[ryan-kipawa]

Closes #47

What and why

A dfsu written by DfsuBuilder with a geographic projection such as LONG/LAT holds its node coordinates in degrees, but the X-coord and Y-coord static items were recorded as eumIGeographicalCoordinate in metre. The check that switches them to eumILatLong in degrees was left commented out (# TODO: reenable) when MapProjection wasn't available yet. Projections.py now has MapProjection.IsValid and IsGeographical, so this PR turns the check back on. Files with a projected coordinate system (UTM, NON-UTM) still get metres.

The new output matches the geographic dfsu files that DHI tools produce, for example mikeio's public test file tests/testdata/wind_north_sea.dfsu (LONG/LAT, X-coord = eumILatLong, eumUdegree; see Evidence).

Commits

1. abd3215 Test that DfsuBuilder writes X/Y in degrees for geographic projections: a parametrized test that builds a two-triangle mesh for LONG/LAT, UTM-33 and NON-UTM and reads back the X/Y quantities. The LONG/LAT case fails at this commit.
2. 25d5f61 Write X/Y as degrees in geographic dfsu files: replaces the commented-out block with live code.
3. 47ec11a Note the geographic X/Y quantity fix in the changelog: one entry under Unreleased / Fixed. It says the file output changes.

Code Review Guide

Glossary

• Static item: a fixed array stored once in a dfs file. A dfsu stores its mesh this way: Node id, X-coord, Y-coord, Z-coord, … each with an EUM quantity (item type and unit).
• eumIGeographicalCoordinate / eumUmeter: the quantity for projected map coordinates in metres.
• eumILatLong / eumUdegree: the quantity for longitude/latitude in degrees.
• MapProjection.IsGeographical(wkt): true when the projection string means lon/lat coordinates (LONG/LAT, a GEOGCS[...] WKT), false for projected ones such as UTM-33.

Where the change sits

flowchart LR
  A["DfsuBuilder.CreateFile<br/>mikecore/DfsuBuilder.py:681"] --> B["CreateDfsu<br/>mikecore/DfsuBuilder.py:691"]
  B --> C["pick xyQuantity<br/>mikecore/DfsuBuilder.py:706-710"]
  C --> M["MapProjection.IsValid / IsGeographical<br/>mikecore/Projections.py:1296, 1359"]
  C --> D["AddCreateStaticItem X-coord, Y-coord<br/>mikecore/DfsuBuilder.py:716, 719"]
  P["SetProjection<br/>mikecore/DfsuBuilder.py:98"] -.-> C
  classDef changed fill:#2da44e,stroke:#1a7f37,color:#fff
  class C changed

Loading

CreateDfsu picks the X/Y quantity from the projection set earlier and uses it for both coordinate static items.

Conventions followed

Optional builder fields are checked with is not None before use
mikecore/DfsuBuilder.py:489 if self.__timeAxis is not None: dfsBuilder.SetTemporalAxis(self.__timeAxis)	mikecore/DfsuBuilder.py:707 if self.__dfsProjection is not None: wkt = self.__dfsProjection.WKTString if MapProjection.IsValid(wkt) and MapProjection.IsGeographical(wkt): xyQuantity = eumQuantity(eumItem.eumILatLong, eumUnit.eumUdegree)
Builder tests write to tmp_path with the shared _builder() mesh and assert what reads back
tests/test_dfsu_builder.py:91 filename = str(tmp_path / "zunit.dfsu") builder = _builder() builder.SetNodes(X, Y, Z, CODE) ... assert eumUnit.eumUfeet == dfsu.ZUnit	tests/test_dfsu_builder.py:114 filename = str(tmp_path / "xyquantity.dfsu") builder = _builder() builder.SetProjection(DfsFactory().CreateProjection(projection)) ... assert xyQuantity == (staticItem.Quantity.Item, staticItem.Quantity.Unit)

Deviations

The test reads the file with DfsFileFactory.DfsGenericOpen, not DfsuFile.Open. Why: DfsuFile doesn't expose the static items' quantities. Alternative: none through the public API.
tests/test_dfsu_builder.py:100 dfsu = DfsuFile.Open(filename) assert eumUnit.eumUfeet == dfsu.ZUnit	tests/test_dfsu_builder.py:122 dfs = DfsFileFactory.DfsGenericOpen(filename) dfs.ReadStaticItemNext() # Node id for name in ["X-coord", "Y-coord"]: staticItem = dfs.ReadStaticItemNext()

Evidence

Before (abd3215, test only):

$ uv run pytest tests/test_dfsu_builder.py -k xy_quantity -q
E           At index 0 diff: <eumItem.eumILatLong: 100157> != <eumItem.eumIGeographicalCoordinate: 100183>
FAILED tests/test_dfsu_builder.py::test_xy_quantity_follows_projection[LONG/LAT-xyQuantity0]
1 failed, 2 passed, 22 deselected in 0.30s

$ uv run python xy.py
LONG/LAT X-coord: eumIGeographicalCoordinate, eumUmeter
LONG/LAT Y-coord: eumIGeographicalCoordinate, eumUmeter
UTM-33   X-coord: eumIGeographicalCoordinate, eumUmeter
UTM-33   Y-coord: eumIGeographicalCoordinate, eumUmeter

After (47ec11a):

$ uv run pytest tests/test_dfsu_builder.py -k xy_quantity -v
tests/test_dfsu_builder.py::test_xy_quantity_follows_projection[LONG/LAT-xyQuantity0] PASSED [ 33%]
tests/test_dfsu_builder.py::test_xy_quantity_follows_projection[UTM-33-xyQuantity1] PASSED [ 66%]
tests/test_dfsu_builder.py::test_xy_quantity_follows_projection[NON-UTM-xyQuantity2] PASSED [100%]

$ uv run python xy.py
LONG/LAT X-coord: eumILatLong, eumUdegree
LONG/LAT Y-coord: eumILatLong, eumUdegree
UTM-33   X-coord: eumIGeographicalCoordinate, eumUmeter
UTM-33   Y-coord: eumIGeographicalCoordinate, eumUmeter

Reference: a geographic dfsu from mikeio's test data already uses this quantity:

$ uv run python -c "...read wind_north_sea.dfsu..."
LONG/LAT
X-coord eumILatLong eumUdegree

Full suite: uv run pytest: 173 passed, 8 xfailed. uvx pre-commit run --all-files: passed. uv run pyrefly check: 0 errors, 329 warnings (the same as master).

Verify it yourself

git fetch origin && git checkout abd3215
uv run pytest tests/test_dfsu_builder.py -k xy_quantity -q     # LONG/LAT fails
git checkout fix/47
uv run pytest tests/test_dfsu_builder.py -k xy_quantity -q     # 3 passed

# Reference file from mikeio
curl -sSLO https://raw.githubusercontent.com/DHI/mikeio/main/tests/testdata/wind_north_sea.dfsu
uv run python -c "
from mikecore.DfsFileFactory import DfsFileFactory
d = DfsFileFactory.DfsGenericOpen('wind_north_sea.dfsu')
print(d.FileInfo.Projection.WKTString[:20]); d.ReadStaticItemNext(); s = d.ReadStaticItemNext()
print(s.Name, s.Quantity.Item.name, s.Quantity.Unit.name); d.Close()"

xy.py: builds a LONG/LAT and a UTM-33 dfsu and prints their X/Y quantities

import datetime, tempfile, os
import numpy as np
from mikecore.DfsFactory import DfsFactory
from mikecore.DfsFileFactory import DfsFileFactory
from mikecore.DfsuBuilder import DfsuBuilder
from mikecore.DfsuFile import DfsuFileType
from mikecore.eum import eumItem, eumQuantity, eumUnit

for proj in ["LONG/LAT", "UTM-33"]:
    b = DfsuBuilder.Create(DfsuFileType.Dfsu2D)
    b.SetProjection(DfsFactory().CreateProjection(proj))
    b.SetTimeInfo(datetime.datetime(2020, 1, 1), 60)
    b.AddDynamicItem("Value", eumQuantity(eumItem.eumIItemUndefined, eumUnit.eumUUnitUndefined))
    b.SetNodes(np.array([0.0, 1, 1, 0]), np.array([0.0, 0, 1, 1]), np.zeros(4), np.ones(4, dtype=np.int32))
    b.SetElements([[1, 2, 3], [1, 3, 4]])
    f = os.path.join(tempfile.mkdtemp(), "xy.dfsu")
    b.CreateFile(f).Close()
    d = DfsFileFactory.DfsGenericOpen(f)
    d.ReadStaticItemNext()
    for _ in range(2):
        s = d.ReadStaticItemNext()
        print(f"{proj:8} {s.Name}: {s.Quantity.Item.name}, {s.Quantity.Unit.name}")
    d.Close()

Review

• Round 1 (fresh code-reviewer on 47ec11a): no must-fix findings, no suggestions, no questions. It checked separately that a full GEOGCS[...] WKT is detected as geographic, that the test fails with master's DfsuBuilder.py, and that pyrefly stays at 329 warnings. Verdict: clean.

Risk

• Output changes for geographic dfsu files only: their X/Y static items now say eumILatLong/degree. The coordinate values are unchanged, and projected files keep the same quantity as before (the UTM-33 and NON-UTM test cases). Readers that look at these quantities see what DHI's own geographic files already carry (the mikeio reference above). MIKE IO's test suite (DHI/mikeio main, through test_mikeio.yml) gives the same result on this branch as on master: 978 passed in every job, with the same two failures that master also has (test_eum.py::test_eum_conversion on all 4 jobs, test_dfs2.py::test_select_area_rotated_UTM_2 on Linux). Runs: fix/47, master. Unproven: code outside MIKE IO that relies on the old metre quantity for LONG/LAT files.

• New import: DfsuBuilder now imports mikecore.Projections. That module is already imported, and its native library already loaded, by mikecore/__init__.py:34, so the import adds no load-time dependency.

• Missing projection: the is not None guard can't change behaviour, because Validate (called first by CreateFile) already rejects a builder without a projection.

• CI: all PR checks passed on 47ec11a (tests on Ubuntu and Windows, Python 3.11 and 3.14; ruff; pyrefly; CodeQL).

Not in this PR

Nothing.

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