questuav datahawkppk accuracy assessment … manual • camera lens ... was carried out by a...

QuestUAV DATAhawkPPK - Accuracy Assessment and Validation v1.1

© QuestUAV Ltd. No publication, presentation or reprocessing without permission of QuestUAV Ltd. 1

QuestUAV DATAhawkPPK Accuracy Assessment and Validation

Accuracy of 3.0cm(X), 3.3cm(Y), 3.9cm(Z)

Nigel King1, Kerstin Traut2, Cameron Weeks3, Chris Mills4, Phil Mills5, Ruairi Hardman6, Stuart King7, Francis Thompson8, Callum Hewitson9, Stefan Frizzel10

1Director QuestUAV, 2Data Analyst QuestUAV, 3Production Engineer QuestUAV, 4Principal Survey Control Services, 5Director Oakley Aerial Surveys, 6General Manager QuestUAV, 7Lead Pilot QuestUAV 8Pilot QuestUAV, 9Pilot QuestUAV, 10System Administrator QuestUAV

Glossary ................................................................................................................................ 2

Introduction .......................................................................................................................... 2

Objectives ............................................................................................................................. 2

Claims ................................................................................................................................... 3

Study Area ............................................................................................................................. 3

Equipment and Workflow ...................................................................................................... 3

Methodology ......................................................................................................................... 3

Reference Data ............................................................................................................ 4

Flight Reference Station ............................................................................................... 4

Aerial Survey ............................................................................................................... 5

Post-Processing ............................................................................................................ 5

Statistics ...................................................................................................................... 5

Results .................................................................................................................................. 5

Verification ............................................................................................................................ 6

Conclusion ............................................................................................................................. 7

Appendix ............................................................................................................................... 8

Per flight RMSE Results ..................................................................................................... 8

Independent Verification Results ..................................................................................... 8

Flight Data ......................................................................................................................... 9



Glossary

DSM Digital Surface Model

GCP Ground Control Point

GIS Geo-Information System

GLONASS Globalnaya Navigatsionnaya Sputnikovaya Sistema (transliteration)

GNSS Global Navigation Satellite System

GPS Global Positioning System

GSD Ground Sampling Distance

OS Ordnance Survey

PPK Post Processing Kinematic

RMSE Root Mean Square Error

RTK Real Time Kinematic

UAV Unmanned Aerial Vehicle

WGS84 World Geodetic System 1984

Introduction

In September 2016, QuestUAV released its first PPK enabled surveying drone allowing users to generate highly-accurate topographic maps and 3D models from aerial photography without the need for physical GCPs.

QuestUAV has continued the product development and successfully integrated the PPK technology to its compact mapping drone, the DATAhawkPPK.

A dual band GPS/GLONASS receiver on board the DATAhawkPPK produces spatial accuracies in the centimetre range for both 2D maps and 3D models.

QuestUAV’s simple and automated PPK workflow saves users hours of mission time since there is a minimal requirement for walking the survey site and measure GCPs and working with GCPs in the post-processing phase.

All GNSS positioning data are stored on board the DATAhawkPPK eliminating the need for a real-time data link with a fixed reference station while still guaranteeing RTK cm-level position accuracy. PPK coordinates can be more accurate than RTK ones, since the processing can be more refined.

Objectives

The objective of this whitepaper is to validate the spatial accuracy of the new PPK enabled DATAhawkPPK aircraft on the basis of independently measured verification points (GCPs) and repeated aerial surveys of a test site in the UK.

Figure 1: Test site for DATAhawk Accuracy Assessment



Claims

QuestUAV claims the following accuracies on the test area using the DATAhawkPPK system without the use of GCPs.

Q-100 DATAhawkPPK Absolute RMSE Accuracies

X Y Z

3.0cm 3.3cm 3.9cm

Study Area

The test site is located on the North East coast of England (Low Hauxley) and covers 100 hectares of agricultural land, coastal dunes and beach.

