Bridge Equipment Flashcards
Compass checks - what, when, how?
- Checking the calculated deviation against the deviation card
- Checked once per watch or after every large alteration of course
Transit when in coastal waters
- True bearing on chart
- Compass bearing
- Find compass error
- Use to find deviation
- Compare with deviation card
Amplitude of the sun at sunrise/sunset
- Bearing of sunrise/sunset - half a diameter above the horizon
- Check declination for the day in nautical almanac
- Note latitude
- Norries tables to find true aziumuth (bearing) at rising or setting
- Compare against compass/gyro
Azimuth of a heavenly body
- Take a bearing of sun/heavenly body. Note time
- Find GHA and declination for the sun/heavenly body at that time from nautical almanac
- Find LHA by +/- latitude from GHA
- Enter rapid sight reduction tables with LHA, Lat and declination
- Find Azimuth (true bearing)
- Compare with magnetic/gyro
Who corrects a compass?
Compass adjuster - must hold a compass adjusting CoC
How does a gyro compass work?
Finds true North by the rotation of the earth
Deviation rising - what would you be checking?
- I would revert back to the compass log and look for a trend.
- Check the fore and aft and athwart ship magnets had not been altered.
- Check the chart for magnetic anomalies.
- Check the area around the magnetic compass for any anomalie.
- Notify the DPA.
- Raise a non-conformity.
Gyro stops working - actions?
- Silence alarms on equipment and switch to hand steering.
- Log the incidence.
- Switch to magnetic.
- Check connections.
- Notify DPA.
- Fill out non-conformity.
What is True North?
The centre of rotation of the Earth.
What is on a deviation card?
All compass headings and how you can convert from magnetic to compass. It will also show the positions of the permanent magnets and where/time the compass was swung.
What errors do you need to be aware of if you’ve been on the same heading for a long period of time?
Retention error - The ship will retain some of the induced magnetism for a short period of time when the course is changed.
When would you adjust a compass?
- First installed
- Becomes unreliable
- Ship undergoes structural repairs
- Elecritcal or magnetic equipment added near the compass
- Two years
Operational compass checks
- Gimbal moves freely
- Card floating freely
- Liquid clear and free od bubbles
- Card is clear and sharp
- Optical system adjusted and clean
- Illumination working
- No leaks
How to do a MerPass
- Take a sextant angle of the sun at MerPass. Note the time
- Combine declination of the sun with sextant reading. This will give latitude
- Calculate difference in time between local MerPass and GMT MerPass.
- Conversion of arc to time to find longitude
What are the characteristics of X and S band radar?
X Band = 3cm wavelength, 9GHz frequency - preferred for navigation, better definition. Not so effective in rain due to its wave length (easily covered up). Required onboard all vessels >300GT as it picks up SARTs
S Band = 10cm wavelength, 3GHz frequency - longer range, early detection, more effective in rain due to its longer wave length
How does a radar work?
Transmitter - Scanner - Receiver - Display
- Pulse transmitted, range calculated by speed x time/2
- Bearing either referenced to ships head or compass
How are you going to set your radar up?
- Check must is clear of personnel and obstructions, no permits to work open
- Switch on and wait for warm up
Then: Big Randy Girls Take Cock
- Brilliance
- Range
- Gain
- Tuning
- Clutter
Pre departure checks
- Performance monitor (once per watch)
- Check VRM against range ring
- Check EBL against compass
- Gyro repeaters correlate
What factors are going to effect radar detection?
MASTS
- Material: wood/fibreglass vs steel/aluminium etc
- Aspect: side aspect or bow on?
- Size - large vs small
- Texture
- Shape
