SO432 Hydrography Lesson objectives 



  1. Know what GI&S stands for, as well as its precursor, MC&G.
  2. Know the major US mapping organizations (NIMA/DMA, NOAA, and USGS).
  3. Know what GIS stands for, and its relationship to the fact  that mapping will soon be almost entirely digital.
  4. Understand that mathematical constructs like projections and datums have practical importance.

History of mapping

  1. Discuss the important developments in mapping in the following time periods: ancient and medieval, Renaissance, Enlightenment, 19th century, and 20th century.
  2. Discuss the relationships among map making, astronomy, mathematics, and navigation.
  3. Discuss why a globe cannot serve as a useful map.
  4. Define the following terms: large scale and small scale, map projection, portolan chart.
  5. Discuss how GIS is becoming part of the mainstream for marine researchers.

Side scan sonar

  1. Discuss the uses of side scan sonar for charting operations.
  2. Discuss how a side scan sonar uses the time of a return and its intensity to build up a picture of the bottom.
  3. Discuss the controls on return strength.
  4. Discuss the geometric and radiometric corrections applied to side scan sonar data.


  1. Discuss the things users might want in a projection: equal-area, conformality, equidistant, azimuthal, and geometry of rhumb lines, small or great circles.
  2. Discuss the three surfaces used to develop geometric projections.
  3. Discuss the Tissot indicatrix to show the distortion on a map.
  4. Differentiate the forward and inverse projection equations.


  1. Discuss the measurements used to define an ellipsoid: a, b, f, and eČ.
  2. Discuss the historical and other reasons why different datums have been used.
  3. Discuss the difference between a local datum like NAD27 and an earth centered datum like WGS84.
  4. Discuss vertical datums and the different vertical height measurements.
  5. Discuss the need for datum transformations.
  6. Discuss how ellipsoids and datums are defined.

GPS survey

  1. Understand the components of the GPS system (space, ground, and user).
  2. Key terms: ephemeris, SPS, PPS, P-code, C/A code, S/A
  3. Discuss the use of 2 frequencies and 2 codes to get position data.

GPS errors

  1. Discuss the sources of error and error measures with GPS surveys: PDOP, CEP, and RMS.

Grids and coordinates

  1. Know the 4 conformal map projections used by the military (Transverse Mercator, polar stereographic, Lambert conformal conic, and Mercator)
  2. Differentiate a grid and graticule.
  3. Discuss how the UTM projection differs from the Mercator.
  4. Discuss the purpose and procedures used with the MGRS.
  5. Know what the Molodenskiy Transformation does.

Computer versus paper mapping

  1. Understand the following computer terms and how they apply to mapping: bit, byte, kilobyte, megabyte, vector, raster, binary, ASCII, dpi, compression (lossy and lossless).
  2. Differentiate the different kinds of map data: vector, raster, grid, and text.
  3. Understand the geometries needed for vector map data: points, lines, and areas.
  4. Discuss some of the advantages and disadvantages of vector versus raster data.

Sub bottom profiling

  1. Discuss the uses of seismic reflection profiling, particularly in the marine environment.
  2. Discuss how the reflection coefficient is determined from the ratio of the difference of the impedances over the sum of the impedances.
  3. Know the tradeoffs between low and high frequency for reflection work.
  4. Understand the controls on impedance: Grain size, Density, and Porosity
GIS at sea
  1. Describe how real time GIS at sea can combine existing  chart/map data, real time input from navigation data and other sensors, and other data sources to improve both navigation and military/science operations.
  2. Discuss the challenges in terms of network administration and system administration to running such a system.
  3. Describe how and why maps are moving toward an interactive GIS model.
Data models
  1. Discuss the difference between vector and raster data, and how grid data like DEMs differs from other raster data.
  2. Discuss the types of compression, and why we would like to compress map data.
  3. Describe why data model  design steps (external, conceptual, logical, and internal) are important to the creation of a GIS

  1. Define a geographic information system (GIS), and the importance of topology

  2. Discuss the components of a GIS and how they interact to solve useful problems.

  3. Discuss the four major functions of a GIS.


Survey operations (NOAA guest lecture)

  1. Understand the division of labor among NOAA, USACE, and USCG in the making of nautical charts.

  2. Discuss how NOAA prioritizes its hydrographic survey operations.

  3. Understand the planning for NOAA survey operations.

  4. Understand how multibeam bathymetry and side scan sonar complement each other.

Emergency survey operations (NOAA guest lecture)

  1. Discuss why NOAA hydrographic survey assets are valuable in emergency search operations.

  2. Disucss the use of search patterns and side scan sonars in emergency search operations.

Tides and water levels

  1. Differentiate the three measures of vertical elevation (ellipsoid/geodetic height, orthometric height, and geoid height)
  2. Understand the problems in measuring sea level, and the terms used: MSL, MLW, MLLW, MHW, MHHW
  3. Understand the difference between a vertical datum like NGVD 1929 or NAVD 88 and any of the measures of sea level.
  4. Discuss the need for tidal epochs on the 19 year Metonic cycle.
  5. Discuss the importance and use of tidal observations during hydrographic surveys.

