RAS Commander Fast-Map

Native Rust 2D flood inundation mapping, distributed as the ras-commander-fast-map Rust crate and Python wheel. It maps computed hydraulic results; it does not run the HEC-RAS hydraulic solver.

Install

pip install ras-commander-fast-map
ras2fim-batch method

Python wheels provide the compatible ras2fim-batch executable on Windows x64 and Linux x64 (glibc 2.28+). A wheel requires no Rust compiler or system GDAL. Python consumers normally install ras-commander[fim], which adds the public RasFim APIs and Python preparation/GeoTIFF delivery dependencies. Remove the former ras2fim-engine package before installing this package if both would own the same executable. The command name and JSON contracts remain compatible.

Rust users can install the CLI or use the library independently of Python:

cargo install ras-commander-fast-map --locked
cargo add ras-commander-fast-map

let methods = ras_commander_fast_map::method_record();
assert!(methods.is_object());

See Rust API documentation and the RasFim guide for request contracts and end-to-end model preparation. The Rust library consumes prepared geometry, profiles and terrain; HDF extraction belongs to ras-commander-fast-hdf and Commander. The CLI does not read a plan HDF directly.

Methods and resource controls

Polygon AOI edge rule (0.10.1)

Horizontal/sloping method records advertise aoi_mask="global-terrain-lattice/1". AOI coverage is computed in source terrain pixel units, at global pixel centers, with y increasing northward. Even-odd scanlines include lower-y/exclude upper-y endpoints; filled spans include the left endpoint and exclude the right. For a rectangle this includes its minimum x/y edges and excludes its maximum x/y edges. Holes and disjoint polygon parts retain the same rule. No epsilon is added, and ring reversal does not change coverage. A cropped mask equals the corresponding crop of a full-grid mask, including pixel-center edge ties.

The rule deliberately replaces origin-dependent legacy AOI masking. It need not reproduce legacy GDAL edge ties. Cell ownership and hydraulic interpolation are unchanged. AOI rows use the request's bounded Rayon pool; planned geometry and per-worker crossing scratch are admitted before payload reads. The pure Rust aoi::mask function accepts a framed Polygon/MultiPolygon WKB path, full source geotransform and integer source window.

• Horizontal: cell-constant WSE with native float32 visibility.
• Sloping: reconstructed cell corners; optional cell faces, depth weighting, and shallow-to-horizontal selection.
• ras2fim-2D Step05: the separate globally prepared SciPy triangulation method.

Terrain decoding and ownership rasterization use terrio with GDAL disabled. Rayon workers share immutable terrain/geometry across bounded in-flight profiles. Bbox/polygon output masks retain global hydraulic topology. Planned allocation admission is not a hard RSS limit. Python delivery may use Rasterio/GDAL; the Rust mapping executable does not link it.

Binary32 operation order and method identifiers are preserved. MIGRATION.json retains the immutable 0.8.0 extraction receipt; SOURCE_MANIFEST.json binds this version's current sources. ras2fim-batch method reports package/build identity and capabilities.

Persistent reach sessions (0.9)

sloping-server accepts serialized JSON-line commands with absolute request and output paths. Each request uses the existing sloping schema and streams the same profile headers/binary arrays, followed by a single {"command_status":"complete"} line. The process retains terrain blocks, mesh/stencils and one Rayon pool. Send {"close":true} or close stdin to release the session. Failed commands terminate the process; callers must reject partial products. Commander owns process lifetime and timeouts through prepared models.

At most the last small window's owner/terrain arrays, exact geometry/AOI key and plain-sloping weights are retained within a separate 64 MiB payload bound. Weights use at most 32 MiB; pixels beyond the bounded prefix keep their original evaluation path. Cell-face/donor-history weights are not cached. Large windows still share terrain blocks and geometry, without retaining their output arrays. Plans include the retained payload budget and the original 64 MiB decoded tile cache; this is allocation admission, not a hard process RSS limit. Native PreparedSession objects provide the same reuse without the CLI.

