Personal GPS Beacons

Personal GPS Beacons

4th June 2013

How high will SPOT Messenger return it’s position?

How high will SPOT Messenger return it’s position? Those who use SPOT for tracking and locating HAB payloads have reported a variety of success or failure in getting a position reported from SPOT once it, and the balloon payload, reaches altitude. SPOT quote over 6500 m.a.s.l.  on their web site

http://www.findmespot.com/en/index.php?cid=102

though many flights report getting locations above this.

A recent HAB flight from Great Tew in Oxfordshire, UK, shed some light on this. The HAB flight in question, which took off on 25^th May 2013,was launched by Richard and his team. The camera payload was tracked using both a SPOT Messenger, TK 102 enhanced GPS tracker, and a radio tracker with a UBLOX GPS.

Here is a map to show the location messages given by the SPOT Messenger and some (but not all) of the location messages given by the radio tracker.

https://maps.google.co.uk/maps/ms?msid=212283995287100842283.0004ddd7250267480fdda&msa=0&ll=51.989029,-1.611042&spn=0.014985,0.042272&iwloc=0004ddddc223a7a83a396

The first thing that jumps out is that in all but one location message by SPOT, there is a high degree of similarity between the two trackers. The last location message reported by SPOT Messenger, with some accuracy, is as follows

SPOT Latitude : 51.98448 Longitude : -1.612125/26/2013 08:32:15 AM Battery State : GOOD

The closest message from the radio tracker is

08:30:04               51.98494              -1.61207               11812 m a s l

So it is fair to assume that the last message from SPOT came at around 11812m above sea level.

Second, it is obvious that the latitude and longitude of the SPOT location message from the Chipping Campden area is out by around 6km. Many HAB flights using SPOT have reported inaccuracies in SPOT location messages above the manufacturers recommended altitude limit.

SPOT Messenger is a great way to locate and partially track your HAB. It also works well beyond the quoted altitude limit, however, the higher it gets beyond those limits, the greater the risk of inaccurate location reports.

Further flight details

Trackers

Running a standard ATMEGA setup plus SPOT Messenger plus GSM/GPRS,

Tracking details – ATMEGA

Callsign: BABSHAB

Frequency: 434.075Mhz

RTTY

450 shift

50 Baud

7 ascii bpc

No parity and 2 stop bits.

2nd January 2013

SPOT1 Hack by Alexie Karpenco

Alexei Karpenco has suggested a hack to overcome power down glitches on the SPOT 1 unit. For more information go to http://www.redyns.com/Projects/TrackMeSpot/index.html

A second SPOT 2 hack is shown here

http://natrium42.com/projects/spot/

12th December 2012

Personal locator beacons compared

Now there are a range of PLB’s on the market, a simple comparison can be made.

	SPOT 2	Yellowbrick	inReach
weight including batteries (g)	148	305	227
minimum operating temp (celsius)	-30	-30	-20
tracking update interval	10 minutes	15 minutes	10 minutes
battery life sendin 1 location tracking every 10 minutes with clear sky	168hrs	504hrs	125 hrs
online tracking	Yes	Yes	Yes
device cost excl shipping	£156	£399	£156.45
service changes for tracking	£80	£11 for 100 credits giving tracking for 25 hours	£76.60
Two way messenging	NO	YES	NO
Smart phone tether	NO	YES	YES
Location pricing	Annual Contract	Contract or Pay as you go	Contract

Experience is everything though. SPOT 2 is extensively tried and tested. While it sometimes gives erroneous positions at altitude or unexpectedly switches off, it is, on the whole, reliable. inReach has been tried several times and has performed well. Yellowbrick, to our knowledge, has not yet been tested in a HAB.

