A Summary of the Data Analysis for Halifax GPS Precision Approach Trials Transport Canada Aviation/Cougar Helicopters Inc. University of New Brunswick

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1 A Summary of the Data Analysis for Halifax GPS Precision Approach Trials Transport Canada Aviation/Cougar Helicopters Inc. University of New Brunswick Attila Komjathy and Richard B. Langley Geodetic Research Laboratory University of New Brunswick Fredericton, NB E3B 5A3 Canada Presented at the Technical University of Budapest March 1996

2 Outline of the Presentation Introduction Step 1: Evaluating the Ashtech ground truth system. Step : Software development assessing the Trimble LDGPS solutions based on Ashtech PNAV solutions. Step 3: Development of statistics and analysis of results. Conclusions Recommendations

3 Objective: to provide evidence that Trimble local differential GPS (LDGPS) can be used for Special CAT I precision runway. Equipment: a Sikorsky S-76A helicopter equipped with Trimble TNL 31 DZUS GPS avionics receiver & Ashtech LM-XII GPS geodetic receiver; base station equipped with Trimble TNL-8G GPS landing system & Ashtech LM-XII GPS geodetic receiver. Data collected: Trimble real-time differential solution & simultaneous Ashtech raw data at base station and onboard for 73 at Halifax International Airport in Feb/March 199. Method used to meet objective: the independent Ashtech solution is used as ground truth with which we compared the Trimble LDGPS solution.

4 Transport Canada Aviation/Cougar Helicopters Inc. GPS Precision Approach Trials Sikorsky S-76A helicopter equipped with Trimble TNL 31 DZUS GPS avionics receiver & Ashtech LM-XII GPS geodetic receiver

5 Airfield of Halifax International Airport

6 Step 1. : We used three different solutions to validate the Ashtech solution: - C/A-code/carrier phase solution (PNAV), - Carrier-phase smoothed C/A-code solution (PNAV), - Postprocessed differential smoothed C/A-code solution (PPDIFF). Figure 1: 1 Shows an example of the comparison between the three solutions along with the estimated position accuracy of the Ashtech solution. Figure : Shows an example of the comparison between the three solutions computed from the raw data without cycle slip editing & checking for data quality. Figure 3: 3 Gives an indication about how noisy the solution and data are, and how good PNAV thinks the solution is. Conclusion from step 1.: 1 Estimated position accuracy from Ashtech data is lower than expected. Why? Because pseudorange observations are biased by multipath; carrier-phase ambiguities are not resolved; and observation periods are too short.

7 Estimated Latitude Differences Referenced to C/A-Code/Carrier Phase Solution (5: 3-GPS) :56. 3:3.5 3:51. :18.5 :6. 5:13.5 5:1. 6:8.5 6:36. 7:3.5 7:31. 7:58.5 8:6. 8:53.5 9:1. 9:8.5 1:16. Latitude differences (m) 1:3.5 11:11. 11:38.5 1:6. 1: :1. Time in minutes and seconds C/A-code/carrier phase (PNAV) minus smoothed C/A-code solution (PNAV) C/A-code/carrier phase (PNAV) minus postprocessed differential smoothed C/A-code solution (PPDIFF) Estimated position error computed by C/A-code/carrier phase solution ( sigma,pnav) Estimated Longitude Differences Referenced to C/A-Code/Carrier Phase Solution (5:3- GPS) Longitude differences (m) :56. 3:3. 3:5. :17. :. 5:11. 5:38. 6:5. 6:3. 6:59. 7:6. 7:53. 8:. 8:7. 9:1. 9:1. 1:8. 1:35. 11:. 11:9. 11:56. 1:3. 1:5. 13:17. Time in minutes and seconds C/A-code/carrier phase (PNAV) minus smoothed C/A-code solution (PNAV) C/A-code/carrier phase (PNAV) minus postprocessed differential smoothed C/A-code solution (PPDIFF) Estimated position error computed by C/A-code/carrier phase solution ( sigma,pnav) Height differences (m) Estimated Height Differences Referenced to C/A-Code/Carrier Phase Solution (5:3-GPS) :56. 3:. 3:8. :1. :. 5:6. 5:3. 5:58. 6:. 6:5. 7:16. 7:. 8:8. 8:3. 9:. 9:6. 9:5. 1:18. 1:. 11:1. 11:36. 1:. 1:8. 1:5. 13:. Time in minutes and seconds C/A-code/carrier phase (PNAV) minus smoothed C/A-code solution (PNAV) C/A-code/carrier phase (PNAV) minus postprocessed differential smoothed C/A-code solution (PPDIFF) Estimated position error computed by C/A-code/carrier phase solution ( sigma,pnav) Figure 1

