This distance learning course provides a broad overview of several topics critical to conducting hydrographic surveys to map the seafloor and create nautical charts. The lessons contained in this course can provide prerequisite material for those pursuing certification in the field of hydrography, or those that work with hydrographers and would benefit from an understanding of the many factors that impact hydrographic surveys. The optional lesson and videos provide additional detail on the topic of survey datums, a topic that is also addressed in the lesson Introduction to Geodesy and Mapping.
Goals and ObjectivesCourse Goal
The goal of this course is to provide students with knowledge of the basic concepts underlying hydrographic surveys and the production of nautical charts.Course Objectives
- State the key elements of a hydrographic survey
- Explain the general operating principles, advantages, and limitations of different seafloor sounding instruments
- Explain system calibration and corrector applications
- Describe the different types of nautical charts and the information they show
- Describe the shape of the Earth
- Describe datums and their importance for referencing horizontal position and height.
- Describe common map projections and their properties
- Describe the various rectangular coordinate systems and their application
- Describe how variations in temperature and salinity with depth affect the speed and refraction of sound waves
- Describe oceanographic conditions that affect acoustic propagation and what effect they have
- List and define the forces that cause and modify tides
- Describe tide prediction methods and explain when to use tidal observations vs. models
Accurate hydrographic surveys and nautical charts yield many societal benefits. Safety of navigation is the single most important result of hydrography. This allows ships to safely travel in and out of ports, saving lives and property and protecting the environment. In addition, humanitarian relief in the aftermath of a natural disaster frequently arrives on a ship. Until a clear and safe route to shore is established by hydrographers, supplies cannot reach those in need. And environmental management in coastal areas depends on knowledge of changes in the marine environment. Hydrographic surveys determine changes to bathymetry and seafloor characteristics.
Hydrography is a multidisciplinary science that draws on many fields to produce a nautical chart.
- Hydrographers use physical oceanography to characterize the properties of the water column, which directly impact ocean acoustics, and to analyze the tidal characteristics of the survey area.
- Most modern surveys use acoustic soundings to determine the water depth, so a successful survey requires a solid understanding of ocean acoustics.
- Datums for horizontal and vertical references require an accurate determination of the geoid and the shape of the Earth.
- Gathering the data together and producing a nautical chart depends on sound cartography.
The lessons in this course all touch on key elements in hydrographic surveys and the production of nautical charts. Introduction to Hydrography provides an overview of sounding techniques and nautical charts. Introduction to Geodesy and Mapping examines the underlying principles of mapmaking: geodesy, datums, map projections, and map coordinate systems. Introduction to Ocean Acoustics looks at propagation of sound waves under water - crucial for hydrographic surveying with echosounders. And last, Introduction to Ocean Tides explores the rise and fall of sea level in response to movement of the Earth, Moon, and Sun, as well as the influence of weather.
One significant aspect of hydrographic surveys that is not covered in this series is an overview of the Global Positioning System. There are many good online resources that cover this topic. One that we like is The Trimble GPS Tutorial (http://www.trimble.com/gps_tutorial/dgps-advanced3.aspx).