JavaScript Map Chart with Heatmap overlay

1import {
2    FastLineRenderableSeries,
3    HeatmapColorMap,
4    HeatmapLegend,
5    MouseWheelZoomModifier,
6    NumberRange,
7    NumericAxis,
8    SciChartSurface,
9    UniformHeatmapDataSeries,
10    UniformHeatmapRenderableSeries,
11    XyDataSeries,
12    ZoomExtentsModifier,
13    ZoomPanModifier,
14} from "scichart";
15import { appTheme } from "../../../theme";
16
17/** Earthquake data structure from CSV */
18interface EarthquakeData {
19    latitude: number;
20    longitude: number;
21    magnitude: number;
22    depth: number;
23}
24
25/** Base URL for fetching data files - handles both local and production environments */
26const baseUrl =
27    typeof window !== "undefined" &&
28    !window.location.hostname.includes("scichart.com") &&
29    !window.location.hostname.includes("localhost")
30        ? "https://www.scichart.com/demo"
31        : "";
32
33/**
34 * Creates a heatmap visualization of earthquake data overlaid on a world map.
35 * The heatmap displays earthquake magnitudes using a color gradient from black (no activity)
36 * to red (highest magnitude).
37 */
38export const drawExample = async (rootElement: string | HTMLDivElement) => {
39    const { sciChartSurface, wasmContext } = await SciChartSurface.create(rootElement, {
40        theme: appTheme.SciChartJsTheme,
41    });
42
43    // World coordinate bounds (standard lat/lon ranges)
44    const worldBounds = {
45        minLat: -90,
46        maxLat: 90,
47        minLon: -180,
48        maxLon: 180,
49    };
50
51    // Configure axes with world coordinate bounds (hidden for clean map appearance)
52    sciChartSurface.xAxes.add(
53        new NumericAxis(wasmContext, {
54            isVisible: false,
55            visibleRange: new NumberRange(worldBounds.minLon, worldBounds.maxLon),
56        })
57    );
58    sciChartSurface.yAxes.add(
59        new NumericAxis(wasmContext, {
60            isVisible: false,
61            visibleRange: new NumberRange(worldBounds.minLat, worldBounds.maxLat),
62        })
63    );
64
65    // Heatmap resolution
66    const heatmapWidth = 600;
67    const heatmapHeight = 400;
68
69    // Magnitude range for color mapping (Richter scale)
70    const colorPaletteMin = 0;
71    const colorPaletteMax = 10;
72
73    // Load earthquake data and world map outlines
74    const earthquakeData = await fetchEarthquakeData();
75    const convertedData = await fetch(baseUrl + "worldConverted.json").then((response) => response.json());
76
77    // Define coordinate bounds for the world map data
78    const minX = -180;
79    const maxX = 180;
80    const minY = -90;
81    const maxY = 90;
82
83    // Transform world map coordinates to match the chart's coordinate system
84    const transformedOutlines = convertedData.map((d: any) => {
85        return d.outline.map((point: number[]) => {
86            const scaledX =
87                worldBounds.minLon + ((point[0] - minX) / (maxX - minX)) * (worldBounds.maxLon - worldBounds.minLon);
88            const scaledY =
89                worldBounds.minLat + ((point[1] - minY) / (maxY - minY)) * (worldBounds.maxLat - worldBounds.minLat);
90            return [scaledX, scaledY];
91        });
92    });
93
94    // Create line series for country/continent outlines
95    const outlinesSC = transformedOutlines.map((outline: number[][]) => {
96        const xVals = outline.map((d: number[]) => d[0]);
97        const yVals = outline.map((d: number[]) => d[1]);
98
99        return new FastLineRenderableSeries(wasmContext, {
100            dataSeries: new XyDataSeries(wasmContext, {
101                xValues: xVals,
102                yValues: yVals,
103            }),
104            stroke: "#ffffff",
105            strokeThickness: 2,
106            opacity: 1,
107        });
108    });
109
110    sciChartSurface.renderableSeries.add(...outlinesSC);
111
