1. Normans Bay: The Battle of the Surveys
Drama and introduction of the different methods and people

2. Normans Bay: The Battle of the Surveys
Also featuring:
James doing the analysis, but me using ClouCompare to do all the analysis for the presentation

3. Why? How do elevations from different platforms compare
In general
Depending on surface type
Which platform is the best overall
Other criteria (speed, coverage, cost, operating conditions, ....)
LIDAR was Jan 2005, ie one of the very first flights for the SE coastal monitoring. If this was gen 1 of the lidar equipment, we are no on gen3 so the issue may no longer exist
Dornbusch, U., Ground survey methods for mixed sand and gravel beaches in intertidal environments: a comparison. Journal of Coastal Research 26, 451–464

4. Short History Initiated by Birkbeck in early 2014
1st attempt in September 2014 – cancelled due to UAV crash before
2nd attempt October 2014 – only unicycle, PCDL and MDL (too windy for UAV)
3rd attempt Spring 2015 – cancelled due to UAV crash before
4th attempt 20 May SUCCESS

5. Caveat
Each individual survey has an uncertainty of several cm for each point!
Essentially, GPS is the ‘weakest point’ with +- 2cm easily
Dornbusch, U., Ground survey methods for mixed sand and gravel beaches in intertidal environments: a comparison. Journal of Coastal Research 26, 451–464. doi:DOI: /
16 Surveys, ~ 160 points each over 90m

6. Unicycle START
Unicycle survey hampered by fist being realtime end then needed to go into postporcessing; the surface of the outfall was surveyed at the start and end and thus with two methods.
Figure shows GPS calculated accuracy in Z which is less than 1cm

7. Unicycle END
The end survey with postprocessing has a much worse GPS accuracy in Z basically >2cm

8. Elevation Difference START - END
Comparidos of the two based on closest point shows offset of 2cm and those with the highest GPS Z uncertainty show the highest negative deviation.

9. Difference START - PCDL
Elevation
Difference START - PCDL
Start survey assumed to be the better one and hence comparsion with that one.
Overall very good comparison

10. Elevation Difference START - MDL
Difference does not folly a normal distrubution, edge issues, generally much higher

11. Difference START - Geomatics
Elevation
Difference START - Geomatics
Very close fit with low stdev and small offset

12. Elevation Difference START - UAV
Pattern suggest terrain variation measured from UAV of >15cm which is not the case!
Difficult surface as concrete and covered with enteromorpha
However, differences average out

13. PCDL quadbike survey
PCDL pattern

14. Unicycle GPSsurvey

15. MDL survey

16. MDL survey detail

17. GEOMatics LIDAR survey Not a LIDAR gap but where UAV is much higher
Only two flight paths, not entire sure this is all there is

18. GEOMatics LIDAR survey detail

19. All methods
Note that MDL does not work at all on the sand except directly under the scanner which is usually not used?

20. Elevation Difference nearest point GEOM - MDL
Using LIDAR as the baseline due to most even distribution.
Differences focussed on structures but also on the paths

21. Elevation Difference nearest point
GEOM - MDL

22. Elevation Difference nearest point GEOM - UAV
Some issues on the upper beach with higher and lower areas close together resulting in overal offset
Elevation Difference nearest point
GEOM - UAV

23. UAV photo density
The UAV model is based on 145 images. Ground resolution 1.7 cm.

24. Elevation Difference nearest point GEOM - PCDL
Differences only concentrated at topographic sharp boundaries, overall spot on
Elevation Difference nearest point
GEOM - PCDL

25. Elevation Difference nearest point GEOM - Unicycle
Differences mainly at the very fine details

26. Dry beach

27. Elevation Difference MDL - UAV Elevation Difference MDL – GEOM Points
PCDL
Unicycle
Elevation Difference
MDL – GEOM

28. Elevation Difference MDL - PCDL Elevation Difference MDL – Unicycle
Points
UAV ,000
GEOM ,875
PCDL
Unicycle
Elevation Difference
MDL – Unicycle

29. Soft clay

30. Elevation Difference UAV - GEOM Elevation Difference UAV - unicycle
Points
UAV
GEOM
MDL
Unicycle 58
Elevation Difference
UAV - unicycle
Elevation Difference
UAV - MDL
Very small area, not covered by
Unicycle 58 points
DNA 77
LIDAR 188
UAV 1538

31. Dry flat
sand

32. Elevation Difference MDL - UAV Elevation Difference MDL – GEOM
Points
UAV
GEOM
PCDL
Unicycle
Elevation Difference
MDL - PCDL
Elevation Difference
MDL - unicycle

33. Wet flat
sand

34. Elevation Difference GEOM - MDL Elevation Difference GEOM -UAV
Points
UAV ,706
MDL ,185
PCDL
Unicycle
Elevation Difference
GEOM - PCDL
Elevation Difference
GEOM - unicycle

35. grass

36. Elevation Difference
GEOM - UAV
Elevation Difference
GEOM - unicycle

37. Cobbles

38. Elevation Difference MDL - UAV Elevation Difference MDL – GEOM
Points
UAV ,461
GEOM ,475
PCDL
Unicycle
Elevation Difference
MDL - PCDL
Elevation Difference
MDL - unicycle

39. Summary I

40. Summary II
More analysis needed

41. Elephant in the room

43. Wet flat
sand