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Merge pull request #14 from SDFIdk/update_gtiff_elevation_methods
Update gtiff elevation methods
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,52 +1,106 @@ | ||
| import { getTerrainGeoTIFF } from './api.js' | ||
| /** | ||
| * Maps a coordinate from the one coordinate system to another based on GeoTiff image dimensions. | ||
| * @param {Array} coord - EPSG:25832 X,Y coordinate pair | ||
| * @param {Array} bbox - Bounding box within input coordinate systtem. Consists of 2 EPSG:25832 coordinate pairs. Example: [x1,y1,x2,y2] | ||
| * @param {Array} imageDimensions - Width and height of a GeoTiff image. This will set the bounding box of the output coordinate system. Note: This coordinate system will have 0,0 set in the top right position of the image. | ||
| */ | ||
| function convertCoordinate(coord, bbox1, imageDimensions) { | ||
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| // Extract the coordinates from the bounding boxes | ||
| const [x1_min, y1_min, x1_max, y1_max] = bbox1 | ||
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| // Extract the coordinate to convert | ||
| const [x1, y1] = coord | ||
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| /** Constrain coordinates to be within a bounding box */ | ||
| function constrainToBbox(bbox, x, y) { | ||
| let new_x = x | ||
| let new_y = y | ||
| if (x < bbox[0]) { | ||
| new_x = bbox[0] + 1 | ||
| } else if (bbox[2] < x) { | ||
| new_x = bbox[2] - 1 | ||
| } | ||
| if (y < bbox[1]) { | ||
| new_y = bbox[1] + 1 | ||
| } else if (bbox[3] < y) { | ||
| new_y = bbox[3] - 1 | ||
| } | ||
| return [new_x, new_y] | ||
| // Calculate the width and height of both bounding boxes | ||
| const width1 = x1_max - x1_min | ||
| const height1 = y1_max - y1_min | ||
| const width2 = imageDimensions[0] | ||
| const height2 = imageDimensions[1] | ||
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| // Calculate the relative position in the first coordinate system | ||
| const x_relative = (x1 - x1_min) / width1 | ||
| const y_relative = (y1 - y1_min) / height1 | ||
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| // Calculate the new position in the second coordinate system | ||
| const x2 = Math.abs(x_relative * width2) | ||
| const y2 = height2 - Math.abs(y_relative * height2) | ||
|
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| return [x2, y2] | ||
| } | ||
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| /** Calculates nearest elevation for given coordinate using geoTIFF terrain data | ||
| * Heavily inspired by https://towardsdatascience.com/geotiff-coordinate-querying-with-javascript-5e6caaaf88cf | ||
| /** | ||
| * Calculates nearest elevation for given coordinate using geoTIFF terrain data | ||
| * @param {number} x - EPSG:25832 X coordinate | ||
| * @param {number} y - EPSG:25832 Y coordinate | ||
| * @param {object} geoTiff - GeoTiff data output from getTerrainGeoTIFF() method | ||
| * @param {object} geoTiff - GeoTiff data output from getTerrainGeoTIFF() or getDenmarkGeoTiff() method | ||
| * @returns {number} Elevation in meters | ||
| */ | ||
| async function getElevation(x, y, geoTiff) { | ||
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| const bbox = geoTiff.getBoundingBox() | ||
| const height = geoTiff.getHeight() | ||
| const width = geoTiff.getWidth() | ||
| const bboxWidth = bbox[2] - bbox[0] | ||
| const bboxHeight = bbox[3] - bbox[1] | ||
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| const xy = constrainToBbox(bbox, x, y) | ||
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| const widthPct = ( xy[0] - bbox[0] ) / bboxWidth | ||
| const heightPct = ( xy[1] - bbox[1] ) / bboxHeight | ||
| const xPx = Math.floor( width * widthPct ) | ||
| const yPx = Math.floor( height * ( 1 - heightPct ) ) | ||
| // Convert lat/lon to geotiff x/y | ||
| const [xPx, yPx] = convertCoordinate([x,y], bbox, [width, height]) | ||
|
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| // Fetch window of raster values around x/y | ||
| const window = [ | ||
| Math.floor(xPx), | ||
| Math.floor(yPx), | ||
| Math.ceil(xPx), | ||
| Math.ceil(yPx) | ||
| ] | ||
|
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| // Fetch elevation value from geoTiff rasters | ||
| const elevation_data = await geoTiff.readRasters({ | ||
| window: window, | ||
| fillValue: 0 | ||
| }) | ||
|
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| return elevation_data[0][0] | ||
| } | ||
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| const window = [ xPx, yPx, xPx + 1, yPx + 1 ] | ||
| const elevation_data = await geoTiff.readRasters( {window} ) | ||
| /** Creates an ASCII visualization of a terrain GeoTiff. Useful for display in a terminal. | ||
| * NOTE: You may want to use a downsmapled GeoTiff to fit within your terminal window. A GeoTiff pixel is represented by 3 characters each. | ||
| * @param {object} gTiff - GeoTiff output from getTerrainGeoTIFF() or getDenmarkGeoTiff() method | ||
| */ | ||
| async function visualizeGeotiff(gTiff) { | ||
| console.log('--- GTIFF visualization ---') | ||
| const float32Arr = await gTiff.readRasters() | ||
| const tiffWidth = gTiff.getWidth() | ||
| const rasters = float32Arr[0] | ||
| let lines = [] | ||
| let line = '' | ||
| for (let i = 0; i < rasters.length; i++) { | ||
| if (i % tiffWidth === 0) { | ||
| lines.push(line) | ||
| line = '' | ||
| } | ||
| line += zeroPadNumber(rasters[i]) | ||
| } | ||
| for (const l of lines) { | ||
| console.log(l) | ||
| } | ||
| } | ||
|
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| return Math.round( elevation_data[0][0] * 10) / 10 | ||
| /** Converts numbers to strings in a 3-letter format. Ex. `002`, `0-3` (for negative numbers), or `123` */ | ||
| function zeroPadNumber(input) { | ||
| if (input === 0) { | ||
| return "..." | ||
| } else if (input < 0) { | ||
| return `0${input.toFixed(0)}` | ||
| } else if (input < 10) { | ||
| return `00${Math.floor(input)}` | ||
| } else if (input < 100) { | ||
| return `0${Math.floor(input)}` | ||
| } else { | ||
| return `${Math.floor(input)}` | ||
| } | ||
| } | ||
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| export { | ||
| getTerrainGeoTIFF, | ||
| getElevation | ||
| getElevation, | ||
| visualizeGeotiff | ||
| } |
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