8 Estimated Latitude Differences Referenced to C/A-Code/Carrier Phase Solution (5:3-GPS) Latitude differences (m) # of satellites tracked :56. 3:3.5 3:51. :18.5 :6. 5:13.5 5:1. 6:8.5 6:36. 7:3.5 7:31. 7:58.5 8:6. 8:53.5 9:1. 9:8.5 1:16. 1:3.5 11:11. 11:38.5 1:6. 1: :1. Time in minutes and seconds C/A-code/carrier phase (PNAV) minus smoothed C/A-code solution (PNAV) C/A-code/carrier phase (PNAV) minus postprocessed differential smoothed C/A-code solution (PPDIFF) # of satellites tracked at a particular epoch Estimated Longitude Differences Referenced to C/A-Code/Carrier Phase Solution (5:3- GPS) Longitude differences (m) # of satellites tracked :56. 3:3.5 3:51. :18.5 :6. 5:13.5 5:1. 6:8.5 6:36. 7:3.5 7:31. 7:58.5 8:6. 8:53.5 9:1. 9:8.5 1:16. 1:3.5 11:11. 11:38.5 1:6. 1: :1. Time in minutes and seconds C/A-code/carrier phase (PNAV) minus smoothed C/A-code solution (PNAV) C/A-code/carrier phase (PNAV) minus postprocessed differential smoothed C/A-code solution (PPDIFF) # of satellites tracked at a particular epoch Estimated Height Differences Referenced to C/A-Code/Carrier Phase Solution (5:3-GPS) Height differences (m) # of satellites tracked :56. 3:3. 3:5. :17. :. 5:11. 5:38. 6:5. 6:3. 6:59. 7:6. 7:53. 8:. 8:7. 9:1. 9:1. 1:8. 1:35. 11:. 11:9. 11:56. 1:3. 1:5. 13:17. Time in minutes and seconds C/A-code/carrier phase (PNAV) minus smoothed C/A-code solution (PNAV) C/A-code/carrier phase (PNAV) minus postprocessed differential smoothed C/A-code solution (PPDIFF) # of satellites tracked at a particular epoch Figure

9 Solutions (A) & (B) in metres Comparison of Three Different Solutions of Estimated Heights Differenced over Time (5:3-GPS) Solution (C) in metres :56. 3:. 3:5. :. :8. 5:16. 5:. 6:1. 6:. 7:8. 7:36. 8:. 8:3. 9:. 9:8. 9:56. 1:. 1:5. 11:. 11:8. 1:16. 1:. 13:1. Time in minutes and seconds C/A-code/carrier phase solution (A) (PNAV) Smoothed C/A-code solution (B) (PNAV) Postprocessed differential smoothed C/A-code solution (C) (PPDIFF) S/N in db S/N For SV#5, Elevation = 5 Degrees (Base & Airborne Receiver) # of epochs S/N for SV#5 (airborne) Loss-of-lock indicator (airborne) S/N for SV#5 (base) Loss-of-lock indicator (base) Accuracy Assessment Provided By PNAV (5: 3-GPS) :56. 3:.5 3:53. :1.5 :5. 5:18.5 5:7. 6:15.5 6:. 7:1.5 7:1. 8:9.5 8:38. 9:6.5 9:35. 1:3.5 1:3. 11:.5 11:9. 11:57.5 1:6. 1:5.5 13:3. r.m.s. of the carrier phase residuals (m) Chi** test Time in minutes and seconds Figure 3

10 Step.: - We used the Ashtech solution as a benchmark against the Trimble DGPS solution. - Software development that performs the analysis: - use aircraft velocity to interpolate aircraft position between epochs, - use of geoidal model that accounts for geoidal undulation, - use aircraft velocities to compute cross-track error and vertical error. Figures & 5 : Show examples of the comparisons between the two sensors. Conclusions from step.: - All 73 were able to be processed. - Trimble solutions show distinct jumps both in cross-track and vertical sense which could be due to: - sudden change in the # of satellites tracked, - delay in airborne receiver solution updates.

