diff --git a/mapper/src/App.js b/mapper/src/App.js
index 9ceec98..a363785 100644
--- a/mapper/src/App.js
+++ b/mapper/src/App.js
@@ -156,12 +156,18 @@ function Map({end, duration, slider, mapState, setMapState}) {
 	const range = useMemo(() => parseSlider(end, duration, slider), [end, duration, slider]);
 
 	const coords = useMemo(() => {
-		if (!data || !data.length) return [];
+		if (!Array.isArray(data)) return [];
 
 		const result = [];
+		const [startTime, endTime] = range;
+
 		for (const point of data) {
-			if ((!range || (point.time >= range[0] && point.time <= range[1]))) {
+			// Ensure the point and its time exist before checking the range
+			if (!point || !point.time) continue;
+
+			if (point.time >= startTime && point.time <= endTime) {
 				const { lat, lon } = point;
+				// Strictest possible check for valid, finite, numeric coordinates
 				if (typeof lat === 'number' && typeof lon === 'number' && isFinite(lat) && isFinite(lon)) {
 					result.push([lat, lon]);
 				}