Does anyone monitor AIS (Ship and Vessel Tracking?)

[abcd567]

Thanks @geckoVN for the map.

My almost nil reception is mainly because of a combination of following two handicaps:

(1) Poor antenna (mag-mount base monopole).

(2) Poor antenna location (inside room) near the Desktop computer as the coax of mag-mount is only 1 meter long.

Next weekend I am planning to build a Quick Spider with 46cm long whip and radials, and using a longer coax, will place it near the window.

By the way, what is the URLof the site which provides the live map you have posted? It can act as a good benchmark for me to compare performance of my installation.

 

[geckoVN]

VHF will penetrate building very well, so being indoors won’t be a problem.
Similarly, an un-tuned antenna will still pull in a lot of signals - particularly as you are above ground level. Despite the claims that a CoCo will filter out-of-band frequencies, I’m using a 1090MHz CoCo quite successfully to receive 403MHz weather balloons - is it ideal? - No. Does it work? - Yes.
While I’m not recommending a 1090MHz CoCo, as can be seen with many junk-antennas, strong and/or local signals can be picked up on anything.

The screen shot came from MarineTraffic - one of many shipping sites.

MarineTraffic: Global Ship Tracking Intelligence | AIS Marine Traffic

[abcd567]

@geckoVN
@dvsvejk

As I live in an urban location, another strong possibility for poor reception of AIS is strong RF noise.

My 1090 MHz reception falls drastically if I remove FA 1090 MHz Blue Cylendrical filter. Based on my 1090 MHz experience, I think I should purchase a 162 MHz Band Pass filter.

RF Noise At My Location (24 MHz ~ 1800 MHz)

 

CLICK ON SCREENSHOTS TO SEE LARGER SIZE

CLICK AGAIN TO SEE FULL SIZE (1200 x 780 px)

 

 

 

 

 

 

[dvsvejk]

As @geckoVN stated an untuned antenna can work, you’ll just need to futz with it and your physical environment to see if it provides you acceptable performance for what you are trying to accomplish. This is what I am using (pic scraped from the web).

I have the mag mount on top of a metal toilet roll holder from IKEA, both to get some elevation and provide some type of ground plane. I found that when the antenna’s wire touched metal reception improved dramatically. So, I put some copper tape on the wire to ensure solid contact and wrapped the wire around the holder. It is oddly elegant in its own way and in the end it just freaking works for my purposes.

[abcd567]

@geckoVN
@dvsvejk

From your posts, I have realized that my problem is not the antenna.
However I have replaced its 12 cm whip by 46 cm wire. The magnetic base is placed over a metal plate. With this arrangement, it is now 1/4 WL ground plane at 162MHz.
Still the reception was near nil.

That leaves main suspects as follows:
(1) Overloading of dongle due to high gain (55~58 due to AGC on)
(2) High RF Noise.at my location as shown by RF Scan (24MHz ~ 1800 MHz) I have posted above.

In view of above, I changed settings as follows:
(1) Turned off AGC
(2) Set gain to 28
(3) Set ppm to -20
(4) Set sample rate to 2304K.

AIS-catcher -v 10 -u 127.0.0.1 10110 -M DT -gr TUNER 28.0 RTLAGC off -s 2304k -p -20 -o 4 >>C:\Users\abcd\Desktop\SHOTCUTS\AIS-Catcher-output.txt

 

Above changes in settings improved reception a little bit. I could get 4 more messages:

{"class":"AIS","device":"AIS-catcher","rxtime":"20220920050410","scaled":true,"channel":"B","nmea":["!AIVDM,1,1,,B,HmiaVH3oRe4Hb4?bU,0*5F"],"signalpower":-47.791080,"ppm":-1.736111,"type":24,"repeat":3,"mmsi":387606112,"partno":0,"shipname":"=8+QFJ!C:)W$;E?101V0"}
{"class":"AIS","device":"AIS-catcher","rxtime":"20220920053734","scaled":true,"channel":"B","nmea":["!AIVDM,1,1,,B,H,0*6D"],"signalpower":-49.589012,"ppm":1.446759,"type":24,"repeat":1,"mmsi":205290458,"partno":1,"shiptype":181,"shiptype_text":"Undefined","vendorid":"\&-","model":8,"serial":335848,"callsign":"! 4U84G","to_bow":73,"to_stern":443,"to_port":4,"to_starboard":35,"mothership_mmsi":154906915}
{"class":"AIS","device":"AIS-catcher","rxtime":"20220920074329","scaled":true,"channel":"A","nmea":["!AIVDM,1,1,,A,936P;:HnuiAT8`L4dthDsD`,0*2F"],"signalpower":-50.101665,"ppm":2.893518,"type":9,"repeat":0,"mmsi":208145193,"alt":2267,"speed":881,"accuracy":false,"lon":-201.821411,"lat":8.217921,"course":126.099998,"second":18,"dte":true,"assigned":false,"raim":true,"radio":479012}
{"class":"AIS","device":"AIS-catcher","rxtime":"20220920075038","scaled":true,"channel":"A","nmea":["!AIVDM,1,1,,A,=:FJVaGJBFqL6bLURrlUF<P55eqGohAFI2rt0jP9b,0*2F"],"signalpower":-57.745670,"ppm":3.761574,"type":13,"repeat":0,"mmsi":694593189,"mmsi1":915561367,"mmsiseq1":0,"mmsi2":111790434,"mmsiseq2":3,"mmsi3":726226482,"mmsiseq3":0,"mmsi4":21346197,"mmsiseq4":3}

 

I tried to find a 162 MHz Band Pass filter. Could find following, but when tried to place order, got notification that the seller is on vacation.

