Use latest liblonlat_bng (#110)

Author: urschrei

README.md

@@ -6,8 +6,8 @@ A utility library for converting decimal [WGS84](http://spatialreference.org/ref
 Conversion is handled by a [Rust binary](https://github.com/urschrei/rust_bng) using FFI, and is quite fast. Some benchmarks can be found [here](https://github.com/urschrei/lonlat_bng#benchmark).
 
 # Installation
-- `pip install convertbng`
 - `uv add convertbng`
+- `pip install convertbng`
 
 ## Installing for local development
 1. Ensure you have a copy of `liblonlat_bng` and `header.h` from https://github.com/urschrei/lonlat_bng/releases, and it's in the `src/convertbng` subdir
@@ -65,6 +65,17 @@ lats_np = np.array(lats)
     res_list_np = convert_bng(lons_np, lats_np)
 ```
 
+# Accuracy
+The [Rust library](https://github.com/urschrei/lonlat_bng) produces the following results when round-tripping the 40 OSTN15 test points (only differences are shown)
+
+| Test Point | Input OSGB36 E (m) | Input OSGB36 N (m) | Lon diff (°) | Lat diff (°) | E diff (m) | N diff (m) |
+|:-----------|-------------------:|-------------------:|-------------:|-------------:|-----------:|-----------:|
+| TP27       | 319188.434         | 670947.534         | —            | —            | —          | +0.001     |
+| TP31       | 9587.909           | 899448.996         | +6×10⁻⁸      | -3×10⁻⁸      | +0.003     | -0.004     |
+| TP32       | 71713.132          | 938516.404         | +2×10⁻⁸      | -1×10⁻⁸      | +0.001     | -0.002     |
+| TP37       | 180862.461         | 1029604.114        | —            | —            | —          | -0.001     |
+| TP38       | 421300.525         | 1072147.239        | —            | —            | —          | -0.001     |
+
 # Cython Module
 If you're comfortable with restricting yourself to `NumPy f64` arrays, you may use the Cython functions instead. These are identical to those listed below, but performance on large datasets is better. They are selected by changing the import statement  
 `from convertbng.util import` to  

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "convertbng"
-version = "0.7.9"
+version = "0.7.10"
 description = "Fast lon, lat to and from ETRS89 and BNG (OSGB36) using the OS OSTN15 transform via Rust FFI"
 readme = "README.md"
 requires-python = ">=3.10"

tests/test_convertbng.py

@@ -80,9 +80,9 @@ def test_non_convergence(self):
             [408884, 333642],
         ]
         expected = [
-            [-1.92485417, 53.26107641],
-            [-1.6233221, 52.06744836],
-            [-1.86937174, 52.90016459],
+            [-1.92485417, 53.26107642],
+            [-1.62332209, 52.06744836],
+            [-1.86937175, 52.9001646],
         ]
         for i, j in zip(extremes, expected):
             exp = ([j[0]], [j[1]])
@@ -91,7 +91,7 @@ def test_non_convergence(self):
 
     def testConvertBNG(self):
         """Test multithreaded BNG --> lon, lat function"""
-        expected = ([-0.32822654, -2.01831267], [51.44533145, 54.58910534])
+        expected = ([-0.32822654, -2.01831268], [51.44533144, 54.58910534])
         result = convert_lonlat([516276, 398915], [173141, 521545])
         self.assertEqual(expected, result)
 
@@ -231,7 +231,7 @@ def test_etrs89_to_osgb36(self):
 
     def test_osgb36_to_etrs89(self):
         """Tests OSGB36 --> ETRS89 Eastings, Northings conversion"""
-        expected = ([651307.003], [313255.686])
+        expected = ([651307.0032098937], [313255.68598407705])
         result = convert_osgb36_to_etrs89(651409.804, 313177.45)
         self.assertEqual(expected, result)