TOPOGRAPHIC SURVEYSThe purpose of a TOPOGRAPHIC SURVEYis to gather survey data about the natural andman-made features of the land, as well as itselevations. From this information a three-dimensional map may be prepared. You mayprepare the topographic map in the office aftercollecting the field data or prepare it right awayin the field by plane table. The work usuallyconsists of the following:1. Establishing horizontal and vertical controlthat will serve as the framework of the survey2. Determining enough horizontal locationand elevation (usually called side shots) of groundpoints to provide enough data for plotting whenthe map is prepared3. Locating natural and man-made featuresthat may be required by the purpose of the survey4. Computing distances, angles, andelevations5. Drawing the topographic mapTopographic surveys are commonly identifiedwith horizontal and/or vertical control of third-and lower-order accuracies.ROUTE SURVEYSThe term route survey refers to surveysnecessary for the location and construction oflines of transportation or communication thatcontinue across country for some distance, suchas highways, railroads, open-conduit systems,pipelines, and power lines. Generally, the pre-liminary survey for this work takes the form ofa topographic survey. In the final stage, the workmay consist of the following:1. Locating the center line, usually marked bystakes at 100-ft intervals called stations2. Determining elevations along and acrossthe center line for plotting profile and crosssections3. Plotting the profile and cross sections andfixing the grades4. Computing the volumes of earthwork andpreparing a mass diagram5. Staking out the extremities for cuts and fills6. Determining drainage areas to be used inthe design of ditches and culverts7. Laying out structures, such as bridges andculverts8. Locating right-of-way boundaries, as wellas staking out fence lines, if necessarySPECIAL SURVEYSAs mentioned earlier in this chapter,SPECIAL SURVEYS are conducted for a specificpurpose and with a special type of surveyingequipment and methods. A brief discussion ofsome of the special surveys familiar to youfollows.Land SurveysLAND SURVEYS (sometimes called cadastralor property surveys) are conducted to establishthe exact location, boundaries, or subdivision ofa tract of land in any specified area. This type ofsurvey requires professional registration in allstates. Presently, land surveys generally consistof the following chores:1. Establishing markers or monuments todefine and thereby preserve the boundaries of landbelonging to a private concern, a corporation, orthe government.2. Relocating markers or monuments legallyestablished by original surveys. This requiresexamining previous survey records and retracingwhat was done. When some markers or monu-ments are missing, they are reestablished followingrecognized procedures, using whatever informa-tion is available.3. Rerunning old land survey lines to deter-mine their lengths and directions. As a result ofthe high cost of land, old lines are remeasured toget more precise measurements.4. Subdividing landed estates into parcels ofpredetermined sizes and shapes.5. Calculating areas, distances, and directionsand preparing the land map to portray the surveydata so that it can be used as a permanent record.6. Writing a technical description for deeds.Control SurveysCONTROL SURVEYS provide “basic con-trol” or horizontal and vertical positions of pointsto which supplementary surveys are adjusted.These types of surveys (sometimes termed geodeticsurveys) are conducted to provide geographicpositions and plane coordinates of triangulationand traverse stations and the elevations of benchmarks. These control points are further used asreferences for hydrographic surveys of the coastalwaters; for topographic control; and for thecontrol of many state, city, and private surveys.11-3
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