Particle Track (Spatial Analyst)
Summary
Calculates the path of a particle through a velocity field, returning an ASCII file of particle tracking data and, optionally, a coverage of track information.
Usage
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The input direction and magnitude rasters should be from the same run of the Darcy Flow tool.
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The path file generated by this tool is an ASCII text file containing information about position, local velocity direction and magnitude, and cumulative length and time of travel along the path. This file is used for input by Porous Puff. The format of this file is as follows:
time x y length flow dir flow mag 0.000000000 0.000000000 482.8400000 0.000000000 90.00000000 0.04418909563 113.1648712 4.999804443 482.7957786 5.000000000 91.01366126 0.04418332249 226.2741353 9.998043277 482.6630814 10.00000000 92.02765240 0.04420504404 339.3574334 14.99315255 482.4419855 15.00000000 93.04094157 0.04421519432 452.3447720 19.98356700 482.1325285 20.00000000 94.05521317 0.04425274599 565.2657591 24.96772671 481.7348453 25.00000000 95.06807622 0.04427874865 678.0514031 29.94406931 481.2490323 30.00000000 96.08254679 0.04433188322 790.7309576 34.91104149 480.6752838 35.00000000 97.09488082 0.04437362239
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No particular system of units is specified by Particle Track. It is important that all data be in a consistent set of units, using the same unit for time (seconds, days, years) and length (feet, meters).
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The source location must be within the boundary of the input rasters and cannot be in an area of NoData.
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The track file will end if the track reaches outside the study area and has not met the specified maximum tracking time.
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If the particle being tracked has reached the edge of the study area at the indicated time and the predictor point is outside the study area, the track file will end.
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If the particle being tracked migrates into a depression at the indicated time, the track file will end. A depression can be created by a discharge well or other sink.
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The two outputs from this tool are:
- A particle track ASCII file using the name specified as output particle track file
- An optional polyline feature class
Syntax
| Parameter | Explanation | Data Type |
in_direction_raster |
An input raster where each cell value represents the direction of the seepage velocity vector (average linear velocity) at the center of the cell. Directions are expressed in compass coordinates, in degrees clockwise from north. This can be created by the Darcy Flow tool. Direction values must be floating point. | Raster Layer |
in_magnitude_raster |
An input raster where each cell value represents the magnitude of the seepage velocity vector (average linear velocity) at the center of the cell. Units are length/time. This can be created by the Darcy Flow tool. | Raster Layer |
source_point |
The location of the source point from which to begin the particle tracking. This is entered as numbers identifying the x,y coordinates of the position in map units. | Point |
out_track_file |
The output ASCII text file that contains the particle tracking data. | File |
step_length (Optional) |
The step length to be used for calculating the particle track. The default is one-half the cell size. Units are length. | Double |
tracking_time (Optional) |
Maximum elapsed time for particle tracking. The algorithm will follow the track until either this time is met or the particle migrates off the raster or into a depression. The default value is infinity. Units are time. | Double |
out_track_polyline_features (Optional) |
The optional output line feature class containing the particle track. This feature class contains a series of arcs with attributes for position, local velocity direction and magnitude, and cumulative length and time of travel along the path. | Feature Class |
Code Sample
This example executes the tool on the required inputs and outputs an ASCII file of particle tracking data and a shapefile featureclass of the particle track.
import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
ParticleTrack("gwdir", "gwmag", arcpy.Point(-200,-200),
"C:/sapyexamples/output/trackfile.txt",10, 100000,
"C:/sapyexamples/output/trackpolyline.shp")
This example executes the tool on the required inputs and outputs an ASCII file of particle tracking data and a shapefile featureclass of the particle track.
# Name: ParticleTrack_Ex_02.py
# Description: Calculates the path of a particle through a velocity field.
# Requirements: Spatial Analyst Extension
# Import system modules
import arcpy
from arcpy import env
from arcpy.sa import *
# Set environment settings
env.workspace = "C:/sapyexamples/data"
# Set local variables
inDirectionRaster = "gwdir"
inMagnitudeRaster = "gwmag"
sourcePoint = arcpy.Point(-200, -200)
outTrackFile = "C:/sapyexamples/output/trackfile.txt"
stepLength = 10
trackingTime = 10000000
outTrackPolylineFeatures = "C:/sapyexamples/output/trackpolyline.shp"
# Check out the ArcGIS Spatial Analyst extension license
arcpy.CheckOutExtension("Spatial")
# Execute ParticleTrack
ParticleTrack(inDirectionRaster, inMagnitudeRaster, sourcePoint, outTrackFile,
stepLength, trackingTime, outTrackPolylineFeatures)