Transits

1. HOW TO USE A
TRANSIT
TABLE OF CONTENTS
Transit History and Description page 3
Transit Setup page 4
Leveling Screws page 4
Checking Transit Accuracy page 6
Adjusting the Level Tube page 7
Measuring a Horizontal Angle page 11
Measuring Vertical Angles page 11
Reading the Vernier (figures A and B) page 12
As Stated in the Berger Instruments PDF:
Setting Points in Line page 12
Plumbing page 13
Slopes and Rates of Grades page 14
Grade Line for a Sewer page 14
Figure 1A - Positioning and Leveling the Instrument page 8
Figure 2A - Move Transit and Mark Rods page 8

2. Figure 3 - Adjusting the Level Tube page 7
Figure 4 - Adjusting the Horizontal Cross-Hair page 8
Figure 5A - Level plane below both elevations page 9
Figure 5B - Level plane is between both elevations page 9
As Stated in the Berger Instruments PDF:
Figure 14 - Points on a property boundary page 11
Figure 15 - Plumbing a vertical column page 13
Figure 16 - Definitions of grades and slopes page 14
Figure 17 - Grade line for a sewer page 14
Figure 18 - Typical layout for sewer batter boards page 14
Figure 19 - Offset Grade Stakes for a 12 foot driveway page 15

3. Transit Definition = A surveying
instrument used to measure
horizontal and vertical angles.
Transit Setup
1. Setup tripod so head (TOP PLATE) is
about level. This will make
leveling the instrument easier.
Drive tripod legs into the
ground by stepping on each
leg.
Transit History and Description:
2. Release horizontal clamp screw and
The notable Philadelphia manufacturer, William J. Young, turn instrument until the
was the self-proclaimed, and generally accepted, inventor of telescope bubble is directly
the first American transit in the year 1831. Young's new over a pair of leveling screws.
transit enabled the perpetuation of a straight line by means 3. Turn both screws either toward or
of turning, or "transiting" the telescope on its horizontal away from each other. One
screw will then be loosened by
axis. The primary purpose of a transit is to measure
the same amount that the
horizontal and vertical angles. The theodolite serves the other is tightened until bubble
same purpose as the transit, and they have many similar is level.
features. The major difference between a transit and a
NOTE:
theodolite is that a transit features measuring circles which
are constructed only of glass and are observed through THE LEFT THUMB RULE STATES THAT
MOVING YOUR LEFT THUMB
magnifying optics to increase the accuracy of angular
TO THE LEFT…AS YOU MOVE
readings. Circles, one vertical and one horizontal, are used YOUR RIGHT THUMB TO THE
for these measurements. The lower transit plate carries the RIGHT…WILL CAUSE THE
graduated circle and the upper transit plate carries the BUBBLE TO MOVE LEFT.
verniers for reading the angles on this circle.The vertical MOVING YOUR LEFT THUMB
TO THE RIGHT…WHILE YOUR
circle, fixed to a horizontal axis that is part of, and at 90
RIGHT THUMB MOVES TO THE
degrees to a telescope, lets the telescope rotate in a vertical LEFT…WILL CAUSE THE BUBBLE
plane. The alidade, or the framework that supports the TO MOVE TOWARD THE RIGHT
telescope axis, has a vertical axis (spindle) attached to its
4. Turn the telescope 90 degrees until
base, which allows the alidade to rotate with respect to the over the other set of leveling
horizontal circle. Level vials, attached to the alidade, are screws or when you have only
used to make the spindle vertical (in line with gravity), so three leveling screws then
that measurement of horizontal angles can be measured. A over the third screw and
adjust.
level vial is also attached to the telescope and provides the
gravity index to measure vertical angles. 5. Repeat the leveling procedure above
alternating from one pair of
For leveling the instrument, there are two spirit levels on the leveling screws to the other
upper plate, one parallel and the other at right angles to the until transit is level.
horizontal axis. The spirit level that is parallel to the axis is
the most important because it controls the position of the
horizontal axis of the telescope. In the transit, the leveling is done by means of four
(sometimes three) leveling screws. The upper plate usually carries a compass-box with
a magnetic needle and a circle graduated to half degrees, so that the transit may also

