Introduction
As. the 200th anniversary of the introduction of the office
of Hydrographer of the Navy approaches, it seems
appropriate to place on record a little of the history of hydrographic
surveying by the Royal Navy. The work of those who carried out survey work has
been given little public recognition, the detached parties who spent long
periods in very isolated places and undertook almost herculean
tasks deserves particular acknowledgement. This articles is intended to set out
a little of the background to hydrographic surveying
by the Navy since 1930.
In 1683, the King Charles II appointed Captain Grenville
Collins as Hydrographer to the King and placed him in
command of the Royal yacht MERLIN, which can be regarded as the first British
warship dedicated to marine survey work as opposed to exploration. Collins
completed the first comprehensive survey of the British coast whilst in command
of the MERLIN.
The responsibility for all survey work considered necessary
for the mobility and security of HM Ships has long been discharged by the Hydrographer of the Navy. His office was first established
in 1795. Before that date the officer responsible for navigation of individual
warship, the Master, was required to undertake survey work aimed at up-dating
existing charts or providing new information to the Admiralty for future use. a special hydrographic
organisation was first established by France in 1720 and a little later by
Denmark. Before the end of the 18th century similar arrangements were made by
the Spanish, American and other navies. The motivation for provision of
navigational information depended upon the extent of colonial development and
foreign trading by individual nations. An International Hydrographic
Bureau was set up in Monaco in 1921 and conferences are held every five years.
The British Hydrographic Service is represented, and
sometimes an HM Survey Ship will go to Monaco to give demonstrations of
equipment and to act as host ship for the British representatives.
Although the first Hydrographer of
the Navy, Alexander Dalrymple, was a civilian
employed by the East India Company, he was relieved by a naval officer, Captain
Thomas Hurd in 1808. Since that date the office has
been exclusive to qualified Surveying Officers of the RN. It was Hurd who established the requirement that surveys at sea
should be carried out by HM Ships, and that all ships deployed specifically for
survey work should be manned by Executive (Seamen) officers. These officers
were to progress in rank based on their surveying capabilities as well as their
basic seamanship abilities. In this way they would be totally fitted to command
ships devoted to survey work. This principle still remains today.
The Hydrographer's Department
produces a series of documents to assist ship navigation. These include charts,
sailing directions, tide tables and other publications dealing with
navigational lights. In order to ensure that users are made aware of changes or
new information, details are promulgated in the form of Notices to Mariners and
distributed to holders of Admiralty charts. With the introduction of steel
ships, gyro compasses, radio beacons and, more recently,
satellite navigational systems, additional supporting publications are now
provided.
Surveying at Sea
Hydrography is concerned with
accurate positioning of points on the surface of the Globe and, where
appropriate, the depth of water available. Early seafarers are known to have
used a type of compass and to have appreciated that some form of distance
measurement was essential to navigation. Until it was generally accepted that
the earth was not flat any charts produced were very inaccurate and parts of
the land and other features were out of proportion. They did, however, describe
coastlines and indicate shallow water but in many cases not the depth.
Before any chart can be produced it is essential that a
datum position is established and expressed in terms of latitude and longitude.
Latitude was determined by astronomical observations and became more accurate
after the sextant replaced the seaman's quadrant. Once a reliable chronometer
was available, the determination of longitude was greatly improved. Charts must
show details of coastal features to assist the mariner to jdc
his position and provided other information, such as, changes in depth of
water, especially near coasts. Data for the preparation of sea charts is
dependent upon accurate measurement of distances between fixed points whose
positions have already been accurately established. However, whereas maps of
land surfaces include details of the height of geographical features, which are
under normal circumstances fixed, the depths of the seas and oceans are
variable due to tidal conditions.
Principles
The properties of a triangle are used to establish the
position of fixed points within the area to be surveyed. The triangulatfon process requires accurate knowledge of the
distance between two of these points and subsequent angular measurements from
these enables the third point to be precisely determined using theodolites or sextants. The position of the first points
is established by using existing datum from earlier surveys, or by astronomical
observations. Out of sight of land special provision has to be made to mark the
fixed points with moored buoys. Extensive use is. therefore,
made of small survey boats which are a distinctive feature of all Survey Ships.
