EMODnet Seabed Habitats Glossary
A guide to terms and phrases used within EMODnet Seabed
Habitats - you may use the links above to jump to a specific
bookmark in the glossary.
This glossary is based on the MESH guide to habitat mapping
glossary, with additional relevant entries.
The degree to which a measured value (either spatial
resolution/precision or attribute) conforms to a true or accepted
value. Accuracy is a measure of correctness. It is distinguished
from precision, which measures exactness
In a habitat mapping context, accuracy describes how closely a
map predicts the actual habitat observed on the seabed at a given
The confusion between classes often due to overlapping and
shared attributes used to define the classes.
ArcCatalog™ is an application used by ESRI's ArcGIS, for
managing spatial data holdings and for recording, viewing, and
managing metadata. ArcCatalog™ provides an integrated and unified
view of all the data files, databases, and ArcGIS documents
available to ArcGIS users.
ArcToolbox™ is one of the applications comprising the ESRI™
desktop GIS package (together with ArcMap™ and ArcCatalog™). The
ArcToolbox™ window is the central place where you find, manage, and
execute geoprocessing tools.
An group of different species that occur together at a given
Non-spatial information describing the characteristics of a map
object (vector geographic feature in a GIS), usually stored in a
database table and linked to the map object by a unique identifier.
For example, a polygon feature drawn on a habitat map will have the
type of habitat present as one of its attributes, where values are
any text entry taken from the EUNIS classification scheme (e.g.
A1.23). In raster datasets, an attribute is the information
associated with each unique value of a raster cell that describes
A database or tabular file containing information about a set of
geographic features, usually arranged so that each row represents a
feature and each column represents one feature attribute. In raster
datasets, each row of an attribute table corresponds to a certain
zone of cells having the same value. In a GIS, attribute tables are
often joined or related to spatial data layers, and the attribute
values they contain can be used to find, query, and symbolize
features or raster cells.
Bathymetry is the study of underwater depth, leading to
topographic maps of the ocean floor. A bathymetric map or chart
usually shows seabed relief or terrain as contour lines or false
colour composite images, using a colour ramp (shades of different
colours) to indicate different depths.
Any deviation from a flat bed, generated by the flow of a
transporting agent (water, ice or air). Bed-forms range in size
from ripples in the sand, a few centimetres apart and a few
millimetres high, to 'dunes' with wavelengths of hundreds of
meters, kilometres in length and a few to tens of meters high.
Relating to the sea floor, including organisms living on or in
A biotope is defined as the combination of an abiotic habitat
and its associated community of species. It can be defined at a
variety of scales (with related corresponding degrees of
similarity) and should be a regularly occurring association to
justify its inclusion within a classification system.
Generally used to describe a map that shows the distribution of
broadly-defined habitat types over a relatively large geographic
area. It is often used instead of the more technically correct
mapping expression small-scale (e.g. 1:250,000). Broad-scale also
implies that the primary purpose of a map is to present an overview
of a large area. As opposed to fine-scale.
Seabed features resulting from the growth of carbonate-producing
organisms and current controlled sedimentation.
Cartographic modelling is a general, but well-defined
methodology that is used to address diverse applications of GIS in
a clear manner. It is a technique used for both vector and raster
based GIS, and as the term suggests, cartographic modelling
involves models (i.e. of geospatial information) represented in
cartographic form (i.e. as maps). Cartographic modelling is used to
simultaneously analyse both the spatial and thematic
characteristics of geospatial information.
The process of making an informative, clear and concise map from
data layers at a certain scale that is fit for purpose. Cartography
places limitations on what can be shown of the underlying data
layers and this should be considered in the planning stages of the
A class is a set of entities grouped together on the basis of
shared attribute values.
Continuous data can be sub-divided into 'chunks' or classes. For
example, a measure of tidal stream strength might range from 0-15
but could be divided into three classes for easier comparison - Low
(0-5.0), Medium (5.1-10) and High (10.1-15). Classes can be created
from complex multivariate data (such as the list of difference
species, their abundance, type of seabed and wave exposure data at
a specific location) by grouping together locations with similar
values for each variable. These classes are the data format is
required for habitat maps.
Classification (as a process)
The process of sorting or arranging entities into groups or
categories. A term commonly used to describe the process of
interpreting remotely sensed data as habitat classes or, sorting
biological samples with lists of species into habitat types.
Systematic arrangement of habitats into more broadly defined
classes on the basis of an analysis of their attributes; the
arrangement is often repeated to create a hierarchy with broadly
defined habitats at the top, sub-dividing into more and more
detailed, narrowly defined classes further down the hierarchy.
