Portal Example¶
The portal example takes trajectory data and attempts to find origin/destination
pairs. It breaks the USA into a grid, identifies what cells are populated by trajectories
and then refines the grid based on desired parameters. Each level of depth
is an
additional layer of refinement of the original grid. Each level is divided into
bin-count
sections in both longitude and latitude. So for each of the cells:
Empty cells are dropped but a cell is only empty if no trajectories pass through it.
This example demonstrates how to:
Read in points using Tracktable’s C++ command line factories
Assemble points into trajectories
Use boost program options to take parameters from command lines (in addition to the factories)
Use
boost::geometry::intersects
to test where trajectories overlap region
The full portal
example source code can be found in the Tracktable source
code distribution in the directory tracktable/Examples
and the example
can be executed by calling the portal
program from the command line provided
that the example is built and it’s location is exposed to the appropriate system path.
Below you will find the execution command for the example as well as the
source files in there entirety for quick reference.
Example Source Files¶
The page listed here contains a direct import of the source code for this example. This is provided for convenience and reference.
Command Line Interface¶
Note
This command is specific to Linux and Mac. Windows machines will have a different command line call.
The command to run the portal
example is as follows.
$ ./portal-- input=/data/flights.tsv --depth=5 --min-value=12 --min-seperation=10 --bin-count=2
This command takes an input parameter of a tab separated value or comma seperated value file
formatted as OBJECTID TIMESTAMP LON LAT
of points to assemble, a depth parameter for refinement,
a minimum parameter for portal pairs, minimum value parameter of portal separation distance in lon-lat, and
a bin-count value for number of sections to divide into per level.
Note
The default delimiter is tab
, if you are using a CSV file
you will need to set the --delimiter
parameter. The default output
is standard out.
The command line interface contains a --help
option that will display all of the possible
switches for the example.
$ ./portal --help
will display:
--help Print help
Point Reader:
--input arg (=-) Filename for input (use '-' for standard
input)
--real-field arg Field name and column number for a
real-valued point field
--string-field arg Field name and column number for a string
point field
--timestamp-field arg Field name and column number for a
timestamp point field
--object-id-column arg (=0) Column containing object ID for points
--timestamp-column arg (=1) Column containing timestamp for points
--x-column arg (=2) Column containing X / longitude coordinate
--y-column arg (=3) Column containing Y / latitude coordinate
--delimiter arg (= ) Delimiter for fields in input file
Assembler:
--separation-distance arg (=100) Set maximum separation distance for
trajectory points
--separation-seconds arg (=1200) Set maximum separation time (in seconds)
for trajectory points
--min-points arg (=10) Trajectories shorter than this will be
discarded
--clean-up-interval arg (=10000) Number of points between cleanup