diff --git a/src/server.js b/src/server.js
index 6e0a7f1..d1029ae 100644
--- a/src/server.js
+++ b/src/server.js
@@ -147,13 +147,13 @@ function adsb2dd(key, json) {
       }
 
       // skip if no change to lat/lon/alt
-      if (dict[key]['out'][hexCode]['lat'] === aircraft['lat'] &&
-        dict[key]['out'][hexCode]['lon'] === aircraft['lon'] &&
-        dict[key]['out'][hexCode]['alt'] === aircraft['alt_geom']) {
+      if (dict[key]['proc'][hexCode]['lat'] === aircraft['lat'] &&
+        dict[key]['proc'][hexCode]['lon'] === aircraft['lon'] &&
+        dict[key]['proc'][hexCode]['alt'] === aircraft['alt_geom']) {
         continue;
       }
 
-      dict[key]['out'][hexCode]['timestamp'] = json.now + aircraft.seen_pos;
+      dict[key]['out'][hexCode]['timestamp'] = json.now - aircraft.seen_pos;
       dict[key]['out'][hexCode]['flight'] = (aircraft.flight);
       dict[key]['proc'][hexCode]['lat'] = aircraft['lat'];
       dict[key]['proc'][hexCode]['lon'] = aircraft['lon'];
@@ -173,7 +173,7 @@ function adsb2dd(key, json) {
 
       // store bistatic delay/timestamps for Doppler
       dict[key]['proc'][hexCode]['delays'].push(delay);
-      dict[key]['proc'][hexCode]['timestamps'].push(json.now + aircraft.seen_pos);
+      dict[key]['proc'][hexCode]['timestamps'].push(json.now - aircraft.seen_pos);
 
       // bistatic Doppler (Hz)
       if (dict[key]['proc'][hexCode]['delays'].length >= 2) {