A measure of how correctly a classified remotely sensed image
matches the classes recorded on the ground by an independent
standard or 'ground truth' sample set.
An assemblage of species, dependent on each other, and
constituting an organized system through which energy, nutrients,
and water are cycled.
A statement about how reliable a map user thinks the map is
given its purpose. This is not a mathematical definition like
accuracy or uncertainty, but is a judgement made by the map-user
and may therefore vary for any map. However, this judgment can be
supported by evidence from:
- Accuracy measures
- Supporting maps show underlying evidence used to interpret
- Evaluation of all contributing data
- Independent validation
- Expert opinion
- User support: Generally found to be acceptable by stakeholders
and the map has stood the test of time
A feature that is not spatially discrete. The transition between
possible values on a continuous surface is without abrupt or
well-defined breaks. A continuous surface can be generated through
interpolation of discrete data points.
A single thematic map, usually in the context of one of many
layers in a GIS. A coverage can be a data layer or overlay, storing
geographic features. In a coverage, features are stored as both
primary features (points, arcs, polygons) and secondary features
(tics, links, annotation). In the MESH context coverage is also
taken to mean that the coverage is full (100% cover) over the
In a data collection context, coverage is also taken to mean
that the actual area of a survey for which remote sensing data are
available. For example, an aerial photograph may cover all the area
(100% coverage) but a sonar survey may record along a series of
non-overlapping corridors with gaps between resulting in only 50%
A GIS database includes data about the position and the
attributes of geographical features that have been coded as points,
lines, areas, pixels or grid cells.
A spheroid used to approximate the shape of the Earth in order
that a coordinate system may be used to locate objects. As the
earth is an imperfect sphere, different datums may be more accurate
in certain geographic locations.
- WGS84, commonly used for worldwide coordinate systems;
- ED50, which focuses on accuracy in Europe;
- NAD27/83 for North American cartography.
A model in which the parameters and variables are not subject to
random fluctuations, so that the system is at any time entirely
defined by the initial conditions chosen. In a habitat mapping
context, the data layers are selected and fixed so that the user
can vary the model parameters to explore the relationship between
the habitat type and the physical data layers in the knowledge that
the physical data itself will not be changed by the modelling
DEF - Data Exchange Format
A Data Exchange Format (DEF) defines the characteristics of data
to be exchanged between parties. These characteristics will
typically cover the data format (e.g. ESRI shapefile), the
geographic co-ordinate system used (e.g. Ordnance Survey of Great
Britain). the attributes required (e.g. depth, seabed type, habitat
class) and their format (e.g. habitat type - text data no longer
than 20 characters; depth - numerical data with no more than 2
DEM - Digital Elevation Model
A digital elevation model (DEM) is a digital representation of
the ground surface topography or terrain. It is also widely known
as a digital terrain model (DTM). A DEM can be represented as a
raster (a grid of squares) or as a triangular irregular network. A
DEM - sometimes also called a digital surface model (DSM) -
generally refers to a representation of the earth's surface (or
subset of this), including features such as vegetation, buildings,
bridges, etc. The DEM often comprises much of the raw dataset,
which may have been acquired through techniques such as
photogrammetry, LiDAR, IfSAR, land surveying, and remote sensing
techniques. DEMs are used often in geographic information systems,
and the most common basis for digitally-produced relief maps. (From
When a user views a remotely-sensed image of the seabed, they
will be able to see patterns that reflect changes in the surface
structure. For example, when a user views an aerial photograph, the
surface structures are clearly visible. A user can draw polygon
shapes around these surface features to encapsulate an area that
'looks' the same and can be truthed / interpreted as a habitat
type. This process of drawing boundaries around habitat types is
called direct mapping; it is also known as segmentation.
Directorate-General for Maritime Affairs and Fisheries (DG
DG MARE is the European Commission department responsible for
the implementation of the Common Fisheries policy and of the
Integrated Maritime Policy. It is the funder of EMODnet.
Basic information that should provide a sufficient description
of a data set to enable the user to establish whether the data meet
their requirements. Typically discovery metadata will answer the
'who? what? where? and when? questions' for a dataset. Technically
the term discovery metadata refers to a high level set of metadata
Discrimination (for habitat mapping)
The ability to distinguish two or more habitat classes. There
are two main stages in the habitat mapping process where
discrimination must take place to map habitats as separate
entities. Firstly, the field sampling system must detect features
which can be used to separate classes. Secondly, the classes must
be separable by their response to remote sensors or by
differentiated on the basis of physical variables.
