In some developing countries, the information available to plan and prioritise hydrographic surveys is typically based on visual inspection of existing nautical charts. However, due to the age of many existing charts and lack of availability of the original source data from which they were compiled (e.g., smooth sheets) this type of analysis is often quite limited. A study was conducted to evaluate the use of a satellite-derived bathymetry (SDB) procedure to map shallow-water bathymetry in a GIS environment, and to identify areas that require a new hydrographic survey. Publically available, multispectral satellite imagery and published algorithms are used to derive estimates of the bathymetry. The study results indicate a potential use of the procedure by national hydrographic offices as a reconnaissance too

Azuike, Chukwuma

Parrish, Christopher

Pe\u27eri, Shachak

English

University of New Hampshire

University of New Hampshire
University of New Hampshire Scholars' Repository
Center for Coastal and Ocean Mapping Center for Coastal and Ocean Mapping
4-12-2013
Satellite-Derived Bathymetry a Reconnaissance
Tool for Hydrography
Shachak Pe'eri
University of New Hampshire, Durham, shachak.peeri@unh.edu
Chukwuma Azuike
University of New Hampshire, Durham
Christopher Parrish
University of New Hampshire, Durham
Follow this and additional works at: https://scholars.unh.edu/ccom
Part of the Oceanography and Atmospheric Sciences and Meteorology Commons
This Journal Article is brought to you for free and open access by the Center for Coastal and Ocean Mapping at University of New Hampshire Scholars'
Repository. It has been accepted for inclusion in Center for Coastal and Ocean Mapping by an authorized administrator of University of New
Hampshire Scholars' Repository. For more information, please contact nicole.hentz@unh.edu.
Recommended Citation
Pe'eri, Shachak; Azuike, Chukwuma; and Parrish, Christopher, "Satellite-Derived Bathymetry a Reconnaissance Tool for
Hydrography" (2013). Hydro International. 1119.
https://scholars.unh.edu/ccom/1119
| OCTOBER 2013 | Hydro INTERNATIONAL16
data must be referenced to a chart 
datum (typically a tidal datum), and 
2) the procedures must be based on 
readily-available, low-cost data and 
software. 
Landsat 7  
Landsat 7 imagery is free and 
publically available ( 1). An eight-
band multispectral-scanning 
radiometer, the Enhanced Th ematic 
Mapper plus (ETM+), collected 
imagery with 185km swath-width 
and an image resolution of up 
to 28.5m. Th e large swath of the 
Landsat imagery can potentially 
cover nautical charts of the scale 
of 1:50,000 to 1:60,000 with a single 
image. Although the Landsat ETM+ 
imagery has fairly coarse resolution, 
it is signifi cantly smaller than the 
maximum allowable spacing between 
charted soundings of 300m (in ground 
distance) of the scale of charts used 
in the study. For the procedure, only 
three (blue, green, and near-infrared) 
of the eight bands are needed. Th e 
Landsat imagery is ortho-rectifi ed 
and referenced to the WGS84 datum 
with a stated positional uncertainty 
of better than 50m. Although Landsat 
7 images that are useful for SDB were 
only collected from April 1999 to June 
2003, this time frame is more recent 
than survey data in many charts of 
developing countries. Many of these 
surveys were conducted more than 50 
years ago.  
Procedure Development 
Th e satellite-derived bathymetry 
procedure was developed using a 
US calibration study site (Rockport, 
Massachusetts), which has a low-
energy wave environment with a tidal 
range of about 2.5m. It is important 
to note that only a few, carefully-
selected chart soundings are used 
in the procedure to reference the 
satellite-derived bathymetry to 
the chart datum. One of the main 
criteria for the selection of this small 
In some developing countries, the information available to plan and prioritise hydrographic surveys is typically based 
on visual inspection of existing nautical charts. However, due to the age of many existing charts and lack of availability 
of the original source data from which they were compiled (e.g., smooth sheets) this type of analysis is often quite 
limited. A study was conducted to evaluate the use of a satellite-derived bathymetry (SDB) procedure to map 
shallow-water bathymetry in a GIS environment, and to identify areas that require a new hydrographic survey. 