4. be used as a compass. The lower spindle fits into a socket in the leveling base. This
base is provided with a ball-and-socket joint and four leveling screws. Both the upper
and lower plates are provided with clamps to hold them in any desired position as well
as tangent screws for setting the telescope, or the circles, in an exact position. Under
the center of the ball-and-socket joint hangs a short chain to which the plumb-line is
attached. The entire head of the instrument can be shifted a fraction of a centimeter
laterally with reference to the tripod and thus can be readily
The Leveling Screws placed exactly over a point on the ground. The horizontal
circle is usually graduated either to half-degrees or to 20-
Mount the instrument on the minute spaces. The graduations are usually numbered from
tripod, lock the telescope in 0° to 360° by two rows of figures running in opposite
place with the lock directions. In some older transits they are numbered from 0°
to 360° in a right-hand direction and, by a second row of
figures, from 0° each way to 180°. The transit is usually
provided with opposite pairs of verniers. The normal or direct
position of the transit is with the upper clamp and its tangent
lever and line up screw nearest the observer and the focusing screw of the
the telescope vial in position telescope on top of the telescope. When the instrument is
#1 as shown. Then grasp turned 180° in azimuth from the direct position, and the
screws A & B so that both telescope is inverted (turned about its horizontal axis), it is
thumbs are moving in opposite said to be in the reversed position. This is often spoken of as
directions, either toward each “plunging” the telescope. If the telescope is provided with a
other or away from each other. long level tube and a vertical circle or arc, it is called an
Note that the bubble moves in “Engineer's Transit”, or “Surveyor's Transit”. If it does not
the same direction as your left have these attachments, it is called a “Plain Transit”.
thumb. Keep about half the
Transit Setup:
length engaged. When the
bubble is centered in position In setting up the transit, first give the tripod sufficient spread
#1, turn the instrument and to insure steadiness, keeping the plate of the instrument
observe the vial in position #2. approximately level, the plumb-bob being nearly over the
Now center the bubble in point. Then, if the instrument is so far from the point that it
position #2 using only screw C. cannot be brought into the correct position by pressing the
The instrument should now be legs into the ground, the instrument should be lifted bodily
leveled, but to be certain, and moved so that the plumb-bob is practically over the
double-check. Rotate the point. Press the legs firmly into the ground, doing this in
instrument 180º so the vial is such a manner as to gradually bring the plumb-bob
reversed. accurately over the point. The nuts on the tripod legs should
be tight enough so that the legs are just about to fall of their
own weight when raised from the ground. If they are loose,
the instrument is not rigid. If they are too tight, it is not in a
stable condition and may shift any moment.
If the point is on sloping ground, it is often convenient, and