Angular measurements are made using sextants, theodolites,
quadrants and station pointers. This latter device enables the position of a vessel
to be plotted with reference to three other known positions.
Distant Measurement
Metallic tapes are used for measurements on land and taut wire
measuring gear, for measurement between datum
offshore. The latter device consisted of a reel of wire mounted in the stern of
a survey ship, from which the wire was pulled off by the forward movement.
These methods have been largely superseded by electronic equipment which is
easier to use and more accurate. The first of these, the tellurometer,
was developed in South Africa for land survey work and introduced into RN
service about 1958. A similar instrument the hydrodist,
specifically designed for marine survey work superseded the tellurometer
and is now in common use.
Depth Measurement
Depth of shallow water is measured using graduated poles
placed in selected sites for tidal records. At these tidal stations the depth
of water is recorded every ten minutes around the times of high and low water
and every thirty minutes intermediately for period of not less than 29 days.
Automatically operated equipment is now available which makes this procedure
much less arduous.
Offshore depth can be measured by the traditional lead and
line or by the Kelvin wire sounding machine for depths up to 2,000 fathoms. The
echo sounder was first developed during the 1930's and echo sounding equipment
is now the method used. It can continuously record the depth of water below a
moving vessel. This type of electronic equipment is fitted in all survey ships
and craft.
In order to establish the minimum depth of water available
in approaches to harbours, special procedures are used to confirm that the
water is clear of obstructions. Minesweeping cable streamed astern of the
survey ship and maintained at a fixed depth. Any wreck or obstruction above the
selected depth will foul the wire and its position can then be marked for
future attention. Clearance sweeping is more usually carried out by one ship, however two small craft can be used in shallow waters.
The availability of more accurate sonar with improved display units enables
wrecks and pinnacles of rock to be examined and positioned with great accuracy.
Once an obstruction has been located it is now common practice to use shallow
water divers to examine it thoroughly and place explosive charges, as
necessary, to ensure no portion remains above the clearance required. Sonar
which has evolved from the echo sounder is also used for the detection of
obstructions.
Types of Hydrographic Work
Hydrographic work can be broadly
divided into two areas — ocean survey and inshore survey. Large vessels able to
carry out their work in sea areas far from land are used for ocean survey and small
craft for inshore and coastal work. Since 1930. at least. 40 survey ships have been employed during
peacetime. These are listed as an Appendix, and this shows that most of them
were converted for survey work with only a few designed and built specifically
for the purpose.
Detached parties with small survey boats are extensively
used for inshore survey work. Their principal functions are to:
Establish clearly visible datum
positions based on existing survey or accurately determined by normal survey practice.
Fix the coastline and conspicuous
features visible from the sea.
Fix the position of islands,
shoals and dangerous obstructions.
Establish tidal stations and make
recordings of depth of water.
Carry out sounding work in
shallow areas not accessible by the parent ship.
Until radio position finding equipment became available
survey work required good visibility for optical measurements and sea
conditions had to be suitable for small craft. The advent of electronic
equipment for accurate position finding enables survey work to be carried out
by day and by night in weather condition: previously impracticable, this has
revolutionised the output produced in each surveying season.
Radio Position Finding Equipment
Radio position finding systems operate on hyperbolic
principles and allow distances from shore based transmitter stations to be
obtained using special receiving equipment fitted onboard ships. Hyperbolic
radio navigational aids were first used by aircraft during World War Two - the
Gee system - and were adapted for use in ships. After the end of hostilities
the British designed Decca Navigator System was set up to provide this facility
for commercial use and Decca Navigator equipment was progressively fitted in RN
ships. It had great potential as a tool for survey work and shipboard equipment
was fitted in all survey ships during the early 1950's. This system enables a
ship's position to be continuously obtained using charts overprinted with a
special lattice network representing radio signal measurements for a given
covered area. The receiving equipment incorporates a display unit from which
readings corresponding with the lattice are obtained to determine position. A
similar system was also developed in the USA during World War Two and is known
as LORAN. A modified form - Two Range Decca - was developed for marine survey
purposes and includes a radio transmitter carried on board the survey ship,
which therefore, became totally independent of the commercial Decca system.
