diff --git a/apps/openstmap/ChangeLog b/apps/openstmap/ChangeLog
index 1b0edaf34..239b89abc 100644
--- a/apps/openstmap/ChangeLog
+++ b/apps/openstmap/ChangeLog
@@ -32,3 +32,4 @@
 0.25: Enable scaled image filtering on 2v19+ firmware
 0.26: Ensure that when redrawing, we always cancel any in-progress track draw
 0.27: Display message if no map is installed
+0.28: Fix rounding errors
diff --git a/apps/openstmap/app.js b/apps/openstmap/app.js
index d66936c29..2d14fbd2a 100644
--- a/apps/openstmap/app.js
+++ b/apps/openstmap/app.js
@@ -65,14 +65,16 @@ function redraw() {
 
 // Draw the POIs
 function drawPOI() {
+  let waypoints;
   try {
-    var waypoints = require("waypoints").load();
+    waypoints = require("waypoints").load();
   } catch (ex) {
     // Waypoints module not available.
     return;
   }
   g.setFont("Vector", 18);
   waypoints.forEach((wp, idx) => {
+    if (wp.lat === undefined || wp.lon === undefined) return;
     var p = m.latLonToXY(wp.lat, wp.lon);
     var sz = 2;
     g.setColor(0,0,0);
@@ -80,7 +82,7 @@ function drawPOI() {
     g.setColor(0,0,0);
     g.drawString(wp.name, p.x, p.y);
     //print(wp.name);
-  })
+  });
 }
 
 function isInside(rect, e, w, h) {
diff --git a/apps/openstmap/interface.html b/apps/openstmap/interface.html
index 3427fa882..a16bfa331 100644
--- a/apps/openstmap/interface.html
+++ b/apps/openstmap/interface.html
@@ -45,7 +45,11 @@
       <div id="map">
       </div>
       <div id="controls">
-        <div style="display:inline-block;text-align:center;vertical-align: top;" id="3bitdiv"> <input type="checkbox" id="3bit"></input><br/><span>3 bit</span></div>
+        <div style="display:inline-block;text-align:left;vertical-align: top;" id="3bitdiv">
+          <input type="checkbox" id="3bit"></input><span>3 bit</span>
+          <br>
+          <input type="checkbox" id="preview"><span>Preview</span>
+        </div>
         <div class="form-group" style="display:inline-block;">
         <select class="form-select" id="mapSize">
           <option value="4">Small (4x4)</option>
@@ -275,7 +279,9 @@ TODO:
             options.width = TILESIZE;
             options.height = TILESIZE;
             var imgstr = imageconverter.RGBAtoString(rgba, options);
-            //ctx.putImageData(imageData,x*TILESIZE, y*TILESIZE); // write preview
+            if (document.getElementById("preview").checked) {
+              ctx.putImageData(imageData,x*TILESIZE, y*TILESIZE); // write preview
+            }
             /*var compress = 'require("heatshrink").decompress('
             if (!imgstr.startsWith(compress)) throw "Data in wrong format";
             imgstr = imgstr.slice(compress.length,-1);*/
diff --git a/apps/openstmap/metadata.json b/apps/openstmap/metadata.json
index 75359d3fa..2b010c576 100644
--- a/apps/openstmap/metadata.json
+++ b/apps/openstmap/metadata.json
@@ -2,7 +2,7 @@
   "id": "openstmap",
   "name": "OpenStreetMap",
   "shortName": "OpenStMap",
-  "version": "0.27",
+  "version": "0.28",
   "description": "Loads map tiles from OpenStreetMap onto your Bangle.js and displays a map of where you are. Once installed this also adds map functionality to `GPS Recorder` and `Recorder` apps",
   "readme": "README.md",
   "icon": "app.png",
diff --git a/apps/openstmap/openstmap.js b/apps/openstmap/openstmap.js
index 9c7c9697d..7e84f66e5 100644
--- a/apps/openstmap/openstmap.js
+++ b/apps/openstmap/openstmap.js
@@ -76,7 +76,7 @@ exports.draw = function() {
     for (var x=ox,ttx=tx; x<mx && ttx<map.w; x+=s,ttx++) {
       for (var y=oy,tty=ty;y<my && tty<map.h;y+=s,tty++) {
         o.frame = ttx+(tty*map.w);
-        g.drawImage(img,x,y,o);
+        g.drawImage(img,Math.round(x),Math.round(y),o);
         count++;
       }
     }
@@ -91,8 +91,8 @@ exports.latLonToXY = function(lat, lon) {
   var cx = g.getWidth()/2;
   var cy = g.getHeight()/2;
   return {
-    x : (q.x-p.x)/m.scale + cx,
-    y : cy - (q.y-p.y)/m.scale
+    x : Math.round((q.x-p.x)/m.scale + cx),
+    y : Math.round(cy - (q.y-p.y)/m.scale)
   };
 };