Description

GreatCircle can be used in conjunction with the GeoDB database application. You can think of GreatCircle as the computation engine and GeoDB holds the location information. However, as of Version 2.0, you can input locations manually.

If you do not have GeoDB installed in your handheld you may also want to install the GeoDB application available here http://davidbray.org/palm/geodb11.zip.

GreatCircle displays the following data:

• Latitude and longitude of two Earth locations -- selected from the GeoDB database and/or manually.
• The great circle distance between the locations in either: kilometers, nautical miles, miles, meters or feet.
• The great circle bearing angle from the 'From' locations to the 'To' location.

We hope you find GreatCircle a useful adjunct to your Palm applications.

Installation

The gc20.zip archive file includes:

gc20.prc

The executable file to be installed in your Palm.

MathLib.prc

The required mathematics library -- V1.1

gc.html

This file -- gc.html

gcmain.gif, gcmenu1.gif, gcmenu2.gif, gcmenu3.gif, gcempty.gif

Images for gc.html

If you do not have GeoDB you should install it. It will make input of location data much easier. To do this download http://davidbray.org/palm/geodb11.zip, read the geodb.html documentation with your internet browser and install GeoDB accordingly.

The included MathLib.prc is the latest version (V1.1 dated 4/14/1999). You may update with this one if you desire.

GreatCircle will be placed in the 'unfiled' category. You may move it to any category.

Using the Application

• From: This heading is also a button to:
  1. Open a new page containing the GeoDB database, listed in the upper right, so that you can select the 'From' location, or
  2. Open a location form to be filled in manually, when 'Pen' is selected.
  GeoDB location selection is done simply by scrolling to the desired location and tapping its name to highlight it. Then tapping the 'Select' button the display will then switch back to the main GreatCircle page and the location data will be filled.
  If you exit the GeoDB page (using Select) without highlighting a record the previously selected location is retained.

  You may use the Data menu (discussed below) to select the desired Database or Pen input before making the From or To selections.
  

• To: This heading is also a button which functions exactly as the 'From' heading button except it fills the 'To' latitude and longitude.

• Distance: This is the distance between the 'From' and 'To' locations in the desire units set using the Units menu, and with the numbers of decimal digits set using the Data/Decimal Digits menu.

• Bearing: This is the great circle bearing angle between the 'From' and 'To' locations, respectively, in the desire units. North is 0 degrees (0 grads) and rotates clockwise. East is 90 degrees (100 grads), etc.

Other controls are available in the 'Data' and 'Units' menus, discussed next.

Data Menu

• Database: This menu item allows you to open another database currently installed in Palm OS memory.
  Tapping Database pops up a dialog box to cycle through all of GeoDB's installed databases. Once a database is Opened the current database is closed (but not deleted) and the opened one becomes active.

• Pen: This menu item allows you to manually enter data for a location.

• Decimal Digits: This menu item allows you to select the number of decimal digits to be displayed for the distance and bearing.

• About -- The About menu tells you the current version number, the build number, and a brief description of GreatCircle.
  Future releases will change the version number only for major changes. All changes will have an increasing Bld: (build) number.
  To be sure that your version is up-to-date check the Bld: number.

Units Menu

• Kilometers -- Display distance in kilometers (km).
• Naut. Miles -- Display distance in nautical miles (nm).
• Miles -- Display distance in statute miles (mi).
• Meters -- Display distance in meters (m).
• Feet -- Display distance in feet (ft).
• Degrees -- Display great circle bearing angle in degrees.
• Grads -- Display great circle bearing angle in grads (grads).
  (There are 100 grads and 90 degrees in a right angle.)

Contact Info

The Bray Palm OS Page can be found at: http://davidbray.org/palm/

Registering

This archive may be freely redistributed, provided it is made available only in its complete, unmodified form with no additional files and for noncommercial purposes only.
Any other use must have prior written authorization from David W. Bray.

Unauthorized commercial use includes, but is not limited to:

• GreatCircle itself as a product for sale.
• Accompanying a magazine, book or other publication for sale.
• Distribution with 'Media', 'Copying' or other incidental costs.
• Available for download with access or download fees.

Disclaimer

Foot Notes

^*Program Changes in Version 2.0

1. Added dummy button for refresh in OS5 (V1.2 Bld:308)
2. Added 'Find' button (V1.2 Bld:309)
3. Added 'Database' menu item to allow selection of GeoDB databases. (V1.3 Bld:315)
4. Changes to improve OS4 compatibility (V1.3 Bld:316)
5. Changed internal data structure to allow From/To locations to be in different databases. (V2.0 Bld:404)
6. Changed the algorithm for more accuracy, thereby allowing very small distances to be displayed. (V2.0 Bld:404)
7. Added "Pen" (manual) location input. (V2.0 Bld:404)
8. Added Feet, and Meters to the Units menu. (V2.0 Bld:404)
9. Added selection of result precision. (V2.0 Bld:404)

The current Bld: is 404.