By being very close to the North Sea, weather conditions are windy and changeable, which aids to performing stress tests for both the QuestUAV aircraft and image data quality.

Equipment and Workflow

The DATAhawkPPK aircraft is equipped with a dual-frequency L1/L2 receiver tracking both GPS and GLONASS signals. 132 hardware channels allow the system to simultaneously track all visible GPS/GLONASS satellites.

In parallel, the receiver records the shutter events of the camera and logs the information during flight on the on-board SD card.

Camera locations are corrected after the flight during the post-processing phase, when GNSS receiver data is combined with base station data to calculate the exact position of each camera exposure. All

camera positions are initially recorded in the global coordinate system World Geodetic System (WGS) 1984 and then transformed to the local coordinate system OSGB 1936 / British National Grid during the post processing phase.

The corrected image positions are recorded in a comma-separated values (.csv) file which are then imported into photogrammetric software packages such as Pix4Dmapper or Agisoft Photoscan.

Figure 2 DATAhawk PPK Miniline launch

The sensor on board the DATAhawkPPK is the Sony RX100 (mk2)

The aircraft is launched with either the standard QuestUAV mini-launch line, or the AirDock (Figure 2) and can be landed via parachute or belly landing.

Methodology

The accuracy of the DATAhawkPPK system is validated by comparing the results of repeated aerial surveys with precisely measured verification points (GCPs). The verification workflow includes the following steps:



Reference Data

A total of 30 target points previously distributed over the 100ha test site and measured by an independent surveying company were used. The majority of the points were placed on tarmac and permanent structures such as rocks and stable stone walls in order to avoid any movements for the duration of the accuracy study.

Figure 3: Surveyor measuring the reference points on the ground.

The reference points consist of white crosses painted on hard surfaces (approx. 15cm

arms) or yellow marker boards with black diagonals elsewhere.

These markers are clearly visible on the aerial imagery and form the basis for assessing the spatial accuracy of Orthomosaic and Digital Surface Models (DSM).

Prior to the flight test commencing all points were measured independently in two separate sessions using Trimble GPS/GLONASS receivers taking RTK corrections from a base station.

For any point the reading spread within a visit was no more than 4mm in xy, 7mm in z. The final accepted value for each reference point was the averaged values of the individual observations.

The base station was located on one of the reference points and run for an eight hour static fix. Baselines were computed from six of the UK Ordnance Survey active stations, giving residuals of 4mm in plan and 12mm in height.

Flight Reference Station

The PPK workflow does not need a real-time data link with a base station during a flight, however the GNSS information has to be recorded by a base station throughout the flight duration, at one second interval, to allow for positioning corrections to be applied during the post-processing phase.

Within the UK, the public domain data released by the Ordnance Survey is at a 30

Reference Data

•Mark verification points on the ground

•Measure verification points using an independent surveying company

Reference Base Station

•Setup a reference base station

Aerial Surveys

•Conduct aerial surveys over the test site with the Q-100 DATAhawkPPK

Post-processing

•Post-process camera locations and process image to create point clouds, othormosaics and DEMs

Statistics

•Extract target points and calculate accuracy statistics

Verification

•Provide datasets to Survey Control Services and Oakley Aerial Surveys for independent verification.



second interval and cannot be used directly

to process data from the DATAhawkPPK aircraft. QuestUAV therefore, set up a permanent reference station about 3.5km from the study site recording GNSS correction data during a flight. Subsequent position corrections during the test phase will be related to this reference station.

Aerial Survey

The test site was flown with the DATAhawkPPK aircraft repeatedly over a five-month period while testing different flight and sensor settings, including:

• Flight altitude: 400ft

• Image overlap: 69m/60m/53m lag distance

• Flight path: Parallel/perpendicular grid lines

• Camera settings: Auto/ aperture priority/ shutter priority/ manual

• Camera lens: 10.4mm wide angle lens. Approximately half of the flights were carried out in sunny weather while the other half were flown in overcast and rainy conditions. Wind speeds were high for the majority of flights with up to 35kts at operational height. During the flight hours, there was no significant geomagnetic activity recorded.

