REQUIREMENTS

updated 2008-03-19 by EM

* Problem

The CNS device will help drivers by guiding them to their destination.

* Background information / Domain analysis

The CNS will be used in cars which can very in type. All types of roads have to be considered. Several companies will offer the CNS. CNS is using the GPS Satellite system to get it's location, which means that big buildings, bad weather and tunnels can impact the performance of the device.

* Environment  / system model

The device must be able to receive and use information from GPS (Global Positioning System) and RDS (Radio Data System). The GPS is used to get the location.
The device must be able to receive and use information from RDS (Radio Data System). RDS is used to get data about traffic jams and other traffic conditions.
The dimensions should be 12 x 12 x 6 cm (width x height x depth), with no greater deviation than 1 cm in each direction.
The screen dimensions must be at least 10 x 10 cm (width x height).
The screen must be touch sensitive (touch input).
The weight should stay below 200 gram.
Energy usage must be kept low, less than 5 Watt.
Buttons:
- power on/off
- select between views (discussed below)
- select
- "+" (zoom in)
- "-" (zoom out)

* Functional requirements

The device has two views (screens):
- main screen (default view on powering up)
- target selecting screen

Main screen:

The device must show a map on screen which shows:
- the car, marked by a green triangle pointed to the current driving direction (or the last driving direction when standing still), centered when no target is selected, and 2 cm from a border directing the opposite direction when driving to a selected target, updated each 1 seconds.
- the environment (choose map based on current location), updated each 5 seconds.
- the route / way to be taken, marked by small (3 mm) dots, updated each 60 seconds.
- if possible, the target, marked by a red circle (a dot of  6 mm), updated each 60 seconds.
- if existent, traffic jams or other problems, marked by a gray shade, updated each 60 seconds.
- current speed (bottom centered), updated each 1 seconds.
- current time (upper left), updated each 1 seconds.
- ETA (estimated time of arrival) (upper right), updated each 15 seconds.
- driving directions (arrows), updated each 3 seconds.

Tapping with a finger on the screen should set a new waypoint to which the driver should be taken first, before the final target is reached.

Target selecting screen:
The device must show a list on screen which shows:
- current target and waypoints, ordered on current distance, and tapping on one of those should select it. Pressing the "-" should delete the selected target / waypoint.
- nearby points of interest and important roads (highways) (first half of the screen), which can be added with "+" as waypoint or with "select" as destination (target).
- a touchscreen virtual keyboard input to specify a target, which can be added with "+" as waypoint or with "select" as destination (target). If the target is not recognized, then it should be shown in red, and not be added as waypoint or destination. If it is recognized, it should be shown in blue. A list of three suggested targets based on the current input should be shown below the text input.

* Usability

The usability is guaranteed by using only a few buttons and where possible the touch screen input. Users instantly see their current position and current map. The usability is further improved by fast updating important information and not showing too much information and arcane options.

* Performance

A performance minimum for updating driving directions, current location and so forth is given in the requirements for the main screen. The performance should allow the driver to act quickly on changing directions and to have a relevant and actual view on his/her environment.

* Accuracy

Here, maximum errors / deviations are given:
- current speed: max 10%
- current location: max 25 meters while driving (less is difficult with current GPS technology) max 12 meters while standing still
- current time: max 2 min.
- ETA: this is a guess, so up to 20% of the time to travel may be wrong 95% of time
- traffic jams: this depends on RDS data, so accuracy cannot be guaranteed by the CNS

* Quality

The device must withstand small drops of water (like when raining), sunshine behind glass, operating temperatures from -20 up to 80 degreed Celsius, drops from table-level heights, and firm finger presses on the touch screen.

The GPS and RDS modules must be replaceable with newer modules.

The internal map must be stored on a removable storage, so make updating possible.

The software should be programmed using the object oriented paradigm.