Detached parties ashore and in survey boats were provided
with suitable portable receive sets to enable them to fix their positions
accurately using large scale charts of the area. A lattice network
corresponding with the shipboard equipment is overprinted on these charts.
Ships fitted with this type of equipment are easily identified by the tall
mainmast structure supporting the radio transmitting aerial system. A later
variant of this special survey system - Hifix - has
gradually replaced the Two Range Decca. This includes portable transmitters
which are set up ashore in precisely located sites and provide a network of
radio position lines over the survey area. A marine radar outfit specially
designed for survey; work and with a range accuracy of within 10 yards is used
for distance measurements between established datum.
Radar transponder beacons, accurately positioned at datum points are also used
to assist modern hydrographic survey work.
Tidal Measurements
Horizontal movement of water on the earth's surface is of
great concern to ship navigation, and demands attention during hydrographic work. Tidal streams are influenced by many
factors, apart from changes in the position of the sun and moon. Seasonal
changes of wind direction and differences in atmospheric pressure are two examples.
Observations are made at the average depth of water required by ships in the
survey area. Records of mean direction and rate of flow are needed at hourly
intervals for up to 50 hours and repeated in different lunar conditions,
a uniform diameter spar is frequently employed and floated vertically. It must
be long enough to reach the depth required and needs a distinctive marker so
that its movement can be assessed from shore or from an accompanying craft.
Additional Equipment used in Hydrographic Survey
Satellite navigation
equipment
Traditional methods of astro-fixing
of position for latitude and longitude measurement have now been replaced by
use of radio satellites. A ship's position is instantaneously available which
is quite invaluable for survey use, as for example, when lines of soundings are
being measured.
Magnetometers
In order to determine the extent of changes in the strength
of the earth's magnetic field, magnetometer design has been much improved to
provide equipment robust enough for towing by a survey ship. The 'Proton'
variant, developed by London University, was extensively used in the Indian
Ocean during an international scientific investigation in the 1960's. Changes in the natural magnetic field owing to the presence of
submarines is one practical application of this type of unit.
Bathythermographs
Trials to establish the effect of different sea temperatures
on acoustic underwater transmissions were first carried out in 1922 in the
Mediterranean and the Red Sea. changes in salinity and
temperature at different depths of water have a significant effect on the
performances of sonar and echo sounding equipment. Bathythermograph equipment
used to measure sea temperature at various depths was developed, during World
War Two, by the famous Woods Hole Institute of Oceanography. Charts and tables issued by
The Hydrographer are based on measurements now made
as a matter of routine by all HM Ships.
Core sampling
equipment
Study of the make up of the earth's crust has become
increasing important. Progressive developments have resulted in the
availability of devices suitable for shipboard use. Samples are obtained during
ocean passages for use by scientists ashore who are carrying out mineralogical
research.
Data processing
outfits - Computers
Modern radar, sonar and navigational aids are able to
provide a continuous supply of information. This has to be analysed and
presented in a format suitable for use by hydrographers.
Automatic data processing equipment is therefore an essential tool and allows
speedy availability of the particular information needed.
Conclusion
The availability of modern techniques has made hydrographic survey a very complex activity and greatly reduce the time taken to complete survey work. It has not
affected the need for dedicated and determined personnel, prepared to work long
hours often far away for the amenities of the modern world. These
characteristics are still a fundamental requirement and cannot be replaced by
any of the technological advances of the latter years of the 20th century.
