0844adbcbe
<message>Modify the first-boot.sh script to include an additional step for managing screen brightness during the provisioning process. Update user-data.bootstrap to improve DNS configuration by ensuring NetworkManager manages /etc/resolv.conf correctly, and remove obsolete scripts related to systemd-resolved. Enhance documentation to reflect these changes and clarify the setup process for users, improving overall network boot functionality and user experience.
164 lines
11 KiB
Markdown
164 lines
11 KiB
Markdown
# Screen Brightness — Maritime Regulations and References
|
||
|
||
This document summarises the international regulations and standards that apply to **display brightness and dimming** on ship bridges, and how the **screen-brightness** daemon on the reTerminal DM is aligned with them. It is intended for vessel operators, integrators, and auditors.
|
||
|
||
---
|
||
|
||
## 1. Overview
|
||
|
||
Bridge equipment that presents navigation-related or alarm information on a display is subject to:
|
||
|
||
- **IMO** (International Maritime Organization) resolutions, which set performance standards.
|
||
- **IEC** (International Electrotechnical Commission) and **IHO** (International Hydrographic Organization) standards, which give technical and test requirements.
|
||
|
||
The reTerminal DM screen-brightness daemon implements behaviour that satisfies the relevant clauses for:
|
||
|
||
- Adjustable brightness that is **never extinguished** (“not to extinction”).
|
||
- A **navigator-resettable** brightness/contrast preset (override).
|
||
- **High luminous intensity** for alarm/alert states.
|
||
- **Night mode** that does not degrade crew night vision.
|
||
- **Three operating modes** (NIGHT / DUSK / DAY) consistent with ECDIS-type display practice.
|
||
|
||
---
|
||
|
||
## 2. IMO MSC.191(79) — Navigational displays
|
||
|
||
**Full title:**
|
||
*Performance Standards for the Presentation of Navigation-Related Information on Shipborne Navigational Displays*
|
||
|
||
**Adoption:** 6 December 2004
|
||
|
||
**Applicability:** Displays that present navigation-related information on the bridge (including ECDIS and other navigational displays). Often referenced for equipment installed after 1 July 2008.
|
||
|
||
**Source (external):**
|
||
- [imorules.com – MSC.191(79)](https://www.imorules.com/MSCRES_191.79.html)
|
||
- IMO official: MSC.191(79) in the IMO Publications catalogue.
|
||
|
||
### 2.1 §8.1 Display adjustment
|
||
|
||
| Requirement | Text (summary) | Implementation in screen-brightness |
|
||
|-------------|-----------------|-------------------------------------|
|
||
| Adjustability | Contrast and brightness shall be adjustable as applicable to the display technology. | Brightness is controlled in steps 1–5 from ambient sensor and/or override. |
|
||
| Dimming | The display shall be capable of being **dimmed**. | NIGHT and DUSK modes set low backlight levels (1–2). |
|
||
| Legibility | The range of control shall allow the display to be **legible under all ambient light conditions**. | Lux thresholds map to levels 1–5 so the display remains usable from night to bright day. |
|
||
| **Not to extinction** | Implicit in “dimmed” and “legible under all conditions”: the display must not be turned off. | **Level 0 is never used.** Minimum level is 1 (“not to extinction”). |
|
||
|
||
### 2.2 §8.1.2 Preset / default
|
||
|
||
| Requirement | Text (summary) | Implementation in screen-brightness |
|
||
|-------------|-----------------|-------------------------------------|
|
||
| Reset to preset | The navigator shall be able to **reset** contrast and/or brightness to a **preset or default condition**. | Override file: `echo <1–5> \| sudo tee /run/screen-brightness/override` sets a fixed level; `echo auto` restores automatic (ambient + buzzer) behaviour. |
|
||
|
||
**Reference (section 8.1):**
|
||
- [imorules.com – 8.1 Display adjustment](https://www.imorules.com/GUID-6B14EB44-F913-4C8F-8E36-F74CE6E8E3DE.html)
|
||
|
||
### 2.3 Position of the brightness control
|
||
|
||
**MSC.191(79), MSC.302(87), IHO S-52, and IEC 62288 do not specify where the brightness (or contrast) control must be located on the screen or in the user interface.** They only require that:
|
||
|
||
- Brightness be adjustable and dimmable.
