At the Crossroads: Seamless Coastal Terrain Models in the Pacific Region

1. 39th ANNUAL SESSION STR “Map Once – Use Many Ways” At the Crossroads: Seamless Coastal Terrain Models in the Pacific Region S O P A C Salesh Kumar and Jens Kruger Ocean and Islands Programme Pacific Islands Applied Geoscience Commission

2. Presentation outline • Coastal Terrain Modelling (CTM) • Brief description of MBES and LiDAR systems • Compare 2 specific countries in the Pacific: Saipan (CNMI) and Funafuti (TUVALU) and the data available for these countries • Look at the costs involved in both these types of survey • Conclusion

3. Seamless CTM • Coastal environment is a complex transitional system between the • terrestrial and marine realms. • The coastal zone is a Constantly changing environment. The • awareness of the issues associated with the coastal zone and the • need to deal with them in an integrated way, are becoming more • prominent in coastal studies. • The ability to seamlessly map topography and bathymetry • is especially valuable for: • Studies examining or modelling coastal patterns and processes, • since many important marine habitats are emergent at low tides • (e.g., intertidal seagrass, salt marshes, mangroves and • some coral reefs).

4. Surveying the coastline is multidisciplinary since it involves both land (topographic data) and water (hydrographic data). Many Pacific Island Countries (PIC’s) have bathymetry data up to 50m Bathymetry data in areas shallower than 50 m do exist in some PIC’s (mostly singlebeam data) Satellite data can be used to extract bathy data in shallow areas. (not done extensively at the moment) Critical gap exists between the Topography and hydrography data in most PIC’s. Teara.gov.nz

5. Factors that are driving the need for new data in coastal zone • Urban expansion in the coastal zone – Waterfront buildings, roads, bridges, harbours. • 2. Tourism – leisure boat traffic, sandy beaches, diving areas. • 3. Oil and gas exploration – oil and gas pipe lines. • 4. Environmental surveying – shore erosion models, water flow currents, sea floor vegetation. • 5. Natural catastrophes mitigation – mitigation of effects of tsunamis, hurricane. • 6. Inland surveys - Wetlands, channels, large lakes

6. LiDAR Overview • Data Collection • - Plane Equipped with GPS, INS & LiDAR • LiDAR sensor works day or night, cloud coverage or not • Collection of 3D points • Laser sent out from Emitter, reflects off terrain, Returns to Receiver • - Receiver measures back scattered electromagnetic radiation (laser intensity) • Time difference determines range to target. • . What Data is Collected During a Flight? “Everything” • Foliage, Bare Earth • Transmission Lines and Towers • Railway Beds,Roadways,Vehicles • Buildings,etc. Optional • Photography • Weather Conditions Oceanservice.noaa.gov

7. Limitations of ship based MBES for data collection in shallow water environments; • Navigation dangers and challengers posed to vessels performing survey work • The inability to collect data in water shallower than approximately15m • Reduced efficiencies due to the proportional relationship between water depth and bottom coverage Banic & Cunningham (1998) Guenther et al. (2000)

8. Advantages of LiDAR systems for mapping shallow water environments • Negligible navigational risks when conducting shallow water surveys • Greater survey efficiencies in shallow-waters, as LiDAR swath width is independent of depth. • Ability to collect seamless, coastal topographic-bathymetric (i.e., land and sea) datasets. • For tidal zone, this is crucial as usually only short tide windows are available for operations. • The rate of coverage is very high, thanks to high sensing frequency, typically about 20km2 and over 50km2 per hour or more for hydrographic and topographic modes, respectively. • Major advantages are fixed width (not dependent on water depth), rapid transit to and conduct surveys, and cost efficiency compared to traditional techniques.

9. Combined datasets • (Funafuti_Tuvalu) • MBES data • Single beam data • Topography data

11. Multibeam data_lagoon Single beam data Topo data Multibeam data_offshore

12. Bathy LiDAR, Saipan

13. Bathymetry LiDAR, Saipan

14. Topography LiDAR, Saipan

15. Combined Data sets Topo & Bathy

16. Combined data: Topography and Bathymetry

17. Field surveys costs in Funafuti

18. Conclusion Offshore, ship based Multi-Beam Echo Sounder (MBES) survey has matured, and the costs decrease as the technology develops. However ship based MBES survey efficiency is poor in complex shallow waters. The cost of multi beam surveys increase dramatically as the depth decreases, and thus the MBES Swath width decreases. Airborne Laser bathymetry Systems (ALBS) have, during the last 10 years, proved their ability to survey large shallow areas quickly and accurately, fulfilling the requirements set by the International Hydrographic Organisation ( for IHO) for production of depth sounding data for charting purposes. LiDAR bathymetry is a cost-efficient method which houses a promising future in shallow water surveys. The advantages, that is high data collection rate and high sensitivity, makes it an ideal choice for coastline surveys and it is obvious that LiDAR will play a major role in geospatial community in the future.

19. Thank You