Try new calculation

README.md

@@ -1,3 +1,7 @@
 # OMSI to LGLN
 
 Convert OMSI URLs to LGLN URLs via a local proxy server.
+
+Example URL:
+
+http://localhost:3000/?&x=53.3332&y=9.8667&z=16

index.js

@@ -34,6 +34,8 @@ module.exports = async function () {
   const app = express()
 
   app.get('/', async (request, response) => {
+    console.log(chalk`\n================================================================================`)
+
     console.log(chalk`\n{bold Request coordinates (lat/long)}`)
     console.log(request.query)
 

lib/convert-coordinates.js

@@ -23,21 +23,24 @@ function convertCoordinates (options) {
     options.z = parseFloat(options.z)
   }
 
+  const latInner = Math.PI * (1 - 2 * options.y / 2 ** options.z)
+  const latSinh = Math.sinh(degToRad(latInner))
+  const latAtan = Math.atan(degToRad(latSinh))
+  const lat = latAtan * 180 / Math.PI
+
+  const long = options.x * 360 / 2 ** options.z - 180
+
   const {
-    easting: centerX,
-    northing: centerY
-  } = utm.fromLatLon(options.x, options.y)
-
-  const C = 40075016.686
-  const tileWidth = C * Math.cos(degToRad(options.x)) / 2 ** options.z
-  const halfTileWidth = tileWidth / 2
-
-  return {
-    x1: centerX - halfTileWidth,
-    y1: centerY - halfTileWidth,
-    x2: centerX + halfTileWidth,
-    y2: centerY + halfTileWidth
-  }
+    easting: x1,
+    northing: y2
+  } = utm.fromLatLon(lat, long)
+
+  const s = 40075016.686 * Math.cos(degToRad(lat)) / 2 ** options.z
+
+  const x2 = x1 + s
+  const y1 = y2 - s
+
+  return { x1, y1, x2, y2 }
 }
 
 module.exports = convertCoordinates

lib/request-map.js

@@ -3,6 +3,15 @@ const chalk = require('chalk')
 
 axios.defaults.baseURL = 'https://www.umweltkarten-niedersachsen.de'
 
+axios.interceptors.response.use(response => {
+  console.log(chalk`\n{bold Request URL}`)
+  console.log(chalk`{blue ${response.request.res.responseUrl}}`)
+
+  return response
+}, error => {
+  return Promise.reject(error)
+})
+
 /**
  * Request map from LGLN
  * @param {Object} options Request options

package.json

@@ -1,6 +1,6 @@
 {
   "name": "omsi-to-lgln",
-  "version": "0.1.0-alpha.3",
+  "version": "0.1.0-alpha.4",
   "description": "Convert OMSI URLs to LGLN URLs",
   "main": "index.js",
   "bin": "bin/omsi-to-lgln.js",