Horizontal and vertical controls generated byland (geodetic) surveys provide coordinatedposition data for all surveyors. It is thereforenecessary that these types of surveys use first-order and second-order accuracies.Hydrographic SurveysHYDROGRAPHIC SURVEYS are made toacquire data required to chart and/or mapshorelines and bottom depths of streams, rivers,lakes, reservoirs, and other larger bodies of water.This type of survey is also of general importanceto navigation and to development of waterresources for flood control, irrigation, electricalpower, and water supply.As in other special surveys, several differenttypes of electronic and radio-acoustical instru-ments are used in hydrographic surveys. Thesespecial devices are commonly used in determiningwater depths and location of objects on thebottom by a method called taking SOUNDINGS.Soundings are taken by measuring the timerequired for sound to travel downward and bereflected back to a receiver aboard a vessel.TYPES OF SURVEYINGOPERATIONSThe practice of surveying actually boils downto fieldwork and office work. The FIELDWORKconsists of taking measurements, collectingengineering data, and testing materials. TheOFFICE WORK includes taking care of thecomputation and drawing the necessary informa-tion for the purpose of the survey.FIELDWORKFIELDWORK is of primary importance in alltypes of surveys. To be a skilled surveyor, youmust spend a certain amount of time in the fieldto acquire needed experience. The study of thistraining manual will enable you to understand theunderlying theory of surveying, the instrumentsand their uses, and the surveying methods.However, a high degree of proficiency in actualsurveying, as in other professions, depends largelyupon the duration, extent, and variation of youractual experience.You should develop the habit of STUDYINGthe problem thoroughly before going into thefield, You should know exactly what is to be done;how you will do it; why you prefer a certainapproach over other possible solutions; and whatinstruments and materials you will need toaccomplish the project.It is essential that you develop SPEEDand CONSISTENT ACCURACY in all yourfieldwork. This means that you will need practicein handling the instruments, taking observationsand keeping field notes, and planning systematicmoves.It is important that you also develop the habitof CORRECTNESS. You should not accept anymeasurement as correct without verification.Verification, as much as possible, should bedifferent from the original method used inmeasurement. The precision of measurement mustbe consistent with the accepted standard for aparticular purpose of the survey.Fieldwork also includes adjusting the instru-ments and caring for field equipment. Do notattempt to adjust any instrument unless youunderstand the workings or functions of its parts.Adjustment of instruments in the early stages ofyour career requires close supervision from asenior EA.Collection of Engineering DataThe collection of ENGINEERING DATA isa part of SEABEE surveying. Engineering datais actually any information that is essential forefficient construction. Most of your fieldwork,such as running a traverse, leveling, and determin-ing cuts and fills, may be classified underthis category. However, compiling these fieldmeasurements and converting them into a com-mon medium that will be of value to the engineerrequires skill that can only be attained throughlong experience. Although the planning andorganization will generally be handled by theengineering officer or by a senior EA, the actualcollection of engineering data will generally bedelegated to you; hence, it is to your advantageto understand the procedures early in your career.This job may take a combination of fieldwork andoffice work. If the same quality of the desiredinformation can be found from sources other thanactual fieldwork, do not hesitate to use them; ifnecessary, use spot checks to verify certain points,depending upon the source.Each project requires the study of a differentset of engineering data, so it is up to theengineering officer or the senior EAs to devise aworkable method of compilation that will suiteach particular project. It is essential that thecompiled data be complete in all respects as11-4
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