Ship’s speed trials

DOC. WO.

SHIP 3'

SPEED TRIALS

!f3qb ¡33l

_f:Z1.i2Z.

by

J.Th.Verstelle; Hyd.rographic Office Royal Netherlands Navy.

(March

₁₉₅₃₎

Ear. 1. ThTRODUCTION.

The old and usual method is to mak _{runs over the measured mile.} Recently a report has been published1) _{about the merican 3.5.} "United States', having made its sea and speed trials using a completely different method, i.e. by means of the electronic

system Radist. (lso recently, mention has been made of speed trials b _{the S.S."Manchester Spinner', using Decca off the Isle} of Man 2)

Different methods of determining ship's speed, diameter of turning circle, head-reach and stern-reach _{on 'crash" stops and} similar .data, will be alsoussed in some detail in this paper.

}ar. 2. THE PROBLEMS TO BE SOLVED.

Durin _{acceptance-trials of new ships several trials are carried.} out in order to try to _{et a reasonalle accurate answer to many} questions of importance in the practical operation o.f the ship.

One of the data sought for, is the speed of the vessel; with regard to the subject of this _{aer, the speed determination} will be considered as the main problem _{to be solved, bein by}

Determination of the ship's velocity per hour (Vh),

/4I

#

freed from disturbinr influences of current and wind. The velocity obtained. may be the ultimate goal of th trial; in most oases however it will just be _{a means to achieve another :çoitl,} for instance determination of most _{economical speed by comparison} with fuel consumption and developed _{power of engines or in orlar} to compare results with those obtained _{in the model tosting tank.} None of these data can b _{determined or is known free from errore.}

llthouch no accurate figuras are known to me, it seems reasonable Raydist Speed-measurin _{equipment oi the S.S. "United States' sea}

trials; the society of naval architota and _{marine engineers, no.}

3-1 952.

Decca Navigator News; July 1952, pa

e6 *.--4-4-4.1 -,

/

NIETJ;SBRIEF HYDRORAFIE no. 18.

to. suppose that data like developed power and. fuel consumption cannot be expected. to be obtainable with an accuracy of better than say 1% and. possibly this is too optimistic.

It is therefore doubtful whether there is any real practical need for making one link in the chain of data much stronger (accurate) than the others. It must however be taken in mind., that a considerably higher accuracy in one of the links may be of value for a special purpose and it will always be valuable _when

one of the sources of errors in a problem is very small compared. with others.

Other problems to be solved during acceptance trials may be

determination of radius of turning circle, headreach and

stern-mach on 'crash' stops, acceleration from stop to fullspeed and

similar problems. The measured mile does not offer means to solve this kind. of problems. Raydist, Decca and (in principle) radar, however do.

Far.

_3.

_METHODS.

3.1.

easured mile; fil. 1.

The track made lood must be perpendicular to the lines of

beacons; only small deviations from this track can be accepted, as explained in par. 4.2. In most cases the measured mile

is established in a location where the tide or current is runnin. _{in the direction of the track to be made good.}

In case the wind. (or combined vector of wind, and current) is not in the direction of the track, its _{influence on the sped} determined., cannot be satisfactorily and completely eleminatel from runs forth and back, as may he _{seen from fig.. 1, where th:}

'

angles _< and.

/3

are unequal. 3.2. Raydist

3);

_{fig. 2.}

The ship carries a continuouswave transmitter/receiver.. "relaystation", consistin,g of a more or less similar equipment is installed, in a freefloating unmoored buoy.

The ship steams in any desired direction _{away fron and. to;.ard} the buoy and the ship's receiver indicates at any desired moment the distance to the buoy.

ny travelled. and measured distance can be used. to determine

the speed.; _{a convenient distance seems to be somethin of the}

order of ₃ to 5 naut.mi., but there are no objections to run a

3) In this application Raydist _{is used. as a pure distance ,measurino}

system, based on the principles of plasecomparison

much longer distance.

