MICHIGAN STATE COLLEGE Paul W

Home , Beam compass, Drafting machine, Micrometer, Ruler, Theodolite

A STUDY OF RECENT DEVELOPMENTS AND INVENTIONS IN ENGINEERING INSTRUMENTS

Thai: for III. Dean. of I. S. MICHIGAN STATE COLLEGE Paul W. Hoynigor I948

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A STUDY OF RECENT DEVELOPMENTS AND INVENTIONS IN

ENGINEERING’INSIRUMENTS

A Thesis Submitted to

The Faculty of

MICHIGAN‘STATE COLLEGE

AGRICULTURE AND.APPLIED SCIENCE

Paul W. Heyniger

Candidate for the Degree of

Batchelor of Science

June 1948 \. HE-UI: PREFACE

This Thesis is submitted to the faculty of Michigan

State College as one of the requirements for a B. S. De- gree in Civil Engineering.'

At this time,I Iish to express my appreciation to c. M. Cade, Professor of Civil Engineering at Michigan State Collegeafor his assistance throughout the course and to the manufacturers,vhose products are represented, for their help by freely giving of the data used in this paper.

In preparing the laterial used in this thesis, it was the authors at: to point out new develop-ants on existing instruments and recent inventions or engineering equipment used principally by the Civil Engineer.

20 6052 TAEEE OF CONTENTS

Chapter One Page Introduction

B. Drafting Equipment ------13

Chapter Two

Telescopic Inprovenents A. Glass Reticles ...... -32 B. Coated Lenses ...... --J.B

Chapter three The Tilting Level- ...... -33

Chapter rear

The First One-Second.Anerican Optical 28

“00d011 ‘6------e------

Chapter rive

Chapter Six The Latest Type Altineter ------...... 5.5 TABLE OF CONTENTS ,

Chapter Seven Page The Most Recent Drafting Machine ...... -39.---

Chapter Eight

Chapter Nine

SmOnnB By Radar ...... ------In”.--

Chapter Ten Conclusion ------...... ”"39.-- CHAPTER ONE

INTRODUCTION

A. Surveying Instruments.

There are numerous reasons why we should consider new developments and inventions in engineer equipment at the present time.

World War Three gave an impetus to develOpment and invention in all phases of science and engineering which produced many new products and techniques which a great number of established and graduating engineers are not familiar with.

These new developments and inventions save time and thereby reduce field and office costs. They are more accurate making possible the performance of a higher order of surveying and they are more flexible which means the equipment and techniques can be adapted to more different types of Jobs.

The study of modern engineers equipment and instruments is more completely understood if the evolution and invention of engineers equipment is traced thru history.

It is probable that surveying instruments had their origin in ancient Egypt. A plan of the villa of a great

Egyptian noble was found in a Theban tomb of the eighteenth dynasty. A tomb of a certain Manna of Thebes contains a representation of two chairmen surveying a corn field and in Ptolemic and Roman papyri measurements of plots of land are described. The dimensions of the great Pyramids clearly illustrates that the early Egyptians had some engineer equipment of considerable accuracy.

The Romans invented the Groma which consisted of two pairs of plumb lines suspended from the ends of two horizontal rods which were fastened at right angles to one another and which enabled them to lay out lines at right angles to one another.

The Romans used ten foot rods for measuring distances. The foot, at that time, measuring 13.2 of our present inches

The Romans also used a crude type of plane table for align- ing their roads. ‘ The Greeks used a form of log line for recording the distances from point to point along the coast while making their slow voyage from the Indus to the Persian Gulf in

300 8.0.

Compasses were used by the Chinese as early as 1600 B.C by making use of the lodestone.

The Plani spheric Astrolobe was invented by the Greek Bipparchus (150Tﬁ.c.) and consisted of an evenly balanced circle or disk of metal or wood, hung by a ring and pro- vided with a rotatable alidade or diametral rule with sights, turning within a circle of degrees Jfor measuring the altitudes of the sun and stars.

Plane tables were in use in Europe in the Sixteenth

Century. The various instruments and equipment used by the engineer fall into five main classes; those for, (1) Measuring distance (2) Determining direction (3) Determining horizontal lines. (4) Measuring angles (5)1Miscelaneous work Chains, tapes, wooden and metallic rods are used for :measuring distances. The chain is of two types ,the Gunter

and the Engineers. The Gunter chain was invented by Ed-

:lnnd Gunter, an.English engineer, in 1620 and is 66 feet

long divided into 100 links each of which is 7.92 inches

long. These links are composed of heavy steel wire and each includesJat every tenth linkJa numbered brass tag, ihile at each end of the chain is a handle. This chain

is need in public land surveys which do not require great accuracy.

The Engineers chain is composed of 100 links each of

which is one foot long. This chain is also used only for

rough.measuring.

Engineer tapes are usually 100 to 200 feet long and made of thin one quarter inch ribbons of steel or nickel-

steel alloy which has a small temperature coefficient and

is known as invar metal. The feet and subdivisions are

etched on these tapes.

