NORBIT DCT – Hydrographic Survey Made Easy
By Pawel Pocwiardowski, Product Director, Sonar Systems, NORBIT Subsea
With the increasing number of maritime operations worldwide, more and more hydrographic surveys are required to be conducted. This exerts a demand for hydrography providers with survey capabilities ranging from single-beam to multibeam echosounders, sub-bottom profilers, lidar, and magnetometers. The developed markets with a long history of bathymetry and hydrography surveys are well prepared to serve the increased demand with professional hydrographers, equipment and software support. However, in emerging markets and developing countries, the professional hydrography market requires a different approach as the backlog of professional hydrographic surveyors is not established yet. The current commercially available tools require ex-tensive training and understanding of the survey setup and for many smaller companies that presents a barrier which is very challenging if not impossible to cross. To address these emerging markets and the need for simple tools to perform basic bathymetry surveys NORBIT has developed the DCT – Data Collection Tool.
Contemporary hydrography needs
Nowadays hydrographic surveys become more and more commoditized due to the standardization of requirements and deliverables. The increased demand in various bathymetry mapping projects propels the development of standard tools and further facilitates the adaptation of the high-resolution mapping technologies across the industries. That ranges from safety of navigation pro-jects, through dredging and various construction and environmental projects like habitat mapping and bottom classification. It crosses commercial markets as well as government and public agencies. These developments extend widely throughout the world from oceans and lakes to rivers, in-land reservoirs, port, channels and man-made basins. With the technology being easier and cheaper to use, the number of applications and use cases has increased dramatically in recent years. Especially an urgent need for integrated simple-to-use mapping and imaging hydrography technology has emerged in the transitional market of users of single-beam (or sidescan) to multibeam technology. That is driven by multibeam wide-coverage, high accuracy, high resolution and efficiency of survey.
For the past years, NORBIT has been leading the manufacturing of ultra-high resolution curved-array bathymetric mapping solution and its technology has been widely accepted by the maritime markets across the world. The integrated hardware offerings have set the grand entry path for the users of these systems, due to simple mobilization and operation of hardware. Survey organizations (commercial and government such as navy), have started to utilize small survey boats with a single person running the operations or utilizing unmanned surface vessels (USV). The cost related to running these survey operations can then be limited and more companies can perform bathymetry missions which in the past would not be in their reach.
However, the survey tools, available commercially, still prove to limit the full potential of the new emerging markets due to its complexity on both, setup, installation and operation as well as data post-processing and final product deliverables.
To address these emerging market needs, NORBIT has recently developed a survey utility called Data Collection Tool (DCT) to facilitate a simpler survey operation and provide a means to collect quality bathymetric data, ready to be post-processed and delivered to the end client.
What is DCT?
The Data Collection Tool (DCT) - is a survey data acquisition utility, part of NORBIT’s offerings aimed to simplify the standard bathymetry survey operations. The general bathymetry grid is dis-played in a web browser allowing quick estimation of the coverage and data quality in real-time while running the survey.
DCT can be operated with a simple touch screen of the navigation plotter, tablet, smartphone or PC by a single person. By reducing the amount of configuration required by the user the real-estate on the screen is maximized allowing for a clear, precise and easy way to understand the interface. With a simple Start/Stop button the user can acquire the needed data which are then recorded on the survey PC. The skipper or boat driver can run the survey without constantly recon-figuring the system, allowing him to concentrate the efforts on safety aspects and any other tasks while running the survey operation. In cases where help from a more experienced surveyor is needed, the displays can be accessed from anywhere in the world (e.g. via VPN over 4G access) and from any terminal equipped with a web browser.
With a tap of a finger or by a mouse click users can draw lines, generate a number of wing lines with given spacing in just seconds. Each line can be adjusted, moved, rotated, resized or deleted as needed. The mission planning can be performed in the office or on the boat. Then the survey scheme can be saved as a disk file and emailed or shared with another PC to be loaded on the sur-vey setup. That allows for mission planning in advance and sharing of the survey plans with other team members. The mission planning can be supervised from the office as long as there is net-work access (e.g. via VPN over 4G) to the boat and simply navigating with the web browser to the survey PC. Then the mission planning can be shared and modified as needed.
A similar feature is available for maps. The Google Maps or Open Street Maps can be cached locally and made available on the survey PC to run the background maps even without the internet access.
Quality-driven mission execution
DCT offers four types of real-time display accessible via simple tap or mouse click under the layer menu button. These are depth, standard deviation, sounding density and backscatter. The depth by default is simply the depth from the sonar to the bottom and can be displayed in a projected reduced chart datum as well. The standard deviation and sounding density are produced per given grid size. By default, 0.5m grid size is selected but can be changed by the user. The backscatter is given as average intensity from each grid cell.
