surveying iii (topographic and geodetic surveys) - Modern Prepper

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Table 5-1. Representative GPS Error-Measurement Statistics for Absolute Point Positioning(continued)PART C - DIFFERENTIAL PRECISE POSITIONING5-19. Reducing Errors. Absolute positioning, as discussed earlier, will not provide the accuraciesneeded for most survey control projects due to existing and induced errors. To eliminate errors andobtain higher accuracies, use GPS in a differential-positioning mode. The terms relative and differentialhave similar meanings. Relative is used when discussing one thing in relation to another. Differential isused when discussing the technique of positioning one thing in relation to another. Differentialpositioning requires that at least two receivers be set up at two stations (usually one is known) to collectsatellite data simultaneously to determine coordinate differences. This method positions the two stationsrelative to each other (hence the term relative positioning) and can provide the accuracy required forbasic land surveying.5-20. Code Pseudorange Tracking. Differential positioning (using code pseudorange) is performedsimilarly to code-pseudorange tracking for absolute positioning. Some of the major uncertainties areeffectively eliminated or minimized. This process results in absolute coordinates of the user on theearth's surface. ErrorsEN0593 5-10
in range are directly reflected in resultant coordinate errors. Differential positioning is not so concernedwith the absolute position of the user but with the relative difference between two user positions, that aresimultaneously observing the same satellites. Since errors in the satellite position and atmospheric-delayestimates are effectively the same at both receiving stations, the errors cancel each other to a largeextent.5-21. Correcting Errors. A pseudorange correction (PRC) can be generated for each satellite beingobserved. If a second receiver is observing at least four of the same satellites and is within a reasonabledistance, it can use these PRCs to obtain a relative position to the known control point since the errorswill be similar. Thus, the relative distance (coordinate difference) between the two stations is relativelyaccurate regardless of poor absolute coordinates. For example, if the true pseudorange distance from aknown control point to a satellite is 100 meters, and the observed or measured pseudorange distance is92 meters, then the pseudorange error or correction is 8 meters for that particular satellite. In effect, theGPS-observed baseline vectors are no different from azimuth/distance observations. As with a totalstation, any type of initial-coordinate reference can be input to start the survey.5-22. Global Positioning System Coordinates. The GPS coordinates will not coincide with the user'slocal-project datum coordinates. Since differential-survey methods are only concerned with relativecoordinate differences, disparities with a global reference system used by the NAVSTAR GPS are notsignificant for topographic purposes. Therefore, GPS coordinate differences can be applied to any typeof local-project reference datum (for example, NAD 27 or NAD 83).5-23. Carrier Phase Tracking. Differential positioning using carrier phase tracking uses a formulationof pseudoranges. The process becomes somewhat more complex when the carrier signals are tracked sothat range changes are measured by phase resolution. In carrier phase tracking, an ambiguity factor isadded, which must be resolved to obtain a derived range. Carrier phase tracking provides a moreaccurate range resolution due to the short wavelength (about 19 centimeters for L1 and 24 centimetersfor L2) and the ability of a receiver to resolve the carrier phase down to about 2 millimeters. Thistechnique has primary application to engineering, topographic, and geodetic surveying and may beemployed with either static or kinematic surveys. There are several techniques which use the carrierphase to determine a station's position. These surveying techniques include static, rapidstatic, kinematic,stop-and-go kinematic, pseudokinematic, and on-the-fly (OTF) kinematic/RTK. Table 5-2 lists thesetechniques and their required components, applications, and accuracies.5-11 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
Page 146 and 147: LESSON 3PRACTICE EXERCISEANSWER KEY
Page 148 and 149: 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 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 198 and 199: Table 5-2. Carrier Phase Trackinga.
Page 200 and 201: exercise extreme caution in applyin
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
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FAR-77 obstructions. Aircraft-movem
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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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