Direction can be measured by the surveyors compass

which consists essentially of two uprights having verti-

cal slits to give a line of sight and which are attached

to horizontal graduated circle at the center of which is

mounted a magnetic needle free to move, the whole being

supported by devices for leveling. This surveyors compass is not used for accurate work.

The prismatic compass is a hand instrument with a

glass prism so arranged that the needle is read while

taking a sight.

The Locke level has no telescOpe but is simply a metal tube with a plain glass cover at each end and a

spirit level on top. The bubble and cross wire ( re-

flected in a prism ) are in the left half and the land-

scape in the right half of the field of view. A point on

the landscape is level with the observers eye when the

reflected image of the bubble is at the center of its

tube.

The Engineers Wye level is most commonly used to determine horizontal lines. This instrmment consists of a telescope with cross hairs to determine the line of sight clamped in Yeshaped uprights rising from a bar and carrying a spirit level and resting on a vertical pivot re-

'volving in a socket in the plate which fastens the instru-

:ment to its tripod or other support. Leveling screws per- ndt the adjustment of the Spirit level bar to a horizontal position, and when the axis of the telescope is parallel

to this bargthe line of sight . is horizontal.

A Bumpy level is similar havtng asshorter telescope with a wider aperature.

The Engineers level rod is graduated to feet and

fractions of feet and has a target which is slid up and

down to coincide with-the line of sight of the level

telescope.

The Engineers Transit consists of a telescOpe mounted so that it may be rotated about its vertical and horizontal axis and it is used for measuring both horizontal and vertical angles. In addition it reads distances by use of the stadia wires, determines bearings by the use of the magnetic needle, levels by means of the spirit level attached to the telescope, and does the work of a solar compass by the use of attachments.

The vernier of the transit is a scale by which the linear or angular magnitude can be read with a much greater degree of accuracy than is possible by mere mechanical division and subdivision,

The verniers of the transit are usually of the direct type, which means a vernier whose equal divisions exceeds the corresponding number on the scale.

The principle of the vernier formula is derived on the following page. The Theodolite is constructed the same as the tran- sitJhowever the telescope cannot make a complete revolu- tion on the horizontal axis. Theodolites are commonly made larger and more powerful than transits and are mostly used in important triangulation work as Coast and Geodetic Surveys.

The Sextant is similarly a telescopic instrument but is used primarily in navigation. Engineers sometimes use the Sextant when angles have to be measured from a boat,as in locating soundings and buoys.

The Plane Table is an instrument for making topo- IO‘.

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graphic surveys and consists of a drafting board mounted on a tripod together with an alidade. The alidade is a telescopic sight line mounted on a vertical support which is attached to a ruler, the edge of which is parallel to the line of sight.

The Aneroid Barometer is a hollow metal corrugated box from which the air has been partially eXpelled and which is so thin that it will change shape when the air pressure changes. The movement of the box t0p is comp municated to a spring and then to a series of levers and a link at the end of which a chain is wound around a shaft to which a pointer is fastened. The pointer indicates two scales on the face of the dial. One scale corresponding to inches of mercury and the other to fact in altitude.

The water current meter for measuring the velocity of flow in a river or stream consists essentially of a wheel with cups or vanes so constructed that the impact of flow- ing water will cause the wheel to revolve , the number of revolutions being indicated by some counting device.

The pedometer records the number of steps taken by a man in walking. The figure thus obtained multiplied by the length of the of the step gives the distance traveled.

The Odometer, Cyclometer, or Speedometer records the number of revolutions of a wheel which when multiplied by the circumference gives the distance traveled.

The Clinometer is an instrument for measuring the dip of a vein. The Planimeter is an instrument for measuring the area

of irregular areas which have been mapped to scale.

The Heliotrope is an instrument which consists of mirrors so arranged that a reflection of the sun can be focused from.one point to an observer at some distance.

B. Drafting Instruments.

Drafting instruments are used by the Engineer to graphically illustrate and record the ideas and informp ation necessary for the building of machines and structures.

Drafting instruments and equipment is used to record graphically on paper or treated cloth actual dimensions of a machine or structure and not its pictorial repre-

sentation or projection as viewed by the eye.

Drafting instruments or equipment consist of:

l. T-squares which are used to draw horizontal

lines

2. Drawing boards or tables on which the draw-

ing paper,tracing;paper or cloth is fastened by

thumb tacks or drafting tape.

3. 45 or 30-60 degree transparent triangles.

4. Pencil and ink compasses to draw circles and

segement s .

Dividers, to divide a line in equal parts.

5.Ruling pens to draw inked lines of equal

thickness. 6.Protractors, to lay off angles. 7. Scales, to lay out a drawing in a fixed pro-

Portions

8. Irregular and railroad curves for drawing

curved lines.

More specialized drafting equipment which is commonly used is:

l. Proportional dividers which consist of double

pointed shafts fastened together by a sliding

pivot so that for any pivot setting the distance between.the pair of points at,one end bf the

I instrument,are prOportional to the distance be-

tween the points at the other end of the instru-

ment .

