RadarSim v4.0.0

A rebuild of the simulator around a correct detection loop, a new desktop interface
and a cleaned-up package. Scenario files, the Python import path and two sign
conventions changed, so this is a major release; see Migrating from 3.x below.

Breaking changes

• The package is now radarsim instead of src: from radarsim.simulation.engine import SimulationEngine.
• One coordinate frame everywhere: ENU (x East, y North, z Up), azimuth clockwise from North.
• Doppler is fd = −2·vr/λ with vr positive when opening; closing targets have negative radial velocity in every output.
• Scenario files are validated against a schema. Unknown keys are errors with a suggestion; required_radar_preset and other unused keys were removed.
• Removed modules that did not work or were never connected: advanced/ (except SAR/ISAR, now radarsim.signal.sar_isar), sensor fusion UI, LPI waveforms, RF spectrum view, WebGL renderer, the matplotlib 3-D view and the old Sphinx documentation.

Detection and physics

• Detection happens only when the beam centre crosses a target (circular, sector and stare scans), giving one look per revisit.
• Pulse-compression gain and the compressed range cell were missing (up to 26 dB of error); noise, jamming and clutter now combine after the matched filter.
• Mean RCS in the SNR with the Swerling statistic only in Pd, removing a double-counted fluctuation.
• Exact Swerling 1 and 2 detection probabilities, Gauss–Legendre integration for cases 3 and 4, cached; checked against a pulse-level Monte Carlo.
• CFAR loss from the Gandhi–Kassam closed forms for CA, GO, SO and OS.
• Clutter enters through the elevation pattern; MTI improvement factor per Skolnik with a 50 dB stability limit.
• Rain attenuation limited to the ITU-R P.839 rain height; P.676 receives the dry-air pressure.
• Terrain masking with Earth bulge, terrain presets and height_above_terrain_m.
• Coordinated-turn motion, deploy times for chaff and decoys, chaff bloom and decay.
• Every random draw goes through one seeded generator; reset() reproduces a run exactly.

Tracking

• Track-while-scan inside the engine with continuous white-noise acceleration, two-point initiation with a velocity gate, misses only when the beam looked, revisit guard and maximum coast time.
• Rewritten monopulse estimator (squinted Gaussian beams).

Interface

• New desktop interface: dark console theme, IBM Plex type, own icon set, PPI, B-scope, A-scope, RHI, range–Doppler and 3-D views.
• Simulation runs at a fixed step on its own thread; rendering adapts to the machine (16, 33 or 50 ms frames) with motion interpolation and a reduce-motion setting.
• New: Pd–range coverage diagram, Monte Carlo panel with Wilson intervals, event log with CSV/JSON report export, scenario editor that draws on the scope and saves canonical YAML.
• English and Turkish.

Tooling

• radarsim --headless SCENARIO --duration --seed --out and radarsim --list; built-in scenarios ship inside the package.
• MkDocs documentation with figures generated by tools/make_figures.py and screenshots by tools/capture_screenshots.py.
• CI runs ruff, mypy, bandit, the translation check, tests on three systems, a wheel check outside the repository and a strict docs build; tagged releases build Windows, Linux and macOS applications.

Migrating from 3.x

1. Replace src. with radarsim. in imports.
2. Re-save old scenarios: load the file, fix the keys the validator reports, and check that positions and headings follow ENU with azimuth from North.
3. If you post-process Doppler or radial velocity, flip the sign of values from 3.x.
4. python run_gui.py still works from a checkout; radarsim is the installed command.