Post-Processing

After flight, camera positions were corrected by combining GNSS recordings of the aircraft with the corresponding information from the flight reference station on the ground to provide more precise cm-level PPK values. These corrected locations are then transformed into a local coordinate system and stored in a csv file for use during photogrammetric processing.

Photogrammetric processing was carried out with the Agisoft PhotoScan software, including the generation of orthomosaic and digital elevation model and their export as GeoTiff files.

Statistics

Data analysis was performed inside the open-source GIS software QGIS. For each flight orthomosaic and DSM were imported into QGIS and the 3D image coordinates of the target points extracted.

The image coordinates were compared with the coordinates measured during the ground survey and their accuracies were determined by using the RMSE.

The RMSE is the standard error measure to estimate geo-spatial precision. It represents the sample standard deviation of the differences between the coordinates measured in flight (p) and the observed coordinates during the ground survey (a).

Results

During the workflow optimisation process, 27 flights were performed for adjustment and refinement purposes to obtain optimal camera settings, aerial positions and flight

parameters (referred to as flights PPK1 -PPK27).

Results were achieved with the Sony RX100 camera. Results were further improved by using manual camera configurations dependent on light and weather conditions.

After the optimisation process the accuracy assessment was carried out on a further 10 flights and processed without using any ground control points as known positions, then compared with known reference points to determine accuracies (referred to as flights PPK28 – PPK37).

The table below summarises the results of the validation.



Table 1: Accuracy assessment on the basis of 10 flights with 30 check points each (ground reference).

X (m) Y (m) Z (m) XY (m) XYZ (m)

Mean Error 0.002 -0.023 -0.002 0.023 0.023

Standard Deviation

0.027 0.023 0.033 0.035 0.049

RMSE 0.030 0.033 0.039 0.045 0.059

RMSE best 0.018 0.021 0.026 0.031 0.042

RMSE worst 0.041 0.059 0.047 0.066 0.077

Verification

Independent verification was carried out by a professional surveying company with long-term experience in the provision of ground control.

Two flights were randomly selected by the independent verifiers for this independent verification. The raw data and imagery for these two flights were reprocessed using Agisoft Photoscan and validated using the point cloud output in Trimble RealWorks.

The independent processed data generally agreed with the QuestUAV processing, with some small variations, typically within 1cm.

Notably, Flight PPK32 contained an anomaly which resulted in an unusually poor Max Negative Error of -0.1593 (see appendix). This point was more than triple the error of the 2nd worst point ( -0.0485) on this particular flight but was still included when calculating the RMSE. This increased the Y RMSE and resulted in the only flight to contain a Y RMSE worse than the Z RMSE. This anomaly was detected both by ourselves and the independent verifiers which further strengthens the accuracy and integrity of our claims.

X 0.0256 0.0336 0.0080

Y 0.0232 0.0326 0.0094

Z 0.0294 0.0339 0.0044

X 0.0293 0.0345 0.0052

Y 0.0238 0.0338 0.0100

Z 0.0342 0.0376 0.0034

X 0.0313 0.0395 0.0082

Y 0.0308 0.0413 0.0105

Z 0.0361 0.0404 0.0043

X 0.0634 0.0870 0.0236

Y 0.0257 0.0520 0.0263

Z 0.0643 0.0710 0.0067

X -0.0702 -0.0740 0.0038

Y -0.1593 -0.1560 0.0033

Z -0.1013 -0.0920 0.0093

Standard

Deviation

RMSE

Max Positive

Error

Max Negative

Error

Verification Results

(Flights PPK32 & PPK35)QuestUAV Independent Difference

Mean Error



Conclusion

Results show that the accuracies which can be achieved by the DATAhawkPPK are 1 x GSD (planar) and 2 x GSD (vertical) without the use of any ground reference information.

