Progress on implementing relative altitude filter

src/pyaro/timeseries/AutoFilterReaderEngine.py

@@ -31,11 +31,7 @@ def supported_filters(cls) -> list[Filter]:
 
         :return: list of filters
         """
-<<<<<<< HEAD
-        supported = "variables,stations,countries,bounding_boxes,duplicates,time_bounds,time_resolution,flags,time_variable_station,altitude".split(
-=======
-        supported = "variables,stations,countries,bounding_boxes,duplicates,time_bounds,time_resolution,flags,time_variable_station,relaltitude".split(
->>>>>>> 0ad9bdf (Boilerplate)
+        supported = "variables,stations,countries,bounding_boxes,duplicates,time_bounds,time_resolution,flags,time_variable_station,altitude,relaltitude".split(
             ","
         )
         return [filters.get(name) for name in supported]

src/pyaro/timeseries/Filter.py

@@ -9,6 +9,7 @@
 from typing import Any
 
 import numpy as np
+import xarray as xr
 
 from .Data import Data, Flag
 from .Station import Station
@@ -857,21 +858,69 @@ def filter_stations(self, stations: dict[str, Station]) -> dict[str, Station]:
 
         return stations
 
+@registered_filter
 class RelativeAltitudeFilter(StationFilter):
     """
     Filter class which filters stations based on the relative difference between
     the station altitude, and the model topography altitude.
 
     https://github.com/metno/pyaro/issues/39
     """
-    def __init__(self):
-        pass
+    def __init__(self, topo_file: str = "/lustre/storeB/project/fou/kl/emep/Auxiliary/topography.nc", topo_var: str = "topography", rtol: float = 1):
+        """
+        :param topo_file : A .nc file from which to read model topography data.
+        :param topo_var : Name of variable that stores altitude.
+        :param rtol : Relative toleranse.
+        """
+        self._file = topo_file
+        self._topo_var = topo_var
+        self._rtol = rtol
+
+        self._topography = xr.open_dataset(self._file)
 
+    def _model_altitude_from_lat_lon(self, lat: float, lon: float) -> float:
+        data = self._topography.sel({"lat": lat, "lon": lon}, method="nearest")
+
+        # Should not vary in time too much so picking the first one here.
+        altitude = data["topography"][0]
+
+        return float(altitude)
+
+    def _is_close(self, altmod: float, altobs: float) -> bool:
+        """
+        Function to check if two altitudes are within a relative tolerance of each
+        other.
+        
+        :param altmod : Model altitude (in meters).
+        :param altobs : Observation / station altitude (in meters).
+
+        :returns :
+            True if the values are close with station altitude as the reference 
+            value.
+        """
+        return abs(altmod-altobs) <= (self._rtol * abs(altobs))
+
     def init_kwargs(self):
-        return {}
+        return {
+            "topo_file": self._file,
+            "topo_var": self._topo_var,
+            "rtol": self._rtol 
+        }
 
     def name(self):
         return "relaltitude"
 
     def filter_stations(self, stations: dict[str, Station]) -> dict[str, Station]:
-        return stations
+        new_stations = dict()
+
+        for name, station in stations.items():
+            lat = station["latitude"]
+            lon = station["longitude"]
+
+            altobs = station["altitude"]
+            altmod = self._model_altitude_from_lat_lon(lat, lon)
+
+            if self._is_close(altmod, altobs):
+                new_stations[name] = station
+
+        return new_stations

tests/test_CSVTimeSeriesReader.py

@@ -485,6 +485,29 @@ def test_altitude_filter_3(self):
             }
         ) as ts:
             self.assertEqual(len(ts.stations()), 1)
+
+    def test_relaltitude_filter_1(self):
+        engines = pyaro.list_timeseries_engines()
+        with engines["csv_timeseries"].open(
+            filename=self.elevation_file,
+            filters=[pyaro.timeseries.filters.get("relaltitude")],
+            columns={
+                "variable": 0,
+                "station": 1,
+                "longitude": 2,
+                "latitude": 3,
+                "value": 4,
+                "units": 5,
+                "start_time": 6,
+                "end_time": 7,
+                "altitude": 9,
+                "country": "NO",
+                "standard_deviation": "NaN",
+                "flag": "0",
+            }
+        ) as ts:
+            ts.stations()
+            self.assertTrue(True)
 
 
 if __name__ == "__main__":