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Author Topic: ShipTrax  (Read 16310 times)

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dorsetderek

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ShipTrax
« on: February 05, 2012, 09:19:08 pm »
Will there be any advantage using a larger aerial with the ShipTrax?, I live quite close to the sea, dorsetderek

Budgie

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Re: ShipTrax
« Reply #1 on: February 05, 2012, 09:56:55 pm »
It's not so much about the size of the aerial as the height and making sure it's the correct type.
AIS uses Marine VHF frequencies and VHF is "line of sight", which basically means if you can see the target then you can hear it.
To get more range then the higher the aerial the better.
I don't know about ShipTrax but any normal AIS unit will work fine with a standard marine antenna.

tarbat

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Re: ShipTrax
« Reply #2 on: February 05, 2012, 10:16:14 pm »
I find that you don't need clear line-of-sight, just "nearly" line-of-sight.  I can't see Invergordon, there are hills (and houses) in-between, but I get a good signal from ships there.

And to be honest, I tried a couple of marine antennae, and actually found that my standard £30 discone antenna gave much better reception of AIS.  I never really understood why, but I get great reception with a cheap discone mounted in the loft, with concrete roof tiles blocking the signal.

That's using the ShipTrax receiver.  Using a Comar AIS-2-USB isn't anywhere near as successful though!!
« Last Edit: February 05, 2012, 10:37:23 pm by tarbat »

jannuh

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Re: ShipTrax
« Reply #3 on: February 06, 2012, 01:15:01 am »
Get here the best results with a combi-antenna for 144/430 mHz, it's abt. 2.25 in length, mechanical very strong; it is now abt. 15 years in use on rooftop and still standing strong.

Tried also a yagi antenna, also a combi for 144-430 mHz, nice if you have the shiptraffic in one direction.

The difference between a (cheap) general scanner antenna and a professional marine antenna will be mainly its mechanical stability of the last one.

Budgie

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Re: ShipTrax
« Reply #4 on: February 06, 2012, 11:38:52 am »
The atmospherics also play a part in the range that can be obtained.
During summer high pressures I've managed to pick up AIS base stations in the Faeroes, that's something like 250 miles.
I currently use something similar to this Metz Manta which is mounted on my anemometer mast on the chimney of the house at about 45m ASL.
You can see the range map of what I get with this and my Comar AIS-2-USB on MarineTraffic.
Note: The reception to the far south, Kyle of Lochlash, is most likely the local Coastguard helicopter rather than shipping. ;-)

tarbat

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Re: ShipTrax
« Reply #5 on: February 06, 2012, 11:43:22 am »
Note: The reception to the far south, Kyle of Lochlash, is most likely the local Coastguard helicopter rather than shipping. ;-)

Yes, helicopters can play havoc with reception range measurements.  I asked Airnav to exclude Type 9 (SAR) messages from the polar chart in ShipTrax.  I also get the occasional long-range signal from the west coast:
« Last Edit: February 06, 2012, 11:44:56 am by tarbat »

eyeinthesky

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Re: ShipTrax
« Reply #6 on: February 06, 2012, 11:58:22 am »
The atmospherics also play a part in the range that can be obtained.
During summer high pressures I've managed to pick up AIS base stations in the Faeroes, that's something like 250 miles.
I currently use something similar to this Metz Manta which is mounted on my anemometer mast on the chimney of the house at about 45m ASL.
You can see the range map of what I get with this and my Comar AIS-2-USB on MarineTraffic.
Note: The reception to the far south, Kyle of Lochlash, is most likely the local Coastguard helicopter rather than shipping. ;-)

Your right I have got ships off Africa-- Italy and India   many many  times over the years with my ShipPlotter program, i use the Watson 6m/2m/70cm Tribander from Waters & Stanton
« Last Edit: February 06, 2012, 12:06:36 pm by eyeinthesky »
Using the Canon 10x30 IS Binoculars with Image Stabilisation, Brilliant job on a clear day.

Peter

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Re: ShipTrax
« Reply #7 on: February 06, 2012, 02:58:39 pm »
I had a marine aerial and like Tarbat, found that my Discone mounted outside on the chimney, at half the specialist aerial cost, is far better on AIS. I'm 12 miles inland, but can see to the 40 mile radius, i.e. 25 - 30 miles out to sea under flat conditions, and sometimes as far as Rotterdam under a lift! I don't use an aerial amplifier, that picks up every thermostatic blip and corrupts the data. I do use top quality coax though, UR67 when I bought a 100m. That has been superceeded with lighter, and no doubt a more user friendly replacement!