Publically available, multispectral satellite imagery and published algorithms are used to derive estimates of the 
bathymetry. The study results indicate a potential use of the procedure by national hydrographic offices as a 
reconnaissance tool. 
A Reconnaissance Tool for Hydrography
Satellite-derived Bathymetry
THE ABILITY TO DERIVE 
bathymetry from multispectral sat-
ellite imagery is a topic that has 
received considerable research atten-
tion since the 1970s. Typical multi-
spectral satellite platforms (e.g., 
Landsat, Ikonos, SPOT, and World-
View) collect data in multiple spectral 
bands that capture a broad spectral 
range (40 to 150nm). Collectively, 
these bands typically span the vis-
ible to infrared portions of the elec-
tromagnetic spectrum. Th e physical 
concept underlying the ability to esti-
mate bathymetry from multispectral 
imagery is the wavelength-depend-
ent attenuation of light in the water 
column. To date, numerous algo-
rithms for bathymetry retrieval have 
been developed. However, a detailed 
study has not been made on the abil-
ity to make use of these algorithms 
and procedures for operational sur-
vey planning in national hydrographic 
offi  ces of developing countries.
Although the accuracy of SDB does 
not meet current International 
Hydrographic Organization (IHO) 
S-44 standards, results from this 
technique suggest that SDB can be a 
useful tool for survey planning and 
prioritisation, especially for national 
hydrographic offi  ces with limited 
resources. However, this application 
has two main requirements: 1) the 
Shachak Pe’eri,
Center for Coastal 
and Ocean 
Mapping, 
University of New 
Hampshire, USA
There is a correlation between 
accuracy of the bathymetric 
model and water clarity
Christopher Parrish,
NGS Remote 
Sensing Division, 
NOAA/NOS, 
National Geodetic 
Survey; Joint 
Hydrographic 
Center, NOAA, USA 
Chukwuma Azuike
Center for Coastal 
and Ocean 
Mapping, 
University of New 
Hampshire, USA
HYD0713_Feat_Pe eri   16 30-09-2013   10:07:26
Hydro INTERNATIONAL | OCTOBER 2013 | 17
subset of reference soundings is 
that the soundings are located in 
areas of relatively stable seafl oor 
that have likely not experienced 
signifi cant change since they were 
charted. Th ese soundings are used 
as control points to determine the 
transformation parameters used 
in the algorithm. Although the 
instantaneous water level at the time 
of satellite image acquisition is very 
unlikely to coincide with the chart 
datum (e.g., Mean Lower Low Water 
(MLLW) or Lowest Astronomical 
Tide (LAT)), there is no need to 
measure the tide height during the 
image acquisition. Th e control points 
reference the bathymetric model 
directly to the chart datum. Th us, the 
procedure eliminates both the need 
for tide-coordinated imagery and for 
tide correctors.  
An Airborne Lidar Bathymetry (ALB) 
survey that was conducted in 2007 by 
the US Army Corps of Engineers was 
used as a reference dataset. Th e ALB 
reference dataset was transformed to 
the MLLW tidal datum using NOAA’s 
VDatum software. ALB is considered 
an accurate survey technology that 
meets IHO Order 1b Total Vertical 
Uncertainty (TVU) specifi cations for 
soundings that are able to penetrate 
at least twice the water depth using 
SDB. Bathymetry from the satellite 
Figure 1: Key step 
of the SDB 
procedure over the 
US calibration site.
imagery was derived using a ratio of 
green-to-blue Landsat band pairs and 
was referenced using chart soundings 
(NOAA chart 13279). Th e high-
resolution ALB reference dataset (4m) 
was gridded at the Landsat’s image 
resolution (28.5m) for purposes of 
comparison.  
Th e study results from the US 
calibration site show that the 
eff ective depth of penetration where 
submersed features are inferred was 
between 5 and 6m. Although the 
average depth diff erence between the 
satellite-derived bathymetry results 
and the ALB reference dataset is 
small (0.30m), the standard deviation 
(1 ) of the depth diff erence is 1.79m. 
Th e results indicate that there is a 
correlation between the accuracy of 
the bathymetric model and the water 
clarity. 
Th e procedures developed using the 
data from the calibration site involve 
four main steps (Figure 1): 1) Satellite 
imagery is downloaded based on the 
