🛠️ Erase

Purpose: > In Erase, the output layer consists of only those portions of the input features falling outside the erase features. Geometries that are coincident between the Input Features and Erase Feature parameter values will be removed.

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🎭 Illustration

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📋 Technical Specifications

Requirement	Detail
Input Feature Types	Any
Output Feature Type	Same or lesser dimension
Map Name	03.erase
inputs GDB	03.input_erase.geodatabase
output GDB	03.output_erase.geodatabase

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🧠 Logic & Arithmetic Operation

Logic: AND NOT / Subtract

⚙️ Parameters & Conditions

Input Parameter: Input Features

Geometry: Any

No. of Inputs: One or more

Order: matters $A - B = B - A$

Coordinate System: Same as 1st input layer

Input and Erase Combinations

The Erase Features parameter defines the extent of erasure.
It can have any geometry type as long as it is the same or of greater dimension than the input layer.

• ❌ A point erase feature cannot be used on a polygon input.
• ✅ The output layer always has the same geometry type as the input.

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📐 Geometry Hierarchy

• Polygon (2D) > Line (1D) > Point (0D)

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🔗 Valid Input–Erase Combinations

Format: (Input, Erase)

1. (Point, Point)
2. (Point, Line)
3. (Line, Line)
4. (Point, Polygon)
5. (Line, Polygon)
6. (Polygon, Polygon)

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🚩 Important Notes

• Unlike Union or Intersect, erasure is not commutative:

\[A - B \neq B - A\]

• For combinations with different geometries (2, 4, 5), output is not possible.
• For combinations with the same geometry type, results differ depending on which layer is input vs. erase.
• This gives us nine possible scenarios to consider when starting experiments.

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📊 Summary Table

Input Geometry	Allowed Erase Geometry	Output Geometry
Point	Point, Line, Polygon	Point
Line	Line, Polygon	Line
Polygon	Polygon	Polygon

🐍 Arcpy Function

arcpy.analysis.Erase(in_features, erase_features, out_feature_class, {cluster_tolerance})

for more on function parameters, check: Arcpy Documentation Here.

🖼️ Figures

📊 Same Input \& Output

Feature Type	Input	Output
Point
Line
Polygon

📊 Order matters for line

| | $\neq$ | | | :—: | :—: | :—: |

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📊 Different Inputs

Feature - Erase	Input	Output
Point - Line
Point - Polygon