|
||
- The navigator be able to reset to a preset or default.
|
||
|
||
So the **position of the brightness control** (e.g. bottom-right overlay icon on the reTerminal DM) is an **implementation and design choice**, not a regulatory requirement. Placement can follow human-factors or vessel-specific guidelines (e.g. readily accessible, non-intrusive) as long as the above requirements are met.
|
||
|
||
---
|
||
|
||
## 3. IMO MSC.302(87) — Bridge alert management
|
||
|
||
**Full title:**
|
||
*Adoption of Performance Standards for Bridge Alert Management*
|
||
|
||
**Adoption:** 17 May 2010
|
||
|
||
**Applicability:** Bridge Alert Management (BAM) and presentation of alerts on the bridge. Recommended for central alert management (CAM) and CAM human-machine interface (CAM-HMI) installed on or after 1 July 2014.
|
||
|
||
**Source (external):**
|
||
- [imorules.com – MSC.302(87)](https://www.imorules.com/MSCRES_302.87.html)
|
||
- IMO official: MSC.302(87) PDF in IMO Knowledge Centre.
|
||
|
||
### 3.1 Visual alarms and night vision
|
||
|
||
| Requirement | Text (summary) | Implementation in screen-brightness |
|
||
|-------------|-----------------|-------------------------------------|
|
||
| Night vision | Visual alarms and indicators shall **not interfere with night vision**. | In ambient mode, NIGHT/DUSK use low levels (1–2); transitions are smooth (one step per poll) to avoid sudden bright flashes. |
|
||
| Dimming not to extinction | **Dimming facilities** shall be incorporated, **though not to extinction**. | Same as MSC.191(79): level 0 is never used; minimum is level 1. |
|
||
| High luminous intensity for alerts | Supplemental **visual indicators** (e.g. for alarms) shall be of **high luminous intensity**. | When the **buzzer** is ON (alarm), backlight is set to **level 5 (maximum)** immediately, with no smooth stepping. |
|
||
| Persistence after alarm | Alerts must remain visible/audible long enough for crew response. | After the buzzer stops, brightness is held at level 5 for a **cooldown period** (default 10 s), then stepped down; duration is configurable in `/etc/screen-brightness.conf`. |
|
||
|
||
**Reference:**
|
||
- IMO MSC.302(87) Annex — Performance Standards for Bridge Alert Management (Modules A–D).
|
||
- [imorules.com – MSC.302(87) Annex](https://www.imorules.com/MSCRES_302.87_ANN.html)
|
||
|
||
---
|
||
|
||
## 4. IHO S-52 and IEC 62288 — ECDIS and display presentation
|
||
|
||
**IHO S-52** (International Hydrographic Organization) specifies chart content and **display aspects** for ECDIS, including colour and luminance behaviour. **IEC 62288** implements and tests these and related IMO requirements for shipborne navigational displays.
|
||
|
||
### 4.1 Three colour / luminance modes
|
||
|
||
| Mode | Typical use | Implementation in screen-brightness |
|
||
|------|-------------|-------------------------------------|
|
||
| **Day** | Bright ambient; high contrast. | DAY-DIM, DAY-NORMAL, DAY-BRIGHT (levels 3–5) by lux bands. |
|
||
| **Dusk/Dawn** | Transition; reduced luminance. | DUSK mode → level 2. |
|
||
| **Night** | Low luminance so as **not to affect the mariner’s night vision**. | NIGHT mode → level 1 (minimum). |
|
||
|
||
**IHO S-52** (e.g. Edition 6.1.1):
|
||
- “The ambient lighting on the bridge varies between the extremes of bright sunlight … and night, when the **light emitted by the display has to be low enough that it does not affect the mariner's night vision**.”
|
||
- Three colour/luminance modes (day, dusk/dawn, night) are defined for ECDIS; the screen-brightness daemon provides a compatible **three-mode luminance framework** (NIGHT / DUSK / DAY-*).
|
||
|
||
**IEC 62288** (e.g. IEC 62288:2021):
|
||
- General requirements, test methods, and required results for the **presentation of navigation-related information** on shipborne navigational displays.
|
||
- Supports IMO MSC.191(79) and MSC.302(87).