5. Quick Method
No Need for Plumb Bob
1. Open the tripod and position roughly over the
traverse point.
insures greater stability, to set two legs downhill 2. Remove the tribach from the instrument (note:
and one uphill. When the instrument is over the not all tribach's are removable).
point, the tripod head can be leveled
3. Attach the tribach to the tripod.
approximately without moving the instrument
away from the point by moving one, sometimes 4. While looking through the optical plumb, grasp
two, of the tripod legs in an arc of a circle about two of the tripod legs. Position the cross-hairs of
the point. Nothing but practice will make one the optical plumb directly in the center of the
traverse point.
expert in setting up the transit.
5. Stick the legs into the ground firmly and
forcefully.
It is desirable to bring the instrument very nearly
level by means of the tripod. This is really a 6. Using the clamps on the tripod legs, adjust the
length of the legs to make the tribach level.
saving of time because under ordinary
conditions it takes longer to level up by the 7. Check the optical plumb and make any
leveling screws than by the tripod. It also saves adjustments necessary to ensure that the tribach is
time on the next setup to have the leveling still over the traverse point.
screws nearly in their mid position. If the transit 8. Place the instrument on the tribach and lock
is set by means of the tripod, say, within 0.01 or down.
0.02 ft. of the point, the exact position can be
9. Using the thumb screws on the tribach and the
readily reached by means of the shifting head,
fine-tuning bubble on the instrument, level the
which may be moved freely after any two instrument.
adjacent leveling screws are loosened. When the
transit has been brought directly over the point, 10. Check the optical plumb and if necessary,
loosen the instrument from the tripod and slide the
the leveling screws should be brought back to a
instrument over the traverse point without spinning
bearing. In the first (rough) setting, the plumb-
the instrument. Re-tighten, re-level and check
bob should hang approximately an inch above again.
the point, but when the shifting head is used, it
should be lowered to within about 1/8 inch or New method eliminates the need for the plumb bob
by using the tribach and leg clamps to get a rough
less of the point.
horizontal and vertical position that is much closer
to the final position than the older method. You
Level in two directions using the plate levels,
ask, "If the tripod is not level during initial view of
each in line with opposite pairs of leveling the traverse point through the optical plumb, why
screws. Rotate horizontal circle 180° to check if doesn't the tripod move off the traverse point when
bubbles stay level. If necessary, try again from adjusting the legs to level tribach?” Answer: The
this position. If you cannot get the bubble to unique design of the tripod. When the legs are
stay centered 180° apart, you'll need to adjust adjusted, the top plate does not just move
horizontally to the ground, but moves about a
the plate level (see the instructions in the next
sphere. If the top plate is pointed at the traverse
paragraph). This is commonly needed, so make point, then the traverse point is relatively close to
sure you have the tool that exactly fits the the radius of the sphere. No matter how the legs
adjustment screws. are changed in order to level the tribach, the
optical plumb will still be pointed relatively close to
This is how to adjust the plate bubble level: the traverse point. Because the tripod is closer to
After centering the bubble in one position, level and positioned almost directly over the point
before the instrument is mounted, the final leveling
done with the thumb-screws does not take very
much time.

6. rotate the horizontal circle 180°. If this is off, you need to adjust that plate level. Use
the leveling screws to correct the bubble half way to center, then use the smooth part
of a 5/64" drill bit, or the tool, to adjust one or the other side of the plate level up or
down to get the bubble centered. You'll be turning the top and bottom capstan screws
the same direction to move that side of the bubble up (counter-clockwise) or down
(clockwise). Note that you have to turn one to loosen it and the other in the same
direction to tighten it in a new position.
In leveling the instrument, first turn the plates so that each plate level is parallel to a
pair of opposite leveling screws. Each level is therefore controlled by the pair of
leveling screws which is parallel to it. Great care should be used in leveling. The
screws must not be loose as this will cause the plates to tip and perhaps to move
horizontally which would change the position of the plumb-bob over the point. On the
other hand, they must not be too tight as this will not only injure the instrument but
will cause errors due to strains in the metal. To level the instrument, grasp one pair of
opposite screws between the thumbs and forefingers and turn so that the thumbs
move either toward each other or away from each other. In this way, one screw is
tightened as much as the other is loosened. The motion of both screws must be
uniform; if they bind, the one which is being loosened should be turned faster. If this
does not appear to remedy matters, then the other pair of screws is binding and
should be loosened slightly. Only experience will teach one to level an instrument
quickly and correctly. It may be convenient for beginners to remember that in leveling
the instrument the bubble will move in the same direction as the left thumb moves.
After one bubble has been brought nearly to the center of its tube, the other bubble is
centered in a similar manner by its pair of leveling screws. Instead of trying to center
one bubble exactly before beginning on the second one, it is better to get both of
them approximately level, after which first one bubble and then the other may be
brought to the center. After the instrument is leveled, the plum-bob should be
examined to see that it has not been moved from over the point during the process of
leveling.
Checking Transit Accuracy:
A general test should be conducted upon receipt of the transit and every three months
thereafter to determine whether the transit requires adjusting by a New England Laser
technician (800-362-8734). The test should determine if there are any alignment
problems, such as confusion of horizontal and vertical angle change.
· Set up transit in an area that is as level as possible and which is about 220 feet
long. Place two matching level rods or two pieces of strapping in the ground
about 200 feet apart with the faces toward each other. Position and level the
instrument so that the distance from the instrument to each rod is the same
measure. (Fig. 1A)

