SPOT Samples

[Nuts]

This is a bit of a work in progress and just of interest to show spot tracking. It is data from a walk into Pelion from Arm River carpark. Most of the terrain is quite open so really the beacon shouldnt be expected to struggle.It was carried flat, in the top of the pack (as recommended).

I'm still looking into this (as time is available) though I do have concerns (and not really the knowledge to know whether these reflect on its use as an emergency beacon (in Tassie) even though the system has been used in some notable rescues.

As can be seen the time that tracking points are noted appear quite random (see point 5/6 12.23-1.55pm )
Is it having trouble finding a satellite, Is this due to the fact that the beacon was moving, Would performance be better if stationary (and hand held) Is this comparable to other GPS reliability, Is the newer model spot device much better????

Lots of questions and dont really know how far to go with this, there seems to be a lot of 'blind faith' in PLB's in general. Is it acceptable to rely on ' anecdotal evidence' from other rescues.

Perhaps when the emergency beacon is activated the continuing signal would mean a 'better than tracking' outcome?
It seems difficult to see without extensive state-wide testing whether this is 'good enuff'... It does appear to 'get thru' as it even sent a few signals from the back of the car when left on for the ride home.

Important to note that i am Not drawing any conclusions here.

Signal Times Recieved

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Map of Signal Source Points

Last edited by Nuts on Tue 15 Dec, 2009 5:09 pm, edited 6 times in total.

[tasadam]

Did you get yourself a SPOT and go for a play?

[Nuts]

It went through the Overland Track last week... similar sort of experience, a few gaps here and there and the odd signal clear of where (google says) the track is...

I'm getting the feeling that the testing required to be satisfied would be beyond resources....
I just want to see it cover enough of the areas we visit to be satisfied for us, perhaps someone else may find the info useful...
Would I buy one in preference to a 'standard' plb... YES, so long as the emergency beacon will operate from an acceptable range of terrain... Is that the case? (see last sentence in above post )

[MJD]

Was it a SPOT version 2 or version 1?

[Nuts]

Spot 1 MJD... I may try the second version at some stage. I like the system (though do want to know if those gaps mean the beacon wont work there in an emergency) The area on the steep hill is quite open..... I'll try a few 'OK' signals from there next time and see what happens...

Last edited by Nuts on Thu 17 Dec, 2009 1:06 pm, edited 1 time in total.

[MJD]

Just got a SPOT2. Unfortunately I ordered it and the shop shipped it the same day that it they were recalled (battery drain issue) and I can't activate it online. Very annoying. See: http://www.equipped.org/blog/?p=172

I use my Garmin GPSMap 60CSx to track my progress - usually at 20m intervals. Does a good job. Occassionally misses a few points in dense scrub.

[Nuts]

Ohh! That's not good! If it comes to a point in the new Year that you need one and not resolved let me know... i wonder if you can still activate an account on the old system (the units are very cheap) and swap over later?

[Nuts]

Return Journey

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[Nuts]

Spot on the South Coast Track (over eight days):

[eddie the eagle]

It's not that random, Nuts.

The unit sends out a signal every 10 minutes - you can calculate its strike rate fairly easy

(tallies with my experiences as well.)

CHeers,

eddie

[flatfoot]

Most GPS receivers are able to display error tolerance information. This is referred to as Horizontal Dilution of Position (HDOP). HDOP is an estimate of the horizontal error. The fewer the number of satellites your receiver can pick up the greater the HDOP (the position error is generally greater for altitude rather than lat long). Likewise, the spot device will be susceptible to poor signal quality at times. Does the spot device display any signal quality information?

The GPS constellation will at times have outages for distinct satellites. Here's where you can find the current status for all the satellites:

http://www.navcen.uscg.gov/navinfo/Gps/ActiveNanu.aspx

You can actually signup to receive outage information by e-mail - http://www.navcen.uscg.gov/gps/subscribe.htm. There are also archives but these are in binary format (so a significant amount of mental effort or more practically appropriate software is needed to interpret them).

Since SPOT is a commercially run service outage or maintenance status may not be available .... ???? Surely they could advise when maintenance outage events are planned or non-planned outage events occur in specific coverage areas. Since I am not a spot user I don't know whether this information is available to members. I could not find any info in their FAQ.

[photohiker]

Flatfoot,

The SPOT2 does not display specific GPS quality information. It flashes the GPS light green when it has sat lock, and red when it hasn't been able to get lock for a period of time.

As far as advising SPOT users of outages, I'm not sure how that could be achieved - SPOT is a one way communication device - there is no way to send a message TO the SPOT.

How frequent are these outages you speak of, and how many sats are involved?

If the SPOT cannot get GPS lock, and you push the SOS button, it will still attempt to transmit the SOS message without GPS co-ordinates. Same goes for the 'Assist' button. This differs from the OK message and Tracking function, which will not be transmitted if there is no GPS lock.

[flatfoot]

Flatfoot,

The SPOT2 does not display specific GPS quality information. It flashes the GPS light green when it has sat lock, and red when it hasn't been able to get lock for a period of time.

As far as advising SPOT users of outages, I'm not sure how that could be achieved - SPOT is a one way communication device - there is no way to send a message TO the SPOT.

I was thinking that with a system like this, there may be planned maintenance windows for the satellites that SPOT uses for messaging ... if there are ... when do they occur? Can advance warning be obtained for when outage for maintenance are planned?

How frequent are these outages you speak of, and how many sats are involved?

I'm not sure. You would need to monitor the alerts or dig into the archives. When I first started using GPS around 12 years ago I signed up for the alerts for interest's sake. They were occasionally interesting reading.

Whilst it might be rare for multiple satellites to be out of action, the impact of an outage of one satellite will depend on where you are. For example, if you are in a canyon and lose a satellite then the ability of the GPS to accurately triangulate your position is likely to significantly deteriorate.

If the SPOT cannot get GPS lock, and you push the SOS button, it will still attempt to transmit the SOS message without GPS co-ordinates. Same goes for the 'Assist' button. This differs from the OK message and Tracking function, which will not be transmitted if there is no GPS lock.

I can see that it's got a message sending light from looking at the manual. This seems to be a visual indication that the message was trasnmitted ... but is that also confirmation that the message was received at the other end ...? The manual is not clear.

[photohiker]

The message sending light, from the manual.

"The Message Sending Light notifies you whether or not your most recent message was transmitted.

* Green - The MSL blinks green after SPOT transmits the most recent message.

* Red - The MSL blinks red if SPOT didn't send the most recent message."

So it must know if it has a link with the Sat network. Knowing that the message has been received by the satphone network does not prove that it has arrived at the end user's system

SPOT does not operate any satellites. The comms sats it uses are the GlobalStar satphone network, so I guess outages might be researched with them. SPOT does not offer any service outage information from what I have seen.