地图常用 | 小胖妙妙屋

使用proj4求两线交点

使用turfJS求交点的时候，遇到一个交点不在两线上的问题，详见这里的issue，原因大概是经纬度计算的误差，投影坐标和地理坐标各有优势，投影坐标更适合用来计算因此，使用proj4将坐标转换成投影坐标后在计算，可达到精准的计算结果

        const line1 = [
            [120.179402, 31.247428, 0],
            [120.700497, 31.365937, 0]
        ]

        const line2 = [
            [120.445638, 31.381745, 0],
            [121.033588, 31.055778, 0],
            [121.094159, 31.046175, 0],
            [121.167627, 31.042088, 0]
        ]

        const point = intesection(line1, line2)

        console.log(point);

        function intesection(line1, line2) {

            const mercator = proj4("EPSG:4326", "EPSG:3857");

            // Convert the lines to Mercator coordinates
            const line1Mercator = line1.map(i => mercator.forward(i))
            const line2Mercator = line2.map(i => mercator.forward(i))

            // Define the lines in the form y = mx + b
            const m1 =
                (line1Mercator[1][1] - line1Mercator[0][1]) /
                (line1Mercator[1][0] - line1Mercator[0][0]);
            const b1 = line1Mercator[0][1] - m1 * line1Mercator[0][0];

            const m2 =
                (line2Mercator[1][1] - line2Mercator[0][1]) /
                (line2Mercator[1][0] - line2Mercator[0][0]);
            const b2 = line2Mercator[0][1] - m2 * line2Mercator[0][0];

            // Find the intersection point
            const x = (b2 - b1) / (m1 - m2);
            const y = m1 * x + b1;

            // Convert the intersection point back to geographic coordinates
            const intersection = mercator.inverse([x, y]);

            return intersection
        }