2. The Pentograph is used for enlarging and re-

ducing drawings in a definate preportion. The

instrument consists essentially of four bars

which for any one setting must form.a parallel- ogram and must have a pivot, tracing point and

marking point in a straight line; and any arrange-

ment of the four arms conforming to the require-

ment will work in true proportion.

3. The Beam.Compass is an instrument for drawing

circles or segments of very large radius.

4. Mechanical lettering devices are based on the

principal of the stylographic pen guided by a sliding.master plate. Wrico, Leroy, Edco, and

Hormagraph are the names of some of the most common types of sets.

5. Drop pens are adjustable inking pens which pivot freely about their own pivot point and

they are used for quickly inking circles.

6. Railroad and border pens are used for inking

double lines.

7. Swivel pens are used for inking map contour

lines freehand.

8. Ellipsographs are instruments which are used for drawing ellipsoidal curves.

9. Vernier Protractors, usually from 8 to 14 inches in diameter have a vernier attachment

to lay off angles with maximumraccuracy.

TO. The parallel-rule attachment is a substitute for the Tbsquare. It consists of an arrangement of pulleys and cords for keeping the edge parallel in any position. 11. Adjustable curves consist of a core of lead,

enclosed by a coil spring,to which is attached a metal strip or"spline" or it may consist of a flexible strip to which weights are attached to hold it in place.

12. Drafting machines combine the functions of

T-squares, triangles, scales, and protractor. It is estimated these machines save 35% and 50% of time in making machine and structural draw-

ings respectively compared.with other methods. In order to reproduce engineering drawings quickly and inexpensively, various processes have been develOped. The drawings are first made on tracing paper or cloth with either pencil or ink. The most common processes are:

l. Blueprinting in which sensitized paper coated with

Citrate of Iron plus Ammonia and Ferricyanide of

Potassium is exposed to light underneath drawing on

tracing paper. This paper is exposed just long

enough to obtain.maximum.brightness and sharpness of

the drawings lines and then it is fixed in a water bath. This fixing arrests the chemical reaction

which has taken place and causes the drawing to

retain its legibility. The print has white lines on a

dark blue background.

2. The Van Dyke process uses thin,sensitized paper

which turns dark brown when exposed to light and fixed by a bath of Hyposulphite of Soda and then a

. water bath. This " negative " is exposed to light

while backed by blueprint sensitized paper, result- ing in a positive blueprint with blue lines. Sensi-

, tized paper is now manufactured Ihich gives positive

prints directly from.the first part of this process.

3. The Ozalid process exposes tracing paper drawings while backed by Diazo compound treated paper. The

black, blue or maroon positive line print is fixed

or developed by exposure to Ammonia vapors. This process has the very desireable advantage that the drawing is always dry,hence will not shrink.

4. The Photostat process consists of taking photographs of the drawing. This process is very useful because drawings of different scales can be matched. CHAPTER TWO

TELESCOPIC IMPROVEMENTS

A. Glass Retieles.

Glass reticles instead of spider webs or Platinum wires are now used in the telescopes of surveying instruments. The reticles are made of thin glass, ground and polished,0ptically flat and precisely etched, Light passes thru these etched lines,to a great extent,so they do not have the tendency to cover or obscure the object, to the same extent,which cross hairs do.

The reticles have the advantages that they make possible more accurate point and stadia measurements; the stadia lines do not extend to the edge of the field of view so they are not confused with the regular cross— lines and the reticles are durable and may be cleaned.

They are furnished in at least six different .1" patterns which are illustrated in the following diagrams. -' \ I' ..‘‘ ‘ .. r Glass, Reiicles I M « K/ ha i A \gx B Ere m"

—_——i" ’8

B. Coated Lenses.

A recent improvement incorporated into the lenses of

telescopes of surveying instruments is coating the lens

with a chemical.

A sudden blinding flash of sunlight reflected from

an automobile windshield or a reflection of a persons

image in a plate glass window, are examples of reflected

light. The reflection of light from the lenses of the

telescOpe of an Engineers level or transit is an example

of light which does not pass thru the telescope. Early

in the nineteenth century, Fresnel, a French physicist,

demonstrated that a glass surface exposed to air reflects

four to six percent of the light reaching the surface.

Tarnish is a darkening of the lens surface upon

exposure to certain weather conditions. This tarnish or

weathering of the lens was once considered harmful and

special effort in the past was made to remove it during

cleaning. Taylor, an.English physicist, demonstrated in 1892 that tarnish, by reducing surface reflection,

actually increased the light transmitted by the lens.

Natural coatings, probably the result of a fungus

growth, were unevenly distributed and in efficient.

Taylor,and other physicists,became interested in pro-

ducing similar coatings artificially under controlled

laboratory conditions. Some methods evolved depended on

chemical action on the lens surface; others deposited a

film on the surface by dipping; but the best method was

developed by the condensation of a vapor on the lens surface.

Evaporation, the name given the last mentioned pro-

cess, is the most commonly used method today because the

thickness of the coating can be closely controlled. Five

and one half millionths of an inch is the necessary coat-

ing thickness which gives the best results and this thick-

Iness must not vary by more than one millionth of an inch.

The modern process of seating lenses in order to

reduce reflection was worked out about 1937 by Turner and

Cartwright at the massachusetts Instute of Technology and

greatly improved during‘World war Two.

The coating of'Magnesium.Flouride is applied by heat

under a high vacuum. The lenses to be coated are placed in

a rack under the top of a glass bell about 30 inches high

and about 18 inches in diameter. This glass bell rests on a heavy steel plate with a gasket between and the air is then pumped out. Inside the bell, under the lenses, a

small Tungsten trough containingImagnesium.Flouride has

been placed. An electric current is passed thru this

trough which acts as a filament producing heat which

vaporizes the magnesium.Flouride thus coating the lenses.

This coated surface is not as durable as the surface of the lens itself so,to avoid scratching and cor— rosion,the outside surfaces of the telescope lenses are

left uncoated. Coated lens surfaces have a characteristic bluish

color because coatings are made to be most efficient in yellow light, to which the eye is most sensitive. Thus the small amount of reflected light is predominately blue.

Coated lenses used in the telescope of a surveying instrument are an improvement in.two ways. The increased transmission insures a brighter image and also a sharper image with greater contrast by reducing the haze caused by internal reflections in uncoated lenses. The light reflected by the surface of the second lens is reflected in turn by the surface of the first lens, to blend with the final image as a general haze. This same thing happens at each surface and in a system of many lenses,as a surveying instrument, the result is a serious blurring of the final image.

Table A. provides a quick means of determining the gains in light transmission in a lens system. Column 1 gives the number of surfaces considered, not the number of lenses; Column 2 gives the percentages of the original amount of light transmitted by the number of uncoated surfaces shown directly opposite in the first oolhmn,

Column 3 shows the percentages transmitted by the corresponding number of coated surfaces; and Column 4 states the actual percentage gain in light-transmission compar- ing the quantities in Columns 2 and 3. To use the table select in Column 1 the number of surfaces coated, and horizontally opposite this number in Columns 2 and13 will be found thecpercentages of light transmitted by such a system with uncoated and coated surfaces, with the net gain shown in Column 4. TABLE A. --LIGHT TRANSMISSION THROUGH LENS SYSTEMS

number of Percentage of Percentage of Percentage Surfaces Light Transmit- Light Transmit- Gain ted By Uneoated ted by Coated Surfaces Surfaces

1 93.5 98.8 3.5

2 91.2 97.5 6.9

3 87.1 96.3 10.6

4 83.2 95.1 14.3

5 79.4 93.9 18.3 6 75.9 92.7 22.1

7 72.4 91.6 26.5

8 69.2 90.4 30.6

9 66.1 89.3 35.1

10 63.1 88.2 39.8

11 60.3 87.1 44.4

57.5 86.0 49.6 N H CHAPTER THREE

THE TILTING LEVEL

The Tilting Level or Prism Level is a recent devel-

Opment which replaces the conventional Wye or Bumpy

level and by the use of which it is possible to accom- plish second and third order differential leveling very

rapidly.

Two features of the Tilting Level.make it possible

to do accurate and rapid leveling of greater precision

than that obtained in the manner.

1. Ibe telescope is constructed so that it can

be set level for each sight.

2. The adjustment can be checked by turning the

telescope through 180 degrees about its aria of

collimation.and taking observations in the two

positions.

The telescope is set level for each sight by a micrometer or slow motion screw located at the end of

the telescope bar. The level bubble is visible at the

time of sighting by means of an adjustable, hinged mirror.

This semi-precise leveling instrument achieves

closer limits of accuracy than the ordinary type of wye or Bumpy level largely because the observer can

Check the level bubble, manipulate the instrument and read the graduated rod without changing stance or mov-

ing the eye from.the observing position at the end of the

telescope.

Level model # lO-X produced by (‘:.L.Berge1I a Sons, Boston, is equipped with apprecision vertical screw hav-

ing a differential motion, drum.and single index, prisms

and mirrors, electric illumination for the telescope and

spirit level vials.

The telescope is equiped with an interior focusing system. The object glass is fired in position and does

not move in focusing. The focusing is accomplished by

moving an interior lens placed between the objective and the ruled glass diaphram. In the interior focusing .system the constant of the instrmment,to be added to the

stadia distances,is so small that it may always be omit-

ted

The telescope may be separated from.the center bar which supports it by removing the shaft on which it ful-

crums. The fulcrum on which the telescope tilts is direct-

ly above the center of the vertical spindle and under the

outside barrel of the telescope thereby insuring no change in the heighth of the instrument while elevating or

depressing the telescope.

Accurate and quick leveling of the spirit level and

the telescope is made thru the use of a special vertical

tilting screw for raising or lowering the telescOpe, in

order to bring the spirit level to the mean of its run.

before each sight is taken on the graduated rod. The tilting screw is on the center bar at the eye

end of the telescope. The threads of the tilting screw

bushing are of different pitches. The drum is not grad-

uated except for a single verticle index line. The drum

with index can be adjusted so that it coincides with the

horizontality of the telescope and its spirit level. The

tilting screw bushing rotates and has an up-and-down

motion of two revelotions each way from.zero. The thread-

ed socket with flange is the only part of the unit which

remains stationary. A white horizontal line found inscribed

on the barrel of this part marks the mdddle of the run of the tilting screw. A white vertical line is also inscribed

on this part to coincide with the index line on the drum.

The drum.head which has two knurled peripheries is fasten-

ed by three screws to the bottom of the tilting screw

bushing. There are also three screws on the large peri-

phery to fasten the drum, in order to establish zero

position of the spirit level and the telescope. The tip

of the stud which contacts the under side of the teles-

cOpe has a width of three eighths inches and produces a

rocker like motion of the telescope which rests upon it.

The tip of the tilting screw stud bears against a flat

block under the telescOpe barrel. The differential motion

for the tilting screw of this semi-precise level has been

adopted. This causes less tendency to excessive motion of

the vial bubble, and a much faster and more delicate move-

:ment is acquired which permits quicker leveling of the telescope and the spirit level.

The telescope vial and magnifier are on the left side of the telescope. The pinion head for the rack:motion of the telescope focusing slide, circular level vial and angular reflection mirror, the cam lever for raising the telescope from.the tilting screw are on the right side of the telescope.

The end stepper of telescOpe vial casing, with vertical adjusting capstan head nuts, is mounted within the bracket and cast integrally with the outer barrel of the telescope. The detachable shield with illuminatom is equipped with one electric lamp bulb and two angular reflecting mirrors for the level vial. The illuminator is fastened to both offset brackets of the telescope by two knurled head capstan screws. The illuminator and the thin vertical plate parallel to it set as downward light deflectors, so that no illumination from.the bulb can be

Deane

Fig. 2

Fig. 3 Side View showing Protective Housing for Prisms and Telescope Spirit Level Vial Berger Engineers’ Tilting Dumpy Level Model No. 10-x

\ Accurate Gurley Precision Tilting level \:\ Self-checking Micrometer Reversible Type i\\\ Rapid, simple operation

w. ". L . F Sum EY. THCY. Nit. 65' 0. ‘\ .r 4 FL l _—.—.—.——-_-_-_-— .—-..---_-___._—_—- \e- f.-. ‘—

,- r‘ 'fer ' 7-“--\.' ,7Bv ,4~ 0 9 e ‘1‘ (I If Showing how reversion level vial and telescope rotate to check bubble adjustment. Mirror routes to right or left. CHAPTER rOUR

THE FIRST AMERICAN ONE‘SECOND OPTICAL THEODOLITE

The Gurley'rour-inch Army Theodolite which was dev-

eloped for the Army by W.and LgE. Gurley of Troy, New

York in 1945, represents the first, and ,up to now, only

completely Optical-reading theodolite to be designed in

this hemisphere.

In 1940 the united States Army Engineers contacted

American instrument manufacturers with the prOposal to

build a light, compact, precise, universal, five-second

theodolite. The Gurley company accepted this preposal

and after several models were constructed it was found

that it was possible to build a one-second instrument. The miniture, precise, graduated circle for this

theodolite was developed by the National Bureau of

Standards and the University of Rochester designed the ' telescope.

The theodolite has a heighth of thirteen inches with horizontal and vertical limbs of four inches diameter. The instrument alone weighs 13% pounds and com-

plete with tripod it weighs twenty-eight pounds. The

least reading for both horizontal and vertical limbs is one second, however the reading can be estrmated to

one tenth second. It has an Optical plummet and all

motions are completely enclosed. The inverting teles- has a power of twenty seven. The telescope has an eye distance of seven.millimeters, a clear aperatuye; of

fortyimillhmeters and a resolving power of four sec-

onds. The lengthslf the telescope is 6% inches over-

all and it has an interchangeable glass reticle with

horizontal and vertical stadia. The telescope reticles

can be illuminated for night reading.

The graduated circles are read by the principle of meaeuring relative angular distances or displacements of

two diametrically Opposite portions of a limb. The Letter

patent granted to Heinrich Wild of Switzerland in 1908

describes this method.

Angular and linear increments which are very small may be considered equal and both can be measured by lin-

ear measuring devices. One second of are only represents 0.000009 inch on the four inch limb of theodolite and

the device by which this is measured is called an optic-

al.micrometer. The four inch limbs of the theodolite are divided

into twenty minute intervals and.the micrometer scale is

ten.minutes long and divided into 600 parts corresponding

to single seconds. The mdcrameter need only cover an interval of ten minutes since a coincidence of limb

graduations is had each ten minute displacement of limb,

due to the fact that the motions of the limb-images are

in opposite directions.

Theodolites of this type are designated as universal instruments due to the fact that they are compact

and can be used for any type of work. The chief military

advantage of this instrument is the speed with which ob-

servers can take sights due to the optical plummet which

eliminates the plumb bob and the difficulties and delays which arise when it is used in the wind. The fact that

the horizontal and vertical circles as well as the plate

and control levels can be read from.the eye end of the

instrument is also a time saver.

This instrument was designed for second order tri-

angulation, specifically, for establishing triangulation

nets for fire control purposes. The observer is usually vulnerable to enemy fire while taking sights so the prep-

erty of being able to make rapid observations is especial-

ly valuable. Present tests have proved that first order

accuracy may be obtained from this instrument. CIKPTER FIVE

THE MICROMETER MICROSCOPE

The repeating theodolite and the direction instru-

ment are the two types of instruments used in triangula-

tion for measuring horizontal angles.

The reppeting theodolite is similar tt(the engineers transit in operation, and in triangulation work the same

‘ angle is read numerous times and a mean is computed to

be equal to the angle.

The direction theodolite determines the angle in one observation by means of a micrometer microscope instead of

a vernier. This instrument has a circle graduated to five

minute divisions which can be turned and clamped in any

position independently from.the lower portion of the

instrwment.

Set on the frame are two or three micrometer micro-

scopes equidistant and which determine the fractional parts of the five minute spaces. Large instruments }{L~ usually have a small index microscppe intended for read-l; 12W

ing the degrees and five minute divisions and the sub- 3“

divisions are read by the micrometers.

Two or more graduations can be seen in the field of

each microscope. In the focal plane of the eyepiece of

each microscope is a micrometer screw which moves a

frame carrying a set of cross hairs. These are in the

form of an.I or consist of two parallel hairs set far enough apart so that a line of the graduation will not

quite fill the space between them. The pitch of the screw

and the focal length of the objective of the microscope

are so related that the whole number of turns equals

one space on the graduated circle. The head of the mic-

rometer is graduated so that the angles can be read to

seconds or to fractions of a second. In the field of

view is a notched scale for counting the whole turns

of the screw. In the center of the scale is a deeper

notch which represents the zero point of the micro-

meter readings. For any point of the telescope the

direction is read by simply turning the micrometer until

the hairs are symetrical with respect to the preceding

line of graduation, reading the scale of the micrometer

head and adding this reading to the direct reading of

the degrees and minutes of the circle. For the purpose

of checking the reading and also to determine the error

of the microscope,a reading is also taken on the next

following graduation.

A micrometer which is not in proper adjustment will

record a difference in the preper number of screw turns

'which difference is referred to as the " run of the

:micrometer ". This causes and error in the reading which

is known as the " error of the run ".

The method most commonly used to correct this is to

assume that the error in the setting of the microscope

heirs and in reading-is accidental and adopt a compen-

sation procedure. I CHAPTER SIX

THE LATEST TYPE ALTIMETER

The most recent development in altimeters is one made by the Wallace & Tiernan Co.,Belleville, New Jersey.

This altimeter consists of a pressure sensitive primary element whose motion is transmitted to a tooth- ed sector by means of a Beryllium Capper spring pivot .

The sector is connected similarly to a pivot post and meshed with a pinion mounted on the pointer shaft which turns in a jeweled bearing. Backlash between the sector and the pinion is eliminated by a filament attached to the sector by a light wire Spring which winds around a sheave mounted on the pointer shaft and having the same pitch as the pinion. Uniform tension between sector and pinion is hereby maintained at all points of engage- ment. This construction keeps friction at a minimum and the pointer responds to the slightest movement of the capsule.

The pressure sensitive capsule is designed to fol- low this curved line function so that equal changes in altitude result in approximately equal pointer movements.

This instrument was tested by Kissam of Princeton

University and found to have a range of from minus 1000 to plus 3000 feet. The graduations are spaced at ten foot intervals and the nearest foot can be accurately estimated. /\£ue.s .- 7" ..

The 100 foot marks are indicated on the dial,while the in

strument is held at standard pressure,and the ten foot marks are interpolated between them. The values in feet

are correlated with barometric pressure in accordance with Smithsonian.Meteorological Table # 51 of 1931 which

is based on the density of dry air of 50 degrees F. at

sea level at latitude 45 degrees 29 minutes. Zero eleva-

tion is set at 29.9 inches of Mercury. The instrument is operated by metal strips rather than gears. The instru- is Jeweled and shows no tendency to backlash.

The two base method of precision altimetry is con-

sidered the most accurate. As illustrated on page an altimeter is placed at lower base station of known elev-

tion below the area which is to be surveyed and another is placed at the upper base whose elevation is also known and which is above the area to be surveyed. The variation between the! altitudes is preportional be-

tween the actual air density and the density for which the instruments were calibrated. The correct altitude is obtained by adjustments in preportion to the altitude differences.

The altimeters located at the vertical extremes of the are. are read simultaneously with the intermediate altimeter. The difference between the intermediate and the upper and lower base altimeters are indicated by‘I and‘Y respectively. 2 is the amount by ‘which the sum.of X and Y'differ from the vertical distance between the bases. The true elevation of the (ﬁg/DER BASE 4 TWO BASE MET 1900 OF MEG/SE ALT/M57???”

//V7’£PMED/A7'E C5771 .

LOWER BASE ’ intermediate altimeter is determined by dividing z in pro portion to X'and I; The base stations should be within

10 miles in distance and 200 and 300 feet in elevation.

