read

Read HERE HD Live Map layer data

Syntax

layerData = read(reader,layerType)

layerData = read(reader,layerType,fields)

Description

layerData = read(reader,layerType) reads HERE HD Live Map^[1] (HERE HDLM) data of a specified layer type from a hereHDLMReader object and returns an array of layer objects. These layer objects contain map layer data for the HERE map tiles whose IDs correspond to the IDs stored in the TileIds property of reader.

layerData = read(reader,layerType,fields) returns an array of layer objects containing data for only the required fields, such as the HereTileId field, and for the specified fields. All other fields in the returned layer objects are returned as empty: []. If you do not require data from all fields within the layer objects, use this syntax to speed up performance of this function.

Examples

Plot and Stream Lane Topology Data from Driving Route

Use the HERE HD Live Map (HERE HDLM) service to read the lane topology data of a driving route and its surrounding area. Plot this data, and then stream the route on a geographic player.

Load the latitude and longitude coordinates of a driving route in Natick, Massachusetts, USA.

route = load(fullfile(matlabroot,'examples','driving','geoSequenceNatickMA.mat'));
lat = route.latitude;
lon = route.longitude;

Stream the coordinates on a geographic player.

player = geoplayer(lat(1),lon(1),'HistoryDepth',5);
plotRoute(player,lat,lon)

for idx = 1:length(lat)
    plotPosition(player,lat(idx),lon(idx))
end

Create a HERE HDLM reader from the route coordinates. If you have not previously set up HERE HDLM credentials, a dialog box prompts you to enter them. The reader contains map data for the two map tiles that the route crosses.

reader = hereHDLMReader(lat,lon);

Read lane topology data from the LaneTopology layer of the map tiles. Plot the lane topology.

laneTopology = read(reader,'LaneTopology');
plot(laneTopology)

Overlay the route data on the plot.

hold on
geoplot(lat,lon,'bo-','DisplayName','Route');
hold off

Overlay the lane topology data on the geographic player. Stream the route again.

plot(laneTopology,'Axes',player.Axes)
for idx = 1:length(lat)
    plotPosition(player,lat(idx),lon(idx))
end

Find Shortest Path Between Two Nodes

Use the HERE HD Live Map (HERE HDLM) web service to read the topology geometry data from a map tile. Use this data to find the shortest path between two nodes within the map tile.

Define a HERE tile ID for an area of Stockholm, Sweden.

tileID = uint32(378373553);

Create a HERE HDLM reader for the tile ID. Configure the reader to search for the tile in only the Western Europe catalog. If you have not previously set up HERE HDLM credentials, a dialog box prompts you to enter them. The reader contains map data for the specified map tile.

config = hereHDLMConfiguration('Western Europe');
reader = hereHDLMReader(tileID,'Configuration',config);

Read the link definitions from the TopologyGeometry layer of the map tile. The returned layer object contains the specified LinksStartingInTile field and the required map tile fields, such as the tile ID. The other fields are empty. Your map data and catalog version might differ from the ones shown here.

topology = read(reader,'TopologyGeometry','LinksStartingInTile')

topology = 
  TopologyGeometry with properties:

   Data:
                    HereTileId: 378373553
          IntersectingLinkRefs: []
           LinksStartingInTile: [1240×1 struct]
                   NodesInTile: []
    TileCenterHere2dCoordinate: [59.3372 18.0505]

   Metadata:
                       Catalog: 'here-hdmap-ext-weu-1'
                CatalogVersion: 3117

  Use plot to visualize TopologyGeometry data.

Find the start and end nodes for each link in the LinksStartingInTile field.

startNodes = [topology.LinksStartingInTile.StartNodeId];
endNodesRef = [topology.LinksStartingInTile.EndNodeRef];
endNodes = [endNodesRef.NodeId];

Find the length of each link in meters.

linkLengths = [topology.LinksStartingInTile.LinkLengthMeters];

Create an undirected graph for the links in the map tile.

G = graph(string(startNodes),string(endNodes),double(linkLengths));
H = plot(G,'Layout','force');
title('Undirected Graph')

Specify a start and end node to find the shortest path between them. Use the first and last node in the graph as the start and end nodes, respectively. Overlay the nodes on the graph.

startNode = G.Nodes.Name(1);
endNode = G.Nodes.Name(end);

highlight(H,[startNode endNode],'NodeColor','red','MarkerSize',6)
title('Undirected Graph - Start and End Nodes')

Find the shortest path between the two nodes. Plot the path.

path = shortestpath(G,startNode,endNode);
highlight(H,path,'EdgeColor','red','LineWidth',2);
title('Undirected Graph - Shortest Path')

Input Arguments

reader — Input HERE HDLM reader

hereHDLMReader object

Input HERE HDLM reader, specified as a hereHDLMReader object.

layerType — Layer type

string scalar | character vector

Layer type from which to read data, specified as a string scalar or character vector. layerType must be a valid layer type for the map tiles stored in reader. To see the list of valid layers, use the Layers property of reader.

Example: "AdasAttributes"

Example: 'LaneTopology'

fields — Layer object fields

string scalar | character vector | string array | cell array of character vectors

Layer object fields from which to read data, specified as a string scalar, character vector, string array, or cell array of character vectors. All fields must be valid fields of the layer specified by layerType. You can specify only the top-level fields of this layer. You cannot specify its metadata fields.

In the returned array of layer objects, only required fields, such as the HereTileId field, and the specified fields contain data. All other fields are returned as empty: [].

For a list of the valid top-level data fields for each layer type, see the data output argument.

Example: 'LinkAttribution'

Example: "NodeAttribution"

Example: ["LinkAttribution" "NodeAttribution"]

Example: {'LinkAttribution','NodeAttribution'}

Output Arguments

layerData — HERE HDLM layer data

T-by-1 array of layer objects

HERE HDLM layer data, returned as a T-by-1 array of layer objects. T is the number of map tile IDs stored in the TileIds property of the specified reader. Each layer object contains map data that is of type layerType, for a HERE map tile that was read from reader. Such data can include the geometry of links (streets) and nodes (intersections and dead-ends) within the map tiles, as well as various road-level and lane-level attributes. The layer objects also contain metadata specifying the catalog and catalog version from which the read function obtained the data.

The properties of the layer objects correspond to valid HERE HDLM layer fields. In these layer objects, the names of the layer fields are modified to fit the MATLAB^® naming convention for object properties. For each layer field name, the first letter and first letter after each underscore are capitalized and the underscores are removed. This table shows sample name changes.

HERE HDLM Layer Fields	MATLAB Layer Object Property
here_tile_id	HereTileId
tile_center_here_2d_coordinate	TileCenterHere2dCoordinate
nodes_in_tile	NodesInTile

The layer objects are MATLAB structures whose properties correspond to structure fields. To access data from these fields, use dot notation.

For example, this code selects the NodeId subfield from the NodeAttribution field of a layer:

layerData.NodeAttribution.NodeId

This table summarizes the valid types of layer objects and their top-level data fields. The available layers are for the Road Centerline Model and HD Lane Model. For an overview of HERE HDLM layers and the models they belong to, see HERE HD Live Map Layers. For a full description of the fields, see HD Live Map Data Specification on the HERE Technologies website.

Layer Object	Description	Top-Level Data Fields (Layer Object Properties)	Plot Support
AdasAttributes	Precision geometry measurements, such as slope, elevation, and curvature of roads. Use this data to develop advanced driver assistance systems (ADAS).	HereTileId LinkAttribution NodeAttribution	Not available
ExternalReferenceAttributes	References to external map links, nodes, and topologies for other HERE maps.	HereTileId LinkAttribution NodeAttribution	Not available
LaneAttributes	Lane-level attributes, such as direction of travel and lane type.	HereTileId LaneGroupAttribution	Not available
LaneGeometryPolyline	3-D lane geometry composed of a set of 3-D points joined into polylines.	HereTileId TileCenterHere3dCoordinate LaneGroupGeometries	Available — Use the plot function.
LaneRoadReferences	Road and lane group references and range information. Use this data to translate positions between the Road Centerline Model and the HD Lane Model.	HereTileId LaneGroupLinkReferences LinkLaneGroupReferences	Not available
LaneTopology	Topologies of the HD Lane model, including lane group, lane group connector, lane, and lane connector topologies. This layer also contains the simplified 2-D boundary geometry of the lane model for determining map tile affinity and overflow.	HereTileId TileCenterHere2dCoordinate LaneGroupsStartingInTile LaneGroupConnectorsInTile IntersectingLaneGroupRefs	Available — Use the plot function.
RoutingAttributes	Road attributes related to navigation and conditions. These attributes are mapped parametrically to the 2-D polyline geometry in the topology layer.	HereTileId LinkAttribution NodeAttribution StrandAttribution AttributionGroupList	Not available
RoutingLaneAttributes	Core navigation lane attributes and conditions, such as the number of lanes in a road. These values are mapped parametrically to 2-D polylines along the road links.	HereTileId LinkAttribution	Not available
SpeedAttributes	Speed-related road attributes, such as speed limits. These attributes are mapped to the 2-D polyline geometry of the topology layer.	HereTileId LinkAttribution	Not available
TopologyGeometry	Topology and 2-D line geometry of the road. This layer also contains definitions of the nodes and links in the map tile.	HereTileId TileCenterHere2dCoordinate NodesInTile LinksStartingInTile IntersectingLinkRefs	Available — Use the plot function.