7. · Take a reading on each rod with the instrument (or mark each piece of strapping
where the cross-hair is sighted).
1. Setup the instrument and
· Move transit to another spot on the line and approximately level the bubble over each
take readings and mark both rods again. pair of opposite leveling screws. Then
(Fig. 2A) carefully center the bubble over one pair of
screws, as shown in view A, Fig. 3. 2.
· The difference between the marks on the Rotate the instrument 180°. If the bubble
rod will be the error of the instrument. The remains centered, then the level tube is
differences should be the same ( A -A' in proper adjustment. If the bubble does
should equal B - B'). The difference between NOT remain centered note the movement
A - A' and B - B' is the instrument error at of the bubble away from center (view B, Fig.
200 feet. The error needs to be corrected. 3). 3. Bring the bubble half the distance
back to the center of the tube by turning
the capstan nuts at one end of the tube
ADJUSTING THE LEVEL TUBE— The vertical axis (view C, Fig. 3). 4. Relevel with the leveling
of rotation of the instrument is the basis for all screws (view D, Fig. 3) and rotate the
adjustments to the engineer’s level. When instrument again. Repeat Step 3 above if
the instrument is set up and leveled the vertical the bubble does not remain at the center of
axis of rotation and the longitudinal axis of the the tube. 5. Check the final adjustment by
level tube should be perpendicular to one another. noting that the bubble remains in the
If they are not perpendicular, then the vertical axis center of the tube during the entire
cannot be made truly vertical. Adjustment of the revolution about the vertical axis
level tube makes the axis of the level tube
perpendicular to the vertical axis.
1. With the instrument carefully leveled,
sight one end of the horizontal cross hair
on a well-defined point at least 250 feet
away. Turn the telescope slowly about the
vertical axis, using the slow motion screw.
FIG. 3 If the cross hairs are in adjustment, the
horizontal cross hair will stay on the point
through its entire length. 2. If it does not
stay on the point, loosen two adjacent
ADJUSTING THE HORIZONTAL CROSS-HAIR—
reticle capstan screws and rotate the reticle
For the horizontal cross-hair to lie in a truly
by lightly tapping two opposite screws. 3.
horizontal plane when the instrument is leveled,
Sight on the point again. If the horizontal
the horizontal cross-hair must be perpendicular
cross hair does not stay on the point
to the vertical axis. Fig. 4
through its entire length, rotate the ring
again.

8. Fig. 4
Out of adjustment
In Adjustment
If the telescope bubble is level, the horizontal cross-hair will indicate a horizontal, or
level, line of sight. Thus all objects in line with the horizontal cross-hair are at the
same elevation as the telescope. With a transit-level, if the telescope clamp (alongside
the telescope) is loosened and the leveling latch opened, pointing the telescope up and
down will indicate a vertical line. This action is used in “plumbing” flagpoles, columns,
etc.
Elevation Leveling: There are two things that can be a little confusing when you first
use a transit. The first occurs when the instrument is placed in its most common
position, which is at a higher elevation than the elevations being measured. Usually in
this position, the higher the number you read, the lower the elevation. Unfortunately,
this isn't always the case.
To find the difference of elevation between two points which can be observed from one
position, set up and level your instrument about midway between these points. Be sure
that a leveling rod held on both opposite points can be read when your telescope is
level. Each point should not be greater than 150 to 200 feet away from the instrument
or you may have difficulty reading the rods. The height of the line of sight (horizontal
cross-hair) above or below each of the points is found by reading the rod. When the
level plane is below both elevations, subtract the lower number (B) from the higher one
(A) to find the difference in elevations. Fig. 5A When the level plane is between
elevations, add the two differences together to get the total difference in elevation
between A and B. Fig. 5B.

9. Fig. 5A
Fig. 5B
When the points whose difference in elevation is desired are far apart or when their
difference in elevation exceeds that obtainable from one set-up of the instrument due
to the limits of the rod lengths, the above process must be repeated by using
intermediate points.
The rod reading on a point whose elevation is known or assumed is called a backsight
and the rod reading on a point whose elevation is sought is called a foresight. In
general, there is only one backsight for any set-up of the instrument but there may be
a number of foresights, depending upon the number of points which are within the
sighting limits, whose elevations are desired.
Points whose elevations are determined and which are marked in a characteristic
manner are called benchmarks. Benchmarks are usually described in order that they
may be recovered and used at any subsequent period.
Your benchmark should be a firm and definite point such as a bolt on a water hydrant,
a spike in the root of a tree, a corner of a stone monument, or a chisel square on a
ledge, and should be located outside the construction area. For a large job, several
benchmarks in convenient locations are helpful. The grades may then be carried
directly to the job by using the “difference in elevation” method illustrated below.

