diff --git a/src/main/lemondronor/advisorycircular.cljs b/src/main/lemondronor/advisorycircular.cljs
index 0e8ef37..3415a29 100644
--- a/src/main/lemondronor/advisorycircular.cljs
+++ b/src/main/lemondronor/advisorycircular.cljs
@@ -35,13 +35,17 @@
 
 (defn parse-adsbexchange-ac-element [e]
   (let [nilstr #(if (= % "") nil %)
-        numstr #(if (= % "") nil (js/parseFloat %))]
+        numstr #(if (= % "") nil (js/parseFloat %))
+        boolstr #(if (or (= % "1") (= (string/lower-case %) "true"))
+                   true
+                   false)]
     {:postime (numstr (e "postime"))
      :lat (numstr (e "lat"))
      :lon (numstr (e "lon"))
      :icao (e "icao")
      :registration (nilstr (e "reg"))
      :alt (numstr (e "alt"))
+     :gnd? (boolstr (e "gnd"))
      :mlat? (= (e "mlat") "1")
      :speed (numstr (e "spd"))
      :squawk (nilstr (e "sqk"))
@@ -195,7 +199,8 @@
 
 
 (defn circling? [ac config]
-  (and (> (geo/flight-curviness (:history ac)) (:curviness-threshold-degrees config))
+  (and (> (geo/flight-curviness (filter #(not (:gnd? %)) (:history ac)))
+          (:curviness-threshold-degrees config))
        (> (:alt ac) 300)))