11 Runway Threshold Approach 1:1-GPS6 Ashtech position error, crosstrack and vertical error (m) Comparison Between Ashtech and Trimble DGPS Solutions (1:1-GPS6) Time (UT) in minutes and seconds 36:38 36:59 37: 37: 38:3 38: 38:6 39:8 39:9 39:5 :1 :33 :55 1:16 1:38 1:59 :1 : 3: 3:5 3:7 :8 :3 :5 5:13 5:35 5:57 6:18 6: 7:1 7:3 7:5 8:6 8:7 8: Aircraft altitude (feet) Distance from runway threshold (nautical miles) Ashtech position error ( sigma) Cross-track error Vertical error Aircraft altitude Comparison Between Ashtech and Trimble DGPS Solutions (1:1-GPS6) Time (UT) in minutes and seconds Ashtech position error, crosstrack and vertical error (m) :38 36:59 37: 37: 38:3 38: 38:6 39:8 39:9 39:5 :1 :33 :55 1:16 1:38 1:59 :1 : 3: 3:5 3:7 :8 :3 :5 5:13 5:35 5:57 6:18 6: 7:1 7:3 7:5 8:6 8:7 8: Aircraft altitude (feet) Distance from runway threshold (nautical miles) Ashtech position error ( sigma) Cross-track error Vertical error Aircraft altitude Aircraft Horizontal Trajectory (1:1-GPS6) Geodetic latitude in degrees Geodetic longitude in degrees Figure

12 Runway Threshold Approach 6:-GPS15 Comparison Between Ashtech and Trimble DGPS Solutions (6:-GPS15) Time (UT) in minutes and seconds 15 37:5 38:16 38:37 38:58 39: :1 8. : 8. : : :7 1:9 1:5 :1 :33 :55 3:17 3:38 : : :3 5:5 5:6 Ashtech position error, crosstrack and vertical error (m) Aircraft altitude (feet) Distance from runway threshold (nautical miles) Ashtech position error ( sigma) Cross-track error Vertical error Aircraft altitude Comparison Between Ashtech and Trimble DGPS Solutions (6:-GPS15) Time (UT) in minutes and seconds 15 37:5 38:16 38:37 38:58 39:19 39:1 : : :5 1:7 1:9 1:5 :1 : :55. 3:17 3:38 : : :3 5:5 5:6 Ashtech position error, crosstrack and vertical error (m) Aircraft altitude (feet) Distance from runway threshold (nautical miles) Ashtech position error ( sigma) Cross-track error Vertical error Aircraft altitude Aircraft Horizontal Trajectory (6:-GPS15) 5. 5 Geodetic latitude in degrees Geodetic longitude in degrees Figure 5

13 Step 3.: - A.) Analysis of the whole data set. - We computed the s & standard deviations of cross-track & vertical errors for all data (Fig.( 6&7). - B.) Setting up categories to develop further statistics. - We also investigated several categories of : - 3 & 6 degree glidepath, - & 1 ft decision height, - missed (landing, left-right, straight), - 5&7 knot. - We looked at the data before & after the Trimble airborne receiver firmware modifications. - We treated: 1.. all the data collected,.. all data except 3 which needed to be eliminated due to bad quality of Ashtech ground truth solution. Figure 8: 8: as an example shows cross-track error statistics for 3 & 6 degree glidepath. Figure 9: 9: shows vertical error statistics for 3 & 6 degree glidepath.

