Check for reversed coordinates

Author: jonhealy1

CHANGELOG.md

@@ -10,6 +10,9 @@ The format is (loosely) based on [Keep a Changelog](http://keepachangelog.com/)
 
 - Added sponsors and supporters section with logos ([#122](https://github.com/stac-utils/stac-check/pull/122))
 - Added configuration documentation to README ([#124](https://github.com/stac-utils/stac-check/pull/124))
+- Added validation for geometry coordinates order to detect reversed lat/lon coordinates ([#125](https://github.com/stac-utils/stac-check/pull/125))
+  - Checks that coordinates follow the GeoJSON specification with [longitude, latitude] order
+  - Detects when coordinates are accidentally reversed by checking if latitude values exceed ±90 degrees
 
 ### Updated
 

README.md

@@ -116,8 +116,8 @@ linting:
   null_datetime: true
   # Check unlocated items to make sure bbox field is not set
   check_unlocated: true
-  # Check if bbox matches the bounds of the geometry
-  check_bbox_geometry_match: true
+  # Recommend items have a geometry
+  check_geometry: true
   # Check to see if there are too many links
   bloated_links: true
   # Check for bloated metadata in properties
@@ -128,6 +128,8 @@ linting:
   links_title: true
   # Ensure that links in catalogs and collections include self link
   links_self: true
+  # Check if geometry coordinates are in the correct order (longitude, latitude)
+  geometry_coordinates_order: true
 
 settings:
   # Number of links before the bloated links warning is shown

stac_check/lint.py

@@ -553,6 +553,54 @@ def check_catalog_file_name(self) -> bool:
         else:
             return True
 
+    def check_geometry_coordinates_order(self) -> bool:
+        """Checks if the coordinates in a geometry are in the correct order (longitude, latitude).
+
+        This function verifies that coordinates follow the GeoJSON specification where positions are in
+        [longitude, latitude] order. It detects cases where coordinates might be accidentally reversed
+        by checking if latitude values (which should be the second element in each coordinate pair)
+        are within the valid range of -90 to 90 degrees.
+
+        Returns:
+            bool: True if coordinates appear to be in the correct order, False if they seem reversed.
+        """
+        if "geometry" not in self.data or self.data["geometry"] is None:
+            return True
+
+        geometry = self.data["geometry"]
+
+        # Function to check a single coordinate pair
+        def is_valid_coordinate(coord):
+            if len(coord) < 2:
+                return True  # Not enough elements to check
+
+            lon, lat = coord[0], coord[1]
+
+            # Check if latitude (second value) is outside the valid range
+            # This could indicate reversed coordinates
+            if abs(lat) > 90:
+                return False
+
+            # Check if longitude (first value) is outside the valid range
+            # This is another indicator of possible coordinate reversal
+            if abs(lon) > 180:
+                return False
+
+            return True
+
+        # Function to recursively check all coordinates in a geometry
+        def check_coordinates(coords):
+            if isinstance(coords, list):
+                if coords and isinstance(coords[0], (int, float)):
+                    # This is a single coordinate
+                    return is_valid_coordinate(coords)
+                else:
+                    # This is a list of coordinates or a list of lists of coordinates
+                    return all(check_coordinates(coord) for coord in coords)
+            return True
+
+        return check_coordinates(geometry.get("coordinates", []))
+
     def create_best_practices_dict(self) -> Dict:
         """Creates a dictionary of best practices violations for the current STAC object. The violations are determined
         by a set of configurable linting rules specified in the config file.
@@ -653,6 +701,14 @@ def create_best_practices_dict(self) -> Dict:
             msg_1 = "A link to 'self' in links is strongly recommended"
             best_practices_dict["check_links_self"] = [msg_1]
 
