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Accessing Example Data
For this example, we use the vessel AIS data from the San Francisco bay, which is provided by ais.exploratorium.edu (you can open this in a browser and see the raw AIS data). You use this query to access the data. Just create a new Odysseus Script file within Odysseus Studio and run this query (with the "green arrow down"-button). When you right click on the query in the "Queries" view and choose "Show Stream Elements" and then "List ...", you can see the key-value objects with readable AIS The query does access the raw AIS data, converts it into key-value objects, filters some data, converts it to a tuple and finally uses latitude and longitude data to create an geo-object. The latter can be used by Odysseus for spatial functionality. If you want to see the data, do the following: after running the query, you should see "System.SanFranciscoAIS" in the Sources-view. Right click and choose "Query source" to view the data.
| Code Block |
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#PARSER PQL
#RUNQUERY
/// Access the data from San Francisco
input = ACCESS({
source='SanFranciscoAIS',
wrapper='GenericPush',
transport='TCPClient',
protocol='NMEA',
datahandler='keyValueObject',
options=[
['host', 'ais.exploratorium.edu'],
['port', '80']
]
}
)
/// Filter the AIS messages to those from vessels
vesselsOnly = SELECT({
predicate = 'isNull(rateOfTurn) = false'
},
input
)
/// Convert the key-value object to a tuple
tuple = TOTUPLE({
schema = [
['rateOfTurn','Integer'],
['navigationStatus','String'],
['maneuverIndicator','String'],
['trueHeading','Integer'],
['positionAccurate','Boolean'],
['latitude','Double'],
['courseOverGround','Double'],
['speedOverGround','Double'],
['sourceMmsi','Integer'],
['longitude','Double'],
['second','Integer'],
['raimFlag','Boolean']
]
},
vesselsOnly
)
/// Create a geoObject from lat/lng
SanFranciscoAIS := MAP({
expressions = [
['FromWKT("POINT (" + toString(latitude) + " " + toString(longitude) + ") ")', 'SpatialPoint']
],
keepinput = true,
removeattributes = ['latitude','longitude'],
name = 'geo_object'
},
tuple
) |
A message you receive could look similar to the following:
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|---|
#PARSER PQL
/// The index structure
#DEFINE dataStructureName 'sanFranciscoStore'
#DEFINE dataStructureType 'mo_geohash'
#RUNQUERY
/// Store the data in an index structure
movingObjectIndex = MOVINGOBJECTSTORE({
/// distance of the trajectory in meters that we keep for every moving object
distancepermo = 100.0,
geometryattribute = 'SpatialPoint',
datastructurename = ${dataStructureName},
idattribute = 'sourceMmsi',
datastructuretype = ${dataStructureType}
},
System.SanFranciscoAIS
) |
...
| Code Block |
|---|
#PARSER PQL
#DEFINE dataStructureName 'sanFranciscoStore'
#ADDQUERY
/// For every vessel we want to know which vessels are near them all the time
range = MOVINGOBJECTRANGE({
geometryattribute = 'SpatialPoint',
datastructurename = ${dataStructureName},
range = 300
},
System.SanFranciscoAIS
) |
Show data on a map
Future Work
The work on this topic is not finished. Here list of things that we want to add in future releases.
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