 

AIS 162 MHz Band Pass Filter Bandpass 160 MHz 161 MHz 162 MHz | eBay

 

[SweetPea11]

@abcd567

(3) Set ppm to -20

How was -20 determined?

S

[abcd567]

@SweetPea11

How was -20 determined?

Few days ago on a spare microSD card, I wrote the image from the site suggested by @geckoVN.

@geckoVN

I’ve just been through the same process with an AIS receiver. The offset with that is opposite sign to bring the error to zero

https://www.sarcnet.org/ais-receiver.html

 

That image has facility to calibrate ppm. I ran that and it gave me a figure of 20.

QUOTE:

Calibrate your AIS Receiver

The operating frequency of the USB RTL-SDR Dongle’s internal Temperature Controlled Crystal Oscillator (TCXO) may not be precisely on frequency, depending on its quality and other factors. However, you can use the RPi clock to calibrate the RTL-AIS service to account for any frequency offset. Note: The frequency offset is measured in Parts Per Million (PPM). Note: For 1PPM RTL-SDRs this step is hardly necessary as the frequency would only be off by +/- 162Hz.

Do the following on the Raspberry Pi:

1. Login:

2. Type: pi

3. Type: Your password

4. Stop the RTL AIS service and run the RTL test

5. Type: sudo systemctl stop rtl_ais.service

6. Type: rtl_test -p60

7. Wait until the cumulative error value (in PPM) remains more-or-less the same for three consecutive minutes

8. Note the last cumulative error value (in PPM).

 

EDIT:

The ppm test can be done on any RPi running RaspberryPi OS image or Piaware SD card image by following method:

sudo apt install rtl-sdr 

sudo systemctl stop piaware dump1090-fa readsb 

rtl_test -p60  

 

[dvsvejk]

FWIW, my indoor setup uses max gain (49.6) and agc=OFF. I’ve been experimenting with the -a option to set a narrower tuner bandwidth currently set at 72Khz. Still evaluating if that helps me or not.

Did you confirm your device can run at 2304K samples without losing data? There is a section in the readme which describes issues on Windows laptops at higher rates. I’m using Linux and a USB3.0 port on my thin client for the dongle.

Blockquote

System USB performance

On some laptops we observed that Windows was struggling with high volume of data transferred from the RTL SDR dongle to the PC. I am not sure why (likely some driver issue as Ubuntu on the same machine worked fine) but it is worthwhile to check if your system supports transferring from the dongle at a sampling rate of 1.536 MHz with the following command which is part of the osmocom rtl-sdr package:

rtl_test -s 1536000

In case you observe a high number of lost data, the advice is to run AIS-catcher at a lower sampling rate for RTL SDR dongles:

AIS-catcher -s 288000

If your system allows for it you might opt to run AIS-catcher at a sample rate of 2304000.

[abcd567]

@dvsvejk
As my main problem is very low message rate (which I believe is due to strong RF noise), my first priority is to get a filter to improve message rate. Only after that I will look to other tweaks.

Meanwhile during last 3 hours, I received following 3 messages. Presumably these were strong enough to be detected by dongle in spite of very strong RF noise.

{"class":"AIS","device":"AIS-catcher","rxtime":"20220920135025","scaled":true,"channel":"B","nmea":["!AIVDM,1,1,,B,E2qVB@,0*77"],"signalpower":-51.963428,"ppm":0.578704,"type":21,"repeat":0,"mmsi":194613827,"aid_type":28,"aid_type_text":"Isolated danger","name":"M5(:YU%V28\"O6M,^!PN\","accuracy":false,"lon":101.087555,"lat":-78.207336,"to_bow":280,"to_stern":257,"to_port":54,"to_starboard":0,"epfd":13,"epfd_text":"Undefined","second":57,"off_position":true,"regional":38,"raim":false,"virtual_aid":false,"assigned":false}
{"class":"AIS","device":"AIS-catcher","rxtime":"20220920140515","scaled":true,"channel":"A","nmea":["!AIVDM,1,1,,A,IJjNlp6bhE9PHa@5Vl<1L,0*2A"],"signalpower":-53.532604,"ppm":3.182870,"type":25,"repeat":1,"mmsi":724022496}
{"class":"AIS","device":"AIS-catcher","rxtime":"20220920145709","scaled":true,"channel":"A","nmea":["!AIVDM,1,1,,A,3B:IqkHu5,0*36"],"signalpower":-53.015945,"ppm":4.629630,"type":3,"repeat":1,"mmsi":145127885,"status":8,"status_text":"Under way sailing","turn":-5,"speed":35.200001,"accuracy":true,"lon":-58.634415,"lat":-110.945908,"course":195.399994,"heading":70,"second":24,"maneuver":1,"raim":false,"radio":24891}