Figure 2: Escravos, Nigeria: A 5m depth contour from the SDB overlaid on assigned depths derived from the chart.  
HYD0713_Feat_Pe eri   17 30-09-2013   10:07:27
Hydro INTERNATIONAL | OCTOBER 2013 | 19
geographic extent and environmental 
conditions (e.g., cloud coverage and 
sun glint), where dry land and most 
of the clouds are removed (masked 
out) using the Near-Infrared band; 
2) ‘Speckle noise’ in the Landsat 
imagery is removed from the blue-
green band using spatial fi ltering; 3) 
A blue-green band ratio algorithm is 
applied to derive bathymetry; and 4) 
Th e optical depth limit for inferring 
bathymetry (also known as, the 
extinction depth) is calculated and 
the algorithm values are referenced 
to the chart datum using the chart 
soundings. 
Evaluation of C-55 Sites 
In addition to the US calibration study 
site, shallow-water bathymetry was 
also evaluated over the coastal waters 
of Nigeria and Belize. Th ese sites were 
selected based on the IHO publication 
C-55, which identifi ed nautical charts 
that contain gaps in their hydro-
graphic data. In Nigeria, the satellite-
derived bathymetry correlated well 
with areas that have been recently 
surveyed (a commercial survey from 
2004) near the entrance to Escravos 
River. Bathymetry derived from the 
procedure identifi ed signifi cant diff er-
ences between depths and chart 
soundings in the northern section of 
the chart over a large area (several 
tens of square kilometers) and in the 
Benin River mouth north to Escravos 
River. In order to simplify the compar-
ison, the depth ranges were 
segmented based on signifi cant navi-
gational depths: from 0m to 5m, 5m 
to 30m, 30m to 40m and greater than 
40m. Based on the source diagram 
and the chart symbols, a probable 
cause of this diff erence is that the 
area has not been surveyed since 1913 
(Figure 2). A notable outcome of the 
study in the Belize study site was that 
the location of a natural channel 
between Belize City and Big Creek 
observed using SDB is east of its loca-
tion in the current nautical charts 
(Figure 3). 
Future Directions 
Based on the results of this study and 
responses from several hydrographic 
groups, this initiative is currently 
being expanded in collaboration 
with the General Bathymetric Chart 
of the Oceans (GEBCO) group and 
Integrated Ocean and Coastal 
Mapping (IOCM) programme in 
National Oceanic and Atmospheric 
Administration (NOAA). Th e 
procedure was documented 
and published in the GEBCO 
Cookbook. Since mid-2013, imagery 
from the new Landsat satellite 
(Landsat 8) is free and publically 
available and can also be used to 
derive bathymetry. 
Acknowledgements 
Th e authors would like to thank Dr 
Lee Alexander and Captain Andrew 
Armstrong (NOAA, ret.) for their 
advice. In addition, we want to 
thank NOAA and the UKHO for the 
copyright permission to use their 
charts for this study. 
1. http://earthexplorer.usgs.gov/
The Authors
Shachak Pe’eri is a research assistant Professor 
at the Center of Coastal and Ocean Mapping 
(CCOM), University of New Hampshire (UNH). 
His research focus is in airborne remote 
sensing with a focus on experimental and 
theoretical studies of airborne Lidar bathymetry, 
topographic Lidar, and terrestrial laser scanning 
and hyperspectral remote sensing. 
Lt Cdr Chukwuma Azuike is a hydrographer with 
the Nigerian Hydrographic Office. He graduated 
with a BSc from the Nigerian Defence Academy 
(2000) and an MSc from CCOM, UNH (2012). 
Christopher Parrish is the lead physical scientist 
in the Remote Sensing Division of NOAA’s 
National Geodetic Survey (NGS) and affiliate 
Professor of Ocean Engineering and Earth 
Sciences at the NOAA-University of New 
Hampshire Joint Hydrographic Center & Center 
for Coastal and Ocean Mapping (JHC-CCOM). 
Further Reading
General Bathymetric Chart of the Oceans 
(GEBCO), 2012. GEBCO Cook Book V2.6.13: 
http://ibis.grdl.noaa.gov/SAT/GEBCO_
Cookbook/index.php. 
International Hydrographic Organization (IHO), 
2004. Publication C-55, Status of Hydrographic 
Surveying and Nautical Charting Worldwide, 
Monaco, third edition (Latest Update 27 
September 2011). 
The procedure eliminates both 
the need for tide-coordinated 
imagery and for tide correctors 
Figure 3:  Big Creek, Belize: Channel path derived from chart soundings (black contour) overlaid on SDB. 
HYD0713_Feat_Pe eri   19 30-09-2013   10:07:27


