Survey (Page 1 to 56)

Preliminary Surveys

(also known as pre-engineering surveys, location surveys, or data gathering surveys) are used to collect measurements showing the location of natural features such as trees, rivers, hills, valleys, and the like and the location of manmade features such as roads, structures, pipelines, and so fourth.

Error Calculation

(distance off line in feet)/2 ------------------------------ 2 x (length of line in feet)

Parts of The Engineer's Transit Part 3

- A graduated circle, called the "vertical circle", mounted on the side of the telescope rotates with the telescope to show the angle above or below level (the vertical angle). This motion is controlled by the "vertical motion screw" and "clamp". - On most transits the telescope may be pointed backward by turning it upside down; this is called "flipping over" or "plunging". To turn the transit in this way was once called to "transit", from which the instrument got its name. Older instruments may not plunge, but are still called transits. - At one time a "theodolite" was the designation for a similar instrument with a telescope too long to plunge, but this distinction is now very vague. Today a theodolite may be merely a transit with more precise graduations and other improvements.

Benchmarked Field Notes

- All bench marks used in a field book should be described in the same book. A simple way is to put the descriptions together in the back of the book so that it is not necessary to repeat them in the body of the notes each time the bench is used. - When books are changed during work, and when bench marks are determined by lines run in two different books, each book should be cross-referenced to the others. Numbers should be given bound field books as soon as the books are received; large firms do this in the office before books are issued so that no two books can have the same number.

Errors in Reading Angles

- On the engineer's transit, as you are reading angles clockwise, you will always use the left-hand half of the vernier. The right-hand half indicates the minutes over the half-degree mark in the other direction; this difference is 8'. Or from another standpoint, since the index is 8' past one 184° mark, it is 22' short of the next one. Since there will be a mark on the right-hand side of the vernier that will correspond to a circle mark, as well as one on the left-hand side, it is important to read the left-hand side only. ** An error often made by beginners is to use the line in the graduated circle that corresponds to the vernier line as a reading. There is no relation between them.

Parts of The Engineer's Transit Part 4

- The "vertical index" is a marked metal plate attached to the side bracket, which indicates the vertical angle on the vertical circle - The "compass" is installed on the side or in the center of most modern instruments. Once the compass has been installed, free the magnetic needle by means of the "compass clamp screw". - When in use, the transit is mounted on a tripod. The "leveling head" provides a level platform, and the "leveling screws" are adjusted to put the leveling head in the level position when the foot plate is off level. - When setting the transit over a point most modern instruments have an "optical plummet" incorporate in to them. The optical plummet allows the instrument person the see a point on the ground that is directly below the instrument. When setting over a known point the student may use a plumb bob.

Parts of The Engineer's Transit Part 1

- The brackets, called "standards", are welded to a disk. This disk is marked at the edges with index marks. This disk rotates to measure, or turn, horizontal angles. - The "telescope" has two hand-turn knobs. - The "objective focus knob" focuses the telescope on the target or the rod. - The "eyepiece focus ring" is turned back and forth, to focus the crosshairs. - Some telescopes have an "eyepiece shutter", or metal disk that covers the eyepiece when it is not in use - The "sunshade" protects the lens of the telescope from reflecting direct sunlight back to the instrument man, which would make the image appear cloudy. - "Dust cap", fitted on the end of the telescope to protect the lens.

Bench Mark Levels

- The construction engineer is seldom required to run bench levels for any considerable distance, but on large construction projects there is some work of this type. The engineering surveyor must set bench mark levels before any other work can be done. Some of these level lines are hundreds of miles long. - With the engineer's level, levels may be run to an accuracy of 0.02 ft per mile, but 0.04 ft per mile is usually considered adequate, and some authorities consider 0.10 ft per mile as good as can be expected. A reasonable rate of progress is about four miles per day.

Construction Surveys

- The layout of proposed construction features - Provide line and grade for a wide variety of construction projects for example, highway, streets, pipeline, bridges, buildings, site grading, and the like. The construction layout marks the horizontal location (line) as well as the vertical location, or elevation (grade) for the proposed works. ** When commencing a construction survey, it is important that the surveyor use the same control survey points as were used for the preliminary survey upon which the construction design was based.

Parts of The Engineer's Transit Part 2

- The telescope, standards, and vertical circle, rotate together; this assembly is the "upper motion". The "horizontal circle", a ring graduated in degrees and fractions, is attached to a second rotating assembly, the "lower motion". - Movement of either of these assemblies,(upper motion, or lower motion), is controlled by a "clamp" and "motion screw". These are pairs of knobs, mounted near each other and usually nearly identical in appearance. - There are three motion screws, one corresponding to each clamp: the "vertical motion screw", the "upper motion screw", and the "lower motion screw". - Motion screws are also called "tangent screws". - The telescope rotates up and down on a pair of side shafts called "trunnions".