DTM - Digital Terrain Models
A digital terrain model (DTM) is (generally) a filtered version
of a Digital Elevation Model (DEM) to remove all the features
on/above the surface (buildings, forests etc). The DTM provides a
so-called bare-earth model, devoid of landscape features. See DEM -
Digital Elevation Models.
In the context of metadata elements, an element domain is the
range of allowable values for that element, for example a set list
EMODnet broad-scale seabed habitat map for Europe
The broad-scale European predictive habitat mapping products
produced by EMODnet Seabed Habitats. Created using a top-down
approach and provided in the EUNIS classification system. For more
information, see "About EUSeaMap".
In phase I of EMODnet Seabed Habitats, the project itself was
also known as "EUSeaMap".
Based on experiment and observation but not necessarily on
proven scientific data, or based entirely on practical
Empirical models are developed using field observations and
practical experience to produce maps that can be tested (by field
samples or observations) to 'prove' their reliability.
European Marine Observation and Data Network (EMODnet)
EMODnet is a DG MARE funded network of organisations supported
by the EU's integrated maritime policy. These organisations work
together to observe the sea, process the data according to
international standards and make that information freely available
as interoperable data layers and data products. It is split by
themes into the following "lots":
- Human Activities
- Seabed Habitats
For more information, please visit EMODnet Central Portal.
Animals (fauna) that live on or are attached to the surface of
A unique identifier created by the European
Group standards agency (now part of The
International Association of Oil & Gas Producers) which refers
to a particular projected, unprojected, or local spatial coordinate
Error (in mapping)
A measure of how far a predicted value or class varies from
observation of the real world.
A ESRI™ vector data storage format for storing the location,
shape, and attributes of geographic features. A shapefile is stored
in a set of related files and contains one feature class.
Shapefiles spatially describe points, polygons and polylines. The
term shapefile is generally used to mean to a collection of files
with '.shp', '.shx', '.dbf', and other extensions on a common
prefix name (i.e. 'habitat.*'). The actual shapefile relates
specifically to files with the '.shp' extension; this file alone is
incomplete for dissemination, as it depends on the other supporting
The EUNIS habitat types classification is a comprehensive
pan-European system to facilitate the harmonised description and
collection of data across Europe through the use of criteria for
habitat identification; it covers all types of habitats from
natural to artificial, from terrestrial to freshwater and
Level A describes all MARINE HABITATS and is broken down into 8
sub-sections: A1 = Littoral rock and other hard substrata, A2 =
Littoral sediment, A3 = Infralittoral rock and other hard
substrata, A4 = Circalittoral rock and other hard substrata, A5 =
Sublittoral sediment, A6 = Deep-sea bed, A7 = Pelagic water column,
A8 = Ice-associated marine habitats.
Habitat is defined as: Plant and animal communities as the
characterising elements of the biotic environment, together with
abiotic factors operating together at a particular scale.
Belonging to a particular group and no other.
A method by which unwanted items are removed from a dataset.
Within the webGIS, this term is used in the context of allowing the
user to view only certain items within specific layers on the
interactive map. For example certain habitat maps from surveys, or
Generally used to describe a map that shows the distribution of
detailed habitat types over a relatively small geographic area. It
is often used instead of the more technically correct mapping
expression large scale (e.g. 1:10,000). Fine-scale also implies
that the primary purpose of a map is to explore the distribution of
small features with a measurable degree of accuracy. As opposed to
Freeform navigation allows the user to chose where they want to
The continuous nature of descriptors is acknowledged by
assigning observations a membership value (e.g. probability) to all
classes. Also see "Matching habitat classes"
A review of the availability of suitable coverages of the
various parameters needed to create a habitat map. Availability
should be assessed in terms of spatial extent and type of data. All
gaps in coverage should be clearly identified and a strategy
developed to secure the necessary data.
Geographic Coordinate System (GCS)
A geographic coordinate system is a reference system used to
define geographic locations on a geographic datum.
Geographic Information Systems (GIS)
An integrated collection of computer software and data used to
view and manage information about geographic places, analyse
spatial relationships, and model spatial processes. A GIS provides
a framework for gathering and organizing spatial data and related
information so that it can be displayed and analysed. GIS are
generally much more powerful than computer assisted drafting (CAD),
although the distinction between them is not well defined.
