--- a/client/src/components/Pdftool.vue	Thu Jan 17 16:42:47 2019 +0100
+++ b/client/src/components/Pdftool.vue	Thu Jan 17 21:48:11 2019 +0100
@@ -81,6 +81,7 @@
  */
 import { mapState } from "vuex";
 import jsPDF from "jspdf";
+import { getPointResolution } from "ol/proj.js";
 
 var paperSizes = {
   // in millimeter, landscape [width, height]
@@ -163,9 +164,15 @@
       // set a callback for after the next complete rendering of the map
       map.once("rendercomplete", function(event) {
         let canvas = event.context.canvas;
+
+        // because we are using Web Mercator, a pixel represents
+        // a differently sizes spot depending on the place of the map.
+        // So we use a value calculated from the center of the current view.
         let view = map.getView();
-        let metersPerPixel = // meters (reality) per pixel (map)
-          view.getResolution() * view.getProjection().getMetersPerUnit();
+        let proj = view.getProjection();
+        let metersPerPixel = // average meters (reality) per pixel (map)
+          getPointResolution(proj, view.getResolution(), view.getCenter()) *
+          proj.getMetersPerUnit();
         console.log("metersPerPixel = ", metersPerPixel);
 
         var data = canvas.toDataURL("image/jpeg");