The buoy is of special construction (draft ₂₃ foot) and. is

therefore supposed and tested to have aprox!matel the same drift due to current as the ship. buoy of this construction has very little leeway from wind and from waves; the construction has been tried out in such a way to guarantee maximum steadiness, even in a hoavy sea.

The radio equipment in t buoy is self-operating and fed. by batteries. The ship's receiver is coupled to a record.in. devic'

on moving raph-paper1 The two coordinates are time and distanc time can at any desired. moment easily be read to the nearest

0.1 and distance to the nearest 2 feet.

The buoy may be launched by the ship herself before startin the trials and picked up later. During the trials of the S.S. United States the buoy however was handled by a separate ship.

The remaining effects of wind and current are eliminated fron

s

__-

a run forth and back.

& 4&WJ

'- I-í

3.3.

Decca; fig.

3 & 4.

The ship carries a Decca receiver and, an instrument for graphical recording of time; the two need not he connected. for automatic recordin and. can operate separately.

run of not less than 10 and not lon.er than 20 minutes is made, steering a true compassoourse, rouhly perpendicular to one set of Docce. hyperbolae (Oreen in fig.

3),

followed by a run back on exactly opposite true compass-course. In both runs no steerin-ocrrections are made to try to allow for leeway due to wind and current.

Durin both runs seconds of time are automatically recorded« a a strip of moving paper of a chronograph, connected to a chrone-acter; the speed. of the saper usually is such, that the distance between the r900rded seconds of time is _; inch, allowing to

interpolate to the nearest 0.02 second if considered. necessary

, key, operated. by an observer, enables to register any desired

moment on this automatic record of time. The observer makes

this reistration every time he notes that the particular (Oren in fi. 3) deoometer reads zero,Çrove more satisftory in order

to avaid coincidence with the 'kicks" of the decometer-needlle at the moments of lane-identification of the Decca chain.

In order to avoid small systematic errors in the Deccareceivcr

(of no importance in normal naviaticn), it might 'ce useful to use a so-called "survey-receiver"; this depends on the ultimate accuracy wanted.

The chronograph is a simple and inexpensive instrument and can be operated on batteries; the chronometer is of the type normally used on board ship and has a small modification for

coupling to the chroraph. oth are not normally carried on

/r any particular reading that miht

hoard of a ship and have to 'be installed for the purpose of the trials.

The aim of the trial is to determine the distances made _ood. in both runs during an exactly known interval of time. Ihon the angle of cut of the two Decoa-patterns is nearly perpendicular -like in fir, 3 _{- the time of taking the readins on the other} decometer (Reö. in fi.

₃₎

is not critical and does not ne automatic registration. However making speed trials, usin a

Decca-patterns like fig.

_4,

it may 'be necessary to make

simultaneous automatic registration of both patterns, in order 'to

ensure adequate accuracy in the distance made good.

High accuracy in the distance made good, can be obtained because of the high short-term 5) _{Stability of Decca-patterns.} 'The exact geographic position of the Decca hyperbolac traversed,

is cf nc or negligable importance in this application, _because the distance made _{ocd is determined from differences in}

coordinates and not from the coordinates themselves.

Normal nautical charts with overprinted Deoca-rid ara by no means sufficiently accurate to take off the distance made good.

It is therefore necessary to choose the area for the trials beforehand, to compute the Dc-oca-lattico accurately for that

particular area and to plot it _{n a large scale - for instance}

i : 25,000 - on stable material (astralon or other plastic).

torking on this scale, the problem of speed determination and other problems can be solved by construction on this sheet, as will he shown later.

It is of course also possible to make the trials in any, not

predetermined, area in a suitable Deccacoverage and to compute the Decca-pattern for that area later.

Ho attempt should 'be made to try to keep the ship's course on a predetermined Dc-cc-a-hyperbola (in most cases not sensibly differing from a straight line) _{- like for instance a Red}

hyperbola in fig.