14 Mean of the Cross-track Errors for All 73 Approaches Frequency [, 3) [ 3,.5) [.5, ) [, 1.5) [ 1.5, 1) [ 1,.5) [.5,) [,.5) [.5,1) [1,1.5) [1.5,) [,.5) [.5,3) [3, ] Mean of the cross-track errors in metres Standard Deviation of the Cross-track Errors for All 73 Approaches 5 Frequency [,.5) [.5,1) [1,1.5) [1.5,) [,.5) [.5,3) [3,3.5) [3.5,) [,.5) [.5,5) [5,5.5) [5.5,6) [6,6.5) [6.5, ] Standard deviation of the cross-track errors in metres Figure 6

15 Mean of the Vertical Errors for All 73 Approaches Frequency 6 [,.5) [.5, ) [, 3.5) [ 3.5, 3) [ 3,.5) [.5, ) [, 1.5) [ 1.5, 1) [ 1,.5) [.5,) [,.5) [.5,1) [1,1.5) [1.5,) [,.5) Mean of the vertical errors in metres [.5,3) [3,3.5) [3.5,) [,.5) [.5, ] Standard Deviation of the Vertical Errors for All 73 Approaches Frequency [,.5) [.5,1) [1,1.5) [1.5,) [,.5) [.5,3) [3,3.5) [3.5,) [,.5) [.5,5) [5,5.5) [5.5,6) [6,6.5) [6.5,7) [7,7.5) [7.5,8) [8,8.5) [8.5,9) [9,9.5) [9.5, ] Standard deviation of the vertical errors in metres Figure 7

16 Vertical Errors for 3&6 Degree Glidepath Approaches Prior to the Software Modifications ( Approaches Eliminated) Maximum variations in metres Max (TH33) Max SD (TH33) Max Mean + SD (TH33) Max (TH) Max SD (TH) Max Mean + SD (TH) Max (TH6) Max SD (TH6) Max Mean + SD (TH6) Max (TH15) Max SD (TH15) Max Mean + SD (TH15) 3 degree glidepath 6 degree glidepath Figure 8

17 Cross-track Errors for 3&6 Degree Glidepath Approaches Prior to Software Modifications ( Approaches Eliminated) Maximum variations in metres Max (TH33) Max SD (TH33) Max Mean + SD (TH33) Max (TH) Max SD (TH) Max Mean + SD (TH) Max (TH6) Max SD (TH6) Max Mean + SD (TH6) Max (TH15) Max SD (TH15) Max Mean + SD (TH15) 3 degree glidepath 6 deg glidepath Figure 9

18 - C.) Investigating categories in.1 nm increments from the threshold: - 3 & 6 degree glidepath, - & 1 ft decision height, - 5&7 knot. Figure 1: : example of horizontal error bars for 3 degree glidepath prior to firmware modifications. Figure 11: : example of vertical error bars for 3 degree glidepath prior to firmware modifications. Analysis of results - A.) Investigating all data without categorizing them Mean of the cross-track errors Standard deviation of the cross-track errors Mean of the vertical errors Standard deviation of the vertical errors 17 (3%) fall into the bin size ranging from. to.5 metres (58%) fall into the bin size ranging from -.5 to 1. metres (3%) fall into the bin size ranging from.5 to 1. metres 35 (8%) fall into the bin size ranging from.5 to 1.5 metres 11 (15%) fall into the bin size ranging from 1. to 1.5 metres 9 (%) fall into the bin size ranging from. to 1.5 metres 15 (1%) fall into the bin size ranging from 1. to 1.5 metres 35 (8%) fall into the bin size ranging from 1. to.5 metres

19 Error in metres Cross-track Errors ( Sigma) for 3 Degree Glidepath Approaches Prior to Receiver Software Modifications (TH6) Distance from runway threshold in.1 NM increments Figure 1

20 5 3 Error in metres Vertical Errors ( sigma) for 3 Degree Glidepath Approaches Prior to Receiver Software Modifications (TH6) Distance from runway threshold in.1 NM increments Figure 11

21 - B.) Investigating the categories and looking at maximum variation, maximum standard deviation variation and maximum + sigma variation (all data, all data minus ). Figure 1: shows the three statistics of horizontal errors for the four thresholds, 6 categories, prior to and after the firmware modifications. Figure 13: shows the three statistics of vertical errors for the four thresholds, 6 categories, prior to and after the receiver firmware modifications. - C.) Investigating the categories in.1 nm increments from the threshold (all data minus ). Figure 1: shows the horizontal error statistics to compare the individual categories, thresholds, prior to and after receiver firmware modification. Figure 15: shows the vertical error statistics to compare the individual categories, thresholds, prior to and after receiver firmware modification.

