diff --git a/lib/tcx.mjs b/lib/tcx.mjs
index e93e7fc..c25d102 100644
--- a/lib/tcx.mjs
+++ b/lib/tcx.mjs
@@ -26,8 +26,8 @@ export function generateTrimlogInput(filename, name = "Walk", type = "walk") {
             time: tp.Time[0],
             longitude: parseFloat(tp.Position?.[0]?.LongitudeDegrees[0]),
             latitude: parseFloat(tp.Position?.[0]?.LatitudeDegrees[0]),
-            altitude: parseFloat(tp.AltitudeMeters[0]),
-            distance: parseFloat(tp.DistanceMeters[0]),
+            altitude: parseFloat(tp.AltitudeMeters?.[0]),
+            distance: parseFloat(tp.DistanceMeters?.[0]),
             pulse: parseFloat(tp.HeartRateBpm?.[0].Value?.[0]),
           };
   
@@ -42,6 +42,11 @@ export function generateTrimlogInput(filename, name = "Walk", type = "walk") {
         }
       }
 
+      const list = Object.keys(map).sort().map(k => map[k]);
+      const firstLon = list.find(e => !!e.longitude)?.longitude;
+      const firstLat = list.find(e => !!e.latitude)?.latitude;
+      const firstAlt = list.find(e => !!e.altitude)?.altitude;
+
       const out = {
         date: dateStr,
         contents: [{rawActivity: {
@@ -49,13 +54,13 @@ export function generateTrimlogInput(filename, name = "Walk", type = "walk") {
           sets: [],
           effortScale: 1,
           weight: 0,
-          measurements: Object.keys(map).sort().map(k => map[k]).map(p => ({
+          measurements: list.map(p => ({
             seconds: Math.round((new Date(p.time) - date) / 1000),
             meters: p.distance,
             pulse: p.pulse,
-            longitude: p.longitude,
-            latitude: p.latitude,
-            altitude: p.altitude,
+            longitude: p.longitude || firstLon,
+            latitude: p.latitude || firstLat,
+            altitude: p.altitude || firstAlt,
           }))
         }}],
         description: name,