MGRS Coordinate Conversion for Python

Common errors

• mgrs.core.MGRSError: Unable to load libmgrs.cpXX-win_amd64.pyd

  cause This error typically occurs when using application packagers like PyInstaller on Windows. The underlying shared library (`.pyd` file) for `mgrs` is not correctly located or bundled in the final executable.
  fix When using PyInstaller, you often need to explicitly include the `mgrs` package's shared libraries in your `.spec` file. A common fix is to add a `datas` entry to copy the `libmgrs*.pyd` file. For example: `datas=[('path/to/venv/Lib/site-packages/mgrs', 'mgrs')]` (adjust paths as necessary to include the `.pyd` file).

• ImportError: cannot import name 'MGRS' from 'mgrs' (or similar during `import mgrs`)

  cause This usually indicates an incomplete or corrupted installation of the `mgrs` package, or a conflict if another package named `mgrs` exists in the Python path. In older versions, it could also stem from failed compilation of the C components.
  fix Perform a clean reinstall of the package: `pip uninstall mgrs` followed by `pip install mgrs --no-cache-dir`. Ensure your Python environment meets the `>=3.9` requirement and that no other `mgrs.py` or `mgrs` package shadows the correct one.

• TypeError: toMGRS() missing 1 required positional argument: 'longitude'

  cause The `toMGRS` method requires both `latitude` and `longitude` arguments. This error means one or both were omitted or passed incorrectly.
  fix Ensure both latitude and longitude are provided as numeric arguments: `m.toMGRS(latitude, longitude)`.

Warnings

• deprecated The `RTreeError` exception was deprecated and aliased to `MGRSError` in version 1.4.0. Direct usage of `RTreeError` should be replaced with `MGRSError` for future compatibility.
  Fix: Replace `except RTreeError:` with `except MGRSError:`.
• breaking Earlier versions (prior to 1.3.4) were reported to incorrectly round MGRS coordinates instead of truncating them, leading to precision errors. MGRS requires truncation.
  Fix: Upgrade to `mgrs` version 1.3.4 or newer to ensure correct truncation behavior for MGRS coordinates.
• gotcha For older Python environments or manual compilation, the `mgrs` library, being a Ctypes wrapper around C code, historically had complex installation challenges on Windows without pre-built wheels. This is largely mitigated by modern `pip` and wheel distributions.
  Fix: Ensure you have a recent `pip` and Python (>=3.9) to leverage pre-built wheels. If issues persist, verify your C compiler setup or use a Linux/macOS environment.

Install

• pip install mgrs Install latest stable version

Imports

• MGRS
  wrong:

  import mgrs; mgrs.MGRS()

  correct:

  from mgrs import MGRS

  While `import mgrs` works, it's generally cleaner to import the `MGRS` class directly for instantiation.

Quickstart

This quickstart demonstrates how to initialize the MGRS converter and perform common operations such as converting between latitude/longitude and MGRS, and between Degrees-Minutes-Seconds (DMS) strings and decimal degrees. Precision can also be controlled in `toMGRS()`.

from mgrs import MGRS

m = MGRS()

# Convert Latitude/Longitude to MGRS
latitude = 42.0
longitude = -93.0
mgrs_coords = m.toMGRS(latitude, longitude)
print(f"({latitude}, {longitude}) -> {mgrs_coords}")

# Convert MGRS to Latitude/Longitude
lat_lon_coords = m.toLatLon(mgrs_coords)
print(f"{mgrs_coords} -> {lat_lon_coords}")

# Convert DMS to Decimal Degrees
dms_str = '321942.29N'
dec_deg = m.dmstodd(dms_str)
print(f"{dms_str} -> {dec_deg}")

# Convert Decimal Degrees to DMS
d, minute, s = m.ddtodms(dec_deg)
print(f"{dec_deg} -> (D:{d}, M:{minute}, S:{s}))")