Care of the Instrument Person

- When you are the transit person, stand in a comfortable position; it is inefficient to bend your back and lean forward when reading the instrument. Your feet should be spread wide apart so that your eye is at the instrument level. A person over 5ft, 8in. tall may have to lean forward, but they should keep their back straight and support him selves by an arm on their knee. Attempting to stand up beside the instrument, twisting the head sidewise, is a mark of an amateur. - You should learn to keep both eyes open when looking through the telescope and magnifying glass. You can then locate targets in the field of view more easily, as one eye sees the crosshairs and the other eye the target, thus preventing eyestrain. If one eye is kept closed, it becomes painful in a very short time. - Hats and glasses should not interfere with the instrument

Mistakes by the Crew in Benchmark Leveling

1. Improperly raised rod. 2. Improper recording. 3. Anticipating readings.

Care of the Instrument

A transit is a rugged instrument when properly used. It will withstand heat, cold, rain, and even immersion in salt water. But since it is made of soft, noncorrosive metal, nearly any part can be damaged with the bare hands; some parts may be damaged by the pressure of two fingers. The pressure applied to the motion clamps and the leveling screws must be light but firm; the tips of the thumb and forefinger are sufficient. Oil should be applied sparingly or not at all; working parts should be lubricated with graphite when needed. Oil collects dust, and in cold weather becomes sticky.

Level Rods

Although the Philadelphia pattern rod is the most common, there are a wide variety of other rods used. Sectional rods, for folding and packing in an automobile, are available in various patterns, and some rods are graduated in feet and inches. ** For bench mark levels, a target on the rod provides greater accuracy. The rod-person is given instructions to lower or raise the target until it is on the crosshairs, and the rod-person himself reads the rod.

Differential Leveling

Elevations are determined by comparison of one point with another one nearby. The point of reference, called a bench mark, is a permanent point of known or assumed elevation. On a construction job, the owner's engineer often sets these points, and the contractor works from them. If there is no reference mark set when the preliminary survey is made, as is often the case on a building survey, the architect will indicate some point of reference, even though it may be a specification requirement that "floor shall be one foot above street curb." In this case the curb, at a specified point, becomes the engineer's bench mark.

Double Lines

For increased accuracy, bench mark levels are often duplicated at the time they are run. This may be done by using two turns rather than one and keeping a double set of notes; or by using two instruments reading the same turning point.

Line and Level

Horizontal lines are measured in a straight line. For accuracy in measuring, alignment by eye is sufficient for most building construction surveying. Lines measured to a point off line, as around a tree, may be adjusted.

Reciprocal Leveling

In order to minimize both instrument errors and curvature of the earth, plus and minus sights are equalized. Instrument error is proportional to distance, and may be equalized by making setups so that the total foresight and total back-sight distances are nearly equal.

Hand Signals

Most of these apply both to level and transit work, with slightly different meanings. l. Hold steady or all right 2. Move right or left 3. Give me a back sight 4. Give me a line 5. Plumb rod signal 6. Establish turning point 7. This is a turning point 8. Wave the rod 9. Face the rod 10. Reverse the rod 11. Boost the rod 12. Move forward move back 13. Up and down 14. Pick up the instrument 15. Come in **Of the signals not illustrated, the double center is important. It is used for extending the line accurately, and consists of rotating the range rod, similar to the "give me a line" signal, but the rod is rotated through the full 360°.

Operations of Head Chain Person

The person on a survey crew who determines the accuracy of the work and sets the pace. The equipment of the head chain-person consists of these tools: 1. The Chain. The zero end is attached to the left wrist (if right-handed) with a looped thong; thus they will not have to bend to pick up the end, and can carry the stakes in the same hand. 2. The hatchet, if the stakes are being used. 3. The range rod, if one is being used, is also carried in the right hand. If no points are to be set exactly on line, or if the distance is short enough that a plumb bob can be seen from the instrument. 4. The plumb bob is of brass with a removable steel tip to keep the point sharp when marking hard materials. 5. The stakes are carried in the left hand, or cradled in the left arm. 6. A machete may be carried in the belt or in a scabbard, if it is likely to be needed.

