Fix inverted resolution check in _line_to_pnts

The warning meant to flag under-resolved line exposures in
`climada.util.lines_polys_handler._line_to_pnts` used an inverted
comparison: it counted lines *longer* than `10 * resolution` while its
comment and message describe lines *shorter* than that. As a result,
genuinely under-resolved lines (which collapse to too few points and
overestimate the re-aggregated impact) were skipped silently, while
well-resolved long lines produced a spurious, self-contradicting warning.

Flip the comparison to `< 10 * res`, correct the message wording and
typos, and update `test_resolution_warning` accordingly.

Fixes #1302

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: 2 people

CHANGELOG.md

@@ -28,6 +28,7 @@ Code freeze date: YYYY-MM-DD
 - Fixed asset count in impact logging message [#1195](https://github.com/CLIMADA-project/climada_python/pull/1195).
 - `Hazard.from_raster_xarray` now returns a sparse matrix instead of a sparse array [#1261](https://github.com/CLIMADA-project/climada_python/pull/1261).
 - Fix TCTracks.from_FAST duplicate loading from year loop [#1269](github.com/CLIMADA-project/climada_python/pull/1269)
+- Fixed inverted resolution check in `climada.util.lines_polys_handler._line_to_pnts`: the "under-resolved lines" warning was triggered for lines *longer* than `10 * resolution` instead of *shorter*, so genuinely under-resolved line exposures were silently disaggregated to too few points (overestimating the re-aggregated impact) while well-resolved lines produced a spurious warning. The warning message wording and typos were also corrected [#1303](https://github.com/CLIMADA-project/climada_python/issues/1302)
 
 ### Deprecated
 - `Impact.calc_freq_curve()` should not be given the parameter `return_per`. Use the parameter `return_periods` in `Impact.calc_freq_curve().interpolate()` instead.

climada/util/lines_polys_handler.py

@@ -957,13 +957,14 @@ def _line_to_pnts(gdf_lines, res, to_meters):
         line_lengths = gdf_lines.length
 
     # Add warning if lines are too short w.r.t. resolution
-    failing_res_check_count = len(line_lengths[line_lengths > 10 * res])
+    failing_res_check_count = len(line_lengths[line_lengths < 10 * res])
     if failing_res_check_count > 0:
         LOGGER.warning(
             "%d lines with a length < 10*resolution were found. "
-            "Each of these lines is disaggregate to one point. "
-            "Reaggregatint values will thus likely lead to overestimattion. "
-            "Consider chosing a smaller resolution or filter out the short lines. ",
+            "Each of these lines is disaggregated to very few points, possibly "
+            "a single one. Reaggregating values will thus likely lead to "
+            "overestimation. Consider choosing a smaller resolution or filtering "
+            "out the short lines. ",
             failing_res_check_count,
         )
 

climada/util/test/test_lines_polys_handler.py

@@ -1097,6 +1097,8 @@ def test_line_fractions(self):
             )
 
     def test_resolution_warning(self):
+        # Only the first line is shorter than 10 * resolution (10 * 1 = 10) and is
+        # therefore under-resolved; the two longer lines must not trigger the warning.
         lines = [
             LineString([[0, 0], [0, 2]]),
             LineString([[0, 0], [0, 12]]),
@@ -1109,10 +1111,11 @@ def test_resolution_warning(self):
             u_lp._line_to_pnts(gdf_lines, 1, False)
         self.assertEqual(
             ctx.records[0].message,
-            f"{2} lines with a length < 10*resolution were found. "
-            "Each of these lines is disaggregate to one point. "
-            "Reaggregatint values will thus likely lead to overestimattion. "
-            "Consider chosing a smaller resolution or filter out the short lines. ",
+            f"{1} lines with a length < 10*resolution were found. "
+            "Each of these lines is disaggregated to very few points, possibly "
+            "a single one. Reaggregating values will thus likely lead to "
+            "overestimation. Consider choosing a smaller resolution or filtering "
+            "out the short lines. ",
         )
 
     def test_gdf_to_grid(self):