Lab 6 [GIS5103]: Working with Geometries

The screenshot above shows the output from this week's lab where skills emphasizing working with geometry objects were addressed. In the output above these skills were used to read a shapefile and then write specific information on each feature to a text file. The items on each line in the output file included the object ID number, vertex count number, X coordinate, Y coordinate, and feature name. The general pseudocode was as follows:

Start

    Step 0: (Setup)

    Setup input filepath

    Setup output filepath

    Step 1: (Prepare output file)

    Create output filename

    Open output file for writing

    Step 2: (Write details to output file)

    Create search cursor to extract OID@, SHAPE@, NAME for each feature

    Iterate through each row/feature in cursor

        Set vertexID to 0

        Iterate through the points in each feature (using getPart)

            Increment vertexID by 1 (starts count at 1 for each set of vertices)

            Convert OID to string

            Convert vertexID to string

            Convert point.x to string

            Convert point.y to string

            Store NAME in string variable

            Write five text strings to output file (ending with line break character)

            Write five text strings to screen (ending with line break character)

    Cleanup: close output file

    Cleanup: delete cursor and row

End

Key take-away points during this lab included proper set-up of the search cursor and then understanding how to use nested loops to iterate through the features and the associated array of geometry objects. The use of geometry tokens was also addressed, including their time-saving utility as shorthands to extract specific geometric properties. Finally, the importance of cleanly formatting screen output as well as text-based output files with the "\n" character was covered.