Distance

Unless otherwise stated, always refers to the distance as measured on a level line

Benchmarks

Vertical reference points that are of a known elevation and are permanent

Surveying

is the art and science of making field measurements on or near the surface of the earth. Survey field measurements include horizontal and slope distances, vertical distances, and horizontal and vertical angles. In addition to taking measurements in the field, the surveyor can derive related distances and directions through geometric and trigonometric analysis.

Planer Surveys

Surveys that ignore the curvature of the earth

Level Net

- In accurate work, levels are run from several directions, and each bench mark elevation determined from several lines. These lines are often of different lengths, and give different results. The elevations of all benches on the lines are adjusted by distributing the error in accordance with length of lines or number of turns. - It is probable that the error of any point on a line of levels is no greater than the error at the end. Many instances occur, however, where the contrary is true; you may run a line to a new bench mark and return to its origin with a small error, only later to find that the bench set is in error by an amount greater than the error of closure. The errors have been compensating.

Reading the Rod

- It is very important that the rod be plumb both ways; if it is a few inches out of plumb the reading will be in error. Normally, the rod-person stands behind the rod, balancing it with his fingers; the rod will balance, if there is no wind, in substantially a plumb position. To plumb the rod toward the instrument person, the rod-person rocks it slightly on the point, forward and back; this is waving the rod. The instrument person reads the lowest point on the rod that the crosshairs reach during this movement; this is the true reading. - The rod may be kept plumb either by attaching or holding a small level against it. These levels are either bullseye (round) or tube types, made for this purpose.

Turning Points

- On a paved road, a square marked on the pavement with yellow keel (lumber crayon) is customary, although if the rod is rocked on a flat surface, it rocks first on one edge and then on another, slightly changing the elevation. This is usually insignificant, and bench marks are made slightly rounded on top to avoid this error. A stake carried by the rod-person usually makes it possible to install the turn at the proper distance. - When a definite distance is being used between the setup and the turning point (150 ft. is typical), each person paces their distance. That is, the instrument person paces from the turn to the setup, and the rod-person paces from the instrument to the turn. For greater accuracy, all three hairs in the level may be read. The center hair gives the level reading, and the upper and lower hairs both check the center reading and give the distance. However, the ordinary engineer's level is not provided with these extra hairs, as they may result accidentally in erroneous readings.

Control Elevations

- On building construction jobs, even though large areas of site work may be involved, the contractor does their own control survey as well as the actual layout and grade stakes. Owner-builders, of course, must always do their own work or sublet it to a surveyor. - Benchmarks should be provided so that it is not necessary to use a turning point in order to set a grade at any location on the project. On long narrow work, like roads, benchmarks are normally set every 1000 ft. Since an instrument may be set up 300 ft from a benchmark and read 300 ft further, each point on the job may be as far as 600 ft from the nearest bench, so that this spacing is adequate. For building sites with a narrower dimension of fewer than 1000 ft, benchmarks may be set around the edge of the site; for larger jobs, they are needed within the area of the work. - It is important that all such points which are to be used for a later reference be checked by the closure as a level net; that is, that each of them is used for a turning point rather than merely determined by a single rod reading. In this way, any error will be detected in the final closure. The setting of benchmarks with a single reading, without moving the instrument, is a side shot; that is, it is not on the main line of the level system. Grade marks are usually set this way, but there is always a possibility of error since an error in reading the rod does not show up in the final closure.

The Engineer's Transit

- The transit is used to measure horizontal angles between lines, to measure angles upward or downward to inclined lines, to measure approximate distances by use of sighting on a rod, to establish elevations by using the telescope as a level, and to establish directions by a compass. - The engineer's transit is the most versatile and frequently used instrument for surveying. The engineer's transit refers to the engineer's instrument not the builder's transit-level, which is similar but lacks many of the features of the engineering instrument. - The transit is usually placed inside a foam-fitted transit box. The box has a carrying handle and, sometimes, a shoulder strap. The box may also have a place for a plumb bob, a compass, and a magnifier. - Tripod legs may be adjustable, so the length of the legs may be changed, or they may be fixed.

Closing the Horizon

- When all angles at one setup are measured and form a complete circle, the instrument man closes the horizon. Although seldom done in ordinary work, it serves as a check on the angles, since they should add up to 360°. - "All angles direct" refers to the fact that the telescope was in the upright, or normal, position. For precise work, both angles are turned this way, with the telescope flipped over, in the reverse position. This eliminates errors caused by the telescope moving up and down in a direction not perfectly plumb, with targets at different elevations.