Independent verification reveals that the DATAhawkPPK provides good positioning, enabling results close or equal to those provided using ground control points. During normal operations, it is advised that some discrete ground control points are provided to provide assurance that the processing systems have performed correctly. The DATAhawkPPK was stress-tested in real-life scenarios, including challenging coastal weather conditions and non-ideal light conditions. System performance was consistent over the whole test site.

The QuestUAV test series have shown that the new DATAhawkPPK aircraft is a robust and reliable system for high accuracy aerial surveys without the need of physical GCPs.

The PPK workflow allows for the easy combination of high-resolution aerial images with high-precision GNSS data during the post-processing phase to create high-quality orthomosaics and digital surface models.



Appendix

Per flight RMSE Results

Independent Verification Results

RMSE PPK29 PPK30 PPK31 PPK32 PPK33 PPK34 PPK35 PPK36 PPK37 PPK38

X 0.045 0.030 0.030 0.031 0.027 0.018 0.031 0.021 0.034 0.041

Y 0.041 0.029 0.059 0.041 0.029 0.025 0.021 0.024 0.024 0.035

Z 0.035 0.042 0.040 0.046 0.047 0.029 0.026 0.032 0.046 0.046

xyz 0.061 0.042 0.066 0.051 0.040 0.031 0.038 0.032 0.041 0.054

XYZ 0.070 0.060 0.077 0.069 0.061 0.042 0.046 0.045 0.062 0.071

QuestUAV Independent Difference QuestUAV Independent Difference QuestUAV Independent Difference

X 0.0157 0.0288 0.0131 -0.0067 -0.0046 0.0022

Y -0.0281 -0.0339 0.0058 -0.0117 -0.0145 0.0027

Z -0.0211 -0.0175 0.0036 0.0006 -0.0150 0.0156

X 0.0634 0.0870 0.0236 0.0573 0.0620 0.0047

Y 0.0076 0.0300 0.0224 0.0257 0.0520 0.0263

Z 0.0643 0.0710 0.0067 0.0543 0.0440 0.0103

X -0.0248 -0.0380 0.0132 -0.0702 -0.0740 0.0038

Y -0.1593 -0.1560 0.0033 -0.0446 -0.0640 0.0194

Z -0.1013 -0.0920 0.0093 -0.0474 -0.0730 0.0256

X 0.0312 0.0433 0.0122 0.0314 0.0357 0.0043 0.0313 0.0395 0.0082

Y 0.0407 0.0516 0.0109 0.0208 0.0310 0.0102 0.0308 0.0413 0.0105

Z 0.0462 0.0461 0.0002 0.0259 0.0346 0.0087 0.0361 0.0404 0.0043

X 0.0274 0.0330 0.0055 0.0312 0.0360 0.0048 0.0293 0.0345 0.0052

Y 0.0300 0.0396 0.0096 0.0175 0.0279 0.0104 0.0238 0.0338 0.0100

Z 0.0419 0.0434 0.0015 0.0264 0.0318 0.0054 0.0342 0.0376 0.0034

X 0.0248 0.0373 0.0126 0.0265 0.0299 0.0034 0.0256 0.0336 0.0080

Y 0.0290 0.0401 0.0111 0.0175 0.0251 0.0077 0.0232 0.0326 0.0094

Z 0.0383 0.0388 0.0005 0.0206 0.0290 0.0083 0.0294 0.0339 0.0044

PPK32 PPK35 Average

Mean

Max Positive Error

RMSE

Standard Deviation

Mean (Absolute

Residuals)

Verification Results

Max Negative Error



Flight Data

Point ID Easting Northing Height Easting Northing Height Easting Northing Height Easting Northing Height Easting Northing Height Easting Northing Height Easting Northing Height Easting Northing Height Easting Northing Height Easting Northing Height Easting Northing Height

1 428286.24 602944.68 3.77 428286.2 602944.6 3.71361 428286.3 602944.6 3.71014 428286.2 602944.6 3.80767 428286.2 602944.7 3.72555 428286.2 602944.7 3.87098 428286.2 602944.7 3.75127 428286.3 602944.6 3.82026 428286.2 602944.7 3.78463 428286.3 602944.7 3.86338 428286.2 602944.7 3.76981

