petra-grid

petra_grid

petra_grid is a Python library for reading grid data in the .GRD file format produced by the Petra™ geological interpretation application

petra_grid is implemented as a set of bindings to the corresponding Rust crate

This library is based on a lot of time spent in a hex editor looking at grid files and poring over publicly-available documentation. It is by necessity incomplete and incorrect, and will remain so until the file format is properly and publicly specified.

However, the library is able to successfully read rectangular and triangulated grids and a good portion of their metadata. Please open an issue if you have trouble reading a grid and are able to share the grid (in GRD and exported form) with the developer.

Example usage

This library can be used to read .GRD grid data from a file or file-like object. Here's a short program for dumping "debug" representations of grid files provided on the command line:

import sys

import petra_grid


def main(argv: list[str]) -> int:
    if len(argv) <= 1:
        print(f'Usage: {argv[0] if argv else "read_grid"} <grd-files>',
          file=sys.stderr)
        return 2

    for path in argv[1:]:
        with open(path, 'rb') as f:
            grid = petra_grid.read_grid(f)
            if grid.is_rectangular:
                print(f'{grid.name}: {grid.rows} x {grid.columns} rectangular grid')
            elif grid.is_triangular:
                print(f'{grid.name}: {grid.n_triangles}-triangle triangular grid')
            print(f'Details: {grid}')

    return 0


if __name__ == '__main__':
    sys.exit(main(sys.argv))

As another example, we can use matplotlib to render images of rectangular or triangular grids.

import sys

import petra_grid

import numpy as np

from matplotlib.tri import Triangulation # type: ignore
import matplotlib.pyplot as plt # type: ignore


def plot_rectangular(grid: petra_grid.Grid) -> None:
    plt.imshow(grid.data, extent=(grid.xmin, grid.xmax, grid.ymin, grid.ymax),
      origin='lower')
    plt.title(f'{grid.name}')
    plt.colorbar()
    plt.show()


def plot_triangular(grid: petra_grid.Grid) -> None:
    triangles = grid.data
    xs = np.ravel(triangles[:, :, 0])
    ys = np.ravel(triangles[:, :, 1])
    ixs = np.reshape(np.indices(xs.shape)[0], (triangles.shape[0], 3))
    triangulation = Triangulation(xs, ys, ixs)
    zs = np.ravel(triangles[:, :, 2])
    fig, ax = plt.subplots()
    ax.set_aspect('equal')
    tc = ax.tripcolor(triangulation, zs)
    ax.set_title(f'{grid.name}')
    fig.colorbar(tc)
    plt.show()


def main(argv: list[str]) -> int:
    if len(argv) <= 1:
        print(f'Usage: {argv[0] if argv else "render_grid"} <grd-files>',
          file=sys.stderr)
        return 2

    for path in argv[1:]:
        with open(path, 'rb') as f:
            grid = petra_grid.read_grid(f)
            if grid.is_rectangular:
                plot_rectangular(grid)
            elif grid.is_triangular:
                plot_triangular(grid)
            print(f'Details: {grid}')

    return 0


if __name__ == '__main__':
    sys.exit(main(sys.argv))

Documentation

Documentation strings and type annotations are provided for all public types, functions, and methods. We recommend viewing "nice" documentation pages using pdoc; e.g. in the same environment as the petra_grid package is installed, install pdoc with pip install pdoc, then run pdoc petra_grid.

Available under the MIT license

(c) 2023 dwt | terminus, LLC