GitLab

Module: transects.js

Comprehensive Analysis of transects.js

Module Name

• transects.js

Primary Objectives

• The primary purpose of this module is to generate and manipulate transects (lines orthogonal to a given polygon) using geospatial data. It provides functionality to create these transects and expand them horizontally.

Critical Functions

1. offsetMapper(extent, origin, theta)

   • Creates a function that maps offsets to transects based on the given extent, origin, and angle (theta).

2. transectAccumulator(step, extent)

   • Accumulates transects by iterating over a list of coordinates, computing the necessary transects at each step.

3. generateOrthogonalTransects(coordinates, step, extent)

   • Generates transects orthogonal to a specified polygon based on the provided coordinates, step size, and extent.

4. expandHorizontally(transects, amount)

   • Expands the generated transects horizontally by a specified amount.

Key Variables

• extent: The width of the transect.
• origin: The starting point for computing displacements.
• theta: The angle used for computing the direction of the transect.
• step: The distance between consecutive transects.
• coordinates: The list of coordinates defining the polygon.
• amount: The amount by which to expand the transects horizontally.

Interdependencies

• Earth Engine (ee): The module heavily relies on Google Earth Engine (GEE) for geospatial computations and data structures.
• Geodesy Module: Functions like computeBearing and computeDisplacement are imported from the geodesy module to perform geospatial calculations.
• Metadata Module: Uses INTERNALS from the metadata module to store additional information in the generated features.

Core vs. Auxiliary Operations

• Core Operations:
  • generateOrthogonalTransects: Main function to generate transects.
  • transectAccumulator: Core logic for accumulating transects.
• Auxiliary Operations:
  • offsetMapper: Helper function for mapping offsets to transects.
  • expandHorizontally: Function to expand transects horizontally.

Operational Sequence

1. Initialization: Import necessary modules and define helper functions.
2. Transect Generation:
   • Use generateOrthogonalTransects to create transects based on input coordinates.
   • Internally, transectAccumulator and offsetMapper are used to compute and accumulate transects.
3. Expansion:
   • Optionally, use expandHorizontally to expand the generated transects.

Performance Aspects

• Efficiency: The use of Earth Engine's efficient data structures and algorithms ensures that the module can handle large geospatial datasets.
• Scalability: Designed to work with GEE, which is optimized for large-scale geospatial analysis.

Reusability

• Modular Design: Functions are designed to be reusable and can be easily integrated into other geospatial analysis workflows.
• Parameterization: Functions accept parameters like coordinates, step, and extent, making them adaptable to different use cases.

Usage

• Geospatial Analysis: Used in applications requiring the generation of transects for environmental monitoring, land use analysis, and other geospatial studies.
• Integration: Can be integrated into larger geospatial analysis pipelines within the GEE environment.

Assumptions

• Coordinate System: Assumes that the input coordinates are in a format compatible with GEE.
• Earth Engine Availability: Assumes that the Google Earth Engine service is available and accessible.
• Geodesy Functions: Assumes that computeBearing and computeDisplacement functions are correctly implemented and available.

This analysis provides a detailed overview of the transects.js module, highlighting its purpose, key components, and usage within geospatial analysis workflows.

Flow Diagram [via mermaid]

graph TD
    A[User] -->|Input Coordinates, Step, Extent| B[generateOrthogonalTransects]
    B -->|Coordinates, Step, Extent| C[transectAccumulator]
    C -->|Extent, Origin, Theta| D[offsetMapper]
    B -->|Transects| E[expandHorizontally]
    E -->|Amount| F[computeBearing]
    E -->|Amount| G[computeDisplacement]
    B -->|Transects| H[Output Transects]
    E -->|Expanded Transects| H

Module: transects.js

Comprehensive Analysis of transects.js

Module Name

• transects.js

Primary Objectives

• The primary purpose of this module is to generate and manipulate transects (lines orthogonal to a given polygon) using geospatial data. It provides functionality to create these transects and expand them horizontally.

Critical Functions

1. offsetMapper(extent, origin, theta)

   • Role: Creates a function that maps offsets to transects based on the given extent, origin, and angle (theta).

2. transectAccumulator(step, extent)

   • Role: Accumulates transects along a path defined by a series of coordinates, using a specified step size and extent.

3. generateOrthogonalTransects(coordinates, step, extent)

   • Role: Generates transects orthogonal to a specified polygon based on given coordinates, step size, and extent.

4. expandHorizontally(transects, amount)

   • Role: Expands the generated transects horizontally by a specified amount.

Key Variables

• extent: Represents the extent of the transect.
• origin: The starting point for displacement calculations.
• theta: The angle used for calculating bearings and displacements.
• step: The step size for generating transects.
• coordinates: List of coordinates defining the polygon.
• amount: The amount by which to expand the transects horizontally.

Interdependencies

• Earth Engine (ee): The module heavily relies on Google Earth Engine (GEE) for geospatial computations and data structures.
• Geodesy Module: Functions like computeBearing and computeDisplacement are imported from the geodesy module for geospatial calculations.
• Metadata Module: Uses INTERNALS from the metadata module to store additional information in features.

Core vs. Auxiliary Operations

• Core Operations:
  • generateOrthogonalTransects: Main function for generating transects.
  • transectAccumulator: Core logic for accumulating transects.
• Auxiliary Operations:
  • offsetMapper: Helper function for mapping offsets to transects.
  • expandHorizontally: Utility function for expanding transects.

Operational Sequence

1. Initialization: Import necessary modules and define helper functions.
2. Transect Generation:
   • Use generateOrthogonalTransects to create transects based on input coordinates.
   • Internally, transectAccumulator and offsetMapper are used to compute and accumulate transects.
3. Expansion:
   • Optionally, use expandHorizontally to expand the generated transects.

Performance Aspects

• Efficiency: The use of Earth Engine's efficient data structures and algorithms ensures that the module can handle large geospatial datasets.
• Scalability: Designed to work with large-scale geospatial data, leveraging GEE's cloud-based processing capabilities.

Reusability

• Modular Design: Functions are designed to be reusable and can be easily integrated into other geospatial analysis workflows.
• Parameterization: Functions accept parameters like coordinates, step, and extent, making them adaptable to different use cases.

Usage

• Geospatial Analysis: Used in applications requiring the generation of transects for environmental monitoring, land use analysis, and other geospatial studies.
• Integration: Can be integrated into larger geospatial data processing pipelines using Google Earth Engine.

Assumptions

• Coordinate System: Assumes input coordinates are in a format compatible with Earth Engine.
• Earth Engine Availability: Assumes that the Google Earth Engine service is available and accessible.
• Geodesy Functions: Assumes that computeBearing and computeDisplacement functions are correctly implemented and available.

This analysis provides a detailed overview of the transects.js module, highlighting its purpose, key components, and usage within geospatial data processing workflows.

Flow Diagram [via mermaid]

graph TD
    A[Input Coordinates, Step, Extent] -->|generateOrthogonalTransects| B[Transects]
    B -->|expandHorizontally| C[Expanded Transects]

    subgraph transects.js
        A --> D[generateOrthogonalTransects]
        D --> E[transectAccumulator]
        E --> F[offsetMapper]
        D --> B
        B --> G[expandHorizontally]
        G --> C
    end