112    // Generate heatmap from earthquake data
113    const initialZValues = generateEarthquakeHeatmap(earthquakeData, heatmapWidth, heatmapHeight);
114
115    // Reverse Y-axis to match geographic orientation (north at top)
116    const reversedZValues = initialZValues.slice().reverse();
117
118    // Create heatmap data series with world coordinate mapping
119    const heatmapDataSeries = new UniformHeatmapDataSeries(wasmContext, {
120        zValues: reversedZValues,
121        xStart: worldBounds.minLon,
122        xStep: (worldBounds.maxLon - worldBounds.minLon) / heatmapWidth,
123        yStart: worldBounds.minLat,
124        yStep: (worldBounds.maxLat - worldBounds.minLat) / heatmapHeight,
125    });
126
127    // Add heatmap with semi-transparent overlay
128    sciChartSurface.renderableSeries.add(
129        new UniformHeatmapRenderableSeries(wasmContext, {
130            dataSeries: heatmapDataSeries,
131            useLinearTextureFiltering: false,
132            opacity: 0.5,
133            colorMap: new HeatmapColorMap({
134                minimum: colorPaletteMin,
135                maximum: colorPaletteMax,
136                gradientStops: [
137                    { offset: 1, color: "#FF0000" }, // Red - highest magnitude
138                    { offset: 0.8, color: "#FF4500" }, // Orange-red
139                    { offset: 0.6, color: "#FFA500" }, // Orange
140                    { offset: 0.4, color: "#FFFF00" }, // Yellow
141                    { offset: 0.2, color: "#90EE90" }, // Light green
142                    { offset: 0, color: "#000000" }, // Black - no activity
143                ],
144            }),
145        })
146    );
147
148    // Add interactive chart modifiers
149    sciChartSurface.chartModifiers.add(new ZoomPanModifier({ enableZoom: true }));
150    sciChartSurface.chartModifiers.add(new ZoomExtentsModifier());
151    sciChartSurface.chartModifiers.add(new MouseWheelZoomModifier());
152
153    return { sciChartSurface };
154};
155
156/**
157 * Creates a heatmap legend showing the magnitude color scale.
158 */
159export const drawHeatmapLegend = async (rootElement: string | HTMLDivElement) => {
160    const { heatmapLegend, wasmContext } = await HeatmapLegend.create(rootElement, {
161        theme: {
162            ...appTheme.SciChartJsTheme,
163            sciChartBackground: appTheme.DarkIndigo + "BB",
164            loadingAnimationBackground: appTheme.DarkIndigo + "BB",
165        },
166        yAxisOptions: {
167            isInnerAxis: true,
168            labelStyle: {
169                fontSize: 12,
170                color: appTheme.ForegroundColor,
171            },
172            axisBorder: {
173                borderRight: 1,
174                color: appTheme.ForegroundColor + "77",
175            },
176            majorTickLineStyle: {
177                color: appTheme.ForegroundColor,
178                tickSize: 6,
179                strokeThickness: 1,
180            },
181            minorTickLineStyle: {
182                color: appTheme.ForegroundColor,
183                tickSize: 3,
184                strokeThickness: 1,
185            },
186        },
187        colorMap: {
188            minimum: 0,
189            maximum: 10,
190            gradientStops: [
191                { offset: 1, color: "#FF0000" }, // Red - highest magnitude
192                { offset: 0.8, color: "#FF4500" }, // Orange-red
193                { offset: 0.6, color: "#FFA500" }, // Orange
194                { offset: 0.4, color: "#FFFF00" }, // Yellow
195                { offset: 0.2, color: "#90EE90" }, // Light green
196                { offset: 0, color: "#0001FF" }, // Blue - no activity
197            ],
198        },
199    });
200
201    return { sciChartSurface: heatmapLegend.innerSciChartSurface.sciChartSurface };
202};
203
204/** Fetches earthquake data from CSV file */
205async function fetchEarthquakeData(): Promise<EarthquakeData[]> {
