surveying iii (topographic and geodetic surveys) - Modern Prepper

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5-37. General. GPS baseline solutions are usually generated through an iterative process. Fromapproximate values of the positions occupied and observation data, theoretical values for the observationperiod are developed. Observed values are compared to computed values and an improved set ofpositions occupied is obtained using least squares minimization procedures and equations that modelpotential error sources. This section discusses general postprocessing issues. Due to the increasingnumber and variety of software packages available, consult the manufacturer's guidelines whenappropriate. Processing time is dependent on the accuracy required, the available software, the computerhardware, the data quality, and the amount of data. In general, high-accuracy solutions, crude computersoftware and hardware, low-quality data, and high volumes of data will cause longer processing times.The user must take special care when attempting a baseline formulation with observations from differentbrands of GPS receivers. It is important to ensure that observables being used for the formulation of thebaseline are of common format. The common data-exchange formats required for a baseline formulationexist only between receivers produced by the same manufacturer, even though there are someexceptions.5-38. Processing Techniques. The capability to determine positions using GPS is dependent on theability of the user to determine the range or distance of the satellite from the receiver located on theearth. There are two general techniques used to determine this range--pseudoranging and carrier beatphase measurement.a. Pseudoranging. The observable pseudorange is calculated from observations recorded during aGPS-S. The observable pseudorange is the difference between the time of signal transmission from thesatellite (measured in the satellite time scale) and the time of signal arrival at the receiver antenna(measured in the receiver time scale). When the differences between the satellite and the receiver clocksare reconciled and applied to the pseudorange observables, the result is corrected pseudorange values.The value found by multiplying this time difference by the speed of light is an approximation of the truerange between the satellite and the receiver. The value can be determined if ionosphere and tropospheredelays, ephemeris errors, measurement noise, and unmodeled influences are taken into account duringpseudoranging calculations. The pseudorange can be obtained from either the C/A-code or the moreprecise P-code.b. Carrier Beat Phase Measurement. The observable carrier beat phase is the phase of the signalremaining after the internal oscillated frequency generated in the receiver is differenced from theincoming carrier signal of the satellite. The observable carrier beat phase can be calculated from theincoming signal or from observations recorded during a GPS-S. By differencing the signal over a periodor epoch of time, the number of wavelengths that cycle through the receiver during any given specificduration of time can be counted. The unknown cycle count passing through the receiver over a specificduration of time is known as the cycle ambiguity. There is one cycle-ambiguity value persatellite/receiver pair as long as the receiver maintains continuous phase lock during the observationperiod. The value found by measuring the number of cycles going through a receiver during a specifictime, when given the definition of the transmitted signal in terms of cycles per second, can be used todevelop a time measurement for transmission of the signal. Again, theEN0593 5-34
time of transmission of the signal can be multiplied by the speed of light to yield an approximation of therange between the satellite and receiver. The biases for carrier beat phase measurements are the same asfor pseudoranges, although a higher accuracy can be obtained using the carrier. A more exact rangebetween the satellite and receiver can be formulated when the biases are taken into account duringderivation of the approximate range between the satellite and the receiver.5-39. Baseline Solution by Linear Combination. The level of accuracy achievable by pseudorangingand carrier beat phase measurement in both absolute and relative positioning surveys can be improvedthrough processing that incorporates differencing of the mathematical models of the observables.Processing by differencing takes advantage of correlation of error (such as GPS signal, satelliteephemeris, receiver clock, and atmospheric-propagation errors) between receivers, satellites, and epochs,or combinations thereof, to improve GPS processing. Through differencing, the effects of the errorscommon to the observations being processed are greatly reduced or eliminated. There are three broadprocessing techniques that incorporate differencing--single, double, and triple. Differenced solutionsgenerally proceed in the following order: differencing between receivers, between satellites, andbetween epochs.a. Single Differencing. There are three general single-differencing processing techniques--betweenreceivers, between satellites, and between epochs.(1) Between Receivers. Single differencing the mathematical models for pseudorange (C/A- orP-code) carrier phase observable measurements between receivers will eliminate or greatly reducesatellite clock errors and a large amount of satellite orbit and atmospheric delays.(2) Between Satellites. Single differencing the mathematical models for pseudorange or carrierphase observable measurements between satellites eliminates receiver clock errors. Single differencingbetween satellites can be done at each individual receiver during observations as a precursor to doubledifferencing and to eliminate receiver clock errors.(3) Between Epochs. Single differencing the mathematical models between epochs takesadvantage of the Doppler shift (apparent change in the frequency of the satellite signal by the relativemotion of the transmitter and the receiver). Single differencing between epochs is generally done in aneffort to eliminate cycle ambiguities. Three forms of single-differencing techniques between epochs areintermittently integrated Doppler, consecutive Doppler counts, and continuously integrated Doppler.b. Double Differencing. Double differencing is a differencing of two single differences. Doubledifferenceprocessing techniques eliminate clock errors. There are two general double-differencingprocessing techniques--receiver time and receiver satellite.5-35 EN0593
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SUBCOURSEEN0593EDITIONAUNITED STATE
Page 3 and 4:
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
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differential leveling. The theodoli
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additional runs are made due to exc
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Figure 4-2. Wild N-3 Precision Leve
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(8) Loosen the azimuth clamp (13),
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4.7. Miscellaneous Equipment. In ad
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(2) To check for gross errors in th
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(a) (1) Begin by completing the inf
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Set up and level the instrument. Re
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Figure 4-8. Sun and Wind Code(5) Th
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(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 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 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 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
Page 250 and 251: Figure 6-3. Approach Surfacesa. Fed
Page 252 and 253: . Federal Aviation Regulation-77, S
Page 254 and 255: Table 6-4. Airport Obstruction Accu
Page 256 and 257: A horizontal scale of 1:12,000 and
Page 258 and 259: Figure 6-4. Sample DA Form 5821 (Ai
Page 260 and 261: Figure 6-5. Sample DA Form 5822 (PA
Page 264: LESSON 6PRACTICE EXERCISEANSWER KEY
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