Display of AIS AtoN on Lowrance HDS-8

Electrical and electronic topics for small boats
jimh
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Display of AIS AtoN on Lowrance HDS-8

Postby jimh » Sat Dec 05, 2015 6:48 am

This series of article describes results of a test using the Lowrance HDS-8 first-generation chart plotter to show AIS Aid-to-Navigation Synthetic marks received from USCG AIS stations in the Great Lakes. The results of the test are very positive and encouraging, considering the age of the chart plotter and the long time since a firmware update for it was provided by the manufacturer.

The United States Coast Guard (USCG) has begun to use the Automatic Identification System to send electronic Aids to Navigation (AIS AtoN) to supplement the physical buoys in the Great Lakes. Just recently, the USCG began transmitting AIS messages sending Message 21 for AIS AtoN navigation aids. I was curious if I could receive these AIS signals on my em-trak R100 AIS receiver, connect the NMEA-0183 data output of the AIS receiver to my Lowrance HDS-8 chart plotter, and observe how these electronic buoys were represented on the electronic chart display of the HDS-8.

Receiving the AIS AtoN signals in my region was not a problem. They are being sent from an N-AIS base station co-located at RESCUE 21 site RFF WAYNE, about 18-miles away from me, originating from a very tall (about 300-feet high) tower. The AIS signals were easily received at my location on an indoor antenna.

My HDS-8 chart plotter is a first-generation device. There has not been any firmware update for it from Lowrance since Februay 2012, almost four years ago. I was skeptical the HDS-8 would have the capability to show AIS AtoN icons because, at the time of the last firmware update, there were practically no such devices in use in the USA. I was very pleasantly surprised to find that my first-generation Lowrance HDS-8 was quite capable of displaying AIS AtoN targets. I demonstrate its capabilities with several screen captures.

shot 11.png
shot 11.png (42.9 KiB) Viewed 8858 times
HDS-8 presentation of AIS AtoN targets.

In the above screen capture, 15 AIS AtoN aids to navigation are shown. Not shown are about five more AIS AtoN marks in the lower Detroit River and Lake Erie. The targets in Lake Huron are over 50-miles from my receiver, but the actual signals for them are originating from the much closer tower at RFF WAYNE.

Having crossed the hurdle of receiving the AIS AtoN signals and seeing them on the chart plotter, the iconic representation of the aid to navigation was the next area of interest. As shown above, the aids are represented by a black rhombus with an internal black crosshair mark. Guidance for how AIS AtoN targets ought to be shown on electronic chart plotters is given by IEC Recommendation 68822. The basic AIS AtoN symbol is a diamond or rhombus shape with a black crosshair in the center, drawn with thin solid black lines. The applicable text from the recommendation says:
Real or synthetic AIS aids to navigation
(AtoN) shall be presented as a diamond with
crossed lines centred at the reported position
of the AtoN. The crossed lines shall be not
more than 2 mm in length and the sides of
the diamond shall be not more than 6 mm in
length.

The diamond and crossed lines shall be
drawn using a thin solid line style.

The symbol representations for a real or synthetic AIS AtoN should look like this:
IEC6288Page76AIS_Real_SyntheticAtoN_Symbols.jpg
IEC6288Page76AIS_Real_SyntheticAtoN_Symbols.jpg (18.48 KiB) Viewed 8741 times
Recommended symbols for Real or Synthetic AIS AtoN

Before we can assess the Lowrance HDS-8 display and its compliance with recommendations, we must first identify the type of AIS AtoN that is being received.

[Article continues below]

jimh
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Re: Display of AIS AtoN on Lowrance HDS-8

Postby jimh » Sat Dec 05, 2015 7:14 am

There are three categories of AIS Aids to Navigation: real, synthetic, and virtual. Again, the USCG announcement explains the difference:

These broadcasts can originate from an AIS station located on an existing physical aid to navigation (Real AIS AtoN) or from another location (i.e., AIS Base Station). An AIS Base Station signal broadcasted to coincide with an existing physical aid to navigation is known as a Synthetic AIS AtoN. An electronically charted, but non-existent as a physical aid to navigation, is identified as a Virtual AIS AtoN.