206    try {
207        const response = await fetch(baseUrl + "earthquakes-23k.csv");
208        const csvText = await response.text();
209        return parseEarthquakeCSV(csvText);
210    } catch (error) {
211        console.error("Error fetching earthquake data:", error);
212        return [];
213    }
214}
215
216/** Parses CSV text into earthquake data objects */
217function parseEarthquakeCSV(csvText: string): EarthquakeData[] {
218    const lines = csvText.trim().split("\n");
219    const earthquakes: EarthquakeData[] = [];
220
221    // CSV format: Date,Latitude,Longitude,Magnitude (skip header row)
222    for (let i = 1; i < lines.length; i++) {
223        const columns = lines[i].split(",");
224
225        if (columns.length >= 4) {
226            const latitude = parseFloat(columns[1]);
227            const longitude = parseFloat(columns[2]);
228            const magnitude = parseFloat(columns[3]);
229
230            // Validate geographic bounds and magnitude
231            if (
232                !isNaN(latitude) &&
233                !isNaN(longitude) &&
234                !isNaN(magnitude) &&
235                latitude >= -90 &&
236                latitude <= 90 &&
237                longitude >= -180 &&
238                longitude <= 180 &&
239                magnitude >= 0
240            ) {
241                earthquakes.push({
242                    latitude,
243                    longitude,
244                    magnitude,
245                    depth: 0, // Not available in this dataset
246                });
247            }
248        }
249    }
250
251    return earthquakes;
252}
253
254/** Generates a heatmap grid from earthquake data */
255function generateEarthquakeHeatmap(earthquakes: EarthquakeData[], width: number, height: number): number[][] {
256    // Initialize grid with zeros
257    const grid: number[][] = [];
258    for (let y = 0; y < height; y++) {
259        grid.push(new Array(width).fill(0));
260    }
261
262    if (earthquakes.length === 0) {
263        return grid;
264    }
265
266    // World map bounds
267    const minLat = -90;
268    const maxLat = 90;
269    const minLon = -180;
270    const maxLon = 180;
271
272    // Map each earthquake to a grid cell
273    earthquakes.forEach((earthquake) => {
274        // Convert lat/lon to grid coordinates
275        const x = Math.floor(((earthquake.longitude - minLon) / (maxLon - minLon)) * width);
276        const y = Math.floor(((maxLat - earthquake.latitude) / (maxLat - minLat)) * height); // Flip Y for proper orientation
277
278        if (x >= 0 && x < width && y >= 0 && y < height) {
279            // Use maximum magnitude when multiple earthquakes fall in the same cell
280            grid[y][x] = Math.max(grid[y][x], earthquake.magnitude);
281        }
282    });
283
284    return smoothHeatmap(grid, width, height);
285}
286
287/** Applies a 3x3 averaging filter to smooth the heatmap */
288function smoothHeatmap(grid: number[][], width: number, height: number): number[][] {
289    const smoothed: number[][] = [];
290
291    for (let y = 0; y < height; y++) {
292        const row: number[] = [];
293        for (let x = 0; x < width; x++) {
294            let sum = 0;
295            let count = 0;
296
297            // Average with neighboring cells (3x3 kernel)
298            for (let dy = -1; dy <= 1; dy++) {
299                for (let dx = -1; dx <= 1; dx++) {
300                    const ny = y + dy;
301                    const nx = x + dx;
302
303                    if (ny >= 0 && ny < height && nx >= 0 && nx < width) {
304                        sum += grid[ny][nx];
305                        count++;
306                    }
307                }
308            }
309
310            row.push(count > 0 ? sum / count : 0);
311        }
312        smoothed.push(row);
313    }
314
315    return smoothed;
316}
317