Satellite-Derived Bathymetry a Reconnaissance Tool for Hydrography

UNH Scholars' Repository

University of New HampshireUniversity of New Hampshire Scholars' RepositoryCenter for Coastal and Ocean Mapping Center for Coastal and Ocean Mapping4-12-2013Satellite-Derived Bathymetry a ReconnaissanceTool for HydrographyShachak Pe'eriUniversity of New Hampshire, Durham, shachak.peeri@unh.eduChukwuma AzuikeUniversity of New Hampshire, DurhamChristopher ParrishUniversity of New Hampshire, DurhamFollow this and additional works at: https://scholars.unh.edu/ccomPart of the Oceanography and Atmospheric Sciences and Meteorology CommonsThis Journal Article is brought to you for free and open access by the Center for Coastal and Ocean Mapping at University of New Hampshire Scholars'Repository. It has been accepted for inclusion in Center for Coastal and Ocean Mapping by an authorized administrator of University of NewHampshire Scholars' Repository. For more information, please contact nicole.hentz@unh.edu.Recommended CitationPe'eri, Shachak; Azuike, Chukwuma; and Parrish, Christopher, "Satellite-Derived Bathymetry a Reconnaissance Tool forHydrography" (2013). Hydro International. 1119.https://scholars.unh.edu/ccom/1119| OCTOBER 2013 | Hydro INTERNATIONAL16data must be referenced to a chart datum (typically a tidal datum), and 2) the procedures must be based on readily-available, low-cost data and software. Landsat 7  Landsat 7 imagery is free and publically available (?1). An eight-band multispectral-scanning radiometer, the Enhanced Th ematic Mapper plus (ETM+), collected imagery with 185km swath-width and an image resolution of up to 28.5m. Th e large swath of the Landsat imagery can potentially cover nautical charts of the scale of 1:50,000 to 1:60,000 with a single image. Although the Landsat ETM+ imagery has fairly coarse resolution, it is signifi cantly smaller than the maximum allowable spacing between charted soundings of 300m (in ground distance) of the scale of charts used in the study. For the procedure, only three (blue, green, and near-infrared) of the eight bands are needed. Th e Landsat imagery is ortho-rectifi ed and referenced to the WGS84 datum with a stated positional uncertainty of better than 50m. Although Landsat 7 images that are useful for SDB were only collected from April 1999 to June 2003, this time frame is more recent than survey data in many charts of developing countries. Many of these surveys were conducted more than 50 years ago.  Procedure Development Th e satellite-derived bathymetry procedure was developed using a US calibration study site (Rockport, Massachusetts), which has a low-energy wave environment with a tidal range of about 2.5m. It is important to note that only a few, carefully-selected chart soundings are used in the procedure to reference the satellite-derived bathymetry to the chart datum. One of the main criteria for the selection of this small In some developing countries, the information available to plan and prioritise hydrographic surveys is typically based on visual inspection of existing nautical charts. However, due to the age of many existing charts and lack of availability of the original source data from which they were compiled (e.g., smooth sheets) this type of analysis is often quite limited. A study was conducted to evaluate the use of a satellite-derived bathymetry (SDB) procedure to map shallow-water bathymetry in a GIS environment, and to identify areas that require a new hydrographic survey. Publically available, multispectral satellite imagery and published algorithms are used to derive estimates of the bathymetry. The study results indicate a potential use of the procedure by national hydrographic offices as a reconnaissance tool. A Reconnaissance Tool for HydrographySatellite-derived BathymetryTHE ABILITY TO DERIVE bathymetry from multispectral sat-ellite imagery is a topic that has received considerable research atten-tion since the 1970s. Typical multi-spectral satellite platforms (e.g., Landsat, Ikonos, SPOT, and