Quiz: Python in ArcGIS Pro

1   Calculation of August precipitation 30-year normal in North Carolina

In this quiz, you want to analyze the zonal mean of August precipitation 30-year normal in North Carolina using nc_spm_08_grass7_exercise.zip. You will use two Shapefiles in this ZIP file:

• precip_30ynormals.shp: Point Shapefile with precipitation 30-year normals; Use the aug field for August precipitation
• boundary_county.shp: Polygon Shapefile with county boundaries; Use the NAME field for zonal statistics

The procedure is simple.

1. Create Thiessen polygons from point precipitation data for August.
2. Convert the precipitation Thiessen polygons to raster.
3. Calculate the mean zonal statistics of the precipitation for each county.

Since this class is a programming class, I don’t accept any output files. Please submit three Python scripts in FirstLastname_quiz1.zip.

2   Penalties

Filenames: -2 each (total up to -8)

• FirstLastname_quiz1.zip should contain
  • thiessen.py
  • polygon_to_raster.py
  • zonal_stats.py
  • thiessen_zonal_stats.py (optional for 10 bonus points)

Debugging: -3 per line added, removed, or edited

• Hard-coded arguments (marked by * in each question) will be debugged!

3   Question 1: Thiessen polygons

Create a Python script called thiessen.py that executes the Create Thiessen Polygons tool. You may use precip_30ynormals.shp as input.

Requirements:

• Filename: thiessen.py
• Tool parameters:
  • Input Features*: precip_30ynormals.shp
  • Output Feature Class*: precip_thiessen.shp
  • Output Fields: All fields
• Two arguments from the command line (marked by * above)
• Usage:

  python thiessen.py precip_30ynormals.shp .\precip_thiessen.shp

4   Question 2: Polygon to raster

Create a Python script called polygon_to_raster.py that executes the Polygon to Raster tool. You may use the output from thiessen.py as input.

Requirements:

• Filename: polygon_to_raster.py
• Tool parameters:
  • Input Features*: precip_thiessen.shp
  • Value field*: aug
  • Output Raster Dataset*: precip_aug.tif
  • Cell assignment type: Cell center
  • Priority field: NONE
  • Cellsize*: 30
• Four arguments from the command line (marked by * above)
• Usage:

  python polygon_to_raster.py precip_thiessen.shp aug .\precip_aug.tif 30

5   Question 3: Zonal statistics

Create a Python script called zonal_stats.py that executes the Zonal Statistics tool. You may use boundary_county.shp and the output from polygon_to_raster.py as input.

Requirements:

• Filename: zonal_stats.py
• Tool parameters:
  • Input raster or feature zone data*: boundary_county.shp
  • Zone field*: NAME
  • Input value raster*: precip_aug.tif
  • Output raster*: precip_aug_county.tif
  • Statistics type*: Mean
• Five arguments from the command line (marked by * above)
• Usage:

  python zonal_stats.py boundary_county.shp NAME precip_aug.tif .\precip_aug_county.tif Mean

6   Bonus question: Combined script

10 points

Combine the three Python scripts into one script file called thiessen_zonal_stats.py.

Requirements:

• Filename: thiessen_zonal_stats.py
• Arguments
  • Point data feature class
  • Output Thiessen polygon feature class
  • Data field
  • Output Thiessen raster
  • Cell size
  • Polygon zone feature class
  • Zone name field
  • Statistics type
  • Output zonal statistics raster
• Usage:

  python thiessen_zonal_stats.py precip_30ynormals.shp .\precip_thiessen.shp aug .\precip_aug.tif 30 boundary_county.shp NAME Mean .\precip_aug_county.tif