13th November 2012

Yellow Brick 3 Personal GPS Beacon www.yellowbrick-tracking.com/

Yellow brick 3 is the first British entrant into the personal GPS beacon field but what does the device offer?

source http://www.yellowbrick-tracking.com/

Yellow Brick 3 it a two way messenger and location beacon which utilises the Iridium satellite network.

source http://www.yellowbrick-tracking.com/

The YB3 has the following technical specifications:-

Weight – 305g

Battery – Internal battery giving 2500 transmissions per charge

Minimum operational temperature – -30 deg C

Water resistance – immersion to 1m

GPS receiver type – 50 channel

Location update frequency – 15 minutes and bursts

Yellow Brick 3 also offers the advantage of being able to purchase message credits as opposed to being lumbered with annual contracts which are more familiar to SPOT messenger and inReach. Like inReach, you can also tether smart phones. One big disadvantage to Yellow Brick is the price. The basic YB3 set is £399. The device is also heavy at 305 g. One great opportunity of the device is the two way messaging. For those who have seen the amazing work of Dave Akerman and his picture transmission from balloons, YB3 offers the hope that this could be available to ‘plug and play’ hobbyists. YB3 has not yet been tested at altitude but a launch is planned soon and we hope to update you on their successes as a balloon tracker.

7th November 2012

DeLorme inReach Personal GPS Beacon

http://www.inreachdelorme.com/

The DeLorme InReach GPS beacon is a competitor to the SPOT Messenger beacon in the HAB tracking sphere but what does the InReach actually offer? Similar to SPOT, it offers online position tracking over the web. Like SPOT, the devise boasts a dustproof, waterproof,  and cold proof unit but is heavier than it’s rival. The quoted tracking update times are also the same at ca 10 minute intervals. The DeLorme devise is considerably more expensive coming in at $250 excluding service charges. There is a one-time activation charge of $19.95. In addition, you need to choose a subscription plan that best fits your needs. You can also move up and down between the plans based on their seasonal activity. There is no charge for moving to a higher-priced plan, but there is a $24.95 charge for moving down.

Specs

• Dimensions: 3.4″ H (4.77″ including antenna), 2.85″ W, 1.73″ D; 8.6 cm H (12.1 cm including antenna), 7.2 cm W, 4.4 cm D
• Weight: 7 oz (198 g) without batteries; 8 oz (227 g) with 2 lithium batteries
• Waterproof and dustproof (IP68) and buoyant (it floats)
• Impact-resistant (Mil STD 810F)
• Operating temperature: −20°C to 70°C (−4°F to 158°F)
• Storage temperature: −45°C to 75°C (−49°F to 167°F)
• SOS locking mechanism complies with RTCM SC-128 for satellite emergency notification devices (SEND); prevents false alarms and supports one-handed gloved operation
• GPS chipset for remote tracking and embedding location coordinates in all sent messages. Accuracy +/− 5 meters
• GPS fix reports position, speed, course, and elevation with each track or message sent

Power

• Uses two AA lithium batteries (included)
• Lithium batteries provide the best performance and are strongly recommended. Alkaline and NiMH batteries also supported
• Battery life: 125 hours (lithium) sending one-track point every 10 minutes; results will vary depending on usage conditions

For more product information go to http://www.inreachdelorme.com/

The unit has already been used in the HAB world by a pair of university students in Newfoundland. To take a look at their experience with the devise, go to http://www.youtube.com/watch?v=cTaKEP9Vlwg

Rogue data from SPOT Messenger 1 20th April 2012 Review posted by Chris Hillcox

Spot tracking with rogue data Today I assisted on a project by South Cheshire college to launch simple payloads on 1200g balloons. I let them use my SPOT tracker with the second payload flown over Shropshire. During the flight the tracker produced 2 rogue data points (point 6 and 7) out by some 30 miles from the probable true location of the tracker. Thankfully the rogue points were not during the landing phase. Spot is a great tracker but I am now mindful that if can have glitches. Here is what the operator of SPOT had to say, “The reason that point 6 is “off” may be due to the fact that the gps tries to get a satellite fix for 3 minutes. If 3 or more satellites are not in direct contact during that time, it gives an estimate . That estimate may not always be accurate.”