3 -,

_{because this will introduce the same sort} of difficulty in eliminating leeway effects as indicated in fir. 1. Making the two runs on exactly opposite true _{compass-course in}

the only correct way to enable to eliminate _{the combined leo-way} effects, as will be shown in par.

_5.

3.4. Radar; recen.

In principle Rayiist could be replaced 'by radar or recen, usin.; a free floating buoy with _{a radar reflector or radar} res-ponder.

As will b seen in par.

_4.5,

radar and recen are not sufficiently accurate for the purpose at hand, unless very speoielize and

comlioated equipment is used.

35. Other methods.

The use of Loran is out of the question, heinj under no ciroumstances sufficiently accurate for this purpose.

Other precision systems for electronic position fiin

-for instance Lorca, Shoran and. Oboe - miht be used, but very

seldom will b available in suitable areas and are too complicoo.d and expensive to be considered. just for the purpose of ships _trials.

lar. 4.

CCURCY.

4.1. General. y no system effects of leeway can be completely

eliminated from the results of a sinle run; at least one run forth

and back will always be necessary.

7vhatever system is used,comlete elimination is possible only when wind and current are constant in irection and force durin

s

the whoLe period of the trial.

In order not to complicate the comparison too much, it will be based on the accuracy attainable in a speed determination by the

different methods under conditions of no wind end nc currentL for this purpose only a sinle run need. b considered.

couracy will be invstjated on the basis of mean square errors

(m.sq.o), as far as their influence may he considered. to be of random character

Notations used: = valocity7hour

t = number of seconds

ô. = distance

m = mean square error in ir

Vh h

mt mean square error in t.

= mean square error in d.

= relative error to he expected. in Vh

Formulae: Vh = 3600 x d

t

2 )2 m2 + (3600 x d)2 m2 = ( 3600 Vh ( ô. ( t2 ) t

4.2. Measured mile; fi.. 1.

The length of the measured mile usually - though not necessarily - in exactly i naut. mi..

In this paper the measured mile is taken at 1852 meter; in actual trials the correct lenfth of course should be used as

jve _{in ailin,g Directions or other publications.} e. meter

n.m. = nautical milo

The distance made _{ood should be perpendicular to the lines} of the beacons indicatin _{the distance; its direction is}

ven

in the above mentoned

publications. Sometimes, but not always, there are facilities (landmarks; _{beacons; buoys) to assist the} shi1 in keepin ori that line.

In practise it will not be possible to realise the prescribed track (or a track parallel to it) free of error. The effect of an error of 1 _{is an en1arement of the distaçe by a factor} secant 1° = 1.00015, i.e.

_{0.28 rn.}

_on

_{1852 m..b) (0.015%}

of distance).

The lines of the terrninatinr _{beacons may be supposed to be} known, marked and observable with an accuracy (mean square errcr cf sornethinR of the arder of

_0.5

_meter.

_{(= 1.6}

_foot)

Suppostirig a rn.sq.. of 10 _{arid a m.sq.e. in both terminals of} 0.5 meter (both perhaps toc optimistic in actual practice), the rn.sq.e. in the distance made good., will b:

md

=\J

(0.28)2

+ (O.50)x '= 0.66

meter,

0.66

resultinI in a relative error of

_{1852 -}

_0.030/0.

The mean square error in time will at both ends be of the order of 0.1 seo., resultin _in:

mt = 0.1

z

V

2

_{0.141 seo.}

ample 1. lTh

= 3600 z 1852 = 66672 rn/h = 36

n.m,/h.

100

m2 =

(3600)2

_{z (0.66)2 + (3600 x}

₁₈₅₂₎₂

_(0141)2

= 9455

100)

_io

97.2

mi/h. h

= 97.2

= 0.146%

_(0.053

_n.m./h.)

66672

xample 2.

= 3600 z 1852 = 33336

ms/h. = 18 n.rn./h.

200

= 26.4 m./h.

= 0.079%

_(0.014

_n.m./ha) ample 3.

= 3600 z 1852 = 16668

m,/h.

