Flight 2 GPS data

I flew my APRS tracker on board this flight and the Garmin Etrex Summit also stores a track log internally. I downloaded that log using the Mapsource software that Garmin sells. Here is a pdf file of the ground track recorded for that flight.

A little explanation will hopefully make this a bit clearer. :-)

The background is from a topographic map and the horizontal and vertical lines are roads at one mile intervals typical in this area. The track starts at bottom center at the prep area, proceeds to safety checkin and then out to the pads as before except with a slightly different route to the pads.

As with the L1060 flight, the first couple of positions during flight are obviously incorrect. This might be caused by the GPS unit being in battery saver mode. I will try it in normal mode next time to see if it makes any difference. Besides going up, the rocket takes a definite path to the west with apogee happening about a half mile west of the launch pad.

After apogee the winds carry it towards the northwest for a while. Then just before it lands (at about 700' AGL) it takes a sharp turn due north. This can be seen in more detail here. The slight knot in the the track is where the rocket landed and where it was found. It then makes a short trip to the back of my car.

I was quite surprised to see that the track continued all the way back to the field. I just put the rocket in the back of my car and didn't make any effort to make sure the GPS could see the sky.

FOr the L1060 flight I had switched the APRS tracker frequency from 144.39 to 441.15 because I noticed that the Walston transmitter in the nose was opening the squelch on the Alinco DJ-C5 transceiver. This would prevent the Tinytrak from operating correctly because it monitors the receiver and will not transmit while the channel is occupied. This happened while I had the APRS system outside of the rocket with the Walston installed in the nose.

For this flight I decided that because of the location and orientation of the DJ-C5 antenna, the Walston might be in the antenna null and not effected too badly. So I assembled the rocket and left the frequency at 144.39. After monitoring the signal for a while I decided it was working OK and left it alone.

Because I was now on the national APRS frequency, my transmitted position packets had a chance of making it to internet gateways so anyone could see where it was. When I returned home and had internet access again, I checked www.findu.com and sure enough some packets had made it out.

The following packets were received:


Some of the packets were relayed by a station that chose not to identify itself (RELAY*) while two were relayed by a station (AB0XM-10) that was over 100 miles away!

Only packets transmitted during flight made it to internet gateways and I think that there is a good chance that these are all of the packets transmitted during flight.

The first part of each packet contains address information up to the colon. After the colon is the position information. Latitude, longitude, course, speed, and altitude.

Because my ground station receiver was accidentally tuned off frequency and I didn't notice it until too late, I did not have a good position available to begin the search with. But I did see the rocket as it drifted over the horizon and locked a bearing into my GPS unit. This would allow me to know if I was close to the correct line of sight while out driving around.

When I started the search, I got a little carried away and started by going two miles north and almost two east before stopping to check for a signal (GPS and Walston). As a result I was much too far out and got nothing. After moving further out and getting nothing again it was time to regroup and move a little closer.

It was at this point that Dave Schaefer (who had accompanied me in the search) said "Let's think about this."

Using ballpark figures for expected altitude (9,000') descent rate (20fps) and wind speed (10mph) we decided that the rocket had drifted about 1.25 miles from the launch site. So I drove back to the road that runs east-west one mile north of the flying field. As I was driving west and noting on the GPS that we were almost on the line of sight, Dave spotted the rocket. The motor and electronics sections were a few hundred feet off the road to the left and the nose a few hundred feet off the road to the right. Amazingly close together since they had recovered on separate parachutes from several thousand feet.

If I had started by driving one mile north and then east, the search would have been much shorter.