Chronological Summary
|
1801 |
First Admiralty Chart published. |
|
1807 |
Naval Chart Committee came into being. |
|
1819 |
Admiralty takes over Royal Observatory,
Greenwich. |
|
1819 |
Permission given to sell Admiralty Charts to
the Merchant Marine |
|
1823 |
First Sailing Directions published by
Hydrographer. |
|
1829 |
First Light List published by Hydrographer. |
|
1832 |
Promulgation of information to keep charts
up-to-date began in the Nautical Magazine. |
|
1833 |
First Tide Tables published by Hydrographer. |
|
1834 |
First Notices to Mariners issued by
Hydrographer. |
|
1842 |
Admiralty compass Department set by Rear
Admiral Sir Francis Beaufort (1774-1857), who was the Hydrographer
for 26 years. He gave his name to the scale used for wind and
weather. |
|
1902 |
International Council for the Exploration of
the Sea established in Copenhagen. |
|
1919 |
World's first International Hydrographic
Conference. |
|
1921 |
International Hydrographic Bureau established
in Monaco. |
|
1922 |
First Admiralty List of Wireless Stations
published. |
|
1967 |
International Hydrographic Bureau is renamed
the International Hydrographic Organisation. |
|
1968 |
Automatic Data Processing equipment (computers)
first introduced in HM survey ships. |
|
1971-80 |
International Decade of Ocean Exploration |
|
1978 |
RN Hydrographic Apartment received the Queen's
Award for Export Achievement. |
ROYAL NAVY SURVEY SHIPS SINCE 1930
Ships Designed as Survey Ships
|
Class, Ship’s Name
|
Displacement Tonnage
|
Period of Service
|
Remarks
|
|
|
|
|
|
|
1 ENDEAVOUR
|
1280
|
1913-42
|
War Service as a Survey Ship
|
|
2 CHALLENGER
|
1140
|
1931-42
|
War Service as a Survey Ship
|
|
3 VIDAL
|
2000
|
1954-71
|
First to have Helicopter facility
|
|
|
|
|
|
|
HECLA Class
|
|
|
|
|
4 HECLA
|
2800
|
1965-
|
A133
|
|
5 HECATE
|
|
1965-90
|
A137 Disposal 1991
|
|
6 HYDRA
|
|
1966-86
|
Sold to Indonesian Navy in 1986 and renamed DEWA KEMBA
|
|
|
|
|
|
|
Improved HECLA
Class
|
|
|
|
|
7 HERALD
|
2900
|
1974-
|
A138
|
|
|
|
|
|
|
BULLDOG Class
|
|
|
|
|
8 BULLDOG
|
1088
|
1968-
|
A317
|
|
9 BEAGLE
|
|
1968-
|
A319
|
|
10 FOX
|
|
1968-90
|
A329
|
|
11 FAWN
|
|
1968
|
A325
|
|
|
|
|
|
|
12 GLEANER
|
20
|
1984
|
A86 Inshore Survey Craft
|
|
13 ROEBUCK
|
1400
|
1986
|
A130
|
Survey Ships converted from other hulls
|
ABERDARE Class
|
|
|
Minesweeper
|
|
14 BEAUFORT
|
800
|
1920-35
|
|
|
15 FITZROY
|
|
1920-38
|
|
|
16 FLINDERS
|
|
1920-38
|
|
|
17 KELLETT
|
|
1920-88
|
|
|
|
|
|
|
|
RACEHORSE Class
|
|
|
Patrol Sloop
|
|
18 IROQUOIS
|
1320
|
1923-31
|
|
|
19 ORMONDE
|
|
1924-36
|
|
|
20 HERALD
|
|
1924-39
|
ex MERRY HAMPTON was taken into
Japanese service as HEIYO; she was mined in 1944.
|
|
|
|
|
|
|
BITTERN Class
|
|
|
Sloop
|
|
21 STORK
|
1190
|
1936-39
|
Then reverted to Escort role
|
|
|
|
|
|
|
HASTINGS Class
|
|
|
|
|
22 SCARBOROUGH
|
1025
|
1938-38
|
Then reverted to Escort role
|
|
23 FOLKESTONE
|
|
1938-38
|
Then reverted to Escort role
|
|
|
|
|
|
|
HALCYON Class
|
|
|
Minesweeper
|
|
24
FRANKLIN
|
815
|
1938-52
|
War Service as Survey Ship
|
|
25 SCOTT
|
|
1939-64
|
War Service as Survey Ship
|
|
26 JASON
|
|
1938-39
|
Reverted to Minesweeper role
|
|
27 GLEANER
|
|
1938-39
|
Reverted to Minesweeper role
|
|
28 SEAGULL
|
|
1946-54
|
Converted 1945-46
|
|
29 SHARPSHOOTER
|
|
1946-59
|
Renamed HMS SHACKLETON in 1955.
|
|
|
|
|
|
|
LOCH/BAY Class
|
|
|
|
|
30
DAMPIER
|
2600
|
1948-68
|
ex LOCH EIL, ex HERNE BAY.