Deterministic inundation boundaries (0.10)

Generate projected-CRS inundation polygons from signed depths with the separate deterministic-zero-depth-contours/1 method:

ras2fim-batch boundary boundary-request.json new-boundary-output

Commander prepares the model and terrain metadata for this command. Rust callers can use boundary_session::Request and boundary_session::run directly. The request schema is ras-commander-boundary-request/1:

Boundary generation supports physical 2D cells with horizontal or plain corner sloping surfaces. Cell-face interpolation, shallow-to-horizontal controls and face depth weighting are rejected. Supply one original, unmodified float32 terrain TIFF and its matching terrain HDF metadata. Retiled/cropped TIFFs, terrain modifications and multi-source mosaics are outside this boundary scope. Commander rejects models containing 1D elements; standalone storage-area surfaces are excluded.

The method retains valid negative depths to locate the zero-depth crossings. The intrinsic cell-wet gate uses float32 WSE > minimum_elevation + 0.001; there is no added pixel-depth cutoff or 0.5-foot postprocessing. Masks/perimeters and stitch triangles come from the terrain HDF; the TIFF alone is insufficient. Bbox/polygon selection limits terrain tiles, while hydraulic topology stays global. AOI clipping follows contour construction, preserving edge samples.

Quantized integer clipping produces coordinates at 0.001 projected CRS units. Tile/profile results are combined in stable order, independent of worker order. Each profile produces one GeoJSON FeatureCollection containing a MultiPolygon; its explicit legacy GeoJSON crs member identifies projected coordinates. These coordinates are not reprojected to RFC 7946 longitude/latitude. The report uses ras-commander-boundary-report/1 and includes profile status, polygon/hole/vertex counts, area in squared CRS units, timings and effective concurrency. Empty boundaries are explicit. Output requires a new or empty directory; a failed batch removes delivered profile polygons and records an aborted report.

Profiles share geometry, terrain blocks, ownership and stencils. model.threads and model.max_inflight_profiles bound work in one Rayon pool; tile workers also share that pool. Planned admission covers prepared data and per-profile contour allowances before payload reads. It is not a hard process RSS limit.

These deterministic polygons are not an exact reproduction of RASMapper vectors. Stable all-subject integer union and quantized intersections can produce different holes and boundary vertices. Repeated native Max exports can also vary with unchanged inputs. Use the native stored-map API when its vector output is required, and retain comparison evidence for the intended model. This separate polygon layer does not change the existing Depth/WSE raster methods, their float32 arithmetic or their qualification claims.

Velocity (sloping requests)

Add per-mesh velocity_normals_files (HDF Faces NormalUnitVector and Length as float32 x, y, length, with length replaced by the face polyline length) and per-profile face_velocity_files (float32 face-normal velocities; for Max, the summary Maximum Face Velocity with Max WSE as the profile values) to a sloping request. Velocity magnitude is written as velocity.bin, or as a third streamed array when the stream header has "velocity": true. It is drawn where rendered depth > 0 and does not depend on the WSE render mode (method rasmapper-sloping-velocity/0).

Native HEC-RAS 7.0.1 comparison: BaldEagleCrkMulti2D bridges p05 (973,532 Max and 402,500 output-time pixels), dam-break p07 2D cells (Max and one output time, valid masks equal to depth) and a 2,500 x 2,500 Spring Creek eBFE AOI (1,101,529 pixels) match bit for bit; Davis p02 Max differs in 5 of 20,560 pixels by at most 2 ulp. Storage areas, boundary requests, shear stress and Max derived products are outside this method.

Whole-simulation products (arrival time, duration, percent inundated)

ras2fim-batch whole-simulation whole-request.json new-output-dir

Schema ras-commander-whole-simulation-request/1 embeds a non-streaming horizontal request whose profiles are the stored output times in order, plus times_hours (one per profile, strictly increasing), threshold, cell_minimum_file (float32 cell minimum elevations in cell order), optional products (default arrival_time, percent_inundated) and allow_unqualified (required for duration and irregular intervals). Output times are evaluated sequentially over the mapped 2D-owned pixels only, in parallel, with 32 bytes per mapped pixel. Products are written to whole_simulation/<product>.bin (float32, NaN = never wet).

