TSD Rally Computer

TSD Rally Computer is an iPad app designed to simplify computations necessary to navigate a traditional time-speed-distance (TSD) automobile rally with manual input of odometer distance.

A TSD rally is comprised of stages set along a route defined by written instructions. The first stage is the Odometer Check stage that allows you to calibrate your car’s odometer with that of the Rallymaster’s odometer.

In later stages you will follow a course at a particular average speed that will change from time to time at places that are generally unknown in advance.

In order to drive the course at the prescribed speeds, you must keep track of your odometer reading along the way. You may get the odometer measurement from any external GPS or precision odometer or third-party app you like

Apple-approved MFi game controllers can be used with the TSD Rally Computer when connected via Bluetooth.

The TSD Rally Computer allows you to do all this and much, much more. For more documentation, download the User's Guide.

Features of the TSD Rally Computer:

  • Log table that records time, speed, distance, and error for various actions such as Control splits and CAST changes
  • Clock time in either minutes and seconds or decimal minutes
  • The clock is a 24-hour clock to simplify computations
  • Distance measurements in either miles or kilometers
  • The car's odometer distance measurement may be the same or different than the official rally odometer distance measurement
  • One button click to reset default conditions for starting a rally
  • The internal iPad clock can be adjusted to match the official rally clock
  • The car's odometer reads up to 99.99 miles or kilometers and can be incremented by simple button clicks including buttons to increment by one of four amounts shown in the selector below the odometer. The optional amounts are 1.00, 0.50, 0.10, and 0.01
  • A Settings button in the top menu bar allows access to the app settings from within the running application including settings for display of certain items
  • Calibrate the car's odometer to the official rally odometer on the odometer check stage via a popup
  • Change average speed (CAST) with a scroll wheel and make incremental changes with either of two buttons
  • Preselect the next CAST to simplify the process of changing speed on each leg
  • The CAST button can be deactivated to prevent accidental touching
  • Preset CAST speeds and times to travel one mile or kilometer at those speeds with via a popup
  • Use scroll wheels to quickly and easily change time, speed, or distance throughout the app
  • As time passes and as the car's odometer is incremented, the actual speed over the course is compared with the expected speed. The difference in seconds or hundredths of a minute is displayed along with an indication to either "Speed Up" or "Slow Down" to stay on pace
  • Pause or gain time on any leg with a toggle button and at times chosen with scroll wheels
  • Handle off-course corrections to time and distance with a toggle button
  • Record "splits" of time and error at any time with a Control button
  • Set next departure time (NDT) from a checkpoint and have the time tick down on the master clock and autostart CAST
  • Use a handy popup to perform ad hoc computations of time, speed, or distance given any other two variables
  • TSD Remote is a compatible heads-up display for the driver that synchs information with the navigator's TSD Rally Computer
  • Apple-approved game controllers are supported via Bluetooth
  • A pair of stopwatches with pause and split times may be operated at any time. You may toggle between each stopwatch with the touch of a button

Note: Use of the TSD Rally Computer during any particular rally will be subject to the rules and instructions governing the rally and may also define your category or class among race participants. Some rallies may, in fact, prohibit use of this app.


changes in version 7.5
  • Updated to reflect changes to iOS and newer versions of the iPad
  • New GUI display for improved visibility and readability in daytime or nighttime
  • Various bug fixes and code improvements
  • More consistent color coding of buttons and other objects
  • Code improvements and error checking to mitigate inadvertent actions and data inputs
  • Added several notes on the displays to guide user actions and to identify active conditions such as when the user is operating in "off course" mode
  • Removed links to Facebook and Twitter
changes in version 7.3
  • Added a "sprocket" button to the top menu bar to access the app settings directly from inside the app
  • In the app settings there are three new appearance options (1) to display the odometer increment buttons on the left side, the right side, or both sides; (2) to show or hide the action log table; and (3) to show or display the dual stopwatches and their activation button
  • The odometer increment buttons can selectively adjust by +/– 1.00, 0.50, 0.10, or 0.01
  • Holding down on any of the four manual odometer distance input buttons will automatically increment every 0.2 seconds
  • To make it easier to add new preset CASTs, there are two new buttons on the CAST Presets popup for quick selection of speed in increments of plus or minus 1 mph or 1 kph
  • Various GUI changes to font and object colors have been made to improve readability
  • Various code changes to enhance performance and simplify processing
changes in version 7.1
  • Added a pair of stopwatches with pause and split times that can be operated at any time. You may toggle between each stopwatch with the touch of a button
  • Code improvements for simplification and performance
changes in version 7.0
  • Major improvements to Next Departure Time (NTD) including quick adjustment to next whole minute and automatic CAST when countdown reaches zero
  • Removed am/pm time with a new default to a 24-hour clock to improve computations
  • Changes to the color-coding of log entries
  • New documentation including game controller button mapping
  • Code improvements and simplification to improve performance
changes in version 6.1
  • Fixed bug that erroneously allowed you to delete preset CASTs by swiping and drop below the five CAST minimum needed to operate the app. Having fewer than five preset CASTs resulted in a fatal app crash
  • This update is essential for all app users. If your app has crashed previously, delete it from your iPad before installing this update

revised: May 10, 2021