22 Thresholds/ Type of approach CROSS-TRACK ERRORS (ALL DATA USED) UNITS IN METRES [MIN,MAX] Approaches prior to the receiver software modifications TH33 TH TH6 TH15 Max Max s.d. Max Max Max s.d. Max Max Max s.d. Max Max Max s.d. Max 3 deg glidepath [-.3,3.65] [.7,.] [1.6,1.9] [-.69,.63] [.53,15.8] [1.7,3.85] [-.17,.3] [.6,1.3] [1.75,.99] [.6,1.83] [.1,.6] [5.,6.75] 6 deg glidepath [-.,.86] [.97,3.33] [.1,8.5] [-.86,.9] [.7,3.97] [1.7,1.3] DH [-.3,3.65] [.7,.] [1.6,1.9] [-.69,.63] [.53,15.8] [1.7,3.85] [-.17,.9] [.6,1.3] [.,.99] [.6,1.83] [.1,.6] [5.,6.75] DH 1 [1.3,.86] [1.9,3.33] [5.6,8.5] Missed approach: landing [-.,.86] [1.67,3.3] [3.77,8.5] [.37] [1.36] [3.9] [-1.,1.6] [.6,.88] [.,3.88] Missed approach: left-right [.18,.76] [.83,.8] [.,5.31] [-.35,-.5] [1.6,5.31] [3.5,1.97] [-1.] [1.1] [.] Missed approach: straight-18 deg 5 knots [-.,.53] [.83,3.33] [.,8.5] [-1.36,.9] [.7,3.55] [.8,9.59] 6 knots [-.17,-.86] [.8,.88] [.6,3.18] 7 knots [1.3] [.8] [5.8] [.6,.3] [1.6,1.3] [3.5,.99] 8 knots [.86] [.51] [7.88] [-1.] [.6] [.] 9 knots [-.88] [.55] [1.98] 1 knots [1.73] [1.8] [.69] Approaches after the receiver software modifications Thresholds/ TH33 TH TH6 TH15 Type of approach [1.57,1.73] [1.8,.7] [.69,5.71] [-.3] [1.] [.7] [-.17,.9] [.7,1.3] [1.7,.99] [.6] [.1] [5.] Max Max s.d. Max Max Max s.d. Max Max Max s.d. Max Max Max s.d. Max 3 deg glidepath [.15,1.9] [.66,.] [1.7,6.7] [-.15,1.3] [.3,6.3] [.61,13.9] [-.39,1.6] [.76,15.81] [3.7,35.61] [-.3,.91] [1.9,7.56] [.61,18.3] 6 deg glidepath [-.59,.66] [.58,.86] [1.1,.38] [-.19,5.] [.8,5.95] [.,17.3] DH [-.15,.66] [.66,.86] [1.7,.38] [-.19,5.] [.91,5.95] [.95,17.3] DH 1 [-.59,1.9] [.58,.] [1.1,.9] [-3.99,.95] [.76,15.81] [.36,35.61] Missed approach: landing [-.5,.66] [.58,.86] [1.75,.38] [.19] [5.16] [1.51] [-3.99,.78] [.76,15.81] [.39,35.61] Missed approach: left-right [.] [.98] [.36] [-.19,-.3] [1.9,.5] [.61,.9] Missed approach: straight&18 deg [-.59,1.9] [.66,.] [1.91,.9] [-.15,-.3] [.3,6.3] [.61,13.9] [.17,1.6] [.8,1.78] [.,.] 5 knots [-.15] [.66] [1.7] [.17,1.9] [.8,.3] [.,.83] 6 knots [-.59,-.5] [.58,.8] [1.1,.19] [.77,.78] [1.9,1.88] [.95,.5] 7 knots [.6,1.9 [.77,.] [3.,.9] [-.15,.19] [.3,5.16] [.61,1.51] [[.7,5.] [.91,5.95] [.95,17.3] [-.19,.91] [1.9,7.56] [.61,18.3] 8 knots [1.3] [6.3] [13.9] [-3.99,.75] [1.9,15.81] [3.5,35.61] 9 knots [-1.55] [.76] [3.7] DH 5 [.19,1.3] [5.16,6.3] [1.51,13.9] [-.19,.91] [1.9,7.56] [.61,18.3] DH 15 [1.9] [.9] [3.9] 65 knots [.66] [.86] [.38] Figure 1.Statistics for cross-track errors of all categories (all data used)