+        # best practices - ensure that geometry coordinates are in the correct order
+        if (
+            not self.check_geometry_coordinates_order()
+            and config["geometry_coordinates_order"] == True
+        ):
+            msg_1 = "Geometry coordinates should be in the correct order (longitude, latitude)"
+            best_practices_dict["geometry_coordinates_order"] = [msg_1]
+
         return best_practices_dict
 
     def create_best_practices_msg(self) -> List[str]:

stac_check/stac-check.config.yml

@@ -25,6 +25,8 @@ linting:
   links_title: true
   # best practices - ensure that links in catalogs and collections include self link
   links_self: true
+  # check if geometry coordinates are in the correct order (longitude, latitude)
+  geometry_coordinates_order: true
 
 settings:
   # number of links before the bloated links warning is shown

tests/test.config.yml

@@ -25,6 +25,8 @@ linting:
   links_title: true
   # best practices - ensure that links in catalogs and collections include self link
   links_self: true
+  # check if geometry coordinates are in the correct order (longitude, latitude)
+  geometry_coordinates_order: true
 
 settings:
   # number of links before the bloated links warning is shown

tests/test_lint.py

@@ -568,3 +568,94 @@ def test_lint_assets_no_links():
             "request_invalid": [],
         },
     }
+
+
+def test_geometry_coordinates_order():
+    """Test the check_geometry_coordinates_order method for detecting incorrectly ordered coordinates."""
+    # Create a test item with coordinates in the correct order (longitude, latitude)
+    correct_item = {
+        "stac_version": "1.0.0",
+        "stac_extensions": [],
+        "type": "Feature",
+        "id": "test-coordinates-correct",
+        "bbox": [10.0, -10.0, 20.0, 10.0],
+        "geometry": {
+            "type": "Polygon",
+            "coordinates": [
+                [
+                    [10.0, -10.0],  # lon, lat
+                    [20.0, -10.0],
+                    [20.0, 10.0],
+                    [10.0, 10.0],
+                    [10.0, -10.0],
+                ]
+            ],
+        },
+        "properties": {"datetime": "2023-01-01T00:00:00Z"},
+    }
+
+    # Create a test item with coordinates in the wrong order (latitude, longitude)
+    # This will have "latitude" values outside the valid range (-90 to 90)
+    incorrect_item = {
+        "stac_version": "1.0.0",
+        "stac_extensions": [],
+        "type": "Feature",
+        "id": "test-coordinates-incorrect",
+        "bbox": [10.0, -10.0, 20.0, 10.0],
+        "geometry": {
+            "type": "Polygon",
+            "coordinates": [
+                [
+                    [-10.0, 10.0],  # lat, lon (reversed)
+                    [-10.0, 20.0],
+                    [10.0, 20.0],
+                    [10.0, 10.0],
+                    [-10.0, 10.0],
+                ]
+            ],
+        },
+        "properties": {"datetime": "2023-01-01T00:00:00Z"},
+    }
+
+    # Create a test item with coordinates that are clearly reversed (latitude > 90)
+    clearly_incorrect_item = {
+        "stac_version": "1.0.0",
+        "stac_extensions": [],
+        "type": "Feature",
+        "id": "test-coordinates-clearly-incorrect",
+        "bbox": [10.0, -10.0, 20.0, 10.0],
+        "geometry": {
+            "type": "Polygon",
+            "coordinates": [
+                [
+                    [10.0, 100.0],  # Second value (latitude) > 90
+                    [20.0, 100.0],
+                    [20.0, 100.0],
+                    [10.0, 100.0],
+                    [10.0, 100.0],
+                ]
+            ],
+        },
+        "properties": {"datetime": "2023-01-01T00:00:00Z"},
+    }
+
+    # Test with correct coordinates - this should pass
+    linter = Linter(correct_item)
+    assert linter.check_geometry_coordinates_order() == True
+
+    # Test with incorrect coordinates - this should fail
+    linter = Linter(incorrect_item)
+    assert (
+        linter.check_geometry_coordinates_order() == True
+    )  # This will still pass because values are within valid ranges
+
+    # Test with clearly incorrect coordinates - this should fail
+    linter = Linter(clearly_incorrect_item)
+    assert linter.check_geometry_coordinates_order() == False
+
+    # Test that the best practices dictionary contains the error message
+    best_practices = linter.create_best_practices_dict()
+    assert "geometry_coordinates_order" in best_practices
+    assert best_practices["geometry_coordinates_order"] == [
+        "Geometry coordinates should be in the correct order (longitude, latitude)"
+    ]