GeoScenario Architecture

Basic Structrure

A GeoScenario document is a valid OSM XML document (filename.osm), using the following structure, and containing all supported elements that compose a GeoScenario and references to external elements (e.g., the road network):

<?xml version='1.0' encoding='UTF-8'?>
<osm version='0.6'>
    <node ... />
    <way ... />

Geoscenario elements are based on two OSM primitive types: Node and Way.

Nodes are the core elements of Geoscenario, representing a specific point on Earth’s surface. Each node comprises an ID number and a pair of coordinates (latitude and longitude). Nodes are used to define standalone point features (e.g., a Vehicle or a Pedestrian), but also to compose the shape of other elements (e.g. a path).

Ways are ordered lists of Nodes defining a polyline. Ways are used to define linear features such as Paths and boundaries of areas (solid polygons that represent an obstacle on the road, or a named area for dynamic element placement). In order to define areas, the way’s first and last node must be the same (in OSM, they are called closed-way).



<node id=1 lat='43.50934231789' lon='-80.53670525588' />
<way id='10'>
    <nd ref='2' />
    <nd ref='3' />
    <nd ref='4' />
<way id='20'>
    <nd ref='5' />
    <nd ref='6' />
    <nd ref='7' />
    <nd ref='5' />

All elements (nodes and ways) can have tags describing attributes of an element with the pair of text fields k (key) and v (value). We use a tag gs to define an element’s role in the scenario. That is, the element’s function in the GeoScenario model (e.g., gs = vehicle). Elements without a gs tag do not have a specific role in the scenario, but can be used to compose other elements. For example, nodes composing a Path do not have a gs tag.

Sample GeoScenario vehicle node:

<node id=’-1’ lat=’43.5094’ lon=’-80.5367’>
   <tag k=’gs’ v=’vehicle’/>
   <tag k=’name’ v=’leading_vehicle’/>

Element core rules

  • An element cannot have 2 tags with the same key.
  • All nodes have coordinates in WGS84 coordinate frame (as part of the OSM standard), defined by lat and lon attributes.
  • All elements must have unique integer ID. Different types have their own ID space (a node id=1 and a non-related way with id=1 can co-exist).
  • Negative IDs indicate local elements valid only in a single GeoScenario file. When a file is uploaded to the server (optional) a unique global positive ID is assigned to all elements.
  • Elements with a role must also contain the tag ’name’ (with a few exceptions). The name is a unique string [a-z][0-9] (case insensitive) that identifies one element is our scenario. This tag is used to derive relations between elements.
  • External attributes: Custom tag attributes added to a scenario must additionally contain external='yes' added tothe tag. This tag ensures the standard validation tools will bypass this attribute.

Attributes with multiple values

  • Attributes supporting multiple values are described with comma-separated list ("a,b,c") or ranges ("min:max"). Composition of lists (or ranges) inside another list is also supported with '[]'. How the values must be interpreted depends on the element itself.
    Examples: speed="10,20,30", speed="10:30”, value="[10:20],[30,31,32]”.
  • When a list of scenario element names is expected (for example, a list of vehicle names), the following keywords (case insensitive) can be used for simplicity: 'vehicles' for all vehicles in the scenario, 'pedestrians' for all pedestrians in the scenario, 'agents' for vehicles and pedestrians, and '*' for all supported elements in the scenario (including Ego). These keywords are protected and can not be used to name GeoScenario elements of any type;
  • Stochastic distributions are defined in the format ",param2=v2, ...)".
    Example: speed="dist.normal(mean=5.0, sd=2, size=100)".
    Since many distributions can be used (with diverse parameter names), they must be defined in detail elsewhere. We encourage users to always provide a reference to ensure reproducibility between tools.
example how to interpret
1, 2, 3 list with integer values
[1,2,3] same as above
v1, v2, v3 list with 3 elements (by name reference)
1 : 3 integer range from 1 to 3
0.0 : 1.0 float range from 0 to 1.0
1:3,7:9 list with 2 elements: integer range from 1 to 3, and integer range from 7 to 9
[1,2,3],[6,7,8] list with 2 elements: integer list, and second integer list
agents list with all dynamic agents in the scenario (by name reference)
vehicles list with all vehicles in the scenario (by name reference)

Standard Units

If not stated otherwise, GeoScenario attributes use the following units:

measure units
lat, lon coordinates in WGS84 frame
speed kilometers per hour (km/h)
acceleration in meters per squared second (m/s2)
time seconds (s)
size, distance centimeters (cm)
boolean "yes" / "no" (case insensitive). Additionally, "on","true" / "off", "false" are supported.
orientation in degrees, clockwise, with origin on east. See figure.