Aligning geographic data (map features) to a known coordinate
system so they can be viewed, queried, and analysed with other
geographic data. Georeferencing may involve shifting, rotating,
scaling, skewing, and in some cases warping, rubber sheeting, or
orthorectifying the features so that they fit the co-ordinate
GeoTIFF is a public domain metadata standard which allows
georeferencing information to be embedded within a TIFF file. TIFF
is a file format used to store raster graphic images.
Globally unique identifier (GUI or GUID)
A string used to uniquely identify an interface, class, type
library, component category, or record. In EMODnet Seabed Habitats,
most commonly used to identify individual habitat map datasets.
Direct observations and samples of the seabed provide
information that can be used to interpret remotely sensed images;
the observations are the 'truth' with regard to the habitats
actually present on the seabed. Observations used in this way
provide ground truth data. The process of using ground truth data
for interpretation is often termed ground truthing. During this
process the relationship between properties of the remote images at
the observation/sample sites (in the form of points, irregular
digitised areas or buffer areas around points) is determined. These
relationships are then applied to the whole image to predict the
distribution of habitat types. Ground truthing is distinct from
Observations can be used to test the predictive power of a
habitat map. The validation dataset is displayed on top of the
habitat map and the predicted habitat class is compared with the
actual class from the validation observation. This is the basis for
many measures of accuracy and uncertainty. The ground validation
dataset should not be the one also used for ground truthing,
although this rule is often broken when sample data are sparse.
These issues are discussed more fully in "How good is my map?" in
the archived MESH guide to mapping.
The use of the term 'habitat' in EMODnet Seabed Habitats means
both the physical and environmental conditions that support a
particular biological community together with community itself.
Used synonymously with biotope.
Habitat classification (including habitat detail)
The organisation of different habitats into specific class
types. These classes can vary in their level of detail from broad
descriptions (e.g. Shallow subtidal sand) to highly detailed
descriptions that include specific organisms (Zostera marina
seagrass beds on clean coarse sand in sheltered water less than 5
m). In general, detailed habitat types will be more geographically
limited to small areas of the seabed.
Habitat classifications scheme
A habitat classification scheme can be defined as a structured
system of habitat types (classes), often arranged in a hierarchy,
where the types are clearly defined and recur in different
A habitat map is a visualisation of our best estimate of habitat
distribution at a point in time making best use of the knowledge we
have available at that time.
Habitat suitability analysis
A habitat requires specific physical (and chemical)
environmental conditions to support its biological community.
Searching a map of physical variables to find the specific
environmental conditions to suit a habitat is called suitability
analysis. In other words, the appropriateness of an area to support
a particular habitat is determined.
A similar approach can be applied to find the suitable
conditions to support an individual species.
Habitat suitability modelling
Habitat distribution is normally defined by multiple
environmental variables (depth, light penetration, incident energy
etc). Habitat suitability models bring together these multiple data
layers to simultaneously select the most appropriate area and
therefore predict habitat (or species) occurrence.
Hard or crisp classes
Classes are usually 'hard' or 'crisp' in that the continuous
nature of the variables have been artificially divided up into a
number of categories with 'boundaries' separating the categories.
Hard classes are especially appropriate for multivariate data.
The amount of diversity (or variability) of a variable (e.g.
sediment type) or class (e.g. habitat type) within a geographic
area. In offshore areas, extensive sediment plains tend to dominate
the seabed with little variability in sediment type - low
heterogeneity. Shallow inshore areas are often a mixture of rocky
outcrops, gravel beds and many sediment types depending upon the
tidal streams and/or wave action - there is much variability over
small areas leading to high heterogeneity. Heterogeneity has
practical implications for mapping at two levels. Firstly, there is
heterogeneity within the minimum mapping unit of a map in which
case what is displayed on the map must either try to represent this
diversity using a mixed class or display some measure of diversity
or the map class must simplify the situation on the ground by
showing the predominant class. Secondly, the map may show many
small polygons of different classes clustered together in which
case there is likely to be reduced confidence in the exact position
of each class. The map shows what might be found in the general
The extent to which attributes are similar within a region. It
is the opposite to heterogeneity.
HTML - Hypertext Markup Language
Hypertext Markup Language is a ubiquitous markup language used
for the creation of web pages. A markup language combines text and
extra information about the text.
A hypothesis consists either of a suggested explanation for
certain facts or observations or of a reasoned proposal suggesting
a possible correlation between multiple phenomena. Experiments,
tests or observations are used to establish whether the (reasoned)
explanation is correct.
The process of drawing a conclusion from given evidence. To
reach a decision by reasoning.
Animals (fauna) that live in the substrate. 'Infaunal
communities' normally consists of animals burrowing into sediment.
