About

Background
Switchback Software develops applications for the iPhone and iPod touch for use with rally car races. As rally hobbyists, we believe the hardware of the iPhone and iPod touch can be leveraged to provide rally drivers and navigators (co-drivers) an exceptional rally computer.

What is Rallying?
From Wikipedia.org:

Road rallies are [...] held on highways open to normal traffic, where the emphasis is not on outright speed but on accurate timekeeping and navigation and on vehicle reliability, often on difficult roads and over long distances. They are now primarily amateur events. There are several types of road rallies testing accuracy, navigation or problem solving. Some common types are: Regularity rally or a Time-Speed-Distance rally (also TSD rally, testing ability to stay on track and on time),[5] others are Monte-Carlo styles (Monte Carlo, Pan Am, Pan Carlo, Continental) rally (testing navigation and timing), and various Gimmick rally types (testing logic and observation).

[...]

Club rallies (e.g. road rallies or regularity rallies) are usually run on public roads with an emphasis on navigation and teamwork. These skills are important fundamentals required for anyone who wishes to progress to higher-level events. (See Categories of rallies.)

Aspects of Regularity Rallies

A typical regularity rally may run for a few hours or it may run over a series of stages over a few days. At the start, competitors are usually briefed about the event and may be required to submit their cars for inspection. Each team is given a route schedule prior to the race. This schedule contains information that the navigator will use to try to keep to the specified route and it contains information about the designated speeds and times for each segment of the route. On some rallies, more than one type of schedule may be prepared for different types of competitors.

Once a team is prepared, they will usually start the rally at a specific time unique to them. Along the route, the team will encounter marshals. The position of the marshals is usually not known to the teams. The time at which the team arrives at each marshal is recorded and used in the scoring. In some cases the marshals are hidden from view. Teams may also encounter open sections where they are guaranteed not to encounter marshals and are not subject to any time penalties. There may be various other features along the route including points at which teams must wait for an ‘exact time of departure’, points at which teams must record their own times, etc.
Every regularity rally should have a deterministic route schedule. This means that the organisers can work out the exact times that should be recorded for each team at all the relevant points along the route. The difference between a team’s actual times and the correct times determine their penalties. (Lateness and earliness both attract penalties.) The team with the lowest number of penalties wins.

It is usually possible to compete in a regularity rally using only a car (or sometimes a motorcycle) and a stopwatch, but many regularity rallyists use various devices in an attempt to reduce their total penalties. The rules of each rally determine which devices are permitted. Some common aids include:

• Odometer: Odometers can range from the odometer included on the dashboard of most cars to specially manufactured rally odometers.
• Speedometer: As with odometers, speedometers used by rallyists range from those built into the vehicle to specially manufactured rally speedometers.
• Stopwatch: Accurate time is essential in regularity rallying.
• GPS: GPS units provide speed, distance and navigational data, but there is some debate as to their usefulness in regularity rallying.
• Computer: Computers ranging from custom-made units to laptops can be used in some regularity rallies.

What is Dead Reckoning?
Dead reckoning is the process of estimating one’s current position based upon a previously determined position, or fix, and advancing that position based upon known or estimated speeds over elapsed time, and course.