This altimeter can be used for Reaphysical and geo- logical prospecting, tapographic surveying, control surveys for aerial mapping, highway, pipeline,and transmission 1ine location, reconnaissance and eXploration, conservation and reclamation projects, and water supply and sewerage studies. W’& T SENSITIVE ALTIMETER

FIELD TEST RESULTS

S I N G L E B A S E M E T H O D

Test 1 Test 2 Test 3

Maximum horizontal 10 miles 5 miles 9 miles distance from base

Maximum vertical 200 feet 228 feet 128 feet distance from.base

number of Observations 208 14 82

Awerage error 261 feet 1.9 feet 2.4 feet

Maxims: error 11.6 feet 7.8 feet '16e3 feet

112 sass £21222

Test 4 Test 5 Test 6

Horizontal base . 10 miles 8 to 25 miles 8 males separation

'Vertical base 200 feet 900 to 2900 feet 11? feet separation

numberof Observations 104 136 24

Average error 1.6 feet 3.4 feet 1e4 feet

Maximum.error 6.7 feet 14.3 feet 5.2 feet CHAPTER SEVEN

THE MOST’RECENT TYPE DRAFTING MACHINE

The latest types of drafting machines which,by use ofa linkage system,combine the functions of triangles,

T-square, scales and protractor, have been greatly improved recently and include some interesting features.

_ . Tempered steel bands which keep the arms of the machine in alignment have been enclosed in rigid tub- lar struts, to protect them. There are two of these struts to each arm. ,

Contact feet under the control knob, in one type of machine, are faced with saphires so that they will glide smoothly without wear or smudging ever even the new, abrasive types of tracing paper.

A centralized control group on the control knob has an automatic uniform toggle clamp which permits selection of any desired baseline. Also in the control group is a push button which selects fifteen degree increments »for the rotation of the scale arms about

‘the control knob. In addition a vernier clamp is imp eluded to make possible the selection of intermediate angles of rotation.

Cartridge stabilizers, which counteract the effects of mavity when the drafting surface is tilted up to twenty degrees, can be attached to the upper and lower arms of the drafting or to both. 40

THE DRAFTING MACHINE

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WITH WEIGHT STABILIZER

CARTRIDGE STABILIZER The length of the two arms of the drafting machine should equal the radius of a semi-circle which will cover a selected drafting surface. Care must be used not to select a machine which is too large.

A weight stabilizer, which automatically compen- sates for the effect of gravity when the drafting surface is tilted from horizontal to vertical, can be attached to the upper ans. CHAPTER EIGHT

THE RECTOPLANOGRAPH

The rectoplanograph is a mapping instrument which

provides the accurate and rapid means of rectifying and

transfering planimetric detail from aerial photographs to maps and charts. Details can be quickly filled in

on aerial photographs after the major control points

have been established.

The instrument is based on the principle of the

camera lucida, with which the eye receives two super-

imposed images, one from a photograph and the other

from.a map manuscript. It also provides an Optical system,in.the form of a double prism and a group of

adjustments,allowing the map maker to plot from any

aerial photograph up to nine by nine inches, Photo-

graphs taken with any focal length camera from.four

inches up to twelve inches can be accommodated, with

the scale of the image varied to match that of the map, and angles of tip and tilt in the photographs can be compensated for.’

The rectoplanograph is portable and light and is

used on top of the drafting table.

" Index:marks on the eye-piece arbor of the instru-

ment permit adjustment of the eye-piece for focal lengths of 6,.8i, and 12 inches, which correspond to

the focal lengths of the cameras most commonly used 4.3

THE REC TOPLANO GRAPH for this work. Some other focal lengths are indicatdd by detents, however any desired length can be set.

The eye-piece and picture holder are supported on a vertical column, and may be raised or lowered through a smoothly operating slow motion control so that the scale Of the image may be varied as needed. The vertical adjustment provides a 2% times range of scale.

A ball and socket arrangement at the back of the picture holder provides a means by which the map maker can rectify the photographic image to compensate for angle errors introduced by tip and tilt. This adjustment provides a ready means for obtaining compensation~ for departures from the vertical ranging from.0 to 70 degrees.

The picture holder is equipped with two sizes of masks to hold aerial photographs ranging from.4 X 4 to 9 X 9 inches in size. Masks hold the picture flat against the holder. Fiducial marks on the holder permit accurate alignment of the picture with the Optical axis of the eye piece prism. The frame is hinged and fastened with a snap lock.

The rectoplanograph can also be used by the indus- trial designer in tracing or in superimposing new parts and sections on a drawing showing an intricate machine design. It can be used in re-tracing faded drawings accurately and can be used in a number of other applic- ations where accurate sketching is necessary. CHAPTER NINE

SURVEYING BY RADAR

Radar surveying of the earths surface has recent-

ly been accomplished at the Illinois Institute of Tech-

nology, Chigago.

Pulses of light are sent out which are reflected

back from the point whose position is to be determined

and the distance is measured by the time the light

takes to travel forward and back.

