fix: capture area rounding TDE-1237 (#1116)

### Motivation

Although the footprint files are rounded to 8 decimal places, when they
are combined into a capture area this can create some co-ordinates with
more than 8 decimal places, which we then need to round.

### Modifications

Use Shapely to round the co-ordinates to 8 decimal places after merging
the footprint geometries.

### Verification

Unit test created, unit tests updated for new capture area rounding.
Manually compared
[capture-area-compare.zip](https://github.com/user-attachments/files/17299987/capture-area-compare.zip).

scripts/stac/imagery/capture_area.py

@@ -3,7 +3,7 @@
 from typing import Any, Sequence
 
 from linz_logger import get_log
-from shapely import BufferCapStyle, BufferJoinStyle, to_geojson, union_all
+from shapely import BufferCapStyle, BufferJoinStyle, to_geojson, union_all, wkt
 from shapely.geometry.base import BaseGeometry
 from shapely.ops import orient
 
@@ -62,9 +62,10 @@ def merge_polygons(polygons: Sequence[BaseGeometry], buffer_distance: float) ->
     # Negative buffer back in the polygons
     union_unbuffered = union_buffered.buffer(-buffer_distance, cap_style=BufferCapStyle.flat, join_style=BufferJoinStyle.mitre)
     union_simplified = union_unbuffered.simplify(buffer_distance)
+    union_rounded = wkt.loads(wkt.dumps(union_simplified, rounding_precision=8))
     # Apply right-hand rule winding order (exterior rings should be counter-clockwise) to the geometry
     # Ref: https://datatracker.ietf.org/doc/html/rfc7946#section-3.1.6
-    oriented_union_simplified = orient(union_simplified, sign=1.0)
+    oriented_union_simplified = orient(union_rounded, sign=1.0)
 
     return oriented_union_simplified
 

scripts/stac/imagery/tests/capture_area_test.py

@@ -58,11 +58,11 @@ def test_merge_polygons_with_rounding_margin_too_big() -> None:
             (1.0, 1.0),
             (0.0, 1.0),
             (0.0, 0.0),
-            (1.9999999999999998, 0.0),
-            (1.9999999999999998, 1.0),
+            (2.0, 0.0),
+            (2.0, 1.0),
             (1.1, 1.0),
-            (1.015018629811984, 0.1501862981198402),
-            (1.0, 0.15093536161009757),
+            (1.01501863, 0.1501863),
+            (1.0, 0.15093536),
             (1.0, 1.0),
         ]
     )
@@ -190,3 +190,42 @@ def test_capture_area_orientation_multipolygon() -> None:
     capture_area = generate_capture_area(polygons, Decimal("0.05"))
     mp_geom = cast(MultiPolygon, shape(capture_area["geometry"]))
     assert is_ccw(get_exterior_ring(mp_geom.geoms[0]))
+
+
+def test_capture_area_rounding_decimal_places() -> None:
+    # Test that the capture area is rounded to 8 decimal places
+    polygons = []
+    polygons.append(
+        shape(
+            {
+                "type": "MultiPolygon",
+                "coordinates": [
+                    [
+                        [
+                            [174.673418475601466, -37.051277768264598],
+                            [174.673425023818197, -37.051550327851878],
+                            [174.673479898051271, -37.051280958541774],
+                            [174.673418475601466, -37.051277768264598],
+                        ]
+                    ]
+                ],
+            }
+        )
+    )
+    capture_area_expected = {
+        "geometry": {
+            "type": "Polygon",
+            "coordinates": [
+                [
+                    [174.67342502, -37.05155033],
+                    [174.6734799, -37.05128096],
+                    [174.67341848, -37.05127777],
+                    [174.67342502, -37.05155033],
+                ]
+            ],
+        },
+        "type": "Feature",
+        "properties": {},
+    }
+    capture_area = generate_capture_area(polygons, Decimal("1"))
+    assert capture_area == capture_area_expected

scripts/stac/imagery/tests/collection_test.py

@@ -310,17 +310,14 @@ def test_capture_area_added(fake_collection_metadata: CollectionMetadata, subtes
 
     with subtests.test():
         assert collection.stac["assets"]["capture_area"]["file:checksum"] in (
-            "1220369cd5d4179f5f68ca0fd9be70b9f66033fcc6bb2f3305c0ad977adc79d7ad53",  # geos 3.11 - geos 3.12 as yet untested
+            "1220ba57cd77defc7fa72e140f4faa0846e8905ae443de04aef99bf381d4650c17a0",  # geos 3.11 - geos 3.12 as yet untested
         )
 
     with subtests.test():
         assert "file:size" in collection.stac["assets"]["capture_area"]
 
     with subtests.test():
-        assert collection.stac["assets"]["capture_area"]["file:size"] in (
-            339,  # geos 3.11
-            299,  # geos 3.12
-        )
+        assert collection.stac["assets"]["capture_area"]["file:size"] in (269,)  # geos 3.11 - geos 3.12 as yet untested
 
 
 def test_event_name_is_present(fake_collection_metadata: CollectionMetadata) -> None: