Port the 8-char (4-pair) Maidenhead grid algorithm from the
"QTH定位器 2.0" app (com.us1pm.gridsquarelocator) into QthConverter
so locator precision matches common grid tools instead of being
truncated to 6 chars.
Previously positionToQth() emitted only 6-char locators and
qthToPosition() discarded everything past the 6th character via
take(6), losing the finer 30" x 15" resolution carried by 8-char
grid squares.
What changed:
- positionToQth(lat, lon, precision = 8) now emits 8-char locators
by default; precision = 6 / 10 available for backwards
compatibility and maximum resolution (1.25" x 0.625").
- qthToPosition() parses 6/8/10-char locators and returns the center
of the finest encoded cell (30" x 15" for 8-char, 1.25" x 0.625"
for 10-char) instead of the 6-char cell center.
- Locator validation regex tightened: 6/8/10 chars accepted,
4-char strings like "JN58" are now rejected as invalid.
- Boundary clamping added so lat = 90 / lon = 180 no longer overflow
the A-R / 0-9 / a-x alphabet (previously produced invalid chars).
Also fixed a pre-existing compile error in RadarView.kt: a delegated
property was assigned after declaration ("by" on an already declared
val). Converted the sweep angle to an if/else expression.
Verification:
- QthConverterTest extended to 5 test cases covering 6/8/10-char
roundtrips, invalid input, boundary coordinates and roundtrip
stability.
- Cross-checked against a Python reference model of the decompiled
APK algorithm: 20k random roundtrips at 8 and 10 chars, 0 failures.
- :core:domain:test green; :app:compileDebugKotlin passes.
mckero
a37fb8f773