Parallel Indices -- Still Relevant?

[requiem]

Originally Posted by Uricanejack

Today my typical small boat Radar has an Electronic curser. It has options of ither a full screen or half screen of parallel lines which match up to the range rings.

I can initially set it parallel to my heading. As in your first heads up picture Diagram.

I think I understand, but it sounds like your radar has actual PI functionality. When you rotate the cursor, all of those lines are rotating around your vessel in the center, correct?

Whereas when adjusting an offset EBL, it would rotate around the point where you placed it? (E.g. so you could find the bearing from a radar target to a third mark.)

[Uricanejack]

Originally Posted by requiem

I think I understand, but it sounds like your radar has actual PI functionality. When you rotate the cursor, all of those lines are rotating around your vessel in the center, correct?

Whereas when adjusting an offset EBL, it would rotate around the point where you placed it? (E.g. so you could find the bearing from a radar target to a third mark.)

Yes. The curser rotates around the center where my vessel is. ( my particular radar is of centred, the curser rotates around the point where the vessel is cantered)
I believe most radars have this functionality.

Adjusting the EBL of ste to achieve the same is possible. You have to be careful to make sure you. Adjust both the bearing and the point of origin of the EBL to be a tangent to the desired range.

It easier with a curser.

fancier radars also have dedicated parallel index lines which work the same way as the curser rotating around the center with adjustable range.

Doing this with a dedicated PI line works.

[Steve Whelan]

As a newbie, I eagerly await the email newsletter with the various topic questions in the forum in order to learn as much as I can. However, I have no clue what your heading means so I followed the link to learn more... Still no clue after reading the post. Any chance you could actually spell out what the abbreviations mean? It will help us greenhorns "A LOT". Cheers

[Uricanejack]

Heading Line is a line on the radar screen directly parallel to or in line with the boats bow and Representing the direction the boat is going or “heading”

Derived I think from “ships Head” or “Heading” which is the compas course being steered.

Requiems diagrams show the heading line with the arrow on it.

Some of the others.

Heads Up. Boats heading line is fixed in center of screen straight up. As the boat turns the heading stays the same and the land appears to move.

North Up. The heading line is lined up to the boats course and the radar picture is aligned with North at the top of the screen. With this display the boats heading moves around the screen as the boat turns while the land stays in the same place like looking down on a chart or map.

GPS global position system.

VRM variable range marker. An adjustable ring to measure range.

EBL Electronic Bearing Line and adjustable line to measure bearings or azimuth.

Stabilized radar picture is steady and heading line moves as vessel turns. Usually stabilized on big ships to a gyro compas on small vessels can be stabilized to GPS.
PI parrlell index

Unstabalised the radar picture is based entirely on the heading and the land moves when boat moves.

Gain, Tune Clutter are basic radar control functions to get the best picture.

If there are any other jargon or abbreviations you are wondering about just ask

[Rising Tide]

This thread and original idea are very helpful. However, it would be much more helpful if acronyms were detailed. Newer sailors and those learning do not know many of the these acronyms. Maybe if posting we detail the proper term followed by the acronym and then continue with the short cut.
Examples include EBL, HU, XTE. I figured only from the title that PI is Parallel Indices. Readers can probably figure some of these after a while, but it is very helpful to follow convention and name these items.

Thanks!

Originally Posted by Dockhead

It may be little known that it is possible to use PI's without doing any actual chart work, on modern MFD's --


Just use the horribly misnamed "set offset EBL" tool. Once offset, of course, it is no longer an EBL . But it can be used to set a perfectly usable PI.


If you use the radar in HU, as I do, then this "offset EBL" is automatically created parallel to your heading.



PI's are incredibly useful -- they show graphically and at a glance, whether you are being set towards some obstacle and whether you are correctly following your track.


They show graphically, the relative motion of everything your radar sees, in relation to your HEADING (and if you use Course Up orientation, then in relation to your course).



Do we need this anymore? After all, we can set a waypoint and have a track line represented on the screen, so that we immediately see if we are drifting off the track. We can even read out XTE in real time from our instruments.


Being oriented to a safe track line is OK for most purposes, I guess, but I find that when sailing hard on the wind, for example, a PI is incredibly useful to show the limit. I often use them to determine where to tack, for example.

[Rising Tide]

TY UJ

Originally Posted by Uricanejack

Heading Line is a line on the radar screen directly parallel to or in line with the boats bow and Representing the direction the boat is going or “heading”

Derived I think from “ships Head” or “Heading” which is the compas course being steered.

Requiems diagrams show the heading line with the arrow on it.

Some of the others.

Heads Up. Boats heading line is fixed in center of screen straight up. As the boat turns the heading stays the same and the land appears to move.