9 n.rn./h.

400 rn7h

8.4

rn./h. 0.050%

_{(0.0045 nvrn./h.)}

6)

sec. =

1.00061,

_{corres;ondiní wih -an enlarement of}

1.13 rn.,

(0.06% of distance)

4.3. Raydist; fi.. 2.

Distancereadins on the Raydist record can be taken to the

nearest foot and possibly still bet-tsr. The actual

accuracy of

a distance however is not that hih. For the distances under

consideration it seems fair to put the

_{msq.e. in a sínle distance}

measurement at 0.7 meter, resultin

in:

md

0.7

= 1

meter

.s mentioned in a note ori par. 3.2. it is possible to take time

reaö.jns as accurate as 0.02 sec.. For a number of reasons it is

however more realistic to put the accuracy at 0.1

_{sec., rc-sultin}

in:

= 0.1 z

= 0.141 sec.

Example 1.

3600 z 6'

36'

66672 me/h.

600

m2

(3600)2

_{x 1}

_{+ (3600 z}

11112)2

z 2 z

ic2=

₂₈₃

(600)

(

36x104

) m

=16.8

16.8

= 0.025%

_{(0.009 n.rn./h.).}

66672

Example 2.

3600

x 6' = 18'

_{33336 m./h.}

1 200 m

4.9 rn./h.

Vh

_4.9

_{= 0.015%}

Vb

33336

xample 3.

vh

3600 i 3'

= 9' = 16668 ms/h.

1 200

= 3.6 ms/h.

rn

-= 3.6

X 0.022 %

Vb

16668

4.4. Decca; fi.. 3 & 4.

Irovided th

trials are taken in an area not further away

from -the transmitters than 100 naut.mi.,the shortterm

_stability

of a Decca pattern (mean square error) may be taken at 0.01

lane in daylight. Phase errors in the decometers (m.sq.e.) will

(0.003 n.rn./h.).

r

8-not exceed 0.01 lane in a well calibrated. r3ceiver. 1Een no

photographic reistration of dacomters is used. - as is suggested

in this paper - the read.in errors also may amount to 0.01 lane. The total mean square error in one hyperbola therefore may be assumed to be 0.01 x

V 3

0.017 lane. in

For an area roughly 45 n.m.S.E. of the

eilly

Islandsthe entrence

to the Erillish Channel end usiriR in the S.W. 3ritish

Decca

Chain, the local lanewidth of the green pattern (fit. 3) is 690 meter; 0.017 lane therefore corresponds with 11.7 meter.

Supposed th track is taken rouhly perpendicular to the Green

pattern, any small error in readin of the ed hyperbola (local

lanewidth 1200 meter) at both terrninal, will have only very

sliht influence on the dtstance made Rood across the Green patteru

th mean square error in this distance may therefore he taken to be

md = 12.0 \,r 16.9 meter (a)

Using a chronorraph, time readins can 'be taken as accurate as 0.02 second, but - like with Raydist - it seems more realistic to

put:

= 0.1 V = 0.141 sec. (a)

These errors depend on the area with respect to the location

of the transmitters. In an area like represented in fi. 4 - for instance a few miles East of Galloper in the 'Torth Sea - the local

lanewidths are: Hgd 1000 m. and Green 1685 meter, with an anle

of cut of about 45 . In this area -the mean square errors will be of the order of:

md = 25 meter ) ) (b) m = 0.141 sec. ) ample 1. (a) 2 m Vh Vh = = = = = vb = 3600 x 22224 = 66672 ms/h. = + (36Go i 22224)2 36 ri.m./h. x 2

i02

(0.028 2

i02

= (0.041 = 2636 ../h.). 5687 n.m./h.) 1 200 600)2 x (16.9)2 (1200) 51.3 51.3 = 0.077 (

144 x

+ (3600 10 ) 22224)2 Vh (b) m2 h h 66672 (3600)2 x (25) (1200)

75.4

m./i.