Based on the above criteria, it would seem that the signals being sent from the AIS AtoN received in my test are likely to be Synthetic AIS AtoN signals, that is, the signals are sent from a Base Station and are meant to coincide with the location of an actual physical aid to navigation. On that basis we can assess the Lowrance representation of the Synthetic AIS AtoN signals.

UPDATED: It appears that in the Lowrance HDS-8 first generation, a Synthetic AIS AtoN is being represented by the most basic icon, just as recommend by the IEC-62288 document (see above).

shot 14.png
shot 14.png (38.72 KiB) Viewed 8857 times
The AIS AtoN for a Synthetic Aid, as rendered on the Lowrance HDS-8 first generation chart plotter with the INSIGHT USA optional charts loaded.

In the HDS-8 chart display, AIS AtoN icons are overlaid on other chart details, so they typically land right atop the charted aid to navigation, as seen above. If the cursor of the chart plotter is moved over the AIS target, an identifying banner will appear.

shot 16.png
shot 16.png (42.32 KiB) Viewed 8857 times
Banner text appears giving the identity of the AIS AtoN target if the cursor is moved to the target

The above screen capture shows the BELLE ISLE NORTH LIGHTED BUOY 113 identified in abbreviated text. If the ENTER button on the HDS is depressed when the cursor is on the target, a details page appears, giving more information on the target.

shot 18.png
shot 18.png (66.17 KiB) Viewed 8857 times
AIS Aid To Navigation (ATON) Details screen

The details screen gives the MMSI of the AIS AtoN and its position, and several other parameters sent in the AIS transmission; see below for the complete list of data that is shown. Note that a range and bearing are not shown; at the moment I took this screen capture my chart plotter had not acquired its own position, so it could not compute a range and bearing to this target.

Overall I am quite pleased with the performance of my first-generation HDS-8 chart plotter and its handling of AIS AtoN signals. I really did not have great expectations for its ability to show AIS AtoN targets due to the age of its firmware. The deployment of AIS AtoN signals in the Great Lakes and elsewhere by the USCG is still in a testing phase, I believe, and I am, again, very pleasantly surprised that the four-year-old firmware in the first-generation HDS-8 is even attempting to show these targets.

jimh
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Re: Display of AIS AtoN on Lowrance HDS-8

Postby jimh » Sat Dec 05, 2015 10:25 am

ASIDE: ON CONNECTING THE AIS RECEIVER AND CHART PLOTTER:

I was able to connect the NMEA-0183 output of my em-trak R100 receiver to the NMEA-0183 input of my Lowrance HDS-8 chart plotter with very little fuss because previously I had wired both interfaces with my UNIVERSAL NMEA-0183 INTERFACE connector and signal layout. To get the two devices talking was just a simple matter of plugging their universally wired connectors into the appropriate ports of my NMEA-0183 universal backplane connector. The total amount of time spent in making these two device communicate was literally about 30 seconds--the time it took to plug the two connectors onto the universal backplane interconnecting device.

You can read more about my NMEA-0183 UNIVERSAL CONNECTION system in the REFERENCE section:

http://continuouswave.com/whaler/reference/UniversalNMEA0183.html

porthole
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Re: Display of AIS AtoN on Lowrance HDS-8

Postby porthole » Sat Dec 05, 2015 12:24 pm

If I see it correctly, the AIS AtoNs are represented on your plotter as either Real or Synthetic. How did you determine the transmission is coming from the Rescue 21 tower and not the actual aid?

I do not know how my radio is receiving the AIS transmissions, only that it is. I thought there must be some type of relay with the Rescue 21 system, as we have four towers in New Jersey, one only a few miles from me and one is in between me and the Ambrose Channel AtoNs.

My Standard Horizon GX-2200 is only using a GAM ELECTRONICS SS-2 VHF antenna. Even if the antenna is laid down, I still receive AIS info on the radio and plotter, including the 24-mile-away Ambrose AtoNs.
Thanks,
Duane

porthole
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Re: Display of AIS AtoN on Lowrance HDS-8

Postby porthole » Sat Dec 05, 2015 12:26 pm

Did you try and bring up the actual AtoN info page, meaning not the AIS page?

