surtgis

High-performance geospatial analysis in the browser via WebAssembly.

SurtGIS compiles 33 terrain, hydrology, imagery, morphology and statistics algorithms to WASM, giving you native-speed raster processing with zero server dependencies.

Live Demo | GitHub

Install

npm install surtgis

Quick Start

Browser (with bundler)

import { SurtGIS } from "surtgis/surtgis.js";

const gis = await SurtGIS.init();

// Load a GeoTIFF as Uint8Array
const dem = new Uint8Array(await fetch("dem.tif").then(r => r.arrayBuffer()));

// Compute slope
const slopeResult = gis.slope(dem, { units: "degrees" });

// Compute hillshade
const hillshade = gis.hillshade(dem, { azimuth: 315, altitude: 45 });

Web Worker (off main thread)

import { SurtGISWorker } from "surtgis/surtgis-worker.js";

const gis = await SurtGISWorker.init();

// All methods return Promise<Uint8Array>
const result = await gis.slope(dem, { units: "degrees" });

gis.terminate(); // when done

Low-level bindings

import { slope, hillshade_compute } from "surtgis";

const slopeBytes = slope(demBytes, "degrees");
const hillshadeBytes = hillshade_compute(demBytes, 315, 45);

API Reference

All functions accept and return Uint8Array (GeoTIFF bytes).

Terrain (17)

| Method | Options | Description | |--------|---------|-------------| | slope(dem, opts?) | { units: "degrees"\|"percent" } | Slope gradient | | aspect(dem) | — | Aspect in degrees (0-360) | | hillshade(dem, opts?) | { azimuth: 315, altitude: 45 } | Analytical hillshade | | multidirectionalHillshade(dem) | — | 6-azimuth combined hillshade | | curvature(dem, opts?) | { type: "general"\|"profile"\|"plan" } | Surface curvature | | tpi(dem, opts?) | { radius: 3 } | Topographic Position Index | | tri(dem) | — | Terrain Ruggedness Index | | twi(dem) | — | Topographic Wetness Index | | geomorphons(dem, opts?) | { flatness: 1.0, radius: 10 } | Landform classification | | northness(dem) | — | Cosine of aspect | | eastness(dem) | — | Sine of aspect | | dev(dem, opts?) | { radius: 10 } | Deviation from Mean Elevation | | shapeIndex(dem) | — | Shape index | | curvedness(dem) | — | Surface curvedness | | skyViewFactor(dem, opts?) | { directions: 16, radius: 10 } | Sky View Factor | | uncertaintySlope(dem, opts?) | { demRmse: 1.0 } | Slope uncertainty (RMSE) | | ssa2dDenoise(dem, opts?) | { window: 10, components: 3 } | 2D-SSA denoising |

Hydrology (5)

| Method | Options | Description | |--------|---------|-------------| | fillSinks(dem) | — | Fill depressions | | priorityFlood(dem) | — | Priority-flood filling (Barnes 2014) | | flowDirectionD8(dem) | — | D8 flow direction | | flowAccumulationD8(fdir) | — | Flow accumulation from D8 directions | | hand(dem, opts?) | { streamThreshold: 1000 } | Height Above Nearest Drainage |

Imagery (4)

| Method | Options | Description | |--------|---------|-------------| | ndvi(nir, red) | — | Normalized Difference Vegetation Index | | ndwi(green, nir) | — | Normalized Difference Water Index | | savi(nir, red, opts?) | { lFactor: 0.5 } | Soil-Adjusted Vegetation Index | | normalizedDifference(a, b) | — | Generic (A-B)/(A+B) |

Morphology (4)

| Method | Options | Description | |--------|---------|-------------| | erode(dem, opts?) | { radius: 1 } | Morphological erosion | | dilate(dem, opts?) | { radius: 1 } | Morphological dilation | | opening(dem, opts?) | { radius: 1 } | Opening (erode + dilate) | | closing(dem, opts?) | { radius: 1 } | Closing (dilate + erode) |

Statistics (3)

| Method | Options | Description | |--------|---------|-------------| | focalMean(dem, opts?) | { radius: 3 } | Focal mean | | focalStd(dem, opts?) | { radius: 3 } | Focal standard deviation | | focalRange(dem, opts?) | { radius: 3 } | Focal range (max - min) |

Bundle Size

| Component | Size | Gzipped | |-----------|------|---------| | WASM binary | ~570 KB | ~195 KB | | JS glue | ~3 KB | ~1 KB |

License

MIT OR Apache-2.0