INT-1 Symbol Reference — Sections P (Lights) and Q (Buoys / Beacons)
INT-1 Section Q — Buoy Shapes
| Code |
Shape |
Notes |
| Q20 |
Conical buoy (nun buoy) |
Pointed top; IALA Region B = green starboard |
| Q21 |
Can buoy (cylindrical) |
Flat top; IALA Region B = red port |
| Q22 |
Spherical buoy |
Ball-shaped |
| Q23 |
Pillar buoy |
Any superstructure on small platform (lantern, topmark, radar) |
| Q24 |
Spar buoy (spindle) |
Long thin pole, nearly vertical |
| Q25 |
Barrel buoy (tun) |
Cask / drum shape |
| Q26 |
Major floating light |
LANBY / light vessel; large platform with full light structure |
INT-1 Section Q — IALA Lateral Marks
IALA Region A (Europe, Africa, Asia, Australasia)
| Mark |
Colour |
Shape |
Topmark |
Light |
| Port (left) |
Red |
Can/Cylinder |
Red can |
Red: any rhythm |
| Starboard (right) |
Green |
Conical |
Green cone point up |
Green: any rhythm |
| Preferred channel to stbd (modified port) |
Red + green band |
Can |
Red can |
Fl(2+1)R |
| Preferred channel to port (modified stbd) |
Green + red band |
Conical |
Green cone up |
Fl(2+1)G |
IALA Region B (Americas, Philippines, Japan, South Korea)
| Mark |
Colour |
Shape |
Topmark |
Light |
| Port (left) |
Green |
Can/Cylinder |
Green can |
Green: any rhythm |
| Starboard (right) |
Red |
Conical |
Red cone point up |
Red: any rhythm |
| Preferred channel to stbd (modified port) |
Green + red band |
Can |
Green can |
Fl(2+1)G |
| Preferred channel to port (modified stbd) |
Red + green band |
Conical |
Red cone up |
Fl(2+1)R |
S-57 attribute CATLAM: 1=port, 2=starboard, 3=preferred channel to stbd, 4=preferred channel to port
INT-1 Section Q — Cardinal Marks (IALA, same both regions)
| Mark |
Colour (top/bottom) |
Topmark |
Light |
Meaning |
| North (N) |
Black over Yellow |
2 cones point UP |
VQ or Q (continuous) |
Pass to the north |
| East (E) |
Black / Yellow / Black |
2 cones base-to-base |
VQ(3) 5s or Q(3) 10s |
Pass to the east |
| South (S) |
Yellow over Black |
2 cones point DOWN |
VQ(6)+LFl 10s or Q(6)+LFl 15s |
Pass to the south |
| West (W) |
Yellow / Black / Yellow |
2 cones point-to-point |
VQ(9) 10s or Q(9) 15s |
Pass to the west |
S-57 attribute CATCAM: 1=N, 2=E, 3=S, 4=W
INT-1 Section Q — Other Special Marks
Isolated Danger Mark (S-57 layer: BOYISD / BCNISD)
- Colour: Black with one or more red horizontal bands
- Topmark: 2 black spheres (one above the other)
- Light: Fl(2) White
- Meaning: Isolated danger with navigable water all around
Safe Water Mark (S-57 layer: BOYSAW)
- Colour: Red and white vertical stripes
- Shape: Spherical, pillar, or spar
- Topmark: Single red sphere
- Light: Iso W, Oc W, LFl W 10s, or Morse "A" (. ―) W
- Meaning: Safe water on all sides (mid-channel, landfall)
Special Purpose Mark (S-57 layer: BOYSPP)
- Colour: Yellow
- Shape: Any (X topmark optional)
- Light: Yellow, any rhythm not used for other marks
- Meaning: Special feature (traffic separation, spoil ground, cable, military, etc.)
Emergency Wreck Marking Buoy (IALA / AISM)
- Colour: Blue and yellow vertical stripes (alternating)
- Shape: Pillar or spar
- Topmark: Single upright yellow cross
- Light: Al.Bu.Y 3s (alternating blue and yellow) or VQ(4) Y + VQ(4) Bu
- AIS: AtoN transponder transmitting
- Meaning: Newly discovered dangerous wreck
INT-1 Section P — Light Characters
| Abbreviation |
Full name |
Description |
| F |
Fixed |
Continuous steady light |
| Oc |
Occulting |
Light longer than darkness; Oc(2) = group of 2 eclipses |
| Iso |
Isophase |
Equal light and dark periods |
| Fl |
Flashing |
Single flash, dark > light; Fl(3) = group of 3 |
| LFl |
Long Flash |
Flash ≥ 2 seconds |
| Q |
Quick |
50–60 flashes/min; Q(6) = group of 6 |
| VQ |
Very Quick |
100–120 flashes/min |
| UQ |
Ultra Quick |
≥ 160 flashes/min |
| Mo |
Morse code |
Dots and dashes; Mo(A), Mo(U), etc. |
| FFl |
Fixed + Flashing |
Steady light with superimposed flashes |
| Al |
Alternating |
Changes colour; Al.WR = alternates White/Red |
Light Colours
| Code |
Colour |
| W |
White |
| R |
Red |
| G |
Green |
| Bu |
Blue |
| Vi |
Violet |
| Y |
Yellow |
| Or |
Orange |
| Am |
Amber |
S-57 LITCHR Numeric Codes (used in ENC data)
| Code |
Abbreviation |
| 1 |
F |
| 2 |
Fl |
| 3 |
LFl |
| 4 |
Q |
| 5 |
VQ |
| 6 |
UQ |
| 7 |
Iso |
| 8 |
Oc |
| 9 |
IQ (interrupted quick) |
| 10 |
IVQ (interrupted very quick) |
| 11 |
IUQ (interrupted ultra quick) |
| 12 |
Mo |
| 13 |
FFl |
| 14 |
Fl+LFl |
| 15 |
Oc+Fl |
| 25 |
Al.Oc |
| 26 |
Al.LFl |
| 27 |
Al.Fl |
| 28 |
Al.Grp |
S-57 COLOUR Numeric Codes
| Code |
Colour |
| 1 |
White (W) |
| 2 |
Black (K) |
| 3 |
Red (R) |
| 4 |
Green (G) |
| 5 |
Blue (Bu) |
| 6 |
Yellow (Y) |
| 7 |
Grey (Gy) |
| 8 |
Brown (Br) |
| 9 |
Amber (Amb) |
| 10 |
Violet (Vi) |
| 11 |
Orange (Or) |
| 12 |
Magenta (Mg) |
INT-1 Section P — Leading Lines / Range Lights
| Code |
Description |
| P20.1 |
Leading lights / range lights: two lights (front and rear) forming a transit. Solid line on chart = the recommended track. |
| P20.2 |
Any two objects in line constitute a transit bearing. |
Leading line light: has the S-57 attribute ORIENT (bearing in True degrees). The backend emits a LDLINE GeoJSON LineString feature projected along that bearing for rendering.
