GIS/ArcPy: extracting land use data from a raster and assignig to shapefile polygons

Question

I have two maps for the same area (1) a raster land use map and (2) a shapefile with thousands of sub-watersheds. I am trying to assign the land use type from the raster (map 1) to each of the sub-watershed (map 2) based on the majority rule. I tried spatial join, but the result seems to be wrong. What is the best way of doing it either in ArcMap or through arcpy?

Answer 1

I would recommend using Zonal Statistics as Table (Spatial Analyst) to accomplish this task. Here is the general workflow:

1. Run Zonal Statistics as Table using the "Majority" statistic.
2. Join the table with the watershed feature class using Join Field (Data Management)

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import arcpy, os
from arcpy.sa import *
arcpy.CheckOutExtension("Spatial")

# Your watershed feature class
watersheds = r'C:\path\to\your\geodatabase.gdb\watersheds'

# Your land cover raster
raster = r'C:\path\to\your\landcover_raster.tif'

# The workspace where the output table will go
zone_table = r'C:\path\to\your\geodatabase.gdb'

# Perform the zonal statistics and output a table
arcpy.sa.ZonalStatisticsAsTable (watersheds, 'watershed_id', raster, zone_table, 'DATA', 'MAJORITY')

# Join the table to the watershed feature class by the OBJECTID field (for feature class)
arcpy.JoinField_management(watersheds, 'watershed_id', zone_table, 'OBJECTID', 'MAJORITY')