Common Features of Note Keeping

1. All notations made in the field 2. All measurements of angles and distances should be written down as soon as they are made 3. When you make a drawing beforehand showing what dimensions should be, as for a layout of a house, do not let these dimensions become confused with the actual measurements you make 4. Record each page number in the upper right-hand of each right page 5. The instrument number should also be recorded in your notes

Some common errors and mistakes in level work caused by the crew are:

1. Bubble not centered. 2. Faulty focusing. 3. Interchange of plus and minus shots entering the readings in the wrong columns. 4. Reading the rod a foot in error. 5. Arithmetical errors. 6. Reading the back of the rod. A reading as much as 7 ft in error may result.

Here are some of the common sources of error on Benchmark Leveling.

1. Instrument not in adjustment. 2. Temperature variations in the instrument. 3. Wind. 4. Settlement of the instrument between shots. 5. Movement of the instrument during reading. 6. Variation of the turning point.

Surveys are usually performed for one of two reasons.

1. Surveys are made to collect data which can then be drawn to scale on a plan or map (preliminary surveys) 2. Surveys are made to layout dimensions shown on a design plan in order to precisely define the field location for the proposed construction facility

Chaining Pins

Are steel rods about l-ft long, with a loop in one end, painted red and white. They are sold in sets of eleven, fastened to a wire loop. The wire loop is worn on the crew person's belt. When conditions are suitable, they speed up the work, as they are lighter and easier to carry than stakes, and may be shoved into the ground instead of being driven. Some of the disadvantages of pins are: 1. The point to which the measurement is made is not as definite as on a stake. 2. In soft ground they are easily accidentally moved off true location. 3. In hard or frozen ground they are difficult to place. 4. In brush they may be stepped on before they are found.

Corrections

Chains are usually true length at a temperature of 68 degrees with a tension of 10 LB when fully supported, as when lying on a pavement. If the temperature is higher, the chain will be longer by about 0.01 ft for each 15 degrees increase in temperature; and for colder weather, it will be shorter by a corresponding amount. For accurate work, this should be taken into account.

Standardization

Chains can be checked by the U. S. Bureau of Standards for a fee. Some engineering firms keep a standardized chain to check other chains. For most construction surveys, new tapes are considered sufficiently accurate without checking against a standard.

ELEV. = HI - FS

From the height of the instrument, you may determine the elevation of any point by a rod reading on the point, or a point can be set at any desired elevation. For example, if the height of instrument is 10.00 ft and you want to set a point at elevation 8.00 ft, the rod reading must be the difference, or 10.00 ft--8.00 ft = 2.00 ft. After the first rod reading, all readings are subtracted from the height of instrument to determine the elevation of the point being read. These readings are called foresight (FS) or minus readings (sighting to an unknown elevation). In the conventional note system (Figure 16), these back-sight and foresight rod readings are shown in the second and fourth columns. It is important that you learn to use columns in this way, and mark them as shown.

Reading the Rod

In reading the rod, the last four operations determine the accuracy of the reading. These are listed here: 1. Check the bubble, which must be centered. 2. Read the rod. 3. Check the bubble, which must still be centered. 4. Then write the number in the book ** The bubble must be centered exactly when the final reading is made. It must therefore be adjusted for each reading, and the bubble must be read at center at least twice for each reading.

Chaining

Is a method of measuring horizontal distances with the use of a chain or chain tape. The term chain comes from the old surveyor's Gunter's chain, which was a 66 ft. link of chain used in England

The Add Tape or 101-ft Tape

Is also marked in feet, but only the last foot is graduated in tenths and hundredths of a foot. But the additional foot, graduated in tenths and hundredths, is included prior to the zero mark

The Fully Graduated Tape

Is marked in feet, all feet graduated in tenths and hundredths of a foot, To measure with a fully graduated tape one chain-person holds on the zero mark and the other chain-person reads the distance, which is graduated in tenths and hundredths

The Cut Tape or 100-ft Tape

Is marked in feet, with the first and last foot graduated in tenths and hundredths of a foot. To measure with a cut tape one chain-person holds on a foot mark and the other chain-person reads the distance on the first foot, which is graduated in tenths and hundredths

Left Thumb Rule

On the engineer's transit, the 0pposite leveling screws are turned at the same time. The leveling head is shifted by turning of these screws. Your thumbs should go toward each other or away from each other at the same time. Keeping the proper pressure on the screws is a matter of practice. Remember, the bubble on the transit plate level follows your left thumb.