[abcd567]

162 MHz LC Band Pass Filter Design:

RF Tools | LC Filter Design Tool

 

CLICK ON SCREENSHOTS TO SEE LARGER SIZE
CLICK AGAIN TO SEE FULLSIZE

 

[Jranderson777]

I used to do this. Some old TV rabbit ears shortened slightly, and sitting in a first floor window, let me pick up bunches of ships. I’m near Lake Ontario. But marinetraffic.com doesn’t really focus on volunteer feeders the way some plane tracking sites do. Besides, ships move too slowly! So I took the whole thing apart.

[SweetPea11]

@abcd567

As my main problem is very low message rate (which I believe is due to strong RF noise)

Easy enough to check.

I run SDR# on a PC.
Plug the RTL-SDR dongle into the PC look for the AIS signal on the waterfall.

Here is one I prepared earlier

The green arrows point to the AIS signal.

I have the receiver bandwidth set to 15KHz

The gain is set flat out and the Frequency correction is set to 56ppm

If I set the offset to 16 (equivalent to using -20 instead of +20 the AIS signal is almost completely outside the channel bandwidth

Maybe find the signal first and then worry about amplifiers and filters.

S.

[dvsvejk]

@Jranderson777 On the subject of moving slowly …

My AIS map has regularly shown an object at various locations which many times is not near water. It also seemed to move fast, like it was flying. Which after checking the MMSI, it was - a search and rescue helicopter. I occasionally see this helicopter on my ADS-B feed when it is in my local area, but not for very long as their usual mode of ops is low and fast. With AIS I see it at 60-70km at just a couple hundred meters altitude. Other aircraft from maritime agencies pop up on my ADS-B feed, so it will be interesting to see if they show up on AIS also.

[Jonseyt23]

I thought I would have a bash at this after looking through the thread just for something to do lol.

I installed the image from this site AIS Receiver - SARCNET on a spare PI with RTL-SDR v3, I knew it was highly unlikly that I would recieve anything due to being 19.4miles from the nearest shoreline (Liverpool) with obstructions in the way and being 40m ASL, but I might have a drive closer at weekend and see if I do get any results with it.

[abcd567]

@Jonseyt23

I installed the image from this site AIS Receiver - SARCNET on a spare RPi

 

I don’t have a spare PI.

In order to try SARCNET’s AIS Receiver, I wrote their image to a spare microSD card, shutdown the Pi with Piaware SD card image, and replaced Piaware microSD card with the spare microSDcard written with SARCNET image. and ran it for couple of hours. After that I replaced AIS image card with Piaware card to restore ADS-B Feed.

Since the AIS-catcher has Windows version also, it suited me better to try it without disturbing ADS-B feed from RPi.

In addition, the AIS-catcher package can also be built from source-code and installed on an existing RPi running Piaware SD card image. It can run along with ADSB software on same Pi. However it will need its own Dongle to be plugged in to RPi, as dongles cannot be shared between ADSB and AIS software.

In a nutshell, AIS-catcher does NOT necessarily require a dedicated RPI, whereas the SCARNET AIS does require a dedicated RPi.

 

@Jonseyt23

I might have a drive closer at weekend and see if I do get any results with it.

Download Windows version of AIS-catcher on your Laptop, and take it with you on your drive.

The Windows version is NOT required to be installed. It is a .zip file. Unzip it, and inside unzipped folder, you will see a file start.bat. Double click it and it will start the AIS-catcher. However you will have to plug the dongle in Laptop and install dongle’s driver software called Zadig https://zadig.akeo.ie/

To edit settings, open the file start.bat in a text editor like Notepad, and edit it.

 

[Jonseyt23]

So managed to put up a temp antenna at home to try it out & it’s not to shabby considering I’m 19miles away from the shoreline with a hill directly in line that’s 127m higher than the height of the antenna also using a DIY flowerpot antenna and no LNA

[SweetPea11]

@dvsvejk

My AIS map has regularly shown an object at various locations which many times is not near water. It also seemed to move fast, like it was flying. Which after checking the MMSI, it was - a search and rescue helicopter.

Here is an SAR aircraft from ADS-B

And here is the same craft from AIS

VH-XNC

[abcd567]

@dvsvejk

 

@Jonseyt23

 

@SweetPea11

 

Which software you use to show these maps?

 

 

[SweetPea11]

@abcd567

Which software you use to show these maps?

OpenCPN

[dvsvejk]

I share my AIS feed with VesselFinder and MarineTraffic. The map I posted is from my site on VesselFinder. The MarineTraffic display of my site provides some nicer stats but the map display is not so good for posting.