North Up. The heading line is lined up to the boats course and the radar picture is aligned with North at the top of the screen. With this display the boats heading moves around the screen as the boat turns while the land stays in the same place like looking down on a chart or map.

GPS global position system.

VRM variable range marker. An adjustable ring to measure range.

EBL Electronic Bearing Line and adjustable line to measure bearings or azimuth.

Stabilized radar picture is steady and heading line moves as vessel turns. Usually stabilized on big ships to a gyro compas on small vessels can be stabilized to GPS.
PI parrlell index

Unstabalised the radar picture is based entirely on the heading and the land moves when boat moves.

Gain, Tune Clutter are basic radar control functions to get the best picture.

If there are any other jargon or abbreviations you are wondering about just ask

[IslandHopper]

Originally Posted by jsestes1

This thread and original idea are very helpful. However, it would be much more helpful if acronyms were detailed. Newer sailors and those learning do not know many of the these acronyms. Maybe if posting we detail the proper term followed by the acronym and then continue with the short cut.
Examples include EBL, HU, XTE. I figured only from the title that PI is Parallel Indices. Readers can probably figure some of these after a while, but it is very helpful to follow convention and name these items.

Thanks!

PI stands for Parallel Index or Indexing, you won't find a reputable Radar manufacturer that will use the term Indices, same for maritime collages, you will be taught Parallel Indexing not Parallel Indicing lol..............

[Lodesman]

Originally Posted by IslandHopper

PI stands for Parallel Index or Indexing, you won't find a reputable Radar manufacturer that will use the term Indices, same for maritime collages, you will be taught Parallel Indexing not Parallel Indicing lol..............

Indices is the plural of index - used when referring to more than one PI.

[IslandHopper]

Originally Posted by Lodesman

Indices is the plural of index - used when referring to more than one PI.

I know, but again, PI in this instance always refers to Parallel Index or Indexing not Indices.....

[Lodesman]

Originally Posted by IslandHopper

I know, but again, PI in this instance always refers to Parallel Index or Indexing not Indices.....

Again, in the singular. But if referring to more than one, 'parallel indices' is correct.

[Pelagic]

Originally Posted by Lodesman

Again, in the singular. But if referring to more than one, 'parallel indices' is correct.

Maybe he would accept that in a parallel universe![emoji57]

[IslandHopper]

Originally Posted by Lodesman

Again, in the singular. But if referring to more than one, 'parallel indices' is correct.

Again....No it's not in the instance i was replying to.....................

My post was in reply to jsestes1 query on what the acronyms meant....

Maybe if posting we detail the proper term followed by the acronym and then continue with the short cut.
Examples include EBL, HU, XTE. I figured only from the title that PI is Parallel Indices.

.........the exercise or technique is called Parallel Indexing, NOT Parallel Indices!

'They are called apple trees or orange trees, not apples trees or oranges trees'

[Lodesman]

Originally Posted by IslandHopper

Again....No it's not in the instance i was replying to.....................

My post was in reply to jsestes1 query on what the acronyms meant....



.........the exercise or technique is called Parallel Indexing, NOT Parallel Indices!

'They are called apple trees or orange trees, not apples trees or oranges trees'

Yes, you would say 'apple trees' when talking about a defined number of trees, greater than one; you would not call them 'apple tree' or 'apple aboriculture.'

You said radar manufacturers and maritime colleges (actually you wrote 'collages', but we can infer your meaning) don't use the term 'indices', but that is incorrect. It would have been correct to say the proper way to abbreviate 'parallel indices' is 'PIs', as in:

"The standard requires 7 PIs on the plotting head", or
"This radar provides 2 dedicated PIs", or
"Where are your PIs, cadet?"

To be truly pedantic, PI is very specifically one parallel index; one would never abbreviate 'parallel indexing', as in "This technique is called PI" - that just sounds wrong.

[jmorrison146]

Originally Posted by Dockhead

I do find nav mode useful for some situations, but your last point is a really good one. I don't use it much when sailing. The sometimes sudden course changes, the pilot makes to get back on the course line, can really play hell with sail trim.

Always "restart" the nav track line before engaging the autopilot. This avoids the autopilot maneuvering to regain the track. On my Simrad, it's simply "Navigation" and "Restart".

[Dockhead]

Originally Posted by jmorrison146

Always "restart" the nav track line before engaging the autopilot. This avoids the autopilot maneuvering to regain the track. On my Simrad, it's simply "Navigation" and "Restart".

Well, it depends -- if you are following a track which is calculated to get you safely between obstacles, then definitely do NOT do this.


"Restart Navigation" will automatically redraw this line, and the plotter doesn't care whether it takes you over a reef. I do use this function to avoid this maneuvering, especially when under sail, but with caution!!