As opposed to epifauna.
Information is loosely defined as data that have been given
meaning through some form of interpretation
The ability of two or more systems, or components to exchange
information, and to use the information that has been exchanged. It
is commonly used to describe the sharing of data on the internet
where a mapping website will draw data from another website to give
context to its data; for example, a website may draw a coastal
outline from a central repository rather than try to maintain its
The estimation of surface values at unsampled points based on
known surface values of surrounding points. Interpolation can be
used to estimate elevation, rainfall, temperature, chemical
dispersion, or other spatially-based phenomena. Interpolation
generates a continuous surface from a series of discrete individual
The process of giving data meaning through directed analysis an
reasoned explanation. More specifically (for habitat mapping) it is
the systematic application of signatures, classification systems,
models and rules to spatial data sets to map the predicted
distribution of features.
The INTERREG IIIB North West Europe Programme provided support
to transnational cooperation projects seeking to improve
territorial development and cohesion in the North West Europe
LiDAR - Light Detecting and Ranging
In the particular case of mapping, LiDAR is an airborne
surveying technique which utilises the travel time of laser light
to measure altitude of the aircraft above the ground. When the
aircraft has a level flight path, variations in the measured
altitude are actually changes in the height of the ground. LiDAR is
the airborne equivalent of sonar. Infrared light is adapted for
ground detection, whilst green light, due to its penetration
ability through water, offers a way to carry out clear water
Scale that covers relatively small area on the ground and has a
higher level of detail in the map features. As opposed to small
The visual representation of a geographic dataset in any digital
map environment. Conceptually, a layer is a slice or stratum of the
geographic reality in a particular area, and is more or less
equivalent to a legend item on a paper map. On a road map, for
example, roads, national parks, political boundaries, and rivers
might be considered different layers.
In ESRI™ ArcGIS, a layer is a reference to a data source, such
as a shapefile, coverage, geodatabase feature class, or raster,
that defines how the data should be symbolized on a map.
A simplified depiction of a space, a navigational aid which
highlights relations between objects within that space. A graphic
representation of a parameter that can be used to derive
information for a specific area.
The concept is a broad-scale classification of the marine
environment based on geophysical parameters such as sediment
characteristics, morphology and hydrodynamics, recognising that
these are important in determining the nature of biological
Generally used to describe a map created to show geographic data
between broad and fine scales.
MESH (Mapping European Seabed Habitats)
MESH was an international marine habitat mapping programme that
ran from 2004-2007 and was carried out by a consortium of 12
partners across the UK, Ireland, the Netherlands, Belgium and
France. MESH aimed to produce seabed habitat maps for north-west
Europe and develop international standards and protocols for seabed
mapping studies. Many of the products from MESH have since been
absorbed into EMODnet Seabed Habitats.
Data about data. For example, giving information about the
characteristics and provenance of the data.
One of the pieces of information recorded in a metadata record.
For example, the title of a data set is a metadata element.
A set of metadata elements that are needed to describe a
particular type of data. Metadata standards are usually defined by
official standards organisations, but they can also be defined by
an organisation or project for a specific purpose: the MESH
metadata standard (www.searchMESH.net/metadata) are the set of
metadata elements necessary to fully describe seabed habitat map
Minimum habitat size
Smallest habitat or example of habitat type in a given area.
Minimum habitat unit (MHU)
This is the smallest size of a habitat, which although not
precisely defined in the EUNIS classification system, is taken
to be about 5 x 5 m for marine habitats. Any feature smaller than
this is regarded as an attribute of the habitat. Note that, whilst
the MHU is well within the resolution of many remote sensing
systems, it is unlikely that the MHU will correspond with the
minimum mapping unit unless the map scale is very small.
Minimum mapping unit (MMU)
This is the smallest object size that is represented on a map
(smaller objects being either 'lost' or subsumed into a larger
unit). In a single thematic map, such as a habitat map, this will
be the minimum size of any habitat class that can be represented on
a map at any given scale. Note that this means the size of the MMU
will change with scale. This is distinct from the minimum habitat
Models and modelling
The dictionary definition of the term 'model' that is most
closely related to habitat mapping is: a simplified representation
used to explain a real world system. Therefore any map
representation of the seabed based on a systematic investigation of
remotely sensed data correlated to ground truth information can be
regarded as a model. Modelling is the process by which data are
simplified to produce the map. All maps should be regarded as
predictive and require testing against the real world. Cartographic
modelling and mathematical modelling provide a more rigorous basis
for maps than conceptual models that are based on expert opinion.
