Accuracy & error calculation

Regarding Precision Accuracy

Since the GPS satellites are controlled by the US Department of Defense they do have a very high level of accuracy, however a multipath due to reflections from buildings and so on could cause errors to occur.

Regarding the Properties of the GPS Electro-Magnetic Waves and Signal Reception

If there are any obstacles between the GPS antenna and the GPS satellite, electromagnetic-waves cannot be received from the satellite.

It is also impossible to use GPS positioning in the following locations as at least three simultaneous electromagnetic-waves are necessary to take measurements.

Also, if there are any obstacles around the GPS antenna, electromagnetic-waves cannot be received from the satellite.


In tunnels	If the immediate area is enclosed by large objects such as skyscrapers	In underground buildings and indoor parking lots

In places with a lot of overgrown trees and so on	Under elevated roads	Roads at the base of cliffs and caves

Because the GPS satellite is in orbit around the earth, the reception status for the electromagnetic waves changes depending on their position at that point in time, even if your vehicle is in the same place. Also, electromagnetic-waves from satellites near the horizon can be easily influenced by surrounding obstacles.

At times, satellites under the control of the US Department of Defence will intentionally drop positioning accuracy.

Regarding Errors in Current Position Display

To pinpoint the current position, the unit uses information from GPS satellite electromagnetic waves. If any of these contain errors, the current position may not match the actual position.

Regarding Vehicle Position Detection Correction Using Map Matching

Map matching is a method of comparing information on the current position acquired by GPS and so on, with the road driven up to that point, and correcting the current position based on the most likely road.

This unit uses information on the current position combined with independent navigation and satellite navigation and matches it to the shape of the road to create the correction.

However, as it cannot avoid the error margins at the current position, the current position may shift away from the actual position even when correcting using map matching.

Also, the vehicle marker may shift if the map data and the shape of the road being driven on differ.

Actual Vehicle Swept Path

Vehicle swept path acquired from each sensor

Corrected using map matching on the screen

: Because it takes a short time for operations to stabilise just after turning on the unit, the vehicle mark may not immediately match the vehicle as it moves. After driving for a while, operations stabilise, and the marker should match the actual driving position.

Regarding the Accuracy of the Current Position and Route Navigation

As in the following images, an accurate display of the current position or route navigation may not be provided, however this is not an indication of a malfunction in the unit, but is due to road conditions or driving conditions.


Shows the current position on roads running in parallel.	Shows the current position on the other road when there is a narrow fork in the road.	Shows the current position on the road ahead or behind when turning right or left.

Shows the current position when travelling up a steep hill.	Shows the current position if the road continues to curve around on itself in the same direction.	Shows the current position after a sudden change in lanes.

Shows the current position when the vehicle is on a parking garage turntable and the ACC is off.	Shows the current position when driving on snowy roads where the vehicle may slip easily, or when driving with snow chains.	Shows the current position in the last confirmed position before moving when using another means of transport, such as a ferry, until the GPS can determine the new position.

It actually navigates through roads that cannot be driven (no entry and so on).	Shows the current position when reversing.

Regarding Roads and Place Name Data

Because road and place names may change after the map data has been created, there may be times when road and place names do not match.

When no information is available in the map data, function such as display of road names, searching for facilities, and route guidance cannot be used.

Regarding Route Navigation


It may deviate from the route navigation when there is a turn at an intersection etc., and a mistake in the voice navigation.	When searching for the route, it may take the long way around.	The route may need you to make a U-turn during navigation.

When driving on a straight road, information may be displayed indicating that you should go straight ahead.(When the intersection shape is not clear and so on.)	The navigation may not indicate that the road curves at an intersection.	The navigation may guide you back to a waypoint if you search for the route again after passing the waypoint and are heading to your destination.

Many place names may be displayed when navigating a district.	Always drive by following the actual traffic regulations.

When searching for a route, it may not be displayed quick enough for the next left or right turn.

Performing a new search while travelling at high speeds may take some time.

The route may not change even after performing another search.

When isolated locations or roads with no surrounding available information are set as the current position/destination, you may not be able to search for a route.

A route may not be displayed when the current position is close to the destination.

Even if you select toll roads as a priority, the route may not guide you through a toll road.

In a similar way, toll roads may be displayed even if you prioritise other roads over toll roads.

(When it is possible to select a toll road or a normal road to create the route, priority is given to the user's toll road preference - use toll roads, or avoid toll roads.)