L54

= 0..113é ( 144 10 ₎ Vh 66672

xample 2. (a) _{Vb 3600 x 11112 33336 r./h. =}

₁₈

_n.m./h, 1200

= 50.9

ms/h. h = 0,153%

33336

(b)

75.1,

mb/h. 75.1 0.225% Vh

33336

Sxampla 3. (a) _vh

3600

x 5556

16668

m./h.

= 9

n.m./h. 1 200 50.8 m./h. = 50.8 _0.305% Vb

16668

(b) m _{75.0 ms/h.} Vh = 75.0 = 0.450% Vb

16668

(0.028 n.m./h.). (0.041 n.m./h,). (0.027 n.m./h.). (0.041 n..m/h.).

&t distances exeedin; 100 n.m.. the short-term stability of the Decca patterns (in daylight) is still quite high.. Due to rapidly decreasing angle of cut, the accuracy in the distance d to be determined, however is rapidly decreasing..

It is difficult to ive a general rule as to maximum distances at which a Decca Navi atjori Chain still can be used for the purpose of speed trials. ach case should be considered separately, takin:

in mind the final accuracy wanted... thyhow there is a wide choice of areas in the North Sea, the nlish Channel, the Irish Sea and the

waters around Denmark, where suitable

_Decca

coverage is available.

4.5.

Radar; racon.

Accordin to official specifications the error in a distance, measured by a normal commercial ship1 s radar should

_£xed

_5%. However in most radars this error certainly will not exeed.

3.

This error is of mixed random and systematic character. Takin the mean of a number of runs, there is some justìfication in treating it as a more or less random error and to put md = 2% of distance.

lo

-sufficient accurate means for d.eterminin the distance made good in a sped. trial. Other object ions a.painst this method - accuracy cf indentification of the echo of the reflector, sea clutter, etc -will therefore not b discussed. here.

In principle there will be no objections to install a

rad.ar-responder (racon) in a free floatin; buoy and to follow a procedur like with Raydist. To et sufficient accuracy, however a spocial radar should be uscii (and installed), havin _{kscope representation.} This method - for many other _{reasons - also dos not sems to be a}

practical and. economic answer to the problem.

4.6.

Other methods.

s arTued in par. 3.5., these methods except Loran

-theoretically could be used for the purpose, but enerally speakin do not seem to offer favourable solutions.

Par.

_5.

DECCA PROCBDTJRB.

The ship runs the true compasscourse indicated by the dotted

line in fig.

3..

The actual run starts at A; the observer presses th key operatin _{the second chrono;raph reistration (the "firs-L} is the continuous re;istration of the seconds of th chronometer) at the exact (mt 0.1 sec.) moment of crossin a Oreen hyper'ool

-preferably, but not necessarily, a _{zero decometerreadin - and} Oreen & Red read.ins are noted. down.

s much care as possible is taken in keepin the correct compass-course. fter some 10 to 20 minutes a convenient terminal is chosen at B (also preferably a zero Oreen reading) and. again Oren ¿ Re2.

readings are noted down.

This enables to plo the distance B made good on the spaciaUy prepared large scale 71 Deccachart.

The ship now turns round and makes a run in exactly the opposite

true compasscourse, indicated by the second dotted line in fir. 3. The same procedure is followed between a convenient 8tartinr point C and a terminal D. This run back is of epproximately - or if desired exactly - the semc- duration as the- first run and also is plotted on the Decca cheet.

Assuming the speed to he constant, a point E can easily he

constructed on the line CD or its extension, makin; CE to represent an interval of time exactly equal to the time taken for the _run The line CE now is shifted parallel to itself to a position where C coïncides with B. The construction now looks like fi;. ₅ (s±raiht

line AB and BE). A straight line is drawn from A to E atid a point exactly midway between _{and B is determined.}

The straiht line BR represents the distance d. in formula (i), freed from disturbing influences of wind and current. ' is the

vector representing the combined effects of wind and current durin _{the period of one sinle run, as may be easily seen from} fig. 5.