I had to click outside the AtoN icon, clicking on the number to get the info page.
Thanks,
Duane

jimh
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Re: Display of AIS AtoN on Lowrance HDS-8

Postby jimh » Sat Dec 05, 2015 1:20 pm

How did you determine the transmission is coming from the Rescue 21 tower and not the actual aid?


The signal I am receiving--and most likely the ones you are, too--cannot be coming from the actual aids because of the impossibility of receiving them at the distance my receiver is located from them, the height of my antenna, the height of the transmitting antenna, the power of the transmitter, and the accompanying path loss. AIS AtoN signals coming from a floating aid [or the short tower of a fixed aid] would have to be powered by a battery that is recharged by a photo-voltaic panel. I doubt the electrical power budget for such as system could afford to send a 25-watt signal. Most real AIS AtoN signals will probably be more like 2-Watt signals. The antenna height would be low, from only be a few feet above the water for a floating aid to perhaps 25-feet for a fixed aid with a tower. The radio horizon for such a signal would only be a few miles. The AIS AtoN signals from Lake Huron are over 56-miles away.

Having monitored for AIS signals from my location before, I know I cannot even receive a CLASS-A AIS transmission from a commercial ship with an antenna mast that is probably 50-feet above the water using my indoor antenna. The path to these signals from my location is across urban terrain with many tall buildings. The signals are all synthetic AIS signals and are being sent from RFF WAYNE as part of the N-AIS program.

jimh
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Re: Display of AIS AtoN on Lowrance HDS-8

Postby jimh » Sat Dec 05, 2015 2:03 pm

Did you try and bring up the actual AtoN info page, meaning not the AIS page?


[I deleted a sidebar discussion with some back and forth until I figured out what PORTHOLE was really asking. He also explained a bit about how his newer Lowrance chart handled AIS AtoN display. See his separate thread about the newer Lowrance Gen3 chart plotter for his screen captures and a good explanation of how to get to the physical aid information page instead of the AIS Details page on that newer plotter.]

OK--now I see your question more clearly: you are asking about the actual physical aid to navigation information, not the AIS AtoN. Sorry, but I misread your question the first five times I read it.

Because the AIS symbol is overlaid on the chart symbol, it is hard to get to the information about the physical aid by positioning the cursor to be on the chart symbol instead of the AIS overlaid symbol. I had to zoom in to a very large scale display in order to get a bit of separation between the icons for the chart's aid and the AIS overlaid aid. Then I could reach the information page by putting the cursor on the charted aid and hitting ENTER.

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Re: Display of AIS AtoN on Lowrance HDS-8

Postby jimh » Sat Dec 05, 2015 2:09 pm

Ahah! I found the trick to get to the information page for a navigation buoy that has an AIS AtoN symbol overlaid. To get to either the AIS AtoN Detail page or the regular chart physical buoy information page on the HDS-8 first generation, you have to:

--put the cursor over the icon for the aid to navigation

--push the MENU key

--a contextual menu pops up; in the menu are two choices: AIS DETAILS or INFO.

Use the cursor keys to highlight AIS DETAILS:

contextualMenuAISdetail.png
contextualMenuAISdetail.png (7.11 KiB) Viewed 8725 times


If you then push ENTER, you will get the AIS DETAILS screen:

Image

While on the contextual menu, you can alternatively highlight the INFO choice:

contextualMenuINFO.png
contextualMenuINFO.png (6.99 KiB) Viewed 8725 times


If you then push ENTER you will get the Chart information screen:

ChartInfo.png
ChartInfo.png (17.79 KiB) Viewed 8725 times

On the INFO page you will see the physical characteristics of the aid to navigation (like color, name, light characteristics, and so on). Note the on-screen soft-key button DETAIL; pushing it will also take you to the AIS DETAILS. They forgot to include the corresponding button on the AIS DETAILS page to get to the INFO page.

