3D Reconstruction of Canal Profiles using Data Acquired from Teleoperated Boat

Over the past three years, Thailand has experienced widespread flooding in several regions across the country. In fact, flooding has always been a recurring hazard in Thailand, but recently, due to rapid urban development and deforestation, flooding has become more severe. In order to reduce the hazard severity and minimize the area affected by flood, flood management personnel need to know the profiles of canals and waterways. The profile data should, at least, include physical descriptions of canal banks, width between two sides of canal, depth of canal bed, water level, and existing structures along the stretches of waterways. This will allow them to effectively direct the water flow in ways that can reduce the amount of flood water.

In this work, we equip a teleoperated boat with a 2D laser scanner, a single-beam depth sounder, and GPS/IMU sensors to make it possible to describe canal banks and bottom profiles during navigation along the waterway.

The 2D laser scanner documents the environment by emitting its laser pulses from the left side to the right side, which covers 270deg. The figure below illustrates the installation of the laser scanner and the moving direction.

The laser range and depth parameters while the boat documenting canal banks and the bottom profiles can be illustrated as the figure below.

Both laser scanner data and depth data are acquired in their own local coordinate systems. In order for these data to be integrated and be able to produce the picture of waterways, they must be georeferenced into the same coordinate system, principally the world coordinate system (GCS). The transformation from one coordinate system to another is basically a series of transformations, each of which is defined by an individual 3D rotation matrix, from the initial coordinate system in which the data is defined into the destination coordinate system. Here, we transform the laser coordinate system (LCS) into the boat coordinate system (BCS) then the North-East-Down coordinate system (NED) and finally the world coordinate system (GCS).

In this work, the application to reconstruct and visualize canals in 3D is developed in the C/C++ language. In order for the application to present 2D/3D graphical images, we employ the OpenGL library (www.opengl.org), which is free from licensing requirements. The graphical user interface for the end users to operate the application and adjust the visualization is implemented with the Qt library (qt-project.org) under open source license. This is how the application looks like.

Some experimental results:

The program is now completed but I haven't created its snapshop video yet. Here is the application at its 70%-completed status (27 May 2014).



Publications:
Tanathong, S., Rudahl, K.T., Goldin, S.E., 2014. 3D reconstruction of canal profiles using data acquired from teleoperated boat. In: Proceedings of Asia GIS, Chiang Mai, Thailand. [PDF]

Presentations:
GeoFest2014 Seminar, King Mongkut's University of Technology Thonburi [Powerpoint]