Depth sounding

  1. Know the three types of methods for depth soundings: sounding poles, lead lines, and echo sounders.
  2. Understand the principles of echo sounder operation, and the corrections that must be applied.
  3. Discuss the advantages of multibeam echo sounders

Imagery and mapping

  1. Describe the uses of imagery, both satellite and aerial photography, in mapping and charting.

  2. Discuss the tradeoffs in image resolution (spatial, spectral, radiometric, and temporal)

  3. Describe how satellite orbits affect imagery.

  4. Discuss the 8 keys used for image analysis (Shape, Size, Pattern, Tone/hue, Textures, Shadows, Site, Association)

  5. Understand the importance of georegistered/geocoded imagery for mapping

NIMA map products

  1. Know why all NIMA digital data uses lat/long coordinates and WGS84.

  2. Understand that NIMA produces different classes of maps and charts, and that the projections and grids used vary in a systematic fashion.

  3. Know what the following digital data sets are: CIB, CADRG, ADRG, and DTED.

  4. Discuss the types of nautical charts: sailing, coastal, approach, and harbor, in terms of their purpose and what they depict.

  5. Explain why NIMA compress imagery and scanned maps.

  6. Differentiate the VPF and RPF.

USGS map products

  1. Know that USGS produces DEMs, DRGs, and DOQs, and how these compare to NIMA products.

  2. Know that USGS uses a UTM projection and coordinates for its digital data, and how this compares with the NIMA use of lat/long coordinates.

Geographic information systems & Cockpit map displays

1.      Discuss the challenges in taking map data and displaying it in the cockpit of an aircraft, especially during military operations

Mapping from Radar altimeters

  1. Discuss why satellite altimeters can greatly improve our mapping of the deep oceans.

  2. Discuss the operation of radar altimeters.

  3. Discuss the history of radar altimeters, and why the GEOSAT Geodetic Mission provided the best data compared to SEASAT, the Exact Repeat Mission, or the current TOPEX/POSEIDON.

  4. Know what the ETOPO5 data set is.

  5. Discuss the importance of crossovers in hydrographic surveying.

Electronic bridge

  1. Know the components of an ECDIS system (hardware, software, ENC data in S57 format converted into SENC), and the precise legal requirements, including provisions for updating the chart data.

  2.  Understand the differences in mapping requirements between a national hydrographic office and military chart makers

  3. Know that DNC is in VPF and DIGEST (NATO) format, and is not yet approved for ECDIS

Map Accuracy and errors
  1. Know what metadata is and why it is important.
  2. Discuss the three types of error
  3. Differentiate accuracy and precision as they apply to mapping.
  4. Understand map accuracy standards, and how the "width of a line" varies with map scale.
Nautical charts and aeronautical charts
  1. Discuss why different scales (series) of nautical and aeronautical charts are used.
  2. Discuss why the grid and handling of magnetic variation change with the different aeronautical charts.


Key concepts

  • Time of transition: paper maps and charts to GIS

  • Military GI&S, from NIMA

  • Always tradeoffs--no perfect map/chart; depends on the needs of the user


Map basics

·        Projection: forward and inverse, properties (conformal)

·        Tissot indicatrix

·        Datum: why and practical importance, both horizontal and vertical

·        Large and small scale

·        Series (harbor, approach, coastal, general)

·        MGRS vs. lat/long

·        Accuracy (width of a line)

·        Metadata: quality and lineage


Digital data

·        Raster and vector and grid (DEM) and text

·        Scale, and blowing up, zooming out

·        Generalization

·        Compression


Chart/map production/methods

·        Depth surveys

·        Imagery (side scan)--100% coverage, high resolution

·        Satellite imagery or photography (coastlines, culture, land maps)

·        Tides: correction and MLLW as chart datum

·        Altimetry for bathymetry

·        LIDAR

·        SRTM

·        Agencies: NIMA, USGS, NOAA, USACE, USCG


Chart Use

·        ECDIS

·        DNC

·        Cockpit moving displays



·        Filter--turn on/off based on your own criteria

·        Query--what is a feature, and what information is available



·        Error measures

·        Basics of the system


NIMA Products

·        DTED

·        CIB

·        CADRG

·        VPF (e.g. DNC)

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