23 Thresholds/ Type of approach VERTICAL ERRORS (ALL DATA USED) UNITS IN METRES [MIN, MAX] Approaches prior to the receiver software modifications TH33 TH TH6 TH15 Max Max s.d. Max Max Max s.d. Max Max Max s.d. Max Max Max s.d. Max 3 deg glidepath [-6.6,.87] [1.,18.8] [.55,38.7] [-.39,9.86] [1.11,16.67] [.61,3.] [-.93,3.1] [.83,18.9] [.7,38.] [.98,.8] [.7,.83] [6.38,8.8] 6 deg glidepath [-.7,5.1] [1.56,13.8] [.3,3.] [.56,7.73] [1.71,16.3] [.1,39.79] DH [-6.6,.87] [1.,18.8] [.55,38.7] [-.9,9.86] [1.11,16.67] [.61,3.] [-.93,7.73] [.83,18.9] [.7,38.] [.98,.8] [.7,.83] [6.38,8.8] DH 1 [-.7,5.1] [.1,13.8] [8.6,3.] Missed approach: landing [-.7,5.1] [1.8,18.7] [.93,37.9] [.9] [6.8] [13.9] [.56,.61] [.83,1.78] [.1,.7] Missed approach: left-right [-6.6,-1.] [1.31,8.88] [.39,.] [1.1,3.6] [1.59,3.3] [6.,7.6] [1.5] [.5] [6.13] Missed approach: straight-18 deg 5 knots [-.7,.18] [1.38,18.7] [.39,37.9] [.33,7.73] [1.78,16.3] [.1,39.79] 6 knots [.67,3.7] [1.71,.3] [6.9,7.13] 7 knots [.87] [8.8] [17.3] [.,.9] [3.3,18.9] [9.98,38.] 8 knots [5.1] [1.1] [5.3] [.61] [.83] [.7] 9 knots [.1] [1.3] [.98] 1 knots [-.3] [3.5] [11.3] Approaches after the receiver software modifications Thresholds/ TH33 TH TH6 TH15 Type of approach [-.3,.18] [3.5,.1] [8.6,11.3] [1.3] [1.31] [3.85] [.33,.9] [.6,18.9] [.5,38.] [.8] [.83] [8.8] Max Max s.d. Max Max Max s.d. Max Max Max s.d. Max Max Max s.d. Max 3 deg glidepath [.17,.37] [1.1,.8] [.55,5.33] [-.,1.3] [1.77,7.1] [.76,8.6] [-.56,3.83] [.9,11.11] [.7,6.78] [.75,16.13] [1.1,9.6] [.95,75.37] 6 deg glidepath [-1.,1.9] [1.16,.1] [3.7,5.6] [-.3,.79] [1.15,3.5] [3.8,89.79] DH [-1.,.17] [1.5,.1] [3.7,.37] [-.56,.75] [1.6,11.11] [.6,6.78] DH 1 [-.5,1.9] [1.1,.8] [.55,5.33] [-1.91,3.83] [.9,3.5] [.7,89.79] Missed approach: landing [-1.,1.9] [1.16,.1] [.,5.6] [1.3] [7.1] [15.67] [-.5,3.83] [.9,3.5] [.7,89.79] Missed approach: left-right [1.7] [.9] [5.5] [.9,.75] [1.1,3.9] [.95,6.87] Missed approach: straight&18 deg [-.5,.7] [1.1,.8] [.55,5.33] [-.,1.] [1.77,.] [.76,8.6] [-.3,1.7] [1.38,6.61] [.6,13.6] 5 knots [.17] [1.5] [3.7] [-1.9,1.7] [1.15,3.8] [.,8.33] 6 knots [-.5,1.9] [1.16,1.1] [3.7,.] [-.56,.] [6.61,11.11] [13.6,6.78] 7 knots [.7,.37] [1.1,.8] [.55,5.33] [1.,1.3] [1.77,7.1] [.76,15.67] [-.3,.79] [1.9,3.5] [.9,89.79] [.9,16.13] [1.1,9.6] [.95,75.37] 8 knots [-.] [.] [8.6] [-.3,3.83] [1.6,1.55] [.6,6.93] 9 knots [.88] [.9] [.7] DH 5 [-.,1.3] [.,7.1] [8.6,15.67] [.9,16.13] [1.1,9.6] [.95,75.37] DH 15 [-.7] [1.38] [3.8] 65 knots [-1.] [.1] [5.6] Figure 13. Statistics for vertical errors of all categories (all data used)