jimh
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Re: Display of AIS AtoN on Lowrance HDS-8

Postby jimh » Sat Dec 05, 2015 9:11 pm

The AIS INFORMATION page for an AIS AtoN on a Lowrance HDS first-generation chart plotter shows the following eight data values being sent in the AIS Message 21 broadcast:

--MMSI of the AIS AtoN
--nature and type of aid (from 32 categories, see below)
--name of the aid to navigation
--position accuracy
--position latitude
--position longitude
--off-position indicator
--status

The categories for nature and type of aid are given in ITU-R M.1371-5 Section 3.19 in Table 74, and are reproduced below:

0 = Default, Type of AtoN not specified
1 = Reference point
2 = RACON
3 = Fixed structures off-shore, such as oil platforms, wind farms. (Should identify an obstruction that is fitted with an AtoN AIS station)
4 = Spare, Reserved for future use

FIXED AtoN

5 = Light, without sectors
6 = Light, with sectors
7= Leading Light Front
8 = Leading Light Rear
9= Beacon, Cardinal N
10 = Beacon, Cardinal E
11 = Beacon, Cardinal S
12 = Beacon, Cardinal W
13 = Beacon, Port hand
14 = Beacon, Starboard hand
15 = Beacon, Preferred Channel port hand
16 = Beacon, Preferred Channel starboard hand
17 = Beacon, Isolated danger
18 = Beacon, Safe water
19 = Beacon, Special mark

FLOATING AtoN

20 = Cardinal Mark N
21 = Cardinal Mark E
22 = Cardinal Mark S
23 = Cardinal Mark W
24 = Port hand Mark
25 = Starboard hand Mark
26 = Preferred Channel Port hand
27 = Preferred Channel Starboard hand
28 = Isolated danger
29 = Safe Water
30 = Special Mark
31 = Light Vessel/LANBY/Rigs

The data field "status" does not seem to be specifically defined in any reference material I can find. It is shown as "Safe" in most instances I have encountered, but I don't know what the other options might be.

There is a bit more information being sent (in the AIS Message #21), but the Lowrance HDS is showing most of it. The information page also computes:

--the distance to the aid
--the bearing to the aid
--the point of closest approach
--the time of closest approach

These data are not sent from the AIS AtoN but are calculated by the chart plotter.

jimh
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Re: Display of AIS AtoN on Lowrance HDS-8

Postby jimh » Mon Dec 07, 2015 8:22 am

For those curious about more technical details regarding AIS AtoN signals, you can obtain on-line and at no cost the actual International Telecommunication Union (ITU) recommended practices document R-REC-M.1371, Technical characteristics for an automatic identification system using time division multiple access in the VHF maritime mobile frequency band.

See Section 3.19 Message 21: Aids-to-navigation report. There TABLE 73 lists all the data parameters being sent.

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Re: Display of AIS AtoN on Lowrance HDS-8

Postby jimh » Tue Dec 08, 2015 1:14 pm

In the case of AIS AtoN signal of the real and synthetic category, there is a physical aid on the water that corresponds to the electronic marker signal being sent. In the case of a virtual AIS AtoN, there is no equivalent physical aid on the water. Just recently I was explaining these three categories to another mariner--my lovely wife and boating partner Chris--and she made a very cogent observation. She said something like, "It would be very confusing to see an AIS AtoN symbol on the chart plotter, and when you approached that location not see any buoy on the water."

Chris's remark was really very instructive for me. It made me realize the symbols used on a chart plotter to represent a virtual AIS AtoN ought to provide a clear distinction from the other two categories, real and synthetic, because for those two types of AIS AtoN there will be a physical buoy or structure at the location of the AIS signal.

The recommendations from IEC 62288 suggest a distinctive marking; the black diamond is to be drawn with dashed lines, not solid lines. Here is the applicable text from the recommendation:

Virtual AIS aids to navigation (AtoN) shall be
presented as a diamond with crossed lines
centred at the reported position of the AtoN...

The diamond shall be drawn using a thin
dashed line style. The crossed lines shall be
drawn using a thin solid line style.


