diff --git a/demod_2400.c b/demod_2400.c
index 8f5ace7..e85db98 100644
--- a/demod_2400.c
+++ b/demod_2400.c
@@ -528,6 +528,7 @@ void demodulate2400AC(struct mag_buf *mag)
         //  ----- X1/X2/X3 average noise
 
         float midpoint = sqrtf(x1x2x3_noise * f1f2_signal); // so that signal/midpoint == midpoint/noise
+        unsigned quiet_threshold = (unsigned) midpoint;
         unsigned noise_threshold = (unsigned) (midpoint * 0.707107 + 0.5); // -3dB from midpoint
         unsigned signal_threshold = (unsigned) (midpoint * 1.414214 + 0.5); // +3dB from midpoint
 
@@ -563,8 +564,8 @@ void demodulate2400AC(struct mag_buf *mag)
             noisy_bits <<= 1;
 
             // check for excessive noise in the quiet period
-            if (m[sample+2] >= noise_threshold) {
-                //fprintf(stderr, "bit %u was not quiet (%u > %u)\n", bit, m[sample+2], signal_threshold);
+            if (m[sample+2] >= quiet_threshold) {
+                //fprintf(stderr, "bit %u was not quiet (%u > %u)\n", bit, m[sample+2], quiet_threshold);
                 noisy_bits |= 1;
                 continue;
             }
diff --git a/public_html/config.js b/public_html/config.js
index b3f173d..16b6e19 100644
--- a/public_html/config.js
+++ b/public_html/config.js
@@ -119,9 +119,17 @@ ChartBundleLayers = false;
 // Provide a Bing Maps API key here to enable the Bing imagery layer.
 // You can obtain a free key (with usage limits) at
 // https://www.bingmapsportal.com/ (you need a "basic key")
+//
+// Be sure to quote your key:
+//   BingMapsAPIKey = "your key here";
+//
 BingMapsAPIKey = null;
 
 // Provide a Mapzen API key here to enable the Mapzen vector tile layer.
 // You can obtain a free key at https://mapzen.com/developers/
 // (you need a "vector tiles" key)
+//
+// Be sure to quote your key:
+//   MapzenAPIKey = "your key here";
+//
 MapzenAPIKey = null;
diff --git a/public_html/layers.js b/public_html/layers.js
index 329cd6d..4e7e13e 100644
--- a/public_html/layers.js
+++ b/public_html/layers.js
@@ -26,6 +26,15 @@ function createBaseLayers() {
                         title: 'Bing Aerial',
                         type: 'base',
                 }));
+                world.push(new ol.layer.Tile({
+                        source: new ol.source.BingMaps({
+                                key: BingMapsAPIKey,
+                                imagerySet: 'Road'
+                        }),
+                        name: 'bing_roads',
+                        title: 'Bing Roads',
+                        type: 'base',
+                }));
         }
 
         if (MapzenAPIKey) {
diff --git a/public_html/planeObject.js b/public_html/planeObject.js
index 13be440..44abb47 100644
--- a/public_html/planeObject.js
+++ b/public_html/planeObject.js
@@ -392,7 +392,7 @@ PlaneObject.prototype.clearMarker = function() {
 
 // Update our marker on the map
 PlaneObject.prototype.updateMarker = function(moved) {
-        if (!this.visible) {
+        if (!this.visible || this.position == null) {
                 this.clearMarker();
                 return;
         }
@@ -414,7 +414,10 @@ PlaneObject.prototype.updateMarker = function(moved) {
 PlaneObject.prototype.updateLines = function() {
         if (!this.selected)
                 return;
-        
+
+        if (this.track_linesegs.length == 0)
+                return;
+
         var estimateStyle = new ol.style.Style({
                 stroke: new ol.style.Stroke({
                         color: '#a08080',
diff --git a/public_html/script.js b/public_html/script.js
index 5fd3723..1f28cab 100644
--- a/public_html/script.js
+++ b/public_html/script.js
@@ -316,6 +316,30 @@ function end_load_history() {
 
 }
 
+// Make a LineString with 'points'-number points
+// that is a closed circle on the sphere such that the
+// great circle distance from 'center' to each point is
+// 'radius' meters
+function make_geodesic_circle(center, radius, points) {
+        var angularDistance = radius / 6378137.0;
+        var lon1 = center[0] * Math.PI / 180.0;
+        var lat1 = center[1] * Math.PI / 180.0;
+        var geom = new ol.geom.LineString();
+        for (var i = 0; i <= points; ++i) {
+                var bearing = i * 2 * Math.PI / points;
+
+                var lat2 = Math.asin( Math.sin(lat1)*Math.cos(angularDistance) +
+                                      Math.cos(lat1)*Math.sin(angularDistance)*Math.cos(bearing) );
+                var lon2 = lon1 + Math.atan2(Math.sin(bearing)*Math.sin(angularDistance)*Math.cos(lat1),
+                                             Math.cos(angularDistance)-Math.sin(lat1)*Math.sin(lat2));
+
+                lat2 = lat2 * 180.0 / Math.PI;
+                lon2 = lon2 * 180.0 / Math.PI;
+                geom.appendCoordinate([lon2, lat2]);
+        }
+        return geom;
+}
+
 // Initalizes the map and starts up our timers to call various functions
 function initialize_map() {
         // Load stored map settings if present
@@ -489,7 +513,9 @@ function initialize_map() {
                                         distance *= 1.852;
                                 }
 
-                                var feature = new ol.Feature(new ol.geom.Circle(ol.proj.fromLonLat(SitePosition), distance));
+                                var circle = make_geodesic_circle(SitePosition, distance, 360);
+                                circle.transform('EPSG:4326', 'EPSG:3857');
+                                var feature = new ol.Feature(circle);
                                 feature.setStyle(circleStyle);
                                 StaticFeatures.push(feature);
                         }