ISYS Systems Ltd.

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• All Products
• Address Location
• ASP.NET AJAX Mapping System
• Custom Mapping
• Find Nearest Road
• Geo Fence
• London Congestion Charge Zone
• London Low Emission Zone
• Multi-Layer Mapping
• Postcode Location
• Route Deviation
• Route Planning

London Low Emission Zone

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Detailed mapping of the London Low Emission zone and a program module to determine if a vehicle location is within the London Low Emission Zone. The vehicle location and direction (if known) are used to determine which road a vehicle is on.

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London Low Emission Zone Map (Larger sample)

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In addition to using a simple geo fence area hit test, this module uses a vehicles Latitude/Longitude location and direction to compute precisely which road a vehicle is on. This is then compared to a database of roads that are known to be within the London Low Emission Zone to determine whether or not the vehicle is within the London Low Emission Zone.

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ISYS Know-How

Even with a 100% accurate vehicle location, vehicle direction is still necessary to determine which road a vehicle is on.

The majority of the map databases from Ordnance Survey and all the map databases from other suppliers (e.g. Navteq, TeleAtlas) contain road centreline coordinates, not road edge coordinates. In addition, coordinates for side roads are 'extended' so as to join the centre-line of the roads they intersect.

A vehicle travelling down a road will generally be to one side of the road centre-line and will cross these side road 'extensions' at every intersection. If the vehicle direction is not taken into account and you simply choose the ‘closest’ road to a vehicle location, then, in the vicinity of road intersections a side road 'extension' will invariably be closer.

By using the vehicle direction and comparing it to the road direction, it is possible to eliminate side roads as possibilities and correctly identify the road a vehicle is on.