Use a dynamically determined grid scale for a region based on size

[lispandfound]

This small change adds a utility function grid_scale_for_region that computes an appropriate grid scale for the region of the pygmt map which we use for the grid spacing in plotting.create_grid. The equation is $\mathrm{max}(5, 2.5x)$, where $x$ is the largest extent (in km) of the region in latitude or longitude. Did this so I can make SRF plots without taking 20 minutes.

[gemini-code-assist]

Summary of Changes

Hello @lispandfound, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the plotting capabilities by implementing a dynamic grid scaling mechanism for PyGMT plots. By adapting the grid resolution to the specific region being plotted, it aims to optimize performance and reduce plot generation times, particularly for large-scale SRF plots, moving away from a fixed, potentially inefficient, grid spacing.

Highlights

• Dynamic Grid Scaling: A new utility function grid_scale_for_region has been introduced to dynamically compute an optimal grid spacing for PyGMT plots based on the region's extent.
• Performance Improvement: The plot_rise and plot_srf functions now utilize this dynamic grid scale instead of a hardcoded value, which is expected to significantly reduce the time required to generate SRF plots, especially for larger geographical regions.
• Adaptive Resolution Formula: The grid scale is calculated using the formula $\mathrm{max}(5, 2.5x)$, where $x$ represents the largest extent (in kilometers) of the region in either latitude or longitude, ensuring a minimum resolution of 5 meters.

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[Copilot]

Pull Request Overview

Adds a utility to compute a dynamic grid scale based on region size and updates SRF and rise plotting functions to use it instead of a hardcoded spacing.

• Introduce grid_scale_for_region in visualisation/utils.py
• Replace "5e/5e" grid spacing with grid_scale in SRF plots
• Replace "5e/5e" grid spacing with grid_scale in rise plots

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
visualisation/utils.py	Added grid_scale_for_region to compute spacing based on region extents.
visualisation/sources/plot_srf.py	Use dynamic grid_scale instead of hardcoded 5e/5e; missing import needs adding.
visualisation/sources/plot_rise.py	Use dynamic grid_scale via plotting.grid_scale_for_region; namespace/import needs correcting.

Comments suppressed due to low confidence (4)

visualisation/utils.py:297

• The return annotation is float but the function always returns an int (and the docstring says Returns int). Update the signature to -> int for consistency.

def grid_scale_for_region(region: tuple[float, float, float, float]) -> float:

visualisation/utils.py:297

• [nitpick] Consider adding unit tests for grid_scale_for_region to verify output for known region sizes and edge cases (e.g., very small or large extents).

def grid_scale_for_region(region: tuple[float, float, float, float]) -> float:

visualisation/sources/plot_srf.py:122

• You need to import grid_scale_for_region (e.g. from visualisation.utils import grid_scale_for_region) at the top of this file, otherwise this reference will be undefined.

    grid_scale = grid_scale_for_region(region)

visualisation/sources/plot_rise.py:56

• grid_scale_for_region is not defined on the plotting module. Either import it from visualisation.utils or call it directly if it's in scope.

    grid_scale = plotting.grid_scale_for_region(region)

[gemini-code-assist]

Code Review

This pull request introduces a utility function to dynamically calculate grid scales for plots. The review identified a logical flaw in the grid_scale_for_region function, and incorrect calls to the function in plot_rise.py and plot_srf.py. A suggestion to align the function's type hint with its implementation was also provided.