The light returning from the reflector falls on

a photo-multiplier,whose output is amplified,to produce

an illuminated spot on a cathode ray tube. Determining

the distance by the transit time of the pulse of light

is accomplished by auxiliary circuits which include a

local crystal-controlled oscillator. The circuits pro-

duce timing markers on the tube which can be made to match the illuminated spot produced by the returning

light.

Angles are measures by an engineers transit. The

Optical system.makes use of a single parabolic search-

light mirror, the outer portion Of which is used for

the transmitted beam. The equipment is portable and

Operates alternatively from storage batteries or frame. J

110 volt alternating current. i CHAPTER TEN

CONCLUSION

The glass reticles discussed in Chapter Two are a decided advancement in telescOpic pointing which were developed by EurOpean instrument manufacturers and which are now being manufactured in this country.

They are more durable Than the cross hairs and are easily cleaned. Older type instruments may be convert- ed from.the ring mounted cross hairs and fitted with glass reticles.

Ceated lenses are a very recent development which in a system.of six lenses produces approximately a 50 percent gain in light transmission. Existing instruments may be taken down, their lenses coated, reassemb- led and collimated but it is not economically advis- able. Coated lenses are such an improvement that no new instrument should be acquired which does not have thi s feature .

Tilting levels are such an improvement in second and third order leveling that the Dumpy and Wye levels are now Obsolete. These are so much faster and more accurate than existing types that no Others should be considered. Accurate results can be obtaindd by this type of level even when not in precise adjustment’by taking ObservatiOns in two positions, the true level being the mean of the two readings. The one-second theodolite is comparable in size to the Wild and Tavistock theodolites. The Speed and con- venience in use and rugged and compactness in design make this instrument very desireable. This instrument was designed originally for military purposes but it is adapted to any work for which a transit or theodolite can be used.

Micrometer microscOpes or direction theodolites are generally used on important triangulation such as the higher grades of work of th U.S. Coast and Geodetic

Survey and the Giclogical Survey. The advantage of this instrument is that it is rapid and accurate. It also eliminates the systematic error due to the action Of clamps and tangent screws which characterizes the repeating instrument. ‘

Precision altimetry today is being used for vertical control more than ever before because of the improved techniques and instruments. GeOphysical prospecting, aerial mapping:and recconnaissance surveying all have the advantage of greater speed, smaller parties, high order accuracy and lower costs. Surveying by radar is a very recent adaptation and at the present time is Of I010 academic interest than a practical advantage to the engineer because equipment is scarce and expensive. BIBLIOGRAPHY

American GeOphysical Union, TRANSACTIONS; Volume 26,

Part I, August 1945.

Berger, 6.1... and Son.Inc., BOOKLET ON BERGERS TILTING LEVEL, 1945, Best... P1348

Birchal, Harold Frank, MODERN SURVEYING FOR THE CIVIL

ENGINEER, Cleveland, The Sherwood Press, 1935 Pp524

Bouchard, Harry, SURVEYING, Scranton, International Textbook ’co. , 1935, prnissae

Breed, Charles L., and Boamer, George L., THE PRINCE-

PLES OF SURVEYING, New York, John Wiley 8. Sons,

1908.

Breed, Charles 1., and Homer, George 1... HI- SUR" VEYING,’ New York, John Wiley a Sons, Inc., 1940, prxii - 6'74, Vol. II.

David White 00., BULLETIN N0. 1047, Surveying-Instru-

ments , Milwaukee.

Davis, Raymond E. ,and Boots, Francis 3., SURVEYING

THEORY AND PRACTISE, New York,~ McGraw-Hill Book

00.,1940, prxvii - 1052.

Encyclopedia Brittanica, Vol 21, 1929, Chicago. French, Thomas E., A MANUAL OF ENGINEERING DRAWING, New York, McGraw-Hill Book Co., 1911, vaiii -

622.

Giesecke, Frederic E., TECHNICAL DRAWING, New York,

The MacMillan CO., 1936, Pp xii - 564.

Good, Warren R., AN INTRODUCTION TO THESIS WRITING? Ann Arbor, The Ann Arbor Press,193'7, Pp4'7.

Kissam, Philip, SURVEYING AND MAPPING, Vol. V, NO. 1,

Jan. 1945.

Merriman, Thaddeus and Wiggin, Thomas 3., AMERICAN

CIVIL ENGINEERS HANDBOOK,New York, John Wiley

8:. Sons, Inc., 1930, Pp2263.

Newsom, N. William,STANDARDC-3 FOR THESIS WRITING, Scran- ton, International Textbook Co.,1936, Pp3l.

SeBoyar, Gerald E. ,MANUAL FOR REPORT AND THESIS WRITING, New York, F.S.Crofts a 00., 1929,vai - 5'7.

Svenson, Carl Lars, mAFTING FOR ENGINEERS, New York,

1927, priv - 554.

The New International Encyclopedia, Ed. II, Vol. 21,

New York, 1930, Dodd,Mead & Co.

Wallace a Tiernan Products Co., TECHNICAL PUBLICATION #250A,7A,3A, Belleville, N.J. ' ‘ \ any 12¢ N .l h... s. . I. (UV... ye i e. u I...

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