|
||
- Full luminance limits (e.g. numerical cd/m² for night) are in the purchased standard; the daemon’s “minimum level 1” and “never 0” satisfy the “dimmed but not to extinction” and “night vision” intent.
|
||
|
||
**Sources (external):**
|
||
- IHO S-52 — Specifications for chart content and display aspects of ECDIS (IHO publication).
|
||
- [IEC 62288:2021](https://webstore.iec.ch/publication/64659) — Maritime navigation and radiocommunication equipment and systems – Presentation of navigation-related information on shipborne navigational displays.
|
||
|
||
---
|
||
|
||
## 5. Summary table — Regulation vs implementation
|
||
|
||
| Regulation | Clause / topic | Daemon behaviour |
|
||
|------------|----------------|------------------|
|
||
| **MSC.191(79)** | §8.1.1 Brightness adjustable, dimmable | Levels 1–5 from ambient sensor; configurable lux→level mapping. |
|
||
| **MSC.191(79)** | §8.1.1 Legible in all ambient conditions | NIGHT / DUSK / DAY-* modes with configurable lux thresholds. |
|
||
| **MSC.191(79)** | §8.1.1 Not to extinction | Level **0 never used**; minimum level 1. |
|
||
| **MSC.191(79)** | §8.1.2 Reset to preset | Override file: fixed level 1–5 or `auto`. |
|
||
| **MSC.302(87)** | Visual alarms high luminance | Buzzer ON → **immediate** level 5. |
|
||
| **MSC.302(87)** | Dimming not to extinction | Same as above; min level 1. |
|
||
| **MSC.302(87)** | Night vision not degraded | NIGHT/DUSK low levels; smooth stepping on transitions. |
|
||
| **MSC.302(87)** | Alert persistence | Cooldown (e.g. 10 s) at level 5 after buzzer stops. |
|
||
| **IHO S-52 / IEC 62288** | Three modes (day / dusk / night) | NIGHT, DUSK, DAY-DIM, DAY-NORMAL, DAY-BRIGHT. |
|
||
| **IHO S-52** | Night luminance low for night vision | NIGHT mode → level 1. |
|
||
|
||
---
|
||
|
||
## 6. Configuration and audit
|
||
|
||
- **Config file:** `/etc/screen-brightness.conf` — lux thresholds, levels per mode, cooldown, hysteresis.
|
||
- **Override (preset):** `/run/screen-brightness/override` — navigator preset (1–5 or `auto`).
|
||
- **State (read-only):** `/run/screen-brightness/state` — current mode, level, lux, buzzer, override.
|
||
- **Reload:** `systemctl reload screen-brightness` (no restart).
|
||
|
||
For vessel-specific tuning or audits, adjust thresholds and levels in `/etc/screen-brightness.conf` and document the chosen values and the fact that level 0 is never used.
|
||
|
||
---
|
||
|
||
## 7. References (URLs and documents)
|
||
|
||
| Reference | Description | URL or source |
|
||
|-----------|-------------|----------------|
|
||
| IMO MSC.191(79) | Performance standards for presentation of navigation-related information on shipborne navigational displays | https://www.imorules.com/MSCRES_191.79.html |
|
||
| IMO MSC.191(79) §8.1 | Display adjustment (brightness, dimming, preset) | https://www.imorules.com/GUID-6B14EB44-F913-4C8F-8E36-F74CE6E8E3DE.html |
|
||
| IMO MSC.302(87) | Performance standards for Bridge Alert Management | https://www.imorules.com/MSCRES_302.87.html |
|
||
| IMO MSC.302(87) Annex | BAM performance standards (Modules A–D) | https://www.imorules.com/MSCRES_302.87_ANN.html |
|
||
| IHO S-52 | Specifications for chart content and display aspects of ECDIS (e.g. Ed. 6.1.1) | IHO publication; see https://iho.int |
|
||
| IEC 62288 | Presentation of navigation-related information on shipborne navigational displays | IEC 62288:2021 (and amendments); https://webstore.iec.ch |
|
||
| reTerminal DM wiki | Hardware interfaces (backlight, buzzer, light sensor) | https://wiki.seeedstudio.com/reterminal-dm/ |
|
||
|
||
---
|
||
|
||
*This document is for guidance only. For formal compliance, refer to the official IMO, IHO, and IEC publications and your flag state / classification society.*
|