|
|
31
DALRYMPLE
|
|
1949-65
|
ex LOCH GLASS, EX LUCE BAY. sold
to Portugal in 1966 and renamed
ALPHONSO DE
ALBUQUERQUE.
|
|
32
OWEN
|
|
1949-65
|
ex LOCH MUICK (2), ex THURSO BAY.
|
|
33
COOK
|
|
1950-64
|
ex LOCH MOCHRUM, ex PEGWELL BAY.
|
|
|
|
|
|
|
E Class
|
|
|
|
|
34 ECHO
|
160
|
1958-84
|
A70 Ex Ham Class
|
|
35 EGERIA
|
|
1958-84
|
A72
|
|
36 ENTERPRISE
|
|
1959-84
|
A71
|
|
37 WOODLARK
|
|
1955-80
|
M2780 Ex YAXHAM
|
|
38 WATERWITCH
|
|
1966-81
|
M2720 Ex POWDERHAM
|
|
|
|
|
|
|
Ton class
|
|
|
|
|
39 MERMAID
|
425
|
1964-68
|
M1184 Ex SULLINGTON
|
|
40 MYRMIDON
|
|
1964-68
|
M1111 Ex EDDERTON. Sold to Malaysia in 1969 and renamed
PERANTAU.
|
|
|
|
|
|
|
41 WHITE BEAR
|
|
1939-45
|
Ex-Yacht ISOLAIRE
|
|
|
|
|
|
|
Special
|
|
|
|
|
42 ENDURANCE
|
3706
|
1968-91
|
A171. Ex-ANITA DAN Ice Patrol Ship converted 1967/68
|
The Hydrographer's Navy — photographic
profile (Photographs being sought)
Survey ships are painted in an internationally agreed colour
scheme .white hull, buff funnel.
® SAS NATAL — this fine photograph illustrates the ex
Loch/Bay class frigate HMS LOCH CREE. Launched by Swan Hunter on 19 June 1944
she was handed over to the South African Navy in 1945 and subsequently
converted for service as a survey vessel. [South African Navy photograph via
author]
® HMS COOK - ex Loch/Bay class frigate
LOCH MUICK/PEGWELL BAY. Launched by Pickersgill
in September 1945 she was converted for service as a survey vessel. While still
resembling her frigate ancestry this photograph clearly shows the large davits
required to handle her Survey Motor Boats. [Admiralty photograph via author]
® HMS BULLDOG — Bulldog class Coastal Survey Ship, built by
Brooke Marine of Lowestoft and commissioned on 21 March 1968. Based on a
commercial design, she and her three sisters are capable of worldwide
operations. Powered by 4 8-cylinder diesel engines she has an endurance of
4,500 nautical miles at 12 knots. Manned by a crew of 4 officers, 9 senior
rates and 38 junior rates — the 4 officers and one PO are surveyors. This ship
is fitted Hydrosearch sonar which is considered the
most advanced in the world. She also carries a 31 foot Survey Motor Boat and an
18 foot Survey Launch. [Builders photograph via ANRS]
® HMS HECATE — Hecla class Ocean Survey Ship, built by
Yarrows at Scotstoun and commissioned in December
1965. Based on a commercial design, she and her two sisters were built for
worldwide hydrographic and oceanographic operations.
She has an ice strengthened hull, a fully equipped flight deck and helicopter
hanger and two 31 foot Survey Motor Boats. Crew 12 officers
and 104 ratings. Main propulsion is diesel-electric with 3 12-cylinder
diesel engines; speed 14 knots This photograph clearly
shows the Hifix position fixing system aerial atop
the hangar. [WSPL]
® HMS EGERIA — E class Inshore Survey Craft. EGERIA and her
two sisters — ECHO and ENTERPRISE formed the Inshore Survey Squadron. This
squadron was first commissioned in 1958 and normally worked out of Chatham
Dockyard. The main role of the squadron was to provide a continuous resurvey of
the East Coast of Great Britain from Dover to the North of Scotland. EGERIA was
launched in September 1958 and the hull design was based on that of the Ham
class inshore minesweeper. Crew 2 officers and 16 ratings.
[WSPL]