The direction of 3F should of course correspond. to the true

compasscourse. if there is any deviation from that course, this

is an indicati.on _{that the influence of wind or current or both hev} 7)The accepted plottin _{error cf 0.2 m.m. (0.04 inch) is correspco:lln.}

with 5 m.

(5.5

yards) on a scale 1 25,000; this error is plottin

not been constant :urin _{the time occupied by the runs forth anC} back; such deviation _{may also be due to compasserrors. There} is no way to eliminate errors in EF 'lue to these changin

conditions, thouh of course in most _{cases it is likely that the}

effect will be _{r:4atly reduced by repeatin the whole procedure} and taking the mean of several determinations of 3F.

Speed trials therefore should he made durin a period when

constant current can be expected and should be timed after consul-tation of current tables _{or stream atlasses. In a carefully planned} speed trials this kind of _{uncertainty can be 1arely avoided.}

Th whole procedure can be improved by making _{intermediate time} re'istrations and taking decomoter reaciins during the runs

and CD, for .nstanoe at the crossinl of every Green hyperbola, i.e. every 700 yards in the area S.E. of the Scilly Islands. This enables to plot intermediate points of the tracks made _oc:

and thus is a control on the combined effects of steering errors as well as changing con1itions of wind and current. In additin

lt will be very useful to observe _{wind direction and force durin:ç'} the whole trials by

means of a selfrecordinanemometer,

_{as has}

been done durin. the trials of the s.s. "United States". It is of course impossible to separate these _{soures of errors from their} combined effect, but _{- as the effect of wind (and especially} wind 'usts during a _{ale) on the superstructure of a large ship}

is considerable - it may happen, that the curve of speed of ship and that of force of wind run more or less parallel in a graph like fig. 6, thus clearly indicatin that variations in speed can be explained by variations in wind resistance of the ship. _{lso fr this reason it is Important that the an;le between}

(true) wind direction and ships course is kept constant by

steerin' exactly opcsite true compasscourses.

A graph of the type of fis. 6 also offers means of control whether full spedd has been reached at start of run. This i. important, because there seems to be a tendency of makinf turno too near startin _point.

As shown in the left lower half of fig. 3 the Decca sheet len may be used. to solve by construction the _{problem of determlnati«'n} of diameter of ships turnin. _{circle, even under conditions cf} wind and current.

It will need no further _{explanation that data like headreach}

and sternreach on 'crash" _{stops, acceleration from stop ta}

full spe''l and similar prob'ems, _{can easily he solved by}

construction on the Decca sheet. No doubt there are many other

problems of interest to the shipowner, desiner and builder

that can be satisfactory solved in this way.

Par. 6.COMP'RIS0N BTN

_{MEASURED MILE, RiYDIST AND ECO'.}

6.1 .General.

12

-must be taken into

consideration, each of them possibly depending on circumstances

and. particular needs. The following

1isng however will give _{a general idea of the most important}

ones. The most important

general conditions to be fulfilled are: (i) fairly deep water; for very fast ships _preferably

not much less than 12 times draft; reasonable distance from _shipyard; reasonable ease of operation; reasonable cost;

room for making turris;

possibility to carry out trials under sea-going conditions _{swell, eto.) if desised;}

in certain

cases (warships): speed not to he attained by unauthorized, _persons.

comparison between the three systems, based/on these conditions, is largely dependent _{on local circumstances and}

availability o:' the 3 aids. It may however been said that _{in the waters surroundin:} great 3ritiari all _{conditions except}

₍₇₎

and, sometimes (2) and to some _{xtent possibly (5) & (6)}

can h _{fulfilled by the method, of} the measured. mile, _{It will be evident that}

Decca under nany circumstances will have

some advantage (in these waters) over the measured mile,

anyhow with repect to (7), but in many cases also with respect to the other conditions. _{It should be remember d.} that (2) is a very important consideration _{from an economic point} of view.