World-View) collect data in multiple spectral bands that capture a broad spectral range (40 to 150nm). Collectively, these bands typically span the vis-ible to infrared portions of the elec-tromagnetic spectrum. Th e physical concept underlying the ability to esti-mate bathymetry from multispectral imagery is the wavelength-depend-ent attenuation of light in the water column. To date, numerous algo-rithms for bathymetry retrieval have been developed. However, a detailed study has not been made on the abil-ity to make use of these algorithms and procedures for operational sur-vey planning in national hydrographic offi  ces of developing countries.Although the accuracy of SDB does not meet current International Hydrographic Organization (IHO) S-44 standards, results from this technique suggest that SDB can be a useful tool for survey planning and prioritisation, especially for national hydrographic offi  ces with limited resources. However, this application has two main requirements: 1) the Shachak Pe’eri,Center for Coastal and Ocean Mapping, University of New Hampshire, USAThere is a correlation between accuracy of the bathymetric model and water clarityChristopher Parrish,NGS Remote Sensing Division, NOAA/NOS, National Geodetic Survey; Joint Hydrographic Center, NOAA, USA Chukwuma AzuikeCenter for Coastal and Ocean Mapping, University of New Hampshire, USAHYD0713_Feat_Pe eri   16 30-09-2013   10:07:26Hydro INTERNATIONAL | OCTOBER 2013 | 17subset of reference soundings is that the soundings are located in areas of relatively stable seafl oor that have likely not experienced signifi cant change since they were charted. Th ese soundings are used as control points to determine the transformation parameters used in the algorithm. Although the instantaneous water level at the time of satellite image acquisition is very unlikely to coincide with the chart datum (e.g., Mean Lower Low Water (MLLW) or Lowest Astronomical Tide (LAT)), there is no need to measure the tide height during the image acquisition. Th e control points reference the bathymetric model directly to the chart datum. Th us, the procedure eliminates both the need for tide-coordinated imagery and for tide correctors.  An Airborne Lidar Bathymetry (ALB) survey that was conducted in 2007 by the US Army Corps of Engineers was used as a reference dataset. Th e ALB reference dataset was transformed to the MLLW tidal datum using NOAA’s VDatum software. ALB is considered an accurate survey technology that meets IHO Order 1b Total Vertical Uncertainty (TVU) specifi cations for soundings that are able to penetrate at least twice the water depth using SDB. Bathymetry from the satellite Figure 1: Key step of the SDB procedure over the US calibration site.imagery was derived using a ratio of green-to-blue Landsat band pairs and was referenced using chart soundings (NOAA chart 13279). Th e high-resolution ALB reference dataset (4m) was gridded at the Landsat’s image resolution (28.5m) for purposes of comparison.  Th e study results from the US calibration site show that the eff ective depth of penetration where submersed features are inferred was between 5 and 6m. Although the average depth diff erence between the satellite-derived bathymetry results and the ALB reference dataset is small (0.30m), the standard deviation (1 ) of the depth diff erence is 1.79m. Th e results indicate that there is a correlation between the accuracy of the bathymetric model and the water clarity. Th e procedures developed using the data from the calibration site involve four main steps (Figure 1): 1) Satellite imagery is downloaded based on the Figure 2: Escravos, Nigeria: A 5m depth contour from the SDB overlaid on assigned depths derived from the chart.  