*Updated on 20th June, 2013 with “Method IV”.*

Consider this speed chart:

Begin (km) | End (km) | Speed (kmph) |
---|---|---|

0.00 | 5.00 | 31 |

5.00 | 10.00 | 29 |

10.00 | 15.00 | 17 |

And now the question: if you were to start driving at 00:00:00, what times should you be at the 4.32, 9.05 and 13.93 km marks? Simple, right?

Apprently not!

Different rally organizers have different ways of calculating ideal times. We have discovered 4 of these:

**Method I**

*Don’t discard any fractions in the intermediate steps, round up the seconds at the end.*

**Method II**

*Don’t discard any fractions in the intermediate steps, but truncate the seconds at the end.*

**Method III**

*Calculate ideal times for each speed sector separately, discard fractions of seconds at each sector, truncate the seconds at the end.*

**Method IV**

*Calculate ideal times for each speed sector separately, round up fractions of seconds at each sector, round up the seconds at the end.*

Sounds confusing just writing it! Let’s try and see if we can figure this out by answering the question using each of these methods.

**4.32**

*Method I*

Time = (4.32 – 0.00) / 31 = 0.139354839 hours

0.139354839 hours = 0.139354839 * 60 minutes = 8.36129034 minutes

0.36129034 minutes = 0.36129034 * 60 seconds = 21.677420 seconds

Rounding up, ideal time at 4.32 = 00:08:22

*Method II*

Time = (4.32 – 0.00) / 31 = 0.139354839 hours

0.139354839 hours = 0.139354839 * 60 minutes = 8.36129034 minutes

0.36129034 minutes = 0.36129034 * 60 seconds = 21.677420 seconds

Truncating, ideal time at 4.32 = 00:08:21

*Method III*

(4.32 is in the 1st speed sector)

Time = (4.32 – 0.00) / 31 = 0.139354839 hours

0.139354839 hours = 0.139354839 * 60 minutes = 8.36129034 minutes

0.36129034 minutes = 0.36129034 * 60 seconds = 21.677420 seconds

Truncating, ideal time at 4.32 = 00:08:21

*Method IV*

(4.32 is in the 1st speed sector)

Time = (4.32 – 0.00) / 31 = 0.139354839 hours

0.139354839 hours = 0.139354839 * 60 minutes = 8.36129034 minutes

0.36129034 minutes = 0.36129034 * 60 seconds = 21.677420 seconds

Rounding up, ideal time at 4.32 = 00:08:22

**9.05**

*Method I*

Time = (5.00 – 0.00) / 31 + (9.05 – 5.00) / 29 = 0.300945495 hours

0.300945495 hours = 0.300945495 * 60 minutes = 18.0567297 minutes

0.0567297 minutes = 0.0567297 * 60 seconds = 3.403782 seconds

Rounding up, ideal time at 9.05 = 00:18:03

*Method II*

Time = (5.00 – 0.00) / 31 + (9.05 – 5.00) / 29 = 0.300945495 hours

0.300945495 hours = 0.300945495 * 60 minutes = 18.0567297 minutes

0.0567297 minutes = 0.0567297 * 60 seconds = 3.403782 seconds

Truncating, ideal time at 9.05 = 00:18:03

*Method III*

9.05 is in the 2nd speed sector

Time to complete 1st speed sector = (5.00 – 0.00) / 31 = 0.161290323 hours

0.161290323 hours = 0.161290323 * 60 minutes = 9.67741938 minutes

0.67741938 minutes = 0.67741938 * 60 seconds = 40.6451628 seconds

Truncating, ideal time at end of 1st speed sector = 00:09:40

Time at 9.05 = 00:09:40 + (9.05 – 5.00) / 29 = 00:09:40 + 0.139655172 hours

0.139655172 hours = 0.139655172 * 60 minutes = 8.37931032 minutes

0.37931032 minutes = 0.37931032 * 60 seconds = 22.7586192 seconds

Truncating, ideal time at 9.05 = 00:09:40 + 00:08:22 = 00:18:02

*Method IV*

9.05 is in the 2nd speed sector

Time to complete 1st speed sector = (5.00 – 0.00) / 31 = 0.161290323 hours

0.161290323 hours = 0.161290323 * 60 minutes = 9.67741938 minutes

0.67741938 minutes = 0.67741938 * 60 seconds = 40.6451628 seconds

Rounding up, ideal time at end of 1st speed sector = 00:09:41

Time at 9.05 = 00:09:41 + (9.05 – 5.00) / 29 = 00:09:41 + 0.139655172 hours

0.139655172 hours = 0.139655172 * 60 minutes = 8.37931032 minutes

0.37931032 minutes = 0.37931032 * 60 seconds = 22.7586192 seconds

Rounding up, ideal time at 9.05 = 00:09:41 + 00:08:23 = 00:18:04

**13.93**

*Method I*

Time = (5.00 – 0.00) / 31 + (10.00 – 5.00) / 29 + (13.93 – 10.00) / 17 = 0.564880586 hours