Cartographic and mathematical modelling are more reproducible since
there is no element of subjectivity in the analysis. Models can be
re-run with changed parameters based on new evidence.
Continuous or repeated observation, measurement, and evaluation
of environmental or technical data, according to prearranged
schedules in space and time, using comparable methods for sensing
and data collection. Monitoring is used to detect trends over
A shearing force per unit area exerted on the seabed by water
movements above the seabed. It is a useful parameter to determine
seabed disturbance arising from waves and from tidal or residual
Convention for the Protection of the Marine Environment of the
North Atlantic (a portmanteau of OSlo and
The 1992 OSPAR Convention is the current instrument guiding
international cooperation on the protection of the marine
environment of the North-East Atlantic. It combined and up-dated
the 1972 Oslo Convention on dumping waste at sea and the 1974 Paris
Convention on land-based sources of marine pollution. The work
under the convention is managed by the OSPAR Commission, made up of
representatives of the Governments of 15 Contracting Parties and
the European Commission, representing the European Community.
A transparent layer placed on an underlying image.
The process of stacking digital representations of various spatial
data on top of each other so that each position in the areas
covered can be analysed in terms of these data.
The smallest unit of information in an image or raster map,
usually square or rectangular, the four sides of a pixel enclose a
small, homogeneous area. Pixel is often used synonymously with
cell. In remote sensing, a pixel is the fundamental unit of data
collection. A pixel is represented in a remotely sensed image as a
cell in an array of data values. The term mixel is used where a
pixel is known to consist of more than one habitat class on the
On a map, a closed shape defined by a connected sequence of x,y
coordinate pairs, where the first and last coordinate pair are the
same and all other pairs are unique. In the context of a habitat
map a polygon is taken to be homogeneous within that enclosed area
(i.e. every point within the shape shares the same attributes).
In habitat mapping, there is confusion between this term and
accuracy. Precision can be defined as the variability between
repeated measurements but this has limited application to habitat
mapping. However, in habitat mapping its more general usage is to
define the likely error of a boundary (e.g. ±100 m, ±10 m). It
could also be applied to the level in a hierarchy that a record has
been assigned to (i.e. a EUNIS level 4 class is less precise than a
level 5 class).
Prediction (of habitats)
All habitat maps derived from classification and modelling are
predictive because the actual habitat present on the seabed has not
been observed/sampled at all points of the map. The mapped habitat
distributions are based on statistical links, assumptions and
hypotheses between the source data (from remote sensing) and the
classes to be mapped (determined from ground truth samples). This
underlying predictive nature of maps is often conveniently ignored,
but all maps must be judged by their predictive power.
The ability of a map to correctly predict what will be found on
the seabed in each minimum mapping unit of the map. Note predictive
power need not only apply to the mapped class – the predictive
power of a map could be widened to include (for example) rarer
biotopes associated with the dominant mapped biotope.
A measure of the likelihood that a particular outcome, such as a
spatial pattern or event, will occur given a set of possible
outcomes. Probability values range from 0 for impossible outcomes
to 1 for completely certain outcomes. The probability that a tossed
coin will land heads-up, for example, is 0.5, since landing
heads-up is one of two possible outcomes.
In a seabed habitat mapping context, it is possible to determine
the probability of a single habitat occurring at every location in
a map: those areas where the prevailing physical conditions are
suitable for the habitat will lead to a higher probability of
occurrence than areas that are clearly unsuitable. When individual
habitat probability maps are overlaid, for each location it is
possible to see 'most likely' habitat (highest probably) to be
found, followed by the next most likely and so on to the least
A method of displaying geography from the 3-dimensional earth
onto a flat plane.
In ecological research, a proxy (variable) is something that can
be easily measured and is known to be a substitute for a variable
that cannot be easily measured. Clearly, the relationship between
the proxy (variable) and the real variable must be understood, and
be consistent. For example, ocean surface colour recorded by
satellite sensors is used as a proxy for water clarity from which
the depth of light penetration may be calculated. Often, the proxy
is probably not in itself of any great interest.
The RAMSAR Convention on Wetlands. Ramsar, Iran, 1971
The Convention on Wetlands, signed in Ramsar, Iran, in 1971, is an
intergovernmental treaty which provides the framework for national
action and international cooperation for the conservation and wise
use of wetlands and their resources. There are presently 153
Contracting Parties to the Convention, with 1634 wetland sites,
totalling 145.6 million hectares, designated for inclusion in the
RAMSAR List of Wetlands of International Importance.
