ENH: Add two functions for converting degrees to and from meters: `ra…

…sters.from_deg_to_meters` and `rasters.from_meters_to_deg`

CHANGES.md

@@ -1,7 +1,8 @@
 # Release History
 
-## 1.45.3 (2025-mm-dd)
+## 1.46.0 (2025-mm-dd)
 
+- **ENH: Add two functions for converting degrees to and from meters: `rasters.from_deg_to_meters` and `rasters.from_meters_to_deg`** 
 - FIX: Don't take nodata value into account in `ci.assert_raster_almost_equal_magnitude`
 
 ## 1.45.2 (2025-02-17)

ci/test_rasters.py

@@ -28,6 +28,7 @@
 from ci.script_utils import KAPUT_KWARGS, dask_env, get_output, rasters_path, s3_env
 from sertit import ci, geometry, path, rasters, unistra, vectors
 from sertit.rasters import (
+    DEG_LAT_TO_M,
     FLOAT_NODATA,
     INT8_NODATA,
     UINT8_NODATA,
@@ -991,3 +992,49 @@ def test_get_notata_from_xr(raster_path):
 
     raster_path = rasters_path().joinpath("dem.tif")
     ci.assert_val(get_nodata_value_from_xr(rasters.read(raster_path)), -9999, "nodata")
+
+
+def test_deg_meters_conversion():
+    """
+    Test conversions between deg and meters
+    https://wiki.openstreetmap.org/wiki/Precision_of_coordinates#Precision_of_latitudes
+    """
+    # from_deg_to_meters
+    ci.assert_val(
+        rasters.from_deg_to_meters(1), DEG_LAT_TO_M, "1 degree of latitude in meters"
+    )
+    ci.assert_val(
+        rasters.from_deg_to_meters(1, lat=45),
+        78573.71,
+        "1 degree of longitude at 45 degrees of latitude in meters",
+    )
+    ci.assert_val(
+        rasters.from_deg_to_meters(1, lat=45, decimals=0),
+        78574,
+        "1 degree of longitude at 45 degrees of latitude in meters with 0 decimal",
+    )
+    ci.assert_val(
+        rasters.from_deg_to_meters(1, lat=45, decimals=0, average_lat_lon=True),
+        round((DEG_LAT_TO_M + 78574) / 2),
+        "1 degree of longitude at 45 degrees of latitude in meters (averaged) with 0 decimal",
+    )
+
+    # from_deg_to_meters
+    ci.assert_val(
+        rasters.from_meters_to_deg(0.5), 4.5e-06, "0.5 meter in degrees of latitude"
+    )
+    ci.assert_val(
+        rasters.from_meters_to_deg(0.5, lat=45),
+        6.4e-06,
+        "0.5 meter in degree of longitude at 45 degrees of latitude",
+    )
+    ci.assert_val(
+        rasters.from_meters_to_deg(0.5, lat=45, decimals=9),
+        6.363e-06,
+        "0.5 meter in degree of longitude at 45 degrees of latitude with 9 decimal",
+    )
+    ci.assert_val(
+        rasters.from_meters_to_deg(0.5, lat=45, decimals=9, average_lat_lon=True),
+        5.432e-06,
+        "0.5 meter in degree of longitude at 45 degrees of latitude (averaged) with 9 decimal",
+    )

sertit/__meta__.py

@@ -17,4 +17,4 @@
 Sertit Utils library
 """
 
-__version__ = "1.45.2"
+__version__ = "1.46.0.dev0"

sertit/rasters.py

@@ -29,8 +29,6 @@
 import xarray as xr
 from shapely.geometry import Polygon
 
-from sertit.rasters_rio import DEG_2_RAD
-
 try:
     import rasterio
     import rioxarray
@@ -63,6 +61,11 @@
 FLOAT_NODATA = rasters_rio.FLOAT_NODATA
 """ :code:`float` nodata """
 
+DEG_LAT_TO_M = 111_120.0
+DEG_2_RAD = rasters_rio.DEG_2_RAD
+
+# https://wiki.openstreetmap.org/wiki/Precision_of_coordinates#Precision_of_latitudes
+
 
 def get_nodata_value_from_xr(xds: AnyXrDataStructure) -> float:
     """
@@ -2033,3 +2036,61 @@ def aspect(xds: AnyRasterType, **kwargs) -> AnyXrDataStructure:
 
 
 # TODO: add other DEM-related functions like 'curvature', etc if needed. Create a dedicated module?
+
+
+def from_deg_to_meters(
+    deg: float, lat: float = None, decimals: float = 2, average_lat_lon: bool = False
+) -> float:
+    """
+    Approximately convert a distance in degrees to a distance in meters.
+
+    Only true at the Equator if lat is not given.
+    Very false for longitude distance elsewhere.
+
+    If lat is given
+
+    See https://wiki.openstreetmap.org/wiki/Precision_of_coordinates
+
+    Args:
+        deg (float): Distance in degrees
+        lat (float): Latitude (useful if the distance is longitudinal)
+        decimals (float): To round the distance, as the precision can be poor here
+        average_lat_lon (bool): Average between lat distance and lon distance
+
+    Returns:
+        float: Distance in meters
+    """
+    dist = float(deg) * DEG_LAT_TO_M
+
+    if lat is not None:
+        dist_lon = dist * np.cos(lat * DEG_2_RAD)
+        dist = (dist + dist_lon) / 2 if average_lat_lon else dist_lon
+
+    return np.round(dist, decimals)
+
+
+def from_meters_to_deg(
+    meters: float, lat: float = None, decimals: float = 7, average_lat_lon: bool = False
+) -> float:
+    """
+    Approximately convert a distance in meters to a distance in degrees. Only true at the Equator.
+    Very false for longitude distance elsewhere.
+
+    See https://wiki.openstreetmap.org/wiki/Precision_of_coordinates
+
+    Args:
+        meters (float): Distance in meters
+        lat (float): Latitude (useful if the distance is longitudinal)
+        decimals (float): To round the distance, as the precision can be poor here. 7 decimals is equivalent to a centimetric precision
+        average_lat_lon (bool): Average between lat distance and lon distance
+
+    Returns:
+        float: Distance in degrees
+    """
+    dist = float(meters) / DEG_LAT_TO_M
+
+    if lat is not None:
+        dist_lon = dist / np.cos(lat * DEG_2_RAD)
+        dist = (dist + dist_lon) / 2 if average_lat_lon else dist_lon
+
+    return np.round(dist, decimals)