add support for velocity mosaics from granule stacks without a common reference date

CHANGELOG.md

@@ -6,6 +6,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [PEP 440](https://www.python.org/dev/peps/pep-0440/)
 and uses [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.4.1]
+### Added
+* Support for generating velocity mosaics from granule stacks without a common reference date 
+
 ## [0.4.0]
 ### Added
 * Ability to update the reference date for OPERA DISP granule xarray objects

src/opera_disp_tms/generate_sw_vel_tile.py

@@ -11,7 +11,7 @@
 
 from opera_disp_tms import generate_sw_disp_tile as sw_disp
 from opera_disp_tms.search import Granule
-from opera_disp_tms.utils import create_buffered_bbox, create_tile_name, get_raster_as_numpy
+from opera_disp_tms.utils import create_buffered_bbox, create_tile_name, get_raster_as_numpy, within_one_day
 
 
 gdal.UseExceptions()
@@ -79,6 +79,20 @@ def parallel_linear_regression(x: np.ndarray, y: np.ndarray) -> np.ndarray:
     return slope_array
 
 
+def align_to_common_reference_date(granule_xrs: list[xr.DataArray]) -> None:
+    previous_granule_xr = granule_xrs[0]
+    correction = np.zeros(previous_granule_xr.shape)
+
+    for granule_xr in granule_xrs:
+        if not within_one_day(granule_xr.attrs['reference_date'], previous_granule_xr.attrs['reference_date']):
+            correction = previous_granule_xr.data
+        granule_xr += correction
+        previous_granule_xr = granule_xr
+
+    for granule_xr in granule_xrs:
+        granule_xr.attrs['reference_date'] = granule_xrs[0].attrs['reference_date']
+
+
 def add_velocity_data_to_array(
     granules: Iterable[Granule],
     geotransform: Affine,
@@ -97,8 +111,10 @@ def add_velocity_data_to_array(
     Returns:
         np.ndarray: The updated array
     """
+    sorted_granules = sorted(granules, key=lambda g: g.secondary_date)
     bbox = create_buffered_bbox(geotransform.to_gdal(), frame_map_array.shape, 90)  # EPSG:3857 is in meters
-    granule_xrs = [sw_disp.load_sw_disp_granule(x, bbox) for x in granules]
+    granule_xrs = [sw_disp.load_sw_disp_granule(x, bbox) for x in sorted_granules]
+    align_to_common_reference_date(granule_xrs)
     cube = xr.concat(granule_xrs, dim='years_since_start')
 
     years_since_start = get_years_since_start([g.attrs['secondary_date'] for g in granule_xrs])

tests/test_generate_sw_vel_tile.py

@@ -1,6 +1,7 @@
 from datetime import datetime
 
 import numpy as np
+import xarray as xr
 
 from opera_disp_tms import generate_sw_vel_tile as sw_vel
 
@@ -54,3 +55,25 @@ def test_parallel_linear_regression():
     x = np.arange(3, dtype='float64')
     slope = sw_vel.parallel_linear_regression(x, y)
     assert np.all(np.isclose(slope, 1.0, atol=1e-6))
+
+
+def test_align_to_common_reference_date():
+    xrs = [
+        xr.DataArray(data=[1., 0.], attrs={'reference_date': datetime(1, 1, 1), 'secondary_date': datetime(1, 1, 2)}),
+        xr.DataArray(data=[5., 0.], attrs={'reference_date': datetime(1, 1, 1), 'secondary_date': datetime(1, 1, 3)}),
+        xr.DataArray(data=[-1., 0.], attrs={'reference_date': datetime(1, 1, 3), 'secondary_date': datetime(1, 1, 4)}),
+        xr.DataArray(data=[7., 0.], attrs={'reference_date': datetime(1, 1, 3), 'secondary_date': datetime(1, 1, 5)}),
+        xr.DataArray(data=[-3., 1.], attrs={'reference_date': datetime(1, 1, 5), 'secondary_date': datetime(1, 1, 6)}),
+    ]
+
+    expected = [
+        xr.DataArray(data=[1., 0.], attrs={'reference_date': datetime(1, 1, 1), 'secondary_date': datetime(1, 1, 2)}),
+        xr.DataArray(data=[5., 0.], attrs={'reference_date': datetime(1, 1, 1), 'secondary_date': datetime(1, 1, 3)}),
+        xr.DataArray(data=[4., 0.], attrs={'reference_date': datetime(1, 1, 1), 'secondary_date': datetime(1, 1, 4)}),
+        xr.DataArray(data=[12., 0.], attrs={'reference_date': datetime(1, 1, 1), 'secondary_date': datetime(1, 1, 5)}),
+        xr.DataArray(data=[9., 1.], attrs={'reference_date': datetime(1, 1, 1), 'secondary_date': datetime(1, 1, 6)}),
+    ]
+
+    sw_vel.align_to_common_reference_date(xrs)
+
+    assert all(a.identical(b) for a, b, in zip(xrs, expected))