GIS Programming - Module 6 Lab

Python 3.6.6 |Anaconda, Inc.| (default, Jun 28 2018, 11:27:44) [MSC v.1900 64 bit (AMD64)] on win32

>>> print ("Hello Everyone!") 

Hello Everyone!

It's so hard to believe that I just completed my second to last GIS Programming module lab! Time sure has flown by in this course. This weeks lab in addition to some other life events really had me stumped in the beginning but after the dust settled and about 6 cups of coffee later the results proved successful! For this weeks lab and lecture, I learned all about geometries. When looking at the geometries of features in GIS there is a hierarchy of understanding that can really help you. The first and highest level is a feature. This essentially is each row in the attribute table. In this weeks lab, I worked with a rivers shapefile from a Hawaii dataset so for this example, each feature would be a stream/river in its entirety. The next level of the hierarchy is an array. An array is essentially the collection of points/vertices that make up a feature. An example would be that a specific feature has an array of 15 vertices. Finally, the last level of the hierarchy is the individual point/vertex. These are usually expressed in the (X, Y) vertex format. Essentially the structure is as follows:

    Feature > Array > Vertex

For this weeks lab, I was tasked with working with the aforementioned geometries. I was given a shapefile containing river features from Hawaii and was tasked with writing the geometries of each feature to a newly created TXT file. For my text file, I needed individual lines that provided me with the following information: Feature ID, Vertex ID, X Point, Y Point, and Feature Name. In total there were 25 features in my data and 247 total vertices that I had to list with their respective X and Y points and feature names. Before I get to the results, I would like to share the basis of my code so you can understand how I got my results.

~To Do:

T 

1.     Set my environment parameters
2.     Create a new TXT file that’s writable
3.     Create a search cursor that calls on OID (Object ID), SHAPE, and NAME
4.     3 For loops:
      a.      First: Iterates Rows
      b.      Second: Iterates Array
      c.      Third: Iterates Vertices
5.     Print and Write my results in the script and new TXT file
      a.      Feature #, Vertex #, X Point, Y Point, Feature Name
6.     Delete row and cursor variables
7.     Close file access

Start
>>>import statements
>>>environment statements (workspace and overwrite)
>>>define feature class
>>>open new writable file
>>>define the cursor
>>>for loop to retrieve rows
>>>for loop to retrieve arrays
>>>for loop to retrieve vertices
>>>print and write to the newly created TXT file
>>>delete row and cursor variables
>>>close file
End

My results turned out better than expected (below):

As you can see, new lines were written to my TXT file starting with Feature 0 then iterating through each Vertex in the array providing you with the X point, Y point and the name. Once Feature 0's (Honokahua Stream) vertex array had been iterated through, Feature 1 (Honokowai Stream) was iterated through next until all 247 vertices were complete for the 25 features total. Overall implementing the nested for loops in my script was the toughest part and caused the most hangup for me. The final module will be one of my favorites in this class as it pertains to Raster data!