I had something strange occur this weekend and I'm looking for some feedback on what could have caused it.
Here's the scenario:
I launched a rocket carrying an eggtimer TRS to ~6500ft. I was not able to maintain visual lock on the rocket throughout the entire flight however I was able to track it during ascent, saw the ejection and some of the initial descent. The prevailing winds that day were SW and that matched the initial trajectory of the rocket under descent.
Once I lost sight of the rocket I watched the flight status screen on my eggfinder LCD. The last position update I received from the TRS was at 84ft AGL. Based solely on the partial visual track I anticipated needing to drive to recover my rocket as it was at least a 1/2 mile away in a field on the other side of the nearby road. As I walked towards my car I switched over to the heading screen on the eggfinder LCD and once I had moved enough for it to compute a valid track I noticed the heading it was displaying was due east. I was a surprised by this at first because it didn't match the NE track I saw during descent and the prevailing SW winds would not have pushed the rocket further south so that I ended up with an east track. I should note that I have flown this hardware in that rocket linked to this LCD multiple times and it has always performed flawlessly. At this point I turned around and started walking east because there was nothing but open farm field to the east.
When I got the the location of the last transmission the rocket was nowhere to be found. This happened to be in the middle of a relatively flat farm field with no obstacles within at least 500' in any direction. Based on the terrain I should have been able to see the rocket. At this point I was pretty confused. I plotted the GPS coordinates into Google Maps and according to it I was in the right location. That seemed to confirm the receiver had taken me to the right position. At this point I decided to abandon electronic tracking and walk north towards the direction of the visual track I had observed. The nearby road I mentioned earlier was approximately 1000ft north of the originally reported rocket location. When I got to the road the LCD received a position update from the rocket. I followed the heading and it took me right to the rocket. The rocket was more than 1/4 but less than 1/2 mile N of the reported position at 84' AGL. I was glad to find the rocket and not lose the motor case, electronics and chute release I had onboard. What I am most confused about is this, clearly the TRS reported its position accurately because once I re-established a connection at the road I tracked right to the rocket. Ok, so why then was the position at 84ft AGL so far off?? There's no way the rocket could have drifted that far in it's final 84ft of descent.
I feel pretty confident in assuming that as long as the TRS and the LCD are getting a good GPS signal they are going to be pretty consistent in terms of positional accuracy. I don't see how it could be accurate to within tens of feet only to be off by 2000 ft 30 minutes earlier unless there was a satellite connection issue. The rocket was reporting connection to 7 or 8 satellites from power up until I lost connection and the orange GPS LED on the LCD was on the entire time so I'm assuming I had good GPS. Perhaps that is a poor assumption and someone can educate me. Beyond that I am left with only two other possibilities - the position difference was caused by user error (I don't see what I did wrong) or someone moved my rocket from it's original landing spot. Both locations were not visible from the launch location so it is possible however I saw no indication of that at all. When I found the rocket it looked like a completely normal landing and the rocket had not been disturbed in any way.
Trying to solve this mystery. Maybe this is not abnormal but I've never had this kind of issue before. Appreciate any advice or feedback.
Here's the scenario:
I launched a rocket carrying an eggtimer TRS to ~6500ft. I was not able to maintain visual lock on the rocket throughout the entire flight however I was able to track it during ascent, saw the ejection and some of the initial descent. The prevailing winds that day were SW and that matched the initial trajectory of the rocket under descent.
Once I lost sight of the rocket I watched the flight status screen on my eggfinder LCD. The last position update I received from the TRS was at 84ft AGL. Based solely on the partial visual track I anticipated needing to drive to recover my rocket as it was at least a 1/2 mile away in a field on the other side of the nearby road. As I walked towards my car I switched over to the heading screen on the eggfinder LCD and once I had moved enough for it to compute a valid track I noticed the heading it was displaying was due east. I was a surprised by this at first because it didn't match the NE track I saw during descent and the prevailing SW winds would not have pushed the rocket further south so that I ended up with an east track. I should note that I have flown this hardware in that rocket linked to this LCD multiple times and it has always performed flawlessly. At this point I turned around and started walking east because there was nothing but open farm field to the east.
When I got the the location of the last transmission the rocket was nowhere to be found. This happened to be in the middle of a relatively flat farm field with no obstacles within at least 500' in any direction. Based on the terrain I should have been able to see the rocket. At this point I was pretty confused. I plotted the GPS coordinates into Google Maps and according to it I was in the right location. That seemed to confirm the receiver had taken me to the right position. At this point I decided to abandon electronic tracking and walk north towards the direction of the visual track I had observed. The nearby road I mentioned earlier was approximately 1000ft north of the originally reported rocket location. When I got to the road the LCD received a position update from the rocket. I followed the heading and it took me right to the rocket. The rocket was more than 1/4 but less than 1/2 mile N of the reported position at 84' AGL. I was glad to find the rocket and not lose the motor case, electronics and chute release I had onboard. What I am most confused about is this, clearly the TRS reported its position accurately because once I re-established a connection at the road I tracked right to the rocket. Ok, so why then was the position at 84ft AGL so far off?? There's no way the rocket could have drifted that far in it's final 84ft of descent.
I feel pretty confident in assuming that as long as the TRS and the LCD are getting a good GPS signal they are going to be pretty consistent in terms of positional accuracy. I don't see how it could be accurate to within tens of feet only to be off by 2000 ft 30 minutes earlier unless there was a satellite connection issue. The rocket was reporting connection to 7 or 8 satellites from power up until I lost connection and the orange GPS LED on the LCD was on the entire time so I'm assuming I had good GPS. Perhaps that is a poor assumption and someone can educate me. Beyond that I am left with only two other possibilities - the position difference was caused by user error (I don't see what I did wrong) or someone moved my rocket from it's original landing spot. Both locations were not visible from the launch location so it is possible however I saw no indication of that at all. When I found the rocket it looked like a completely normal landing and the rocket had not been disturbed in any way.
Trying to solve this mystery. Maybe this is not abnormal but I've never had this kind of issue before. Appreciate any advice or feedback.