View Full Version : On the PPI scope, what do the three different lines represent?
On the PPI scope, what do the three different lines represent? It looks like the top one is for range and the last two are for bearing. Is this right?
On the PPI scope, what do the three different lines represent? It looks like the top one is for range and the last two are for bearing. Is this right?
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Sgian Dubh
04-09-07, 12:13 PM
I think there is confusion here, perhaps on my part. The PPI in "PPI scope" stands for "Plan Position Indicator". The PPI scope is associated with the (I thought) surface-search RADAR.
The three lines on the screen (that I have seen) were on the air-search RADAR. Or am I mixing too much SH1 with SH4?
The Air-search RADAR should only show strength and range, not vector.
The three lines are differenct range settings for the air-search radar (at least that is what I thought). Some one please correct me if I have this wrong....
I don't know about SHIV, since I've not yet in a boat with PPI scope, however at least in SHI the PPI scope was simply presenting a 360° radar sweep with your sub in the center. You could put the radar beam on scan or "fix" it on a given direction.
akdavis
04-09-07, 03:28 PM
1. Only surface search radar has a display. If you are equipped only with SD air search radar, neither radar display will be functioning. (However, I believe some surface search radar in the game incorrectly returns air contacts.)
2. The buttons on the toolbar to jump to a display are reversed. The "clock face" display is PPI, while the "heart monitor" display is A-scope. The PPI display (think classic movie radar) was developed later in the war and appears to be available too early in game. For the majority of the war, radar used an A-scope type display.
The A-scope represents a slice of radar energy directed down the axis of the radars current facing (rotate radar manually with the HOME and END keys). The three lines represent different range scales (from the top: short, medium, long beginning) and the numbers on the lines are the range in hundreds of yards (or maybe meters considering the state of the game).
You can change the active range display by toggling one of the switches beneath the display. You determine bearing by rotating the radar until you see a contact. (But here the game is lame and you are not given any indication of bearing on the display.) Contacts are represented by "spikes" in the horizontal flat lines. The height of the spike is an indication of the size of the contact (or at least I think it is). Where this spike occurs along the active line is an indication of range.
I don't know about the SJ giving air contacts, but my 1941 SD is giving me directional surface contacts. I kinda like this bug though. It just helped me find a 2-destroyer TF patrolling in a straight line, when I spent something like 4 torpedoes and 5 shells to destroy just 1.
(However, I believe some surface search radar in the game incorrectly returns air contacts.)
It is vise-versa: The surface to air radar (SD) returns also surface contacts. Not with exact range, but with exact bearing and "short/medium/long" range information. That's quite a biggy, since it took the subs a while to get surface search radar, while SD was available from early on and is so in the game. Also, SD was only capable of providing range to air contacts, not bearing.
Werewolf13
04-09-07, 04:53 PM
The buttons that choose the SD and SJ radars are backwards in SH4. In other words if you select the PPI icon you'll get the A Scope display and vice versa.
The PPI is the Planned Position Indicator and is the scope with the rotating sweep. The blips position on the scope relative to the center shows range and bearing.
The air search or A Scope is the radar with the lines. The lines indicate range and depending on the type of A scope bearing. A scopes are usually tied to emmiters that point in just one direction. On a WWII sub the air search radar did not rotate the sub had to turn to search with it.
The PPI is self explanatory.
Using the A Scope is not self evident and never having used that type of display while I was in the Navy can't comment on it with any authority.
flyingdane
04-09-07, 04:59 PM
Yes the buttons are backwards a simple fix i'll bet. ;)
Dunno if these were responses to my last posting, but if they were, that's not the heart of the problem: Even if the SD is the only radar installation on board, it will still give out surface contacts (by crew reports).
akdavis
04-09-07, 07:11 PM
(However, I believe some surface search radar in the game incorrectly returns air contacts.)
It is vise-versa: The surface to air radar (SD) returns also surface contacts. Not with exact range, but with exact bearing and "short/medium/long" range information. That's quite a biggy, since it took the subs a while to get surface search radar, while SD was available from early on and is so in the game. Also, SD was only capable of providing range to air contacts, not bearing.
That is separate issue unrelated to the displays. However, the SJ radar does display air contacts on both the A-scope and PPI display. This can be seen easily in the Artillery training mission. Possibly SD radar information is being incorrectly fed to the SJ radar displays. I suppose someone could do a mission edit to set up a sub with SJ radar but without SD radar and test this.
However, my theory is that they are actually the same issue. I'm thinking there is no substantial difference between SD, SJ and SJ-1 radar other than access to the displays, i.e. installing SJ radar simply makes the displays and commands active. This would explain both why SD radar returns range and bearing information and surface contacts, and why when you turn off SJ radar, your displays go blank, but your crew continues to feed you surface contact information.
Now here is how things should be in summary:
-SD radar: range and relative motion only. Range greatly shortened. No surface contacts (save possibly very close). Able to be detected by enemy with RI gear as all radar should. Able to be turned on/off. (should this have an A-scope type display? don't know)
-Improved SD: unknown? Is this supposed to be SV radar? If so, it should not be available until 1945.
-SJ radar: A-scope display only.
-SJ-1 radar: A-scope and PPI displays.
-oh, and radar should function regardless of your sub's compass heading. ;)
Some things missing needed for full implementation of radar:
-bearing indication at radar station (sonar has that little notepad, but why not radar).
-ability to send surface contact bearing and range to TDC and orders for crew to do so.
-same orders as available as sonar (report contact/track contact).
-ability to scan only a sector with surface-search radar and receive more precise and timely information (i.e. scan only forward quarter, etc.)
-land should return a signal, should make finding targets near shoreline very difficult. land should be visible in plan form on PPI display, providing aid to navigation.
-ST radar: antenna in periscope. Used to capture precise range to target to be fed to TDC, just as with the stadimeter.
-SV air-search radar (or at least proper time for this if same as improved SD)
Thanks for the explanations. Has the bug about the reversed radar buttons been reported in the bug thread?
EDIT: the issue with the reversed radar buttons is the text, not the icons themselves. Go into your menu.txt file and paste in the following text:
5681=GO TO A-SCOPE RADAR|Takes you immediately to the A-scope radar. The A-scope radar is only effective when the submarine is surfaced.
5682=GO TO PPI RADAR|Takes you immediately to the radar station room. The PPI radar is only effective when the submarine is surfaced.
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