surveying iii (topographic and geodetic surveys) - Modern Prepper

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exercise extreme caution in applying GPS height determinations to projects that are based onconventional orthometric elevations.The heights obtained from GPS are in a different height system than those historically obtainedwith geodetic leveling. GPS data can be readily processed to obtain the ellipsoidal height. This is theheight above or below a simple ellipsoid model of the earth. Geodetic leveling gives rise to aorthometric height, often known as the height above the MSL. These heights are found on topographicmaps, stamped on markers, or stored in innumerable digital and paper data sets. To transform betweenthese height systems requires the geoid height. These height systems are related by the followingequation:Where--h = H + Nh = ellipsoidal heightH = orthometric heightN = geoid height5-27. Differential Error Sources. Error sources encountered in using differential GPS positioningtechniques are the same as for absolute positioning. In addition to these error sources, the user mustensure that the receiver maintains satellite lock on at least three satellites for 2D positioning and foursatellites for 3D positioning. When loss of lock occurs, a cycle slip (discontinuity of an integer numberof cycles in the measured carrier beat phase as recorded by the receiver) may occur. In GPS absolutesurveying, if satellite lock is not maintained, positional results will not be formulated. In GPS staticsurveying, if satellite lock is not maintained, positional results may be degraded resulting in incorrectformulations. In GPS static surveying, if the observation period is long enough, postprocessing softwaremay be able to average out loss of lock and cycle slips over the duration of the observation period andformulate positional results that are adequate. If this is not the case, reoccupation of the stations may berequired. In all differential-surveying techniques, if loss of lock does occur on some of the satellites,data processing can continue easily if a minimum of four satellites are tracked. Generally, the moresatellites tracked by the receiver, the more insensitive the receiver is to loss of lock. In general, cycleslips can be repaired.5-28. Differential Accuracies. There are two levels of accuracy obtainable from GPS using differentialtechniques. The first level is based on pseudorange formulations, while the other is based on carrier beatphase formulations.a. Pseudorange formulations can be developed from either the C/A-code or the more precise P-code. Pseudorange accuracies are generally accepted to be 1 percent of the period between successivecode epochs. Use of the P-code, where successive epochs are 0.1 millisecond apart, produces resultsthat are about 1 percent of 0.1 millisecond (about 1 nanosecond). Multiplying this value by the speed oflight gives a theoretical-resultant range measurement of around 30 centimeters. If using pseudorangeformulation with the C/A-code, results can be ten times less precise (a range-measurement precision ofaround 3 meters). Point-positioning accuracy for aEN0593 5-14
differential pseudorange solution is generally found to be in the range of 0.5 to 10 meters. Theseaccuracies are largely dependent on the type of GPS receiver used.b. Carrier beat phase formulations can be based on the L1, the L2, or both carrier signals.Accuracies achievable using the carrier beat phase measurement are generally accepted to be 1 percent ofthe wavelength. Using the L1 frequency where the wavelength is around 19 centimeters, the theoreticalresultant range measurement is 1 percent of 19 centimeters (about 2 millimeters). The L2 carrier canonly be used with receivers that employ cross correlation, squaring, or another technique to get aroundthe effects of AS.PART D - PLANNING PRECISE-POSITIONING SURVEYS5-29. General. Using differential carrier phase surveying to establish control for military projectsrequires operational and procedural specifications for a project-specific function of the control beingestablished. To accomplish these surveys in the most efficient and cost-effective manner and to ensurethat the required accuracy criteria are obtained, a detailed survey-planning phase is essential. Thissection defines global positioning system-survey (GPS-S) design criteria and other specifications that arerequired to establish control for survey projects.5-30. Planning a Control Survey. The first step in planning a control survey is to determine theultimate accuracy requirements. Survey accuracy requirements are a direct function of the project'sfunctional needs--the basic requirements needed to support the planning, engineering design,maintenance, and operations. This is true for GPS or conventional surveying in order to establish projectcontrol. Most military activities require relative accuracies (accuracies between adjacent control points)ranging from 1:1,000 to 1:50,000, depending on the nature and scope of the project. Few topographicprojects demand positional accuracies higher than the 1:50,000 level (second-order, Class I). Although aGPS-S may be designed and performed to support lower-accuracy project-control requirements, theactual results could generally be several magnitudes better than the requirement. Although higheraccuracy levels are easily achievable with GPS, it is important to consider the ultimate use of the controlon the project in planning and designing GPS control networks. Thus, GPS-S adequacy evaluationsshould be based on the project's accuracy standards, not those theoretically obtainable with GPS.a. Project Functional Requirements. Project functional requirements must include planned andfuture design and mapping activities. Control density within a given project is determined from factorssuch as planned construction, site plan mapping scales, master plan mapping scales, andartillery/aviation survey positioning requirements. The relative accuracy for project control is alsodetermined based on such things as mapping scales, design needs, and project types.b. Project Control Surveys. Project control surveys should be planned, designed, and executed toachieve the minimum accuracy demanded of the project's functional requirements. To most efficientlyuse resources, control surveys should5-15 EN0593
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SUBCOURSEEN0593EDITIONAUNITED STATE
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TERMINAL LEARNING OBJECTIVE:ACTION:
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Part G: Adjusting Precise-Positioni
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PART A - FIGURES OF THE EARTH1-1. T
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Figure 1-2. Flattening Fractiona. T
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1-3. Geoid. In geodesy, precise com
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point in the survey to provide the
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one side of a triangle and all of t
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Figure 1-10. Simple Triangulation N
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observation, contains a light sourc
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of a horizontal rod with a small sp
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The Airy theory, announced by G. B.