10. Leveling is the process of determining the elevation of points on, above or below the
surface of the earth. Many different types of surveys can be used depending on the
desired results. Differential and profile leveling are two surveying methods that are
very useful for agricultural and horticultural projects. They are both useful for planning
and layout of projects. For planning purposes they are used to provide the information
needed to develop the maps, charts, and drawings necessary to lay out buildings,
roads, drains, etc. They can also be used for layout. Layout is used to establish the
boundaries, lines, and elevation for the construction of those structures. Differential
and profile leveling rank next to the measurement of distance in importance as a
surveying technique.
Depending on the particular project, the reference line may be a single straight
segment, as in the case of a short sewer line, a series of connected straight segments
which change direction at angle points, as with transmission lines, or straight
segments joined by curves, which occur with highways and railroads. The required

11. alignment for any proposed facility will normally have been selected as the result of a
preliminary design, which is usually based on a study of existing maps and aerial
photos. The reference alignment will most often be the proposed construction
centerline, although frequently offset reference lines are used.
To stake the proposed reference line, key points such as the starting and ending points
and angle points will be set first. Then intermediate stakes will be placed on line,
usually at 100-ft intervals. Metric stakes are usually placed at 10-, 20-, 30-, or 40-m
spacing, depending on conditions. Distances for staking can be taped or measured
using the electronic distance measuring (EDM) component of a total station instrument
operating in its tracking mode.
To measure or lay out angles, the instrument must be set over a point on the ground.
A hook, centered below the instrument, is provided for suspending a plumb bob. The
plumb bob is used to place the level directly over a particular point. To set up over a
point, suspend the plumb bob from the instrument. Secure it with a slip knot. Move
the tripod and instrument so that the plumb bob appears to be over the point. (p)
Press the legs of the tripod into the ground. Lower the plumb bob by moving the slip
knot until it is about 1/4 inch above the point on the ground. The final centering of
the instrument can be made by loosening any two adjacent leveling screws and slowly
shifting the instrument until the plumb bob is directly over the point. Retighten the
same two leveling screws that were previously loosened and level the instrument. Shift
the instrument on the base plate until the plumb bob is directly over the point. Check
the levelness of the instrument. Adjust, if necessary.
Measuring a Horizontal Angle. After leveling the instrument over the point of an
angle, called its vertex, loosen the horizontal clamp screw. Rotate the instrument until
the vertical cross-hair is nearly in line with a distant point on one side of the angle.
Tighten the clamp screw. Then turn the tangent screw until the vertical cross-hair is
exactly in line with the point.
If the point is above or below the line of sight, release the locking lever and tilt the
telescope to sight the point. By hand, turn the horizontal circle scale to zero. Loosen
the clamp screw. Swing the telescope until the vertical cross-hair lines up with a point
on the other side of the angle. Tighten the horizontal clamp screw. Then turn the
tangent screw for a find adjustment, if necessary. Read the degrees on the circle scale
and minutes on the vernier scale.
Measuring Vertical Angles. To measure a vertical angle, the instrument is carefully
leveled and the telescope is directed to the object. When the object is observed in the
telescope, the vertical motion is clamped and by means of the vertical tangent screw,
the middle horizontal cross-hair is set exactly on the point. The reading on the vertical
arc is the vertical angle. When the point is above the horizontal plane, the angle is
called a positive angle or angle of elevation; when the point is below the horizontal