2 428326.71 602952.81 3.57 428326.8 602952.8 3.53287 428326.8 602952.8 3.53158 428326.7 602952.8 3.5771 428326.7 602952.8 3.5739 428326.7 602952.8 3.63399 428326.7 602952.8 3.55589 428326.8 602952.8 3.60545 428326.7 602952.8 3.60201 428326.7 602952.8 3.67757 428326.7 602952.8 3.56145

3 428368.40 602962.58 3.84 428368.5 602962.6 3.85972 428368.4 602962.6 3.84275 428368.3 602962.5 3.88959 428368.4 602962.6 3.80628 428368.4 602962.6 3.90437 428368.4 602962.6 3.82946 428368.4 602962.6 3.85678 428368.4 602962.6 3.89055 428368.4 602962.5 3.92428 428368.3 602962.6 3.83686

4 428404.48 602973.68 4.08 428404.5 602973.7 4.08922 428404.5 602973.6 4.04734 428404.5 602973.6 4.12259 428404.5 602973.7 4.03349 428404.4 602973.7 4.14393 428404.5 602973.7 4.06655 428404.5 602973.7 4.10793 428404.5 602973.7 4.11413 428404.5 602973.7 4.14829 428404.4 602973.7 4.09095

5 428438.04 602986.81 4.16 428438.1 602986.8 4.17362 428438.1 602986.8 4.09569 428438.1 602986.8 4.16115 428438.1 602986.8 4.13416 428438 602986.8 4.19184 428438 602986.8 4.08781 428438 602986.8 4.18348 428438 602986.8 4.15173 428438.1 602986.8 4.21584 428438 602986.8 4.11048

6 428471.49 602997.58 4.17 428471.6 602997.6 4.17811 428471.5 602997.6 4.11537 428471.5 602997.5 4.21664 428471.5 602997.5 4.2056 428471.5 602997.6 4.18286 428471.5 602997.6 4.13215 428471.5 602997.6 4.17244 428471.5 602997.6 4.17541 428471.6 602997.6 4.19776 428471.5 602997.6 4.16683

7 428511.52 603008.97 3.91 428511.5 603008.9 3.90934 428511.5 603008.9 3.8639 428511.5 603008.9 3.95097 428511.5 603008.9 3.97327 428511.5 603008.9 3.91493 428511.5 603009 3.89311 428511.5 603008.9 3.90031 428511.5 603009 3.89746 428511.5 603009 3.93376 428511.5 603009 3.90783

8 428572.87 603020.23 4.97 428572.9 603020.2 4.98666 428572.9 603020.2 4.89103 428572.8 603020.2 4.99872 428572.9 603020.2 4.9575 428572.8 603020.2 4.97914 428572.9 603020.2 4.95664 428572.8 603020.2 4.95614 428572.9 603020.2 4.94044 428572.9 603020.2 4.96912 428572.8 603020.2 4.94036

9 428574.47 602962.73 5.51 428574.5 602962.7 5.53796 428574.5 602962.7 5.5072 428574.5 602962.7 5.55735 428574.5 602962.7 5.52227 428574.4 602962.7 5.52622 428574.5 602962.7 5.50535 428574.5 602962.7 5.5194 428574.4 602962.7 5.51938 428574.4 602962.7 5.52652 428574.4 602962.7 5.54855

10 428576.58 602905.85 5.30 428576.7 602905.8 5.28347 428576.7 602905.8 5.24919 428576.6 602905.8 5.3488 428576.6 602905.8 5.33598 428576.6 602905.8 5.25373 428576.6 602905.8 5.29664 428576.6 602905.9 5.30242 428576.6 602905.8 5.29198 428576.6 602905.8 5.35696 428576.5 602905.8 5.33915