The symbol representation should appear as shown below:

IEC6288Page77AIS_VirtualAtoN_Symbols.jpg
IEC6288Page77AIS_VirtualAtoN_Symbols.jpg (18.15 KiB) Viewed 8746 times
AIS AtoN Symbols for Virtual Aids

In my testing so far, I do not believe I have encountered a virtual AIS AtoN signal, so I don't know how it will be rendered on my Lowrance HDS first-generation chart plotter display.

jimh
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Re: Display of AIS AtoN on Lowrance HDS-8

Postby jimh » Fri Dec 11, 2015 12:00 pm

Just when you thought this thread could not get any better: I found an VIRTUAL AIS AtoN signal in my area! As it happens, I can also receive AIS signals for many, many AIS AtoN electronic navigation marks in Lake Erie recently added by the USCG to their testing. Some of them are virtual AIS AtoNs, that is, there is no longer a physical aid to navigation at the location, but just the electronic marker being send via radio. A listing in the Local Notice to Mariners (LNM) gave me the location of an in-range virtual AIS AtoN:

Maumee Bay Lighted Buoy “21” (LLNR 6155) Virtual AIS ATON


I was delighted to find that I could receive the AIS signal for this aid. This provides the opportunity to further test the chart plotter's representation. Because this is a virtual aid-to-navigation, its symbol should distinguish it from a real or synthetic aid-to-navigation. The screen captures below show how the first-generation Lowrance HDS-8 chart plotter rendered the data.

1MaumeeBayLB21ChartedView.png
1MaumeeBayLB21ChartedView.png (47.81 KiB) Viewed 8720 times
HDS-8 chart view of Maumee Bay Lighted Buoy 21 with AIS overlay

The AIS AtoN symbol appears to be the same basic symbol used for real or synthetic AIS AtoN electronic marks. According to recommendations, this symbol should be drawn with dashed lines for the diamond or rhombus.

2MaumeeBayLB21Zoom.png
2MaumeeBayLB21Zoom.png (16.86 KiB) Viewed 8720 times
As above, but with a larger scale chart presentation

There is no sign of any dashed lines in the drawing of the rhombus symbol. Moving the chart cursor over the symbol brings up an identification banner:

3MaumeeBayLB21Banner.png
3MaumeeBayLB21Banner.png (17.83 KiB) Viewed 8720 times
HDS-8 shows the identity of the navigation mark when the cursor is positioned on it

So far there is no sign that this aid-to-navigation is a virtual AIS AtoN.

The electronic chart continues to show a floating aid to navigation at that position. This is to be expected because when the chart was created, there was a floating aid at that position. The chart would have no way to modify its position based on a Notice to Mariners that the floating aid was being removed for the winter season by the Coast Guard, so the chart still shows a physical aid in that location.

[Continues in next posting]

jimh
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Re: Display of AIS AtoN on Lowrance HDS-8

Postby jimh » Fri Dec 11, 2015 12:10 pm

As already mentioned, when an AIS symbol overlays a chart object, you can get to the two separate information or detail pages, one for the AIS target and another for the chart object, by using the contextual menu for that presentation. (ASIDE: the term "contextual menu" refers to the concept that the contents of the menu will change depending on the context or situation in which the menu is called upon for display. In this case, when an AIS object is part of the chart area under the cursor, the menu adds an option for AIS detail. On the HDS-8 the contextual menu is invoked by hitting the MENU button.)

Selecting the AIS DETAIL option from the contextual menu gives this page of data:

4MaumeeBayLB21AISDetail.png
4MaumeeBayLB21AISDetail.png (20.14 KiB) Viewed 8720 times
AIS Detail Page for virtual AIS AtoN

There does not appear to be any indication in the AIS DETAIL page that this AIS AtoN is of the category virtual. The information presented is the same as was given for synthetic AIS AtoNs.

