2000. The "color" is a number from 1 to 15 according to the following table: Black = 0 Gray = 8 Blue = 1 LtBlue = 9 Green = 2 LtGreen = 10 Cyan = 3 LtCyan = 11 Red = 4 LtRed = 12 Magenta = 5 LtMagenta = 13 Brown = 6 Yellow = 14 White = 7 LtWhite = 15 The color Black is ignored and is only shown for completeness. If the color is a NEGATIVE number, the small circle marking the location of the city or feature will NOT be displayed. Thus, if the a mountain range or river is to be labeled, you may wish to set the color negative. The latitude and longitude are expressed in degrees and decimal fractions of a degree. Note that many atlases show a number such as "24.45" which is actually 24 degrees and 45 minutes (NOT 24.45 degrees!) and should be entered as "24.75" (24 + 45/60). There is no restriction on the length of the location name. However, avoid long names if possible so as to minimize location names displaying on top of one another. The program performs no error checking on the contents of file EARTH.LOC. Be sure to use a simple ASCII editor or use your word processor in the "Non-Document" mode when editing file EARTH.LOC. Very strange results can appear if the wrong data are present or the wrong number of items is in a data line! Map Database Detail ------------------- The map database used for ORTHOGRAPHIC EARTH is an adaptation of the Micro World Database II, placed in the public domain by Peter Pospeschil and Antonio Riveria. The original data were from the US Central Intelligence Agency (CIA) as distributed by the National Technical Information Service (NTIS). In order to obtain maximum performance, the map database has been converted to geocentric coordinates from the original latitude/longitude data and split into a data file (*.XYZ) and an index file (*.MCX). Several versions of the database are available, differing only in the amount of map detail included. Two such databases are included in the standard distribution of ORTHOGRAPHIC EARTH, and a third, more detailed database is available separately via my bulletin board systems. The available map databases are: EARTH4.* Lowest level of detail and required for operation of the program. EARTH3.* Optional intermediate level of detail selected (if present) for Zoom Factors of 300% or greater. EARTH2.* Optional highest level of detail, selected (if present) for Zoom Factors of 1000% or greater. ORTHOGRAPHIC EARTH checks to see which map databases are present in the default directory when it starts. The EARTH4.* files MUST be present. The remaining map databases are optional. Increasing the level of detail greatly improves the map appearance at higher Zoom Factors. As usual, however, there is no free lunch. EARTH3 requires approximately twice the time to draw the map as does EARTH4. Similarly, EARTH2 requires approximately three times as long as EARTH3 to draw a given map. Note that the EARTH2.* files are large, approximately 500K bytes, in order to yield much greater detail. Other map databases may be made available periodically, depending upon my available time and user interest. Comments and suggestions are welcome. Keyboard Rotation Modes ----------------------- Automatic Rotation may be initiated any time the message "Press ESC to quit" is displayed by pressing the "R" key (upper or lower case). The map will begin rotating at the current latitude. The demonstration (identical to that requested by the "/D" command line option), may be initiated any time the message "Press ESC to quit" is displayed by pressing the "D" key (upper or lower case). The demonstration automatically enables the display of selected locations. Version 9233, August 1992 ------------------------- -Location names added with file EARTH.LOC. As released, the file includes 365 selected cities around the world. -Display algorithm speed has been greatly improved for zoom factors larger than 100%. Typical improvement is a factor of 2 or 3 in mid and equatorial latitudes. The effectiveness of the new algorithm decreases as the map center moves toward the polar regions. -"C" command added to prompt the user for new map center coordinates while map is displayed. -"D" command added to initiate the demonstration sequence (identical to the sequence displayed with the "/D" command line option is used. -"L" command added to toggle location display. -"R" command added to initiate automatic rotation from the current map center. -All map database files from Version 9232 are unchanged and may be used with this version. -Various cosmetic changes. Version 9232, August 1992 ------------------------- -Added PgUp, PgDn, Home, End, and arrow keys to allow manual adjustment of the map center. -Corrected the direction of rotation of the Earth to correspond to the "real thing". Silly mistake! Thanks to Dave Mullenix for pointing it out to me. -Added the "/D" command line option to bypass all prompts and immediately do the demonstration. -Changed the map database from EARTH.MCP to EARTH.XYZ to eliminate the conversion of map coordinates from latitude/longitude to geocentric X-Y-Z coordinates. This typically saved an additional 25% in map drawing time. -Added additional error trapping to try and detect problems on certain machines. Version 9230, July 1992 ----------------------- -The original code for ORTHOGRAPHIC EARTH was written by Matthew Merrill to work out the details of the projection and test to the features for use in his program SOLAR. Motion and EGA were not included. -Version 9230 has been re-written by Dave Ransom to improve the speed performance, to include EGA compatibility for use on systems so equipped, and to allow for motion. Note that the EGA mode on some VGA-equipped systems does NOT always perform correctly or may appear "squeezed" vertically.