A spatial data model that defines space as an array of equally
sized cells (pixels)arranged in rows and columns, and comprised of
single or multiple bands. Each cell contains an attribute value and
location coordinates. Unlike a vector structure, which stores
coordinates explicitly, raster coordinates are contained in the
ordering of the matrix. Groups of cells that share the same value
represent the same type of geographic feature. Many single map and
multi-map operations in a GIS involve raster maths that are not
possible with vector format layers.
Raster format is a graphics image or data file representing a
generally rectangular grid of pixels, or points of colour, on a
computer monitor, paper, or other display medium. The colour of
each pixel is individually defined; for example colour images often
consist of coloured pixels defined by three values — one each for
red, green and blue. Raster graphics are distinguished from vector
graphics in that vector graphics represent an image through the use
of geometric objects such as curves and polygons.
The quality of a raster image is determined by the total number
of pixels (resolution), and the amount of information in each pixel
(often called colour depth). Raster graphics cannot be scaled to a
higher resolution without loss of apparent quality. This is in
contrast to vector graphics being dimensionless), which easily
scale to the quality of the device on which they are rendered.
Acquiring information about an object without contracting it
physically, methods include: aerial photography; radar and
The smallest spacing between two display elements, expressed as
dots per inch, pixels per line, or lines per millimetre.
Areas (large or small) sampled or designated for sampling.
Is the ratio or relationship between a distance between the same
two points on the earth's surface. A map scale of 1/100,000 or
1:100,000 means that one unit of measure on the map equals 100,000
of the same unit on the earth. For example, if two points are
10,000 cm (100 m) apart on land and 1 cm apart on a map, the map's
scale is 1:10,000. A small ratio (1:250,000) is a small scale and
shows objects to be small. A large ratio (1:10,000) is a large
scale and shows objects to be large. There is often confusion over
these terms and, where possible, MESH uses the terms broad-scale to
indicate that the map scale is small and fine-scale to indicate
that it is large.
Sediment is solid fragmental material which has been eroded,
transported and deposited by wind, water or ice; chemically
precipitated; or secreted by organisms. It forms in loose,
unconsolidated layers. Sediment type varies according to various
parameters, including lithology, particle size distribution,
compaction/ bulk density, cohesiveness, shell content, and moisture
content. It reflects a history of erosion, transportation and
accumulation in different sedimentary environments.
Site condition monitoring
'Condition' is the defined quality or status of the biological
features at a site. Assessing the current status of the features
against the defined standard is termed site condition monitoring.
Repeating these assessments over time will establish whether any
changes in status may be linked to any trends in the physical
environment or human activities.
A map scale that covers a relatively large geographic area and
shows the map objects to be small. See map scale.
Smallest cartographic unit (SCU)
Is the smallest polygonal element that can be drawn on a map; it
determines the resolution of the map layer. It is linked to the
scale of the map.
The distance of a map coordinate from its correct location on
the earth's surface. Spatial error is a measurement of inaccuracy
and may be derived from an error in the measurement of a coordinate
in the field, an error during the map making process, or both.
A measure of the variation in position that might be expected in
a mapped object as judged against real position (this could be
expressed as the number of significant decimal places of a
measurement) or the size of the error envelope from a series of
measurements of the same object.
Special Area of Conservation (SAC)
Special Areas of Conservation are strictly protected sites
designated under the EC Habitats Directive.
A method for classifying images whereby thematic classes are
defined by the characteristics for pixels within an image that
correspond to training areas in the field chosen to represent known
features (e.g. habitats). Each pixel within the image is then
assigned to a thematic class using one of several decision
It is a major tool for integrating ground-truth samples and
remotely-sensed images. The user supervises feature classification
by setting up prototypes (collections of field sample points) for
each feature, class, or habitat type to be mapped. During this
process the relationship between properties of the remote images
spatially associated with the sample sites (in the form of points,
irregular digitised areas or buffer areas around points) are then
applied to the whole image.
It is the actual area of the seabed imaged by a remote sensor
during one 'pass'. Side scan and multibeam sonars project a beam of
sound out to either side of the vessel's towpath to ensonify a wide
region of the seafloor. Both right and left sonar channels added
together make up the swath. Swath width is dependent on the water
depth and can also be changed by altering the range setting of the
sonar device. Swath width is an important factor in determining the
lane spacing of vessel tracks in achieving the desired coverage of
the survey area.
A similar principle applies to airborne remote sensing devices
(cameras, LiDAR etc) where the sensor images an area of the seabed.
The area imaged will depend on the altitude of the aircraft and the
range settings of the sensor. Coverage will depend on these
settings and the flight path of the aircraft.