A pixel is wet when its horizontal depth is > threshold and its cell passes RAS Mapper's thresholded gate wse > minimum + threshold. Storage areas are not rendered; Commander refuses plans that contain them. Arrival is the first wet time and percent is 100 * wet / n. Duration runs from arrival to the first dry time after the last wet one, or to the last wet time when that dry time would be the final output or there is none. Times are float32 hours. Irregular output intervals are refused unless allow_unqualified is set. Initially wet pixels, multi-period pixels and threshold-equal samples are reported.

Qualification (native HEC-RAS 7.0.1, threshold 0.5 ft, storage-area-free models): Davis pipes/conduits p02 (217 output times, 4,879 valid pixels) and BaldEagleCrkMulti2D bridges p05 (433 times, 959,043 pixels) match in every valid-mask pixel and every arrival and percent value bit for bit, including initially wet, multi-period and threshold-equal samples. RAS Mapper gives the same products in horizontal and sloping render modes on both models, so this horizontal pass covers sloping maps too. Duration is opt-in and unqualified: 103 (Davis) and 11 (bridges) native durations are one output interval shorter. Bridges runs in 8.9 s at 383 MiB peak against about 25 s for the native call.

Top-priority source terrain (no RAS Mapper export)

RAS Mapper writes stored maps per terrain source, on each source's own grid. sloping (plain) and horizontal requests may map directly on the original TIFF of the highest-priority source of a multi-source terrain, instead of a RAS Mapper terrain export, by adding:

"terrain_scope": {"kind": "top_priority_source", "source_count": 2,
  "mask": {"path": "mask.u1", "dtype": "|u1", "shape": [513, 65536]}}

mask is the source's full level-0 tile mask from the terrain HDF (Terrain/<source>/0/Mask, tiles row-major); bit 0 is the source footprint. Owned pixels outside the footprint are refused unless the result cannot depend on their terrain: sloping pixels of cells that fail the native wet gate are never drawn. Foreign pixels of wet cells, foreign pixels in horizontal rendering and cell-face sloping are refused (method top-priority-source-footprint/1). Boundary requests refuse it.

Qualification (plain sloping, native HEC-RAS 7.0.1, two-source Terrain50): BaldEagleCrkMulti2D bridges p05 Max on the priority-1 dtm_20ft TIFF matches in all 973,902 valid pixels and float32 bits, with 28 foreign 2D pixels all in dry cells; the dam-break p07 2D cells also match for Max and one output time. Lower-priority sources are not mosaicked: RAS Mapper's export resamples them with a rule close to, but not, pixel-centre bilinear (84% of float32 values reproduced), so a native mosaic is unqualified.

Qualification and limits

The retained five-model comparisons cover raw Depth/WSE validity masks and float32 bits against native HEC-RAS 7.0.1, without an added depth cutoff. Those published timing observations predate this packaging extraction; no new speedup is claimed for renaming/distribution.

Mapping covers physical 2D cells. Commander rejects models with 1D river/cross- section geometry. Standalone storage-area surfaces are excluded. Cell-face matching preserves the original source TIFF grid and 256-square tile layout; arbitrary retiled/cropped terrain and multi-source mosaics are unqualified. Depth weighting needs stored corner ground elevations. When absent, explicit corner preparation still uses Windows/HEC-RAS 7.0.1 through Commander and pythonnet; it has not been implemented in Rust. Once prepared, ordinary mapping runs on Windows/Linux without HEC-RAS. Source terrain must match the effective terrain used by the native reference.

Build and verify

cargo fmt --check
cargo test --locked --all-targets
cargo clippy --locked --all-targets -- -D warnings -A clippy::chunks_exact_to_as_chunks
cargo publish --locked --dry-run
python scripts/verify_sources.py

CI builds and smoke-tests Windows/Linux wheels. Tagged releases attach the wheels, source distribution, provenance and checksums to GitHub Releases. See release instructions for PyPI/crates.io publishing.

License and attribution

Our code retains its MIT license. Step05/SciPy reuse retains BSD-3-Clause notices; see LICENSE, THIRD_PARTY_NOTICES.md and licenses/. The crate license expression is MIT AND BSD-3-Clause. The unmodified Clipper2 dependency retains its Boost Software License 1.0 notice. Dependency notices accompany distributions. HEC-RAS assemblies and model data are not distributed. This independent project is not affiliated with or endorsed by HEC/USACE.