0.564880586 hours = 0.564880586 * 60 minutes = 33.8928352 minutes

0.8928352 minutes = 0.8928352 * 60 seconds = 53.570112 seconds

Rounding up, ideal time at 13.93 = 00:33:54

*Method II*

Time = (5.00 – 0.00) / 31 + (10.00 – 5.00) / 29 + (13.93 – 10.00) / 17 = 0.564880586 hours

0.564880586 hours = 0.564880586 * 60 minutes = 33.8928352 minutes

0.8928352 minutes = 0.8928352 * 60 seconds = 53.570112 seconds

Truncating, ideal time at 13.93 = 00:33:53

*Method III*

13.93 is in the 3rd speed sector

Time to complete 1st speed sector = (5.00 – 0.00) / 31 = 0.161290323 hours

0.161290323 hours = 0.161290323 * 60 minutes = 9.67741938 minutes

0.67741938 minutes = 0.67741938 * 60 seconds = 40.6451628 seconds

Truncating, ideal time at end of 1st speed sector = 00:09:40

Time to complete 2nd speed sector = 00:09:40 + (10.00 – 5.00) / 29 = 00:09:40 + 0.172413793 hours

0.172413793 hours = 0.172413793 * 60 minutes = 10.34482769 minutes

0.34482769 minutes = 0.34482769 * 60 seconds = 20.6896614 seconds

Truncating, ideal time at end of 2nd speed sector = 00:09:40 + 00:10:20 = 00:20:00

Time at 13.93 = 00:20:00 + (13.93 – 10.00) / 17 = 00:20:00 + 0.231176471 hours

0.231176471 hours = 0.231176471 * 60 minutes = 13.8705883 minutes

0.8705883 minutes = 0.8705883 * 60 seconds = 52.235298 seconds

Truncating, ideal time at 13.93 = 00:20:00 + 00:13:52 = 00:33:52

*Method IV*

13.93 is in the 3rd speed sector

Time to complete 1st speed sector = (5.00 – 0.00) / 31 = 0.161290323 hours

0.161290323 hours = 0.161290323 * 60 minutes = 9.67741938 minutes

0.67741938 minutes = 0.67741938 * 60 seconds = 40.6451628 seconds

Rounding up, ideal time at end of 1st speed sector = 00:09:41

Time to complete 2nd speed sector = 00:09:41 + (10.00 – 5.00) / 29 = 00:09:41 + 0.172413793 hours

0.172413793 hours = 0.172413793 * 60 minutes = 10.34482769 minutes

0.34482769 minutes = 0.34482769 * 60 seconds = 20.6896614 seconds

Rounding up, ideal time at end of 2nd speed sector = 00:09:41 + 00:10:21 = 00:20:02

Time at 13.93 = 00:20:02 + (13.93 – 10.00) / 17 = 00:20:02 + 0.231176471 hours

0.231176471 hours = 0.231176471 * 60 minutes = 13.8705883 minutes

0.8705883 minutes = 0.8705883 * 60 seconds = 52.235298 seconds

Rounding up, ideal time at 13.93 = 00:20:02 + 00:13:52 = 00:33:54

To summarize:

Method I | Method II | Method III | Method IV | |
---|---|---|---|---|

4.32 | 00:08:22 | 00:08:21 | 00:08:21 | 00:08:22 |

9.05 | 00:18:03 | 00:18:03 | 00:18:02 | 00:18:04 |

13.93 | 00:33:54 | 00:33:53 | 00:33:52 | 00:33:54 |

So how do you get around this?

Before the rally, talk to the organizer and figure out how they are calculating ideal times. If it is one of the 4 ways described above, go to “Results Type” in your TSDMeter Settings screen and choose “Computer” (*Method I*), “PB” (*Method II*), “Calcutta” (*Method III*) or “HMA” (*Method IV*). If not, let us know!