GPS Rally Odometer

This iPhone app is designed for various types of automobile rallies that require measurement of time, speed, and distance between segments of the rally route including stages and checkpoints.

To make sure that all initial conditions are set properly when using GPS, touch the "Reset/Pause" button and choose the "Reset, New Rally" option.

Begin computing distance, time, and speed by touching the "Start Rally" button. Alternatively, when the app has been either restarted to zero distance or paused, you may select a minute for the "Next Starting Time."

GPS inputs trace the path along the rally route. From time to time you may measure time, speed, and distance for a stage or a checkpoint. These measurements will be stored in a table and the points will be indicated on a map.

An alternative view showing the odometer measurements more prominently is available by touching the "Mode" button in the upper menu bar.

Options include subtraction of distance when you travel off course. A toggle button switches between on course (blue line) and off course (red line) travel.

Distance measurement can be set to miles or kilometers and time measurement can be set to minutes and seconds or decimal minutes. The distance may be displayed with either 2 or 3 digit precision. Make your selections in the app preferences in the iPhone Settings linked with a "sprocket" button beside the "About" button.

You may fine-tune the app's distance and time figures to the rally's official measures with the options in the Adjustments popup. Unlock to make adjustments and lock to save the changes you make and to prevent inadvertent changes.

There are two ways to adjust distance measurement. An adjustment factor between 0.800 and 1.200 can be used to synchronize distance measured by GPS to rally distance. This adjustment applies to all distance measurements shown after the adjustment has been selected. Also, you may pause or gain time on a particular stage by adding or subtracting time from the reported time on a stage.

If the app's Time of Day (T.O.D.) clock does not match the rally's official clock, you may synchronize the two clocks by making small adjustments as required.

A log view shows additional information at each stage including the latitude, longitude, and the current speed at the time the New Stage button was touched.

For better GPS reception and improved accuracy while racing, third-party wireless GPS receivers are recommended. This app has been tested with Bluetooth connectivity to a Dual XGPS150A Universal GPS Receiver.

Disclaimer: Continued use of GPS running in the background can dramatically decrease battery life.


changes in version 5.0
  • Added a second presentation view where the odometer measures are more prominently displayed and you may toggle between Odo A and Odo B with the flip of the "switch." You may toggle between presentation views with the "Mode" button in the upper menu bar. The default mode shows a view with a map and a table of each stage or control point selected
  • Some bug fixes
  • Various GUI enhancements
changes in version 4.9
  • Added a more complete and separately viewable log of stages or controls including the latitude, longitude, and current speed at the time the stage or control is recorded
  • Various code improvements for better performance
changes in version 4.8
  • Changed minimum required iOS version to 10.3 to resolve some issues and to accommodate new technology
  • Reduced from 10 meters to 1.5 meters (33 feet to 5 feet) the minimum distance computed from a pair of GPS coordinates suitable for incrementing distance. This improves displayed distance measurement to 0.001 mile accuracy, which is especially important at speeds less than 15 mph
  • Various changes to accommodate iOS 11
changes in version 4.6
  • Added estimate of distance travelled between GPS distance signals. This improves the accuracy of the distance measurement and importantly reduces the large incremental changes in distance and speed computations and displays
  • GUI modifications to improve readability
changes in version 4.3
  • Added option to adjust T.O.D. clock to match official rally clock, if necessary
  • Added option to display distance to either 2-digit or 3-digit precision. The option is available in the app settings
  • Changed the way you may enter time Gains or Pauses. A slider will allow you to select half-minute increments quickly and easily

revised: March 24, 2018