HYD0713_Feat_Pe eri   17 30-09-2013   10:07:27Hydro INTERNATIONAL | OCTOBER 2013 | 19geographic extent and environmental conditions (e.g., cloud coverage and sun glint), where dry land and most of the clouds are removed (masked out) using the Near-Infrared band; 2) ‘Speckle noise’ in the Landsat imagery is removed from the blue-green band using spatial fi ltering; 3) A blue-green band ratio algorithm is applied to derive bathymetry; and 4) Th e optical depth limit for inferring bathymetry (also known as, the extinction depth) is calculated and the algorithm values are referenced to the chart datum using the chart soundings. Evaluation of C-55 Sites In addition to the US calibration study site, shallow-water bathymetry was also evaluated over the coastal waters of Nigeria and Belize. Th ese sites were selected based on the IHO publication C-55, which identifi ed nautical charts that contain gaps in their hydro-graphic data. In Nigeria, the satellite-derived bathymetry correlated well with areas that have been recently surveyed (a commercial survey from 2004) near the entrance to Escravos River. Bathymetry derived from the procedure identifi ed signifi cant diff er-ences between depths and chart soundings in the northern section of the chart over a large area (several tens of square kilometers) and in the Benin River mouth north to Escravos River. In order to simplify the compar-ison, the depth ranges were segmented based on signifi cant navi-gational depths: from 0m to 5m, 5m to 30m, 30m to 40m and greater than 40m. Based on the source diagram and the chart symbols, a probable cause of this diff erence is that the area has not been surveyed since 1913 (Figure 2). A notable outcome of the study in the Belize study site was that the location of a natural channel between Belize City and Big Creek observed using SDB is east of its loca-tion in the current nautical charts (Figure 3). Future Directions Based on the results of this study and responses from several hydrographic groups, this initiative is currently being expanded in collaboration with the General Bathymetric Chart of the Oceans (GEBCO) group and Integrated Ocean and Coastal Mapping (IOCM) programme in National Oceanic and Atmospheric Administration (NOAA). Th e procedure was documented and published in the GEBCO Cookbook. Since mid-2013, imagery from the new Landsat satellite (Landsat 8) is free and publically available and can also be used to derive bathymetry. Acknowledgements Th e authors would like to thank Dr Lee Alexander and Captain Andrew Armstrong (NOAA, ret.) for their advice. In addition, we want to thank NOAA and the UKHO for the copyright permission to use their charts for this study. 1. http://earthexplorer.usgs.gov/The AuthorsShachak Pe’eri is a research assistant Professor at the Center of Coastal and Ocean Mapping (CCOM), University of New Hampshire (UNH). His research focus is in airborne remote sensing with a focus on experimental and theoretical studies of airborne Lidar bathymetry, topographic Lidar, and terrestrial laser scanning and hyperspectral remote sensing. Lt Cdr Chukwuma Azuike is a hydrographer with the Nigerian Hydrographic Office. He graduated with a BSc from the Nigerian Defence Academy (2000) and an MSc from CCOM, UNH (2012). Christopher Parrish is the lead physical scientist in the Remote Sensing Division of NOAA’s National Geodetic Survey (NGS) and affiliate Professor of Ocean Engineering and Earth Sciences at the NOAA-University of New Hampshire Joint Hydrographic Center & Center for Coastal and Ocean Mapping (JHC-CCOM). Further ReadingGeneral Bathymetric Chart of the Oceans (GEBCO), 2012. GEBCO Cook Book V2.6.13: http://ibis.grdl.noaa.gov/SAT/GEBCO_Cookbook/index.php. International Hydrographic Organization (IHO), 2004. Publication C-55, Status of Hydrographic Surveying and Nautical Charting Worldwide, Monaco, third edition (Latest Update 27 September 2011). The procedure eliminates both the need for tide-coordinated imagery and for tide correctors Figure 3:  Big Creek, Belize: Channel path derived from chart soundings (black contour) overlaid on SDB. HYD0713_Feat_Pe eri   19 30-09-2013   10:07:27

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Satellite-Derived Bathymetry a Reconnaissance Tool for Hydrography

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