The success of assigning an observation to a particular biotope
or habitat class (confidence of the operator in their analysis).
This is not the same as classification accuracy, though it is
sometimes assumed to be so.
The level of detail (hierarchical level) of habitat classes
depicted on a map, ranging from high level (broadly defined
classes) to low level (finely defined classes).
Topology is the spatial relationships between connecting or
adjacent features in a geographic data layer (for example, arcs,
nodes, polygons, and points). In geodatabases, topology can define
and enforce data integrity rules (for example, there should be no
gaps between polygons).
A defined area of an image where the habitat class is known
(normally from ground truth sampling) that is used for gathering
image data to derive the relationship (correlation) between the
habitat class and image. This relationship can then be used to seek
other areas of the image that match and may be assumed to be the
same habitat type. These original areas are 'training' the
The distance between two adjacent parallel survey lines is known
as track spacing. See swath width.
A habitat that has been converted from one classification system
into another via any means. For example a correlation table or
Within EMODnet Seabed Habitats, "Translated Habitat maps" are
those that have been converted to use the EUNIS habitat
In mathematics, truncation is the term used for reducing the
number of digits right of the decimal point, by discarding the
least significant ones. In taxonomy, there is a similar concept,
reducing the precision to which an organism is
identified/classified. For example, truncating the barnacle Balanus
balanoides to progressively higher taxonomic levels such as Genus
(Balanus), Family (Balanidae) or Order (Sessilia).
The degree to which the measured value of some quantity is
estimated to vary from the true value. Uncertainty can arise from a
variety of sources, including limitations on the precision or
accuracy of a measuring instrument or system; measurement error;
the integration of data that uses different scales or that describe
phenomena differently; conflicting representations of the same
phenomena; the variable, unquantifiable, or indefinite nature of
the phenomena being measured; or the limits of human knowledge.
Uncertainty is the opposite of confidence.
USBL - Ultra-short baseline
A position fixing method for establishing the real position of
an instrument (towed camera, towed sonar fish, a diver) below a
survey vessel. It uses a sonar transponder - responder fitted to
the deployed instrument and a transceiver mounted on a vessel at a
known and surveyed position below the water line. The direction of
origin of received signal from the instrument mounted
transponder-responder indicates the towed instrument position
relative to the support vessel, while the time delay between
transceiver emitted signal and transponder/ responder return signal
provides its distance. Positioning of the vessel mounted
transceiver is related by survey to the position of GPS antenna,
enabling accurate positioning relative the GPS defined position of
Generally found to be acceptable by stakeholders and the map has
stood the test of time.
Comparing data with known information (patterns, ranges, check
digits) to verify that the data is correct, includes what is
commonly thought of as testing and comparing test results to
expected results. Validation occurs at the end of the development
A sub-set of samples collected during a ground-truth survey that
are set aside in order to test the accuracy of the habitat map once
it has been made. They are explicitly excluded from any process
involved in the initial production of the map (see also Ground
Variability and error
Random error in independent measurements as the result of
repeated application of the process under specific conditions.
A GIS data format where objects are represented by a
coordinate-based data model that represents geographic features as
points, lines, and polygons. Each point feature is represented as a
single coordinate pair, while line and polygon features are
represented as ordered lists of vertices. Many attributes are
associated with each vector feature, as opposed to a raster data
model, which associates only one attribute with a grid cell
Vector graphics is the use of non-dimensional geometrical
primitives such as points, lines, curves, and polygons, which are
all based upon mathematical equations to represent images in
computer graphics. It is used by contrast to the term raster
graphics, which is the representation of images as a collection of
pixels (dots) which represent a given surface on the ground.
A GIS (Geographic Information System) available over the
Web Map Service (WMS)
A standardised service for delivering georeferenced geographic
images over the internet.
The common name for WGS84/Pseudo-Mercator, a widely used
projection system for displaying geographic data on the internet.
It is currently used by the major internet map suppliers.
It is identified by the EPSG code 3857.
World Geodetic System 1984
The most widely used geocentric datum and geographic coordinate
system today, designed by the U.S. Department of Defense to replace
WGS72. GPS measurements are based on WGS84.
It is identified by the EPSG code 4326.
Extensible Markup Language (XML) files are often used for
exchanging information, both on and off the Web. Like HTML
(Hypertext Markup Language) files, XML files use start and end tags
to format their content. However, XML tags define the structure of
elements in a document, whereas HTML tags define how elements
should look. XML is extensible because you can extend it by adding