It cannot he the aim of this _{paper to quote prices of equipmn±.} It is however important

to know the order of _{manitude, being} roughly £ 400.- a year for hirin _{a Decca receiver (the} trans-mitters are ari existing _{aid to navietion and}

they need not to be paid for) plus _{£ 200.- for purchasin}

a chronograph and chronometer, _{vhile the purchasing coast of a complete/f £}

15,000.-;

in both cases the

equipment can be purchased by the shipyard or some central institution,

to be used for as many ships trials as desired. This difference in cost of course is _{a quite importent} and in N.a. European waters even decisive _{argument, quite apart} from the meritoriousness _{of the two syst3ms. On}

the other hand. it would be quite

impractical to purchase and install a Decca chain in the United _{States just for the only}

purpose of making ship's trials.

6.2. Technical _{possibilities.}

Sorno items

- incomplete, but considered. to he

_{the most}

impornt-are listed below:

/aydist

_{equipment is of the}

order

Measured.

mil e

Reydist Deoca

(a) _{Complete elimination}

of effects of wind arid

current, provided.

cori-stant during trial

not

possible possible possible

From this list i-t will be seen that for all practical _purposes Raydist and Decca may he valuated equally hiíh. The accuracy of distance determination by Raydist certainly is higher,. but for the. purpose a _{hand this hiTher accuracy has nc or little practi"al} value. Both Raydit and. Decca however have _{many advantages over}

the measured mile.

Par.

_7.

_CONCLUSIONS.

Rayciist and Decca offer widerpossibiliti.es than the measured mile for determinin _{a number of data durinç acceptance trials of} a ship.

From the point of accuracy, both Raydist and Decca seem to 1e equally suitable for practical purposes.

In areas covered by Decca Navigation Chains, this _{system in many} cases is to be preferred to the measured mile.

A suitable area (dependin _{on circumstances, distance to ship} yard, required. ultima-te accuracy, depth of water, etc.) should be chosen for the trials and a special large scale chart for that area say 15 x 15 naut.mi. - need te computed and drafted (to he done in the office).

Many suitable areas are available in N.W. 1iropean waters. Iv. In areas not covered by Decca, Raydist offers _{excellent means}

and in many cases is to he preferred to the measured mileo No preliminaty computations and no charts aro necessary. 'To answer can be Tiven to the question whether calibration of the radioequipment and layin: and. pickin1 up of the buoy need. to he considered as time, and therefore money, consumin

(b) practical elimination of (a)

possible possible possible

(c) _{accuracy of speed}

determination

good excellent very oc

(d.) _{determination of wind} offect on speed. not possible possible possible (e) deternination of diameter of turnino circle not possible

good very good

headreach and stern

reaeh riot possible possible possible acceleraticn ,not Po s s ib le possible possible (h) _{possibility of control}

whether full speed has been reached. at start

of run no-t possible possible possible

13

-' P4ILE

T/iIS7

DcC

Gezien.:

De Chef der Hydrcrrafie,

6

Th.K.brn.v. :sbeck. Schout bij 'Tacht.

istributie: Bibliotheek CHYD.

sousChef Hydro;raf±e

Cart o.;rafen :ydrorafie. Cdtn. HDG en ZFK. Ktz. Boe'corn ₎ Kltz. Steensrna ₎ Ltz. I Laneraar ) Ltz.

SD 2 de

it ₎ persoonuijk

Ltz. SD 2

van d Oever)

Ltz. SD

2 van .alderén) Bibliotheek HYMZ.

i3ihliotheek Kementsrian Pelajaran

HYMZ Gezahe'cer ?IBimasakti!

)

Hr.J.j.J.de Groot (1CI.F. persoonuijk).

Hr.

J.vari

Foon. Marid (3 ex.).

i-.H. I..

-operations; possi1ly they.are, possibly not in a serious way.

T. _{t the distances under consideration, Faydist could be used for}

niht trials; it is not known whether this would 'ce a real

practical advantae or not.