24 Thresholds/ Type of approach CROSS-TRACK ERROR STATISTICS IN METRES Approaches prior to the receiver software modifications TH33 TH TH6 TH15 All Thresholds 3 deg glidepath deg glidepath DH DH knots knots Approaches after the receiver software modifications Thresholds/ Type of approach TH33 TH TH6 TH15 All Thresholds 3 deg glidepath deg glidepath DH DH knots knots Figure 1. Statistics for cross-track errors of 6 categories using readings sampled at.1 NM increments

25 Thresholds/ Type of approach VERTICAL ERROR STATISTICS IN METRES Approaches prior to the receiver software modifications TH33 TH TH6 TH15 All Thresholds 3 deg glidepath deg glidepath DH DH knots knots Approaches after the receiver software modifications Thresholds/ Type of approach TH33 TH TH6 TH15 All Thresholds 3 deg glidepath deg glidepath DH DH knots knots Figure 15. Statistics for vertical errors of 6 categories using readings sampled at.1 NM increments

26 Conclusions - Four eliminated (1 for lost VHF link, 3 for inadequate quality of Ashtech ground truth data). - Worse case scenario: in the case of horizontal errors the maximum +sigma = 18. metres due to jumps in the Trimble positions. Fig.1 - Worse case scenario: in the case of vertical errors the maximum + sigma = 89.8 metres due to jumps in the Trimble positions. Fig 13 - There is a marginal improvement in the Trimble positions after the receiver firmware modifications took place (Fig 1 & 15). - In the case of horizontal errors (Fig 1): - 6 degree glidepath app. proved to have performed better than the 3deg, - ft decision height app. proved to have performed better than the 1 ft, - 5 knot app. proved to have performed better than the 7 knot. - In the case of vertical errors (Fig 15): - comparing 3 and 6 degree app. is inconclusive, - 1 ft decision height app. proved to have performed better than the 1 ft, - 5 knot app. proved to have performed better than the 7.

27 - The number of vary from category to category. Also, investigation C.) only takes sample every.1 nm so it does not contain all data pertaining to a particular approach. Therefore, jumps in positions provided by Trimble are only reflected in investigation A.) and B.) not in C.). - The accuracy requirements for CAT 1 precision are: - in horizontal sense 17. m at sigma level, - in vertical sense 7. m at sigma level. - The LDGPS system provided this accuracy for 68 (93%) in horizontal sense but failed to fulfill the vertical requirements for 3 (7%). Why? - jumps in Trimble solution, - required vertical accuracy is inherently higher than the horizontal. Recommendations: - More accurate ground truth system is required such as by using Ashtech Z-1s. - More repeated of the same kind and careful design of are needed.

Surveying. Session GPS Surveying 1. GPS Surveying. Carrier-Phase (RTK) Pseudo-Range (DGPS) Slide 1

Surveying. Session GPS Surveying 1. GPS Surveying. Carrier-Phase (RTK) Pseudo-Range (DGPS) Slide 1 GPS Surveying Slide 1 GPS Surveying Surveying Mapping Standalone Relative Relative Standalone Post-Processed Real-Time Static / Fast Static Kinematic Stop & Go Rapid-Static Carrier-Phase (RTK) Pseudo-Range