11 428578.87 602869.56 5.10 428578.9 602869.5 5.12797 428578.9 602869.5 5.12217 428578.8 602869.5 5.17354 428578.9 602869.5 5.13004 428578.8 602869.5 5.099 428578.9 602869.5 5.07644 428578.8 602869.6 5.10877 428578.9 602869.5 5.14523 428578.9 602869.5 5.12172 428578.8 602869.6 5.1375

12 428582.03 602795.75 5.21 428582.1 602795.8 5.29814 428582.1 602795.7 5.17922 428582.1 602795.7 5.26699 428582.1 602795.7 5.22936 428582 602795.8 5.19792 428582.1 602795.7 5.22784 428582 602795.7 5.19156 428582 602795.8 5.23045 428582.1 602795.7 5.2464 428582 602795.8 5.20247

13 428642.38 603017.94 6.88 428642.4 603017.9 6.84711 428642.4 603017.9 6.90855 428642.4 603017.9 6.87372 428642.4 603017.9 6.88824

14 428595.92 603041.00 5.94 428595.9 603041 5.95219 428595.9 603041 5.89507 428595.9 603040.9 5.96166 428595.9 603041 5.96004 428595.9 603041 5.90602 428595.9 603041 5.95612 428595.9 603041 5.93647 428595.9 603041 5.93403 428595.9 603041 5.95212 428595.9 603041 5.92975

15 428614.25 603081.82 6.94 428614.3 603081.8 6.9436 428614.3 603081.8 6.90953 428614.2 603081.8 6.95303 428614.2 603081.8 6.98002 428614.2 603081.8 6.9299

16 428624.79 603108.12 8.05 428624.8 603108.1 8.04497 428624.8 603108.1 8.02899 428624.7 603108 8.06696 428624.8 603108.1 8.04619 428624.8 603108.1 8.02111 428624.8 603108.1 8.07356 428624.8 603108.1 8.04283 428624.8 603108.1 8.06429 428624.8 603108.1 8.047 428624.8 603108.1 8.00932

17 428630.74 603126.03 8.78 428630.8 603126 8.75341 428630.7 603126 8.7656 428630.7 603126 8.84448 428630.8 603126 8.74348 428630.8 603126 8.72181 428630.8 603126 8.82889 428630.8 603126 8.76252 428630.8 603126 8.81715 428630.8 603126 8.80991 428630.8 603126 8.7167

18 428648.69 603120.43 9.59 428648.7 603120.4 9.5501 428648.7 603120.4 9.56222 428648.7 603120.4 9.61705 428648.7 603120.4 9.52299 428648.7 603120.4 9.54563 428648.7 603120.4 9.61269 428648.7 603120.4 9.56416 428648.7 603120.4 9.57772 428648.7 603120.4 9.53459 428648.7 603120.4 9.49544

19 428651.67 603128.29 9.57 428651.7 603128.3 9.55374 428651.6 603128.3 9.57457 428651.6 603128.2 9.64102 428651.7 603128.3 9.50896 428651.7 603128.3 9.5349 428651.7 603128.3 9.59278 428651.7 603128.3 9.57846 428651.7 603128.3 9.61325 428651.7 603128.3 9.55503 428651.7 603128.3 9.51773

20 428636.47 603146.17 9.22 428636.5 603146.2 9.16868 428636.5 603146.2 9.17504 428636.4 603146.1 9.2472 428636.5 603146.1 9.15927 428636.5 603146.1 9.14891 428636.5 603146.1 9.24229 428636.5 603146.1 9.17563 428636.5 603146.1 9.26204 428636.5 603146.1 9.21182 428636.5 603146.1 9.13669

21 428639.53 603164.84 9.55 428639.6 603164.8 9.52668 428639.6 603164.8 9.49 428639.5 603164.7 9.60137 428639.6 603164.8 9.47491 428639.5 603164.8 9.47717 428639.5 603164.8 9.57595 428639.5 603164.8 9.55314 428639.5 603164.8 9.5863 428639.6 603164.8 9.50455 428639.5 603164.8 9.48214

