測深光達原理、現有系統與服務

The Principles of the Bathymetric Lidar and the Current Systems and Services

地形測量所使用之空載光達系統多使用紅外波段1064nm 波長之雷射光，該波段對水體之穿透力低，若經倍頻後所得532nm 波長之雷射光，則屬綠光波段，具有透水能力。使用綠光波段構建之光達系統，可用以進行水深與水底地形測量。與聲波測深系統之成果相比較，其成果雖然尚不能達到IHO 規範之特級要求，但是由測試案例與國外實測經驗顯示，目前空載測深光達已可達IHO 規範之一級要求。雖然精度並非超越聲波測深系統，空載測深光達具有近岸淺水與礁石區作業之方便性，與船測相較，安全度高，而且作業速度亦高。相較於陸域之空載光達，測深光達之產品成熟度尚低。本研究分析現有商業性儀器，就儀器而言有三種系統，加拿大Optech 之SHOALS、澳洲Fugro-LADS （Tenix-LADS）之LADS、瑞典Airborne Hydrography AB 之Hawk Eye。而就研究性之系統而言，美國USGS 使用中之EAARL為一具有未來性之作業中系統。就服務之提供而言，除澳洲Fugro-LADS 本身亦提供測深服務，實質進行專案承包外，美國Fugro-Pelagos 使用Optech 之SHOALS 系統，歐洲BLOM 則使用瑞典Airborne Hydrography AB 之Hawk Eye II，另一家歐洲公司，英國的Pelydryn 則亦使用Hawk Eye II 系統。本文謹就測深光達原理、現有系統與服務，歸納研究成果。 The most common wavelength of the laser beam used by airborne topographic lidar systems is 1064nm. This wavelength belongs to the infrared portion of the spectrum, which does not penetrate the water well. The 532 nm laser beam generated from the 1064 nm utilizingthe double frequency process, has good water penetrating capability. The bathymetric lidarsystems utilize the 532 nm laser, which can be used for the bathymetric survey and substratemapping. Validated with the sonar based bathymetric systems, the bathymetric lidar may notreach the IHO special order, but can fulfill the IHO specification of first order. The airborne lidaris not superior in accuracy than the acoustic based systems. But, the airborne system has manyadvantages for the operation in the shallow water area. Studying the current systems availablecommercially, there are three, namely, Optech SHOALS from Canada, Fugro LADS fromAustralia, Airborne Hydrography AB Hawk Eye from Sweden. In the non-commercial sector, EAARL system operated by USGS of the States is featured with advanced designs. Fugro-LADSis the only company which provides both systems and services. Besides Fugro-LADS, Fugro-Pelagos of the States operates with an Optech SHOALS, and BLOM from Europe andPelydryn from U.K. operate with Airborne Hydrography AB Hawk Eye II. This paper introducesthe bathymetric lidar system, including the principle, the systems, and the services.

The most common wavelength of the laser beam used by airborne topographic lidar systems is 1064nm. This wavelength belongs to the infrared portion of the spectrum, which does not penetrate the water well. The 532 nm laser beam generated from the 1064 nm utilizingthe double frequency process, has good water penetrating capability. The bathymetric lidarsystems utilize the 532 nm laser, which can be used for the bathymetric survey and substratemapping. Validated with the sonar based bathymetric systems, the bathymetric lidar may notreach the IHO special order, but can fulfill the IHO specification of first order. The airborne lidaris not superior in accuracy than the acoustic based systems. But, the airborne system has manyadvantages for the operation in the shallow water area. Studying the current systems availablecommercially, there are three, namely, Optech SHOALS from Canada, Fugro LADS fromAustralia, Airborne Hydrography AB Hawk Eye from Sweden. In the non-commercial sector,EAARL system operated by USGS of the States is featured with advanced designs. Fugro-LADSis the only company which provides both systems and services. Besides Fugro-LADS,Fugro-Pelagos of the States operates with an Optech SHOALS, and BLOM from Europe andPelydryn from U.K. operate with Airborne Hydrography AB Hawk Eye II. This paper introducesthe bathymetric lidar system, including the principle, the systems, and the services.