For hih accuracy, the use o± Deäca should he limited to th' period between 1 hour after sunrise tnd 1 hour before sunset, unless the distance to the transmitters is 5rnall or unless

reduced accuracy cati be acceptedL

sGravenhae,

27 Februari _1951.

)e- Cart ora

4

6

i 1

-jt

-Staatsoommissie Onderzoek Radiotechnische Hulpmiddelen v/d Navigatie

Bij gemeenschappelijke besohikking van de Minister van Verkeer en Waterstaat en van de Minister van Marino van 8 Januari 1947 werd een Comznissie Inge-steld. tot bet bestucleren van de verschillend.e vraagstukken, welke zieh tot bevordering van do veiligheid bij de toepassing van radar en andere

eiectrcnische navigatierniddelen, zowel bij d.c zeevaart als b±j de luchtvaart voordoen of waarschijnlijk zullen voordoen, bet cord.ineren der belangen, die de ond.erscheiden diensten daarbij hebben of zullen blijken te hebben en bet uitbrengen van adviozen terzake, zowel op verzoek als op eigen

initia-ti cf.

De coznmissie is thans als voigt samengesteld.:

Voorzitter A.J.W,van Anrooy, oud. Hoofdinspooteur, Hoofd. v/d Dienst van Scheepvaart in N.I., oud. Inspecteur in aig. dienst der PTT; Secretarisg A.C.Portgens, ref 2e kl PTT;

Ledon: Th.K.Baron van Asbeck, Scheut bij nacht, Chef Hydrografie der Kon. Marine;

Ir P.HBoukema, Hoofdingonieur der PTT;

E.Crone, Lid studiecentrum voor Scheepbouw en Navigatie der T.N.O., voorzittor Mon. Aardrijkskund.ig Genootschap;

J.J.vanDeldcn, Luit, t/zee der le kia8ae werkzaam bij ilarinestaf;

Drs A.Haue, adj.directeur van bet Kon.Ncd.Met.Instituut te do

But;

J.Houtsmulle, Kapitein t/zee b.d., hoof dingeniour der PTT; C.in 't Void, Hoofd.ingcnieur-Directeur Rijkswaterstaat;

J.C.Jurrens, Kapitein-luit.t/zee, gedetaoheerd. bij de eieotr, dienst v/h Min.van Marine;

J.Kuper, Hoofd. Dienst Mobiele Radio der PTT; Ir M. H.W.Moorrees, Ingenieur Rijkskus tverlichting;

Ir J.F.Sch5nfeld, Hoofdingenieur Directeur Rijkswaterstaat, Inspecteur vTd Rijnvaart;

O.J.Seiis, Hoofdinspecteur Rijksluchtvaartdienst;

J.Tissot van PQtOt, Kapiteln t/zee, Directeur van bet Loodswe-zen in hot 4e en

5e

district;

J.Th.Verstelle, Wetenschappelijk rneclewerker bij de HydrDienst der Kon.Marine;

E.A.Vree, Schout bij nacht,b.cI., Secretaris der Ned..Redersver-eniging;

Prof. Jhr Ir J.L.W.C.von Weiler, Hoogleraar b/a Technische Hogeschool, kapiteln luit. t7zee veer speciale dieflsten; .Adv.leden J.M.F.A.van Dij, directeur van bet Ned.Radarproefr'tation te

Noordwijk a/zee;

Jhr A.van Foreest, Kapt. t/zeo b.d., ad.viseur bij de N.V.Phulips Telecommunicatie Mij;

Ir H.J.Hylkema, Ingenieur bij de N.V.Teiegi'aaf Mij Radio Holland; Ir LA.J.Liebart, Directeur N.V.Telegraaf Mij Radio Holland.; Dr Ir A.E.Pannenborg, Natuurkundig Laboratorium Philips Gloci-lampenfabrieken en

N.Schimmol, Hoof d. Laboratorium v/h Ned.Radarproefetation te Noordwijk a/zee.