All four displays can run concurrently (see Fig. 4) on one or several clients, e.g. skipper can view depth display and surveyor or QA remote assistant can view standard deviation and sounding density display. The background maps (Google maps or Open Street maps) can be selected according to user preferences differently on different clients. Zooming, panning and boat location/tracking options are available also on all displays.
The entire data collection process is driven by Max Quality Rule, which is a unique offering from NORBIT. Each time the record button is pressed all raw sensor data (bathymetry, navigation, etc.) are being collected into the NORBIT local data repository (as a data file) and a new grid line is generated (as an entry in the database). The overlapping grid lines compete for quality, and the grid bins with lower standard deviation replace the data with high noise (high standard deviation usually meaning worse quality data).
The Max Quality rule is outlined in Fig. 5 where two lines are overlapping. The multibeam detections of outer beams, usually have a higher standard deviation (higher spread) than in the nadir region. The nadir region data will thus prevail and replace the gridded data of lower quality with higher quality data. This functionality makes it easier for the operator to collect the data with highest accuracy as DCT will always display high accuracy data over low accuracy data and will show the standard deviation on the color display allowing the operator to take corrective actions if needed.
The depth display will also be driven by the Max Quality Rule and adequately follow the standard deviation display and show high-quality data over low-quality data. In that way, the operator can take quick corrective actions and re-run the areas with low accuracy to ensure full coverage with properly collected data. It eases the tasks related to removing the bad data and simply running over the noisy data will replace them on the display (all original data is still recorded safely and preserved).
As a part of mission execution tools, users can, if needed, delete a portion of the grid or entire se-lected lines. This functionality allows for elimination of the erroneous overlapping grid lines from the display without the need to re-acquire all underlying data. The data is only removed from the displayed grid to help operators better assess the quality of the collected survey data. That saves time and greatly improves the efficiency of the survey.
Where DCT can be used.
The primary use for DCT is a simple standard survey where the multibeam integrated GNSS/INS system constitutes a complete solution. NORBIT iLiDAR laser sensor support will be added in future versions. The ease of use, however, qualifies the DCT to be used on various platforms starting from one-man operated surface vessels to recently blooming market of USVs.
Especially for USVs the DCT offers a great advantage as the entire data collection can be done on the local drive onboard the USV and only the HTTP-based map with coverage and quality indicators are transmitted over to the operator using any web browser device. Several USVs can be monitored using the same terminal or PC as long as they have a radio connection. Even if the radio link to the monitoring terminal breaks down, the data is securely stored on the local drive and once the connection is re-established the image re-appears on the monitoring terminal. The USV manufacturers can use the web browser directly or easily integrate the HTTP based DCT’s protocol via NORBIT’s Open Source Hydrography platform, which is a DCT backbone and comprises of tools and utilities allowing for data access and manipulation similar to the web browser operations. The access is facilitated by open source frameworks which are supported by the GIS community all around the World. The DCT supports both Windows and Linux operating systems that allows for integration to multiple platforms and multiple manufacturers.
Post-processing and product delivery
It is important to note that DCT is not a bathymetry processing software. It is a utility to securely and efficiently run hydrographic surveys, collect high-quality survey data and make them available for the processing software. The DCT records the data in NORBIT *.wbm file as well as in popular *.s7k file. The s7k file contains all raw bathy points and navigation datagrams which makes it very easy to drag and drop to processing software such as CARIS HIPS&SIPS or Qimera and start the da-ta processing right away. It is also possible to use automated tools such as CARIS on-board or Qimera Live for immediate processing results. The data is always collected in WGS84 coordinates, and all data is time stamped in the NORBIT hardware. The speed of sound profile is also saved in the same file (or can be added to the processing software if needed). At the same time the raw GNSS/INS observables are recorded and allow for navigation postprocessing of a complete navigation solution even if the RTK dropout happen during the survey or no RTK was available at a survey time.
NORBIT’s latest Data Collection Tool (DCT) is a simple and useful tool for new markets to emerge onto the hydrography survey world. The web browser interface allows conduction of the survey in an efficient way. It is suitable for small boats and single person operations as well as unmanned vehicles with low-bandwidth radio connectivity to the operator. DCT concentrates on data quality and helps the operator gather high-quality data with Max Quality Rule operating in real time. Through web-based displays, DCT allows access to the survey results and monitoring of the progress from any terminal in the network either local or remote.