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Figure 1-15. Products of the Gravim
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a. If the shape of the earth was ex
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Figure 1-16. Single Astronomic Stat
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Figure 1-17. Astro-Geodetic Deflect
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Figure 1-19. Astro-Geodetic Datum O
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(c) The significance of a gravity-o
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absolute deflections of the vertica
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Figure 1-23. Preferred Datumsa. The
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1-17. The World Geodetic System. Be
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Figure 1-25. Using the Same Referen
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LESSON 1PRACTICE EXERCISEThe follow
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12. Which of the following is assum
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LESSON 1PRACTICE EXERCISEANSWER KEY
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THIS PAGE IS INTENTIONALLY LEFT BLA
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for all military and civilian activ
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i. Additional support for other top
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2-7. Status. At present, topographi
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in both. (North American Datum of 1
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water can impede leveling operation
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A field recording booklet. A single
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PART I - OFFICE WORK2-24. General.
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PART J - SURVEY COMMUNICATION2-28.
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length or side is known, and all th
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second-order, Class I net. The leng
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The number of observations required
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to perform the reconnaissance. Fail
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and cultivated, or fields may have
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e an alphanumeric symbol that is st
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2-53. Intervisibility of Stations.
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station is (K/2) 2 x 0.0676, or one
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Figure 2-8. Similar Triangles Solut
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2-54. Height of Obstructions. It is
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authorized to change the name, it s
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Figure 2-12. Cells Connected in Par
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added as the cells weaken. Three un
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Figure 2-16. Construction Details f
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2-60. Wooden Towers. When it become
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11. The face of the 5-inch signal l
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average line in a triangulation sys
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3-4. Slope Measurements. The slope
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strip as close as possible to its f
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. Sight along the tops of both of t
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Column 1. Record the station number
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stake to steady it. With the back o
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Figure 3-3. DA Form 4446 (Sample of
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micrometer in this optical system i
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laterally across the front of the e
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Figure 3-7. Horizontal Circle and M
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out of adjustment. If the index mar
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(1) In order to avoid instrumental
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location of the vertical circle on
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Figure 3-13. Open Traversec. Closed
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designate the exact point of refere
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example, a line with an azimuth of
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When adjusting a traverse that star
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11. The unit of graduation on a hor
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THIS PAGE IS INTENTIONALLY LEFT BLA
Page 150 and 151: differential leveling. The theodoli
Page 152 and 153: additional runs are made due to exc
Page 154 and 155: Figure 4-2. Wild N-3 Precision Leve
Page 156 and 157: (8) Loosen the azimuth clamp (13),
Page 158 and 159: 4.7. Miscellaneous Equipment. In ad
Page 160 and 161: (2) To check for gross errors in th
Page 162 and 163: (a) (1) Begin by completing the inf
Page 164 and 165: Set up and level the instrument. Re
Page 166 and 167: Figure 4-8. Sun and Wind Code(5) Th
Page 168 and 169: (10) Enter the interval between the
Page 170 and 171: Figure 4-9. Closed-Circuit River Cr
Page 172 and 173: Figure 4-11. Sample DA Form 5820 (R
Page 174 and 175: is 0. When the telescope is pointed
Page 176 and 177: stations. However, since all statio
Page 178 and 179: a. Complete the heading, as shown.b
Page 180 and 181: a. (1) Enter the date, as in the sa
Page 182 and 183: LESSON 4PRACTICE EXERCISEThe follow
Page 184 and 185: 11. The maximum length of site to o
Page 186 and 187: LESSON 4PRACTICE EXERCISEANSWER KEY
Page 188 and 189: PART A - GLOBAL POSITIONING SYSTEM
Page 190 and 191: 5-7. Pseudorange. A pseudorange is
Page 192 and 193: 5-15. Number of Pseudorange Observa
Page 194 and 195: i. Probable Error Measures. The acc
Page 196 and 197: Table 5-1. Representative GPS Error
Page 198 and 199: Table 5-2. Carrier Phase Trackinga.
Page 202 and 203: not be designed or performed to ach
Page 204 and 205: Table 5-3. GPS-S Design, Geometry,
Page 206 and 207: f. Multiple/Repeat Baseline Connect
Page 208 and 209: possible ionospheric and tropospher
Page 210 and 211: Figures 5-4. PDOP Versus Time PlotP
Page 212 and 213: e. Field Processing and Verificatio
Page 214 and 215: All carrier phase relative-surveyin
Page 216 and 217: time spent and the cost of conducti
Page 218 and 219: movement between occupation sites,
Page 220 and 221: 5-37. General. GPS baseline solutio
Page 222 and 223: (1) Receiver Time. This technique u
Page 224 and 225: NOTE: Repeated baselines should be
Page 226 and 227: 5-43. Loop Closure Checks. Postproc
Page 228 and 229: necessary to determine approximate
Page 230 and 231: This will ensure that future work w
Page 232 and 233: may (and usually does) far exceed t
Page 234 and 235: important in evaluating the overall
Page 236 and 237: i. Relative GPS baseline standard e
Page 238 and 239: LESSON 5PRACTICE EXERCISEThe follow
Page 240 and 241: 12. When the networking method is s
Page 242 and 243: LESSON 5PRACTICE EXERCISEANSWER KEY
Page 244 and 245: THIS PAGE IS INTENTIONALLY LEFT BLA
Page 246 and 247: FAR-77 obstructions. Aircraft-movem
Page 248 and 249: Figure 6-1. Imaginary SurfacesEN059
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Figure 6-3. Approach Surfacesa. Fed
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. Federal Aviation Regulation-77, S
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Table 6-4. Airport Obstruction Accu
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A horizontal scale of 1:12,000 and
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Figure 6-4. Sample DA Form 5821 (Ai
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Figure 6-5. Sample DA Form 5822 (PA
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