Skip to main content

Known Limitations

tile57 runs the official IHO S-101 Portrayal Catalogue, and on the test cells (US4MD81M.000, US5MD1MC.000 + updates) every feature now portrays with zero rule errors — depth areas and contours, soundings, coastline and land, buoys and beacons, lights, dangers (obstructions / wrecks / rocks), data-quality zones, restricted/anchorage areas, and text labels.

But "no rule errors" is not the same as "pixel-perfect S-52", and this project is an AI-built experiment and learning tool — do not use it for navigation. This page is an honest list of what is still incomplete, taken from the engine code.

Not for navigation

See the warning on the introduction. NOAA ENC charts are U.S. public domain and not for navigation; this renderer adds its own gaps on top.

Geometry-construction instructions​

The catalogue builds some figures from geometry-construction instructions (AugmentedRay, AugmentedPath, ArcByRadius, CoverageFill). The engine does not lower all of these into tile geometry — features that depend on a construction the engine does not handle lose that constructed part (the rest of the feature — its symbol, fill, or label — still draws).

Portrayal / live-path gaps​

The live cell→MVT path emits the layers in the tile schema including the *_scamin declutter buckets and draw_prio ordering. The spatial / geometry Host binding now serves real point geometry to the rules (so dangers and soundings portray without the earlier nil-depth crash / "C stack overflow"), and orientation + clearance complex attributes are synthesized. Remaining gaps:

  • Approximate-position (QUAPOS) dashing. QUAPOS is parsed and aggregated per feature, but the solid→dashed line-style switch for low-accuracy geometry is not applied yet.
  • Light sectors — sectored/directional light legs and arcs are not yet emitted by the live path (they exist in the Go baker).
  • Native S-52 fallbacks for unportrayed classes. Some S-57 classes have no usable S-101 rule output and the Go reference draws a native S-52 placeholder. SweptArea/SWPARE (dashed CHGRD boundary + SWPARE51 bracket + "swept to" label) and the NEWOBJ new-object box (dashed CHMGF outline) are now drawn; the navigational-system-of-marks boundary (M_NSYS, Go's navSystemBuild) is still omitted.
  • Single-primitive rules vs. non-conformant geometry. Some S-101 rules handle only one primitive (e.g. RecommendedTrack is Curve-only); a cell that encodes the feature with another primitive (an area-encoded recommended track) errors in the rule and the feature is suppressed.

The tile57 CLI baker runs the same full S-101 portrayal as the live chart path, so a baked archive matches live generation.

ENC_ROOT loading​

Opening an ENC_ROOT (Source.openCells / openCellsStreaming) builds a cheap spatial index (band + bbox per cell) and generates tiles on demand, parsing + portraying only the cells a requested tile needs (best-available scale band per tile, recent cells held in an LRU). The catalogue opens in seconds; memory stays bounded. Caveats:

  • First-view latency. The first tile over a fresh area parses + portrays its 1–4 cells (tens of ms), then they're cached. Opening the whole NOAA catalogue also pays a one-time index scan (a few seconds, parsing every cell header).
  • Offline bake. For smooth panning everywhere, bake the ENC_ROOT once to a cached PMTiles archive (tile57 bake, or bakeArchive / tile57_bake_pmtiles) and open that instead. The whole catalogue is a multi-minute one-time bake; a region is far quicker.
  • Low zoom is style-gated. The generated style's vector-source minzoom (9 in the bundled styles) means nothing draws below it regardless of the data.
  • Update merge gaps. Feature/vector insert/delete/modify and the SGCC/FSPC control fields (indexed coordinate / spatial-pointer edits) are applied; VRPC (indexed edits to an edge's begin/end node pointers) is not modelled — a VRPT update is taken as a full replacement.