Peter

Budgie

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Re: ShipTrax
« Reply #8 on: February 06, 2012, 07:24:02 pm »
Yes, helicopters can play havoc with reception range measurements.  I asked Airnav to exclude Type 9 (SAR) messages from the polar chart in ShipTrax.
The only problem with excluding Type 9 is that you're also excluding all the rig stand-by vessels and maybe the RNLI Lifeboats as well as the SAR aircraft. Considering that there are only 4 Coastguard Helos in Scotland, and only two of those will normally be flying (one from Stornoway and one from Sumburgh) then it's denying you quite a lot to save very little. ;-)

Lou

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Re: ShipTrax
« Reply #9 on: February 07, 2012, 01:54:20 pm »
Hi All I`ve been using Shiptrax since saturday,first impressions not bad i`m finding the software a bit clunky like the first iterations of the RadarBox software. I`m used to shipplotter so was surprised not to be able to see the Thames RNLI boats, I could hear them on the marine radio, so now I know why a bit of a bummer really as I live in London my range is quite limited is there a workaround to re-instate. Regards Lou.

eyeinthesky

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Re: ShipTrax
« Reply #10 on: February 07, 2012, 02:35:47 pm »
Lou.
Keep them reports coming.

What range are you getting, and report the likes and dislikes and a few photos would be niece.

Thanks.
« Last Edit: February 07, 2012, 02:38:26 pm by eyeinthesky »
Using the Canon 10x30 IS Binoculars with Image Stabilisation, Brilliant job on a clear day.

tarbat

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Re: ShipTrax
« Reply #11 on: February 07, 2012, 03:36:06 pm »
The only problem with excluding Type 9 is that you're also excluding all the rig stand-by vessels and maybe the RNLI Lifeboats as well as the SAR aircraft.

As I understand it, type 9 messages are for SAR aircraft only, not ships.  See http://gpsd.berlios.de/AIVDM.html#_type_9_standard_sar_aircraft_position_report
I would not expect rig stand-by vessels to be transmitting aircraft messages.  In fact I think I've seen several rig stand-by vessels in Shiptrax on there way in and out of Invergordon.  But even if there are ships transmitting type 9 messages, surely they are most likely to be in areas covered by other ships anyway.  The problem with including SAR helicopters in the polar chart was that it quickly got distorted by returns from helicopters >60 miles away.

Hi All I`ve been using Shiptrax since saturday,first impressions not bad i`m finding the software a bit clunky like the first iterations of the RadarBox software.

I didn't realise Airnav had started shipping ShipTrax to customers, so great to see some real users.  Do you have anything specific about it being a bit clunky?  Maybe there are suggestions to help make it less clunky for you.

I`m used to shipplotter so was surprised not to be able to see the Thames RNLI boats, I could hear them on the marine radio, so now I know why a bit of a bummer really as I live in London my range is quite limited is there a workaround to re-instate.

Type 9 messages are all displayed in ShipTrax, they are only excluded from the polar chart.  here's an example:


Maybe the Thames RNLI boats aren't AIS equipped?
« Last Edit: February 07, 2012, 04:20:38 pm by tarbat »

Budgie

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Re: ShipTrax
« Reply #12 on: February 07, 2012, 10:48:08 pm »
As I understand it, type 9 messages are for SAR aircraft only, not ships. 
Looks like you're correct, we only see "SAR" in the type box on both ships and aircraft so I wasn't aware they transmit different raw data packets. 

tarbat

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Re: ShipTrax
« Reply #13 on: February 09, 2012, 12:02:10 pm »
Looks like you're correct, we only see "SAR" in the type box on both ships and aircraft so I wasn't aware they transmit different raw data packets. 

In ShipTrax you'll also see the type as SAR.  Here's an example from today:


Lou

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Re: ShipTrax
« Reply #14 on: February 11, 2012, 03:59:41 pm »
Hi Tarbat is it ppossible you could PM me,I have a problem I would respect your advicee on.Regards Lou ( no nothing is dropping off)