Selecting the INFO option from the contextual menu gives this page of data:

5MaumeeBayLB21ChartInfo.png
5MaumeeBayLB21ChartInfo.png (20.06 KiB) Viewed 8720 times
Chart Info Page for the charted object

So far as I can tell from this example, the first-generation Lowrance HDS chart plotter is not drawing the electronic chart symbol or presenting information details for a virtual AIS AtoN in any different manner from a real or synthetic AIS AtoN. While this is a slight disappointment, I still am impressed overall with the ability of the first-generation HDS to show these electronic navigation marks.

ASIDE: I have not captured and analyzed the AIS Message 21 data that is actually being sent to verify that the actual data contained in the radio signal does indicate a virtual aid category for this mark. I am assuming the USCG is transmitting it as a virtual AIS AtoN based on the notice to mariners.

jimh
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Re: Display of AIS AtoN on Lowrance HDS-8

Postby jimh » Sun Dec 13, 2015 12:38 pm

To complete my testing of how the Lowrance HDS first generation chart plotter renders AIS AtoN signals into chart presentation, I checked the presentation when using a different electronic chart. The results were interesting. Compare the prior screen captures with this one:

shot 38.png
shot 38.png (40.6 KiB) Viewed 8701 times
Lake Huron Cut Buoys 11 and 12, Navionics Chart with AIS AtoN symbols showing

The above screen capture shows two synthetic AIS AtoNs in Lake Huron as presented with a Navionics chart. The most remarkable difference involves the way the AIS AtoN diamond symbol is drawn for the electronic aid with respect to the chart's own symbol for the physical aid. In this presentation, the AIS AtoN symbol is drawn underneath or behind the chart symbol for the physical aid. This presentation is the opposite of that seen earlier. In those earlier screen captures, the chart in use was the Lowrance built-in chart. (My HDS-8 has the upgraded option for included USA charts called "INSIGHT USA" charts.) The electronic marker (black diamond) was drawn over the chart marker on those Lowrance charts. On this Navionics chart, the electronic marker (black diamond) is drawn behind the chart marker. This presentation does not obscure the original chart icon for the marker.

I assume the difference in presentation must be related to the structure of the electronic data in the charts in particular layers or tiers, and in the Navionics charts the AIS overlay layer must be underneath the chart buoy icon layer.

ASIDE: About a week ago, when I first began this testing process, I noticed that there was an error in the position of the AIS AtoN for Lake Huron Cut LB 12. The electronic position for this aid was being sent with the latitude off by about two miles. I called the local USCG facility (Group Detroit) on Saturday, December 5, 2015. I spoke to the officer on duty and explained the discrepancy I was seeing between the AIS AtoN position and the usual position for the aid. He said he would pass on this information to the appropriate command or sector for the AIS AtoN. The Coast Guard corrected the AIS AtoN position being transmitted by the time I checked it on the following Friday, December 11, when I made the screen capture (above) showing the buoy in its proper position. (The latitude of LB12 was being sent as 43-deg 03.466-min N; the corrected position is now being sent as 43-deg 05.466-min N. The error was probably a typo when entering data into the N-AIS base station transmitter configuration for the AIS AtoN.) In a conversation I recently had with a Coast Guard official involved in AtoN work, he said they got a lot of reports about the AIS AtoN being in the wrong position.

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Re: Display of AIS AtoN on Lowrance HDS-8

Postby jimh » Mon Dec 14, 2015 2:07 pm

In reviewing the screen captures I show above, there may be another error related to the AIS AtoN. Almost all the AIS AtoN types are shown as "Fixed (13)" or "Fixed (14)." The particular AIS AtoNs I have shown (above) are related to the position of floating buoys. My initial reaction is that the AIS AtoN type ought to reflect a floating aid, so the type designation perhaps should reflect that, and thus be listed as "Floating (24)" or "Floating (25)".

On the other hand, perhaps the type description of the AIS AtoN refers to where the signal originates. Since none of these AIS signals are from Real AtoNs, where the signal would originate from a floating location, but rather are all for Synthetic or Virtual AtoNs, where the signal originates from a fixed location, the AIS Base Station making the actual transmission of the signals, the description of them as "fixed" may be more appropriate. I have asked the local District 9 Coast Guard specialist in Aids to Navigation to comment about the type designators being used.


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