12. plane, the angle is called a negative angle or
angle of depression. In the survey notes, they
are designated by a + sign and a - sign,
respectively. If the instrument's line of sight
and the axis of the telescope bubble are not in
adjustment, it is impossible to obtain a correct
vertical angle with the vertical arc only. If the
instrument has a full vertical circle, the error
can be eliminated by reading the vertical angle
first with the telescope direct and then
reversed and the average of the two readings
can be determined.
Reading the Vernier
Figure A shows a circle and double vernier on a builders' transit. Note that the circle is
divided into degrees (units of 60') and that 12 spaces on the vernier equal 11 spaces
on the graduated circle. This indicates that the least count is 60' x 1/12, or 5'.
Therefore, the smallest angle that can be read is to 5'. Figure B shows the same circle
and vernier when the telescope has been revolved to a new position. If the telescope
has been turned clockwise, the index points to a reading of 66° plus some minutes.
Reading in the same direction (to the left of the index), we see that the fourth space on
the vernier coincides with a space on the graduated circle. Therefore, since the least
counts is 5', 4 x 5 = 20'. Hence the reading is 66° 20'. In a similar manner, if the
telescope had been turned counterclockwise, the angle is read
293° 40'.
As Stated in the Berger Instruments PDF:
Setting Points in Line
Points A and B are two points which are on a line such as a property boundary (Fig. 14).
When erecting a fence, additional points between A and B, and also on the other side
of B from A, may be needed. Center and level your instrument over point A and sight
on point B. Bring the vertical hair exactly on point B by means of the horizontal clamp
and tangent screw. A pencil held vertically at B is useful to show this point. Keeping the
horizontal clamp tightened, depress the telescope to set points between A and B on
line.

13. If the top of a stake cannot be seen, when you come to set point C, sight with the aid
of a plumb bob, first, to find where to drive the stake, and second to note the point on
the top of the stake. If it is necessary to continue this line beyond point C, center and
level your instrument over point B, sight point C and continue this procedure.
9.2 Plumbing
Instruments of the transit-level type can be used to advantage in plumbing such
objects as building walls, columns, and flagpoles. Set and level your instrument at a
point which is about as far away from the object as the object is tall. Select a point at
the base of the object which is to be plumbed. Sight your telescope on this point and
set the intersection of cross wires directly on it. By raising your telescope, you will find,
through use of the line of sight and the cross-hairs, whether or not the object is
plumb. If it is plumb, the object will appear not to move away from the cross-hair
intersection. To completely check the plumb of the object, set the instrument at a
position which is at an angle of 90° from the first position of the instrument and repeat
the procedure. A corner post of a wood frame building is shown (Fig. 15) being
plumbed.

14. Slopes and Rates of Grades
Several methods of defining slopes are shown above (Fig. 16).
1. Horizontal distance to rise (or fall) in vertical; thus the grade is 4 to 1, or, more
completely, 4 horizontal to 1 vertical.
2. Rise or fall for each 100 feet horizontal. The slope, if extended for 100 feet
horizontally would rise 25 feet. This is referred to as a 25% slope.
3. Rise or fall for each one foot horizontal. Again, this would be designated as 0.25
foot per foot, or three inches per foot.
4. Angle of slope is 14 degrees, 2 minutes (14° 2').
11.1. Grade Line for a Sewer
Steps to find the slope necessary for a household sewer connection are shown below
(Fig. 17). Notice that the invert or flow-line of the pipe is used in each instance. The
invert is the bottom of the pipe and this line is the reference from which grades are
commonly given.
11.2. Batter Boards for a Sewer
Sewers are normally placed at some depth below the surface of the ground, so batter
boards are placed somewhat higher above the invert grade. A typical layout for sewer
batter boards is shown below (Fig.18). The vertical strip nailed to the horizontal board
is set with one edge along the line of the sewer. A nail is placed in this vertical strip at
an even number of feet above the invert. By stretching a taut line between these nails,
the sewer line is easily referenced. A board notched about 8 feet from its bottom is
used to set the pipe.

15. Distance measurement can be done using the stadia hairs of the reticle.
Read the length of a level rod shown between the stadia hairs. The distance to
the target is 100 multiplied by . The distance between point A and point B is L.
L = 100 x
On a rod showing inches & eighths, you must convert the inches & eighths to the

16. decimal form of a foot to get a correct reading. This is done by taking the partial
foot reading, say 7 1/8 inches, and converting by dividing by 12.
= 7.125"/12 = .59 FT.
L = .59 x 100 = 59 FT.
If were 1' 7 1/8" then would equal 1.59 ft. & L = 159 ft.
New England Laser & Transit Company
8 Reeds Mill Road, Newport, NH 03773
800-362-8734