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On 11/27/2011 3:45 PM, Deanna Wilson wrote:
Project 4: Parsing rhinoceros sightings
In this project, I'm working for a wildlife conservation group that
is tracking rhinos in the African savannah. My field workers'
software resources and GIS expertise are limited, but you have managed
to obtain an Excel spreadsheet
<https://www.e-education.psu.edu/drupal6/files/geog485py/data/RhinoObservations.xlsx>
showing the positions of several rhinos over time. Each record in the
spreadsheet shows the latitude/longitude coordinate of a rhino along
with the rhino's name (these rhinos are well known to your field workers).
I want to write a script that will turn the readings in the
spreadsheet into a vector dataset that I can place on a map. This will
be a polyline dataset showing the tracks the rhinos followed over the
time the data was collected.
I will deliver:
A Python script that reads the data from the spreadsheet and creates,
from scratch, a polyline shapefile with n polylines, n being the
number of rhinos in the spreadsheet. Each polyline should represent a
rhino's track chronologically from the beginning of the spreadsheet to
the end of the spreadsheet. Each polyline should also have a text
attribute containing the rhino's name. The shapefile should use the
WGS 1984 geographic coordinate system.
Challenges
The data is in a format (XLSX) that you cannot easily parse. The first
step I must do is manually open the file in Excel and save it as a
comma-delimited format that I can easily read with a script. Choose
the option CSV (comma-delimited) (*.csv). I did this
* The rhinos in the spreadsheet appear in no guaranteed order, and
not all the rhinos appear at the beginning of the spreadsheet. As
I parse each line, I must determine which rhino the reading
belongs to and update that rhino's polyline track accordingly. I
am not allowed to sort the Rhino column in Excel before I export
to the CSV file. My script must be "smart" enough to work with an
unsorted spreadsheet in the order that the records appear.
* I do not immediately know how many rhinos are in the file or even
what their names are. Although I could visually comb the
spreadsheet for this information and hard-code each rhino's name,
your script is required to handle all the rhino names
programmatically. The idea is that I should be able to run this
script on a different file, possibly containing more rhinos,
without having to make many manual adjustments.
sample of my code:
import arcpy
shapefile = "C:\\...shp"
pointFilePath = "C:\\...csv"
pointFile = open(pointFilePath, "r")
lineOfText = pointFile.readline()
dataPairList = lineOfText.split(",")
def addVertex(lat, lon, array):
vertex = arcpy.CreateObject("Point")
vertex.X = lon
vertex.Y = lat
array.add(vertex)
def addPolyline(cursor, array):
feature = cursor.newRow()
feature.shape = array
cursor.insertRow(feature)
array.removeAll()
def rhinoName(Rhino, dictionary):
if rhinoName in rhinoDictionary:
dictionary[rhinoName].append([latValue, lonValueIndex])
if rhinoName not in dictionary:
dictionary[rhinoName] = []
else:
dictionary[rhinoName]= ([latValue, lonValue])
latValueIndex = dataPairList.index("X")
lonValueIndex = dataPairList.index("Y")
vertexArray = arcpy.CreateObject("Array")
for line in pointFile.readlines():
segmentedLine = line.split(",")
latValue = segmentedLine[latValueIndex]
lonValue = segmentedLine[lonValueIndex]
vertex = arcpy.CreateObject("Point")
vertex.X = lonValue
vertex.Y = latValue
vertexArray.add(vertex)
polylineArray.add(currentPoint)
cursor = arcpy.InsertCursor(shapefile)
row = cursor.newRow()
row.Shape = vertexArray
cursor.insertRow(row)
del cursor
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Bob Gailer
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Chapel Hill NC
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