22 428621.58 603194.12 10.13 428621.6 603194.1 10.11662 428621.6 603194.1 10.0699 428621.6 603194 10.15557 428621.6 603194.1 10.04918 428621.6 603194.1 10.10824 428621.6 603194.1 10.13429 428621.6 603194.1 10.13804 428621.6 603194.1 10.14159 428621.6 603194.1 10.13305 428621.6 603194.1 10.05206

23 428582.92 603223.25 10.37 428583 603223.2 10.31645 428583 603223.2 10.32524 428582.9 603223.2 10.37813 428583 603223.2 10.32804 428582.9 603223.3 10.33352 428582.9 603223.2 10.36989 428582.9 603223.3 10.34584 428582.9 603223.2 10.40387 428582.9 603223.2 10.36964 428582.9 603223.3 10.3403

24 428571.42 603249.71 10.34 428571.4 603249.7 10.29012 428571.4 603249.7 10.31236 428571.4 603249.7 10.33587 428571.4 603249.7 10.37606 428571.4 603249.7 10.38121 428571.4 603249.7 10.30035

25 428564.37 603268.12 10.95 428564.3 603268.1 10.86903 428564.3 603268.1 10.95013 428564.3 603268.1 10.90147 428564.3 603268.1 10.92072 428564.3 603268.1 10.94078 428564.3 603268.1 10.90972 428564.3 603268.1 11.00234 428564.3 603268.1 10.98513 428564.3 603268.1 10.91189

26 428535.93 603265.60 10.38 428535.9 603265.6 10.30383 428535.9 603265.6 10.33018 428536 603265.6 10.34783 428536 603265.6 10.38648 428535.9 603265.6 10.3401 428535.9 603265.6 10.39051 428535.9 603265.6 10.34736 428535.9 603265.5 10.42375 428536 603265.6 10.41736 428535.9 603265.6 10.34474

27 428456.43 603361.11 8.43 428456.4 603361.1 8.40803 428456.4 603360.9 8.43921 428456.4 603361.1 8.43609 428456.4 603361.1 8.40769 428456.4 603361.1 8.47823 428456.4 603361 8.50145 428456.4 603361.1 8.49784 428456.4 603361.2 8.36991

28 428659.88 603171.05 12.11 428659.9 603171 12.08981 428659.9 603171 12.08687 428659.9 603170.9 12.11413 428659.9 603171 12.06582 428659.9 603171 12.06074 428659.9 603171 12.11351 428659.9 603171 12.08278 428659.9 603171 12.13404 428659.9 603171 12.07758 428659.9 603171 12.03908

29 428662.22 603145.02 11.38 428662.3 603145 11.37879 428662.2 603145 11.35709 428662.2 603144.9 11.39401 428662.3 603145 11.28074 428662.2 603145 11.33334 428662.2 603145 11.44974 428662.2 603145 11.35465 428662.2 603145 11.38076 428662.2 603145 11.36531 428662.2 603145 11.32831

30 428651.69 603100.37 8.63 428651.7 603100.3 8.66583 428651.7 603100.3 8.623 428651.7 603100.3 8.6777 428651.7 603100.3 8.59961 428651.7 603100.3 8.6319 428651.7 603100.3 8.692 428651.6 603100.3 8.66833 428651.7 603100.4 8.66571 428651.7 603100.3 8.66151 428651.7 603100.3 8.62038

FLIGHT SURVEY FLIGHT SURVEY FLIGHT SURVEY FLIGHT SURVEYGROUND SURVEY FLIGHT SURVEY FLIGHT SURVEY FLIGHT SURVEY FLIGHT SURVEY FLIGHT SURVEY FLIGHT SURVEY

PPK34 PPK35 PPK36 PPK37 PPK38PPK33Ground Survey PPK29 PPK30 PPK31 PPK32

questuav datahawkppk accuracy assessment … manual • camera lens ... was carried out by a...

Documents