The Horizontal Circle

On the engineer's transit, the angle is indicated both by number and marked divisions on the outer ring (horizontal circle on lower motion), and by the zero mark on the inner index (upper motion). The horizontal circle is usually marked in both directions from zero; clockwise from 0 to 360°, and counterclockwise from 0 to 180°, starting over again and running to 180°, but instruments vary. Since the angle can always be read clockwise, all references in this manual are to clockwise readings, or to angles turned in a clockwise direction. Transits are graduated so that the finest reading is 1', 30", or 20".

Geodetic Surveys

Surveys that cover a large geographic area-for example state or provincial boundary surveys-must have corrections made to the field measurements so that these measurements will reflect the curved (ellipsoidal) shape of the earth

Accuracy

The best accuracy accomplished with the methods here outlined is about 0.01 ft. in 100 ft. or 0.5 ft. in a mile. In most cases, this accuracy will not be attained. Measurements can be repeated with less difference than this, however, because a chain-person tends to repeat the same errors. If you use too much or too little pull, your error is uniform, and if the temperature does not change, temperature errors will not be discovered. ** You should be able to repeat the measurement of a 1200-ft distance with a difference of 0.15 ft or less

Chaining Along a Line

The head chain-person starts off with ten stakes, and tail chain-person with one. When 1000 ft. have been measured the head chain-person is out of stakes. The tail chain-person, who has been removing used stakes, give his stakes to the head chain-person, who can then measure another 1000 ft. an extra stake is in the ground when the transfer is made). In this way only the number of thousands of feet need be recorded

Layout Surveys

The layout of proposed property lines and corners as required in land division

Field Notes

The notes kept for land surveys and building construction layouts are drawings that show measurements and angles. Notes for many kinds of engineering mapping and construction have been reduced to routine, and are standardized by use of certain accepted symbols and methods of recording data, so an actual picture is not necessary.

Read in Thousands

The ordinary level rod may be readily read to thousandths at the distances encountered in building construction work, and there is no objection to doing so, if the level person feels the additional accuracy is useful. However, such reading must be consistent; if any readings are to be made in this way, all of them must be.

Operations for Rear Chain Person

The rear chain-person carries a plumb bob, and the stakes that he pulls up as he goes. 1. He stands at the rear stake as the chain passes by, picking it up as the end approaches him. When about 6 ft. to the end remains, he calls "chain" to tell the head chain-person he must stop after the next step. 2. As the chain passes through his fingers, he has his hand on his hip or thigh at such a location that when the end of the chain reaches his hand, the 100-ft mark will be approximately over the stake. 4. When the head chain-person turns, and again when necessary, the rear chain-person gives him line by signaling with the right hand, putting his eye over the line. 5. Since a chain cannot be held exactly on a point, the rear chain-person calls "good" when his mark is exactly right. 6. When the head chain-person calls "my side" or otherwise, to indicate another point to which measurement is made, the rear chain-person immediately lets go of the tape, pulls his stake, picks up his load and starts walking

HI = ELEV. + BS

This first measurement is a back-sight (BS)or plus reading (sighting to a known elevation), as it is added to the elevation of the bench mark to determine the elevation of the center of the instrument. The elevation of the instrument is the height of instrument, abbreviated as HI.

Self-Reading Rod

This measurement is made by reading the rod directly with the telescope, at the intersection of the crosshairs with the figures on the rod.. Such a rod, the common type, is called a self-reading rod. The vertical hair in the level should be just off the rod for this reading; if on the rod, it may interfere with the reading and if too far off it, some error may be introduced if the horizontal hair is not exactly horizontal, or if there is distortion in the instrument.

Breaking Chain

When the ground elevation difference between the ends of the chain is greater than 5 ft., it becomes impractical to use a plumb bob at the low end. Instead, stakes are set at shorter distances, so the distance to plumb will be less. Rather than set off several distances, such as 20 ft., 30 ft., 50 ft., and add them together, lay the chain out over the full 100 ft. and set stakes at even marks on the chain. In this way, no addition is necessary and there is less chance for error.

Using the Transit as a Level

When used for setting grade stakes, or for other work requiring many shots (readings) from each location, the transit requires more care in setting up if it is to rotate with the telescope remaining level. This adjustment is for speed and convenience; releveling the instrument for each reading does not affect the accuracy of the work. The popular idea, implied in some engineering texts, that a level will not do accurate work merely because the bubble goes off center when the instrument is rotating, is not true.

Engineering Surveying

activities involved in the planning and execution of surveys for the location, design, construction maintenance, and operation of civil and other engineered projects. ** does not include surveys for the retracement of existing land ownership boundaries or the creation of new boundaries; these activities are reserved for licensed property surveyors also known as land surveyors.

Control Surveys

establish reference points and reference lines for preliminary and construction surveys