Route matching not only snaps the fuzzy GPS points onto the roads, but also provides all the map context needed for safety analytics, risk assessment, cost estimations etc.
Road link attributes, like speed limit or slope, can be retrieved directly in the response. This is an alternative to calling Map Attributes API along the route, for select use cases. Use the request parameter
&attributes=... list of layers and attributes out of each layer ...
When to retrieve attributes directly in the route match call and when to fetch them afterwards from Map Attributes API?
In general, a matched route spans a few tiles only, because the major part of a route is on functional class 1 roads (motorways) that are stored in layers with large tiles. Hence, after a route match, the distinct set of tiles to load from the Map Attributes API should rarely exceed 20 or 30, resulting in a few Map Attributes API requests, because each Map Attributes API request can ask for multiple tiles of multiple layers.
The advantage of using Map Attributes API is that the retrieved full tile content can be cached for up to a month, and hence repeated transmission is avoided, if the assets are repeatedly driving in similar areas, which is usually the case.
However, asking for the attributes directly in the route match request is easier on client side, and only the data of the links along the route are actually transferred. Where this is important, attributes should be fetched directly with the route match call.
Note: When using the more attributes option additional transactions are counted similarly as if requested directly from Map Attributes.
Currently, the following layers can be requested:
ADAS_ATTRIB_FCn BASIC_HEIGHT_FCn DISTANCE_MARKERS_FCn LANE_FCn LINK_FCn LINK_ATTRIBUTE_FCn LINK_ATTRIBUTE2_FCn LINK_TMC_FCn ROAD_ADMIN_FCn ROAD_GEOM_FCn ROAD_NAME_FCn ROAD_ROUGHNESS_FCn ROUNDABOUT_FCn SPEED_LIMITS_FCn SPEED_LIMITS_COND_FCn SPEED_LIMITS_VAR_FCn TOLL_BOOTH_FCn TOLL_LINK_FCn TRAFFIC_PATTERN_FCn TRAFFIC_SIGN_FCn TRUCK_SPEED_LIMITS_FCn TRUCK_RESTR_FCn TURN_RESTR_FCn
Please contact Technical Customer Support how to retrieve other map attributes.
HERE Route Matching v8 is based on and offers simple on access to all HERE map data and customers' private map data. Therefore the HERE Route Matching v8 works with multiple maps, e.g.:
HERE Route Matching v8 uses HERE maps and customers' maps. A map is a collection of layers. A layer contains map objects with geometry and attribution. A layer's content is cut into tiles, for efficient search, map display, routing, map matching and driver warnings.
Resource /1/doc/maps.html shows the available maps. The core map content is divided into regional maps, but can always be used as a single, global map. Other content is delivered in dedicated - mostly worldwide - maps.
THE HERE Route Matching v8 groups HERE map data into thematic layers. Each layer contains rows (map objects), like road segments, points of interest, river polygons - their geometry and attributes (columns). Some layers just extend the objects of another layer by additional attributes, like the speed limits for a road segment layer. Layers without geometry are called "attribute" layers, as opposed to "geometry" layers.
Layers are made for certain use cases:
Use the appropriate layer to request only the relevant data to minimize data transfer. Since the layers offered by the HERE Route Matching v8 change often, check the currently supported layers with the resource layers.
Resource /1/doc/layer.html shows the attributes (columns) of a speed limit layer.
Example speed limit layer tile content:
Sometimes, the order of the columns in the layers may change and new columns may be introduced. Make sure that your applications take this into account.
A typical example for using layers is when you need to retrieve information along a particular route. A route usually starts on smaller roads, follows bigger roads, then stays on motorway-like roads for the main part of the journey, and finally returns onto smaller roads when approaching the destination. Retrieving all the information about smaller roads along the whole route can result in an overwhelming amount of data transfer. Therefore, road link related layers are split into five layers each corresponding to the functional classes used in HERE maps. To keep the data processing simple, each layer consists of a single flat table with simple records in numbers or text strings represented as attribute key/value pairs.
To reduce the volume of data transferred, some columns are denormalized or encoded. Denormalization is done by storing a list of comma-separated values in a column. Encoding is done by using abbreviations or numbers to represent static string values, bit mask for a vehicle's type, and so on. For example, each geometry is delivered in a single column per coordinate (x, y, z-level columns). Each coordinate is a comma-separated list of integer values in 1E-5 WGS degrees (or 1E-7 for ADAS accuracy). The first value is absolute. Each subsequent value is relative to the previous value; a zero (0) value is reduced to an empty string.