The CZ Rally app is designed for a particular type of automobile rally called a Control Zone Rally or for any rally with a single stage having a single average speed the must be maintained over the entire stage.

In a Control Zone Rally you are given some combination of time, speed, and distance required to traverse a course from a defined starting point to a finish line. Your starting time will also be assigned as some minute or half minute after the hour in which the race begins.

Set these conditions by touching the Setup button to access a screen where the starting time, course time, course speed, or course distance can be entered. When you've set these conditions, touch the green New Rally button in the upper right hand corner of the screen to return to the main screen where a map and your progress will be recorded.

The Start Now! button allows starting a new rally or a leg of a rally with a single click. This allows you to preset time, speed, and distance for the upcoming leg, and to touch the button exactly when the new leg begins. In other words, with the Start Now! feature, the user doesn't wait until the clock ticks down to a defined starting minute or minute and a half.

GPS inputs trace the path along the rally route. Measurements of actual versus ideal time and distance will be shown in seconds ahead or behind schedule. From time to time you may also record time and distance covered an the error against the ideal course time and distance by touching the "Add Split" button.

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. Time splits can be set for automatic error checks.

Distance measurement can be set to miles or kilometers and time measurement can be set to minutes and seconds or decimal minutes. Make your selections in the app preferences in the iPhone Settings.

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

Distance measurement can be set to miles or kilometers and time measurement can be set to minutes and seconds or decimal minutes. Make your selections in the app preferences in the iPhone Settings linked with a "sprocket" button beside the "About" button..

The app is designed to adjust the GPS coordinates of a moving vehicle owing to the time between reception of new GPS signals and to the time lag between the time the signal was generated from satellites and the time when processing actually occurs in the app.

Also, you may adjust the location coordinate by the distance between the GPS receiver in the car (either the iPhone or iPad) and the position on the car where a rally may measure time or location at timed controls (sometimes this is the front of the car or the center of the front wheels).

These three potential errors in coordinate measurement are discussed at length in a 6-part thread in the Facebook "Road Rally Tech Talk" forum.

To fine-tune the app's distance between GPS receiver and front wheels (if necessary) and clock 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.

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

A heads-up display for the Driver shows the time error, the time remaining for the course, the distance error, and the average speed for the course.

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