higher national diploma in fisheries science for...

Higher National Diploma in Fisheries Science

for Mediterranean Countries.Department of Fisheries and Aquaculture (Malta),in collaboration with University of Plymouth (UK) and COPEMED (FAO)

GIS in fisheries managementMalta, 12 - 15 March 2001

GIS in fisheries management Malta, 12 - 15 March 2001

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Part 1 - GIS Definition

Information or data?

Data is a collection of attributes (numeric, alphanumeric, figures, pictures) about entities (things, events, activities)

Information is the organization of data such that it is valuable for analysis, evaluation, and decision making

Information Systems and Planning

Information systems are the means to transform data into information.

Information systems are used in planning and managing resources.


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What are Geographic Information Systems?.

Computer based systems including: Hardware, software, data and personnel that allows the user to question and manipulate various layers of spatial data . The data represents real-world entities (trees to woodlots to forests to world scale) including both spatial (geo-referenced) and quantitative attributes of these entities.

Functions of a GIS:

•Capture •Store •Check •Manipulate •Analyse•Model •Display

Spatial and non spatial data are treated to create new information to be displayed, generally in the form of a map but also as charts and/or tables.

Diagram showing the relationship of layers of data in a GIS.

Diagram by ESRI Inc.


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GIS versus other similar computer systems

GIS, CAC, CAD, DBMS, RS

Geographic Information Systems (GIS): information system which uses georeferenceddata to answer questions.

Computer Assisted Cartographic system (CAC): set of graphic elements for map display and printing. Not a GIS!

Computer Assisted Drafting system (CAD): set of graphic elements for engineering and architectural design. Some GIS elements in high-end software. Some have GIS modules as add-ons

Database Management Systems (DBMS): developed to store and manipulate alphanumeric data, but with scarce graphic capacities.

Image Analysis Systems (IAS): Classify the intensity of radiation emitted by the earth surface (Remote sensing analysts) or aerial photography, but very reduced capacity of analysis.

The current rapid emergence of GIS is part of a complex amalgam of processes like:

• Proliferation of data: over the last two decades, there as been a surge in the development of data gathering methodologies, plus the increasing ability to electronically transfer data

• Reduction of computer cost and increase of computer capacities in term of storage, processing speed, display and output devices

• Integration of parallel developments: CAD, Remote Sensing, spatial and images analysis, digital cartography, surveying and geodesy, etc…

• Increasing demand of GIS output, in public and private sectors => Ability and need to cope with vast amounts of data has grown exponentially. Data must be captured, stored, transferred, shared, maintained and generally managed.


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Most of GIS have many features in common with all other Systems as GIS have evolved from them.

GIS

CAC IAS

DBMS CAD

Characteristics of GIS

1. Capacity of perform spatial operations : (Spatial search, and overlaying are considered unique of GIS).

2. Generation and conservation of topological relationships(Vicinity, inclusion, adjacency)

3. Generation of new cartography as result of analysis of the input data.


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Questions that a GIS can answer

1. Location: What is at...?

2. Quantification: How big, How long ...?. How many in ..?

3. Routing: Which is the best way to..?

4. Condition: Where is it...?

5. Trends: What has changed since...?

6. Patterns: What spatial patterns exist...?

7. Modelling: What if...?

The type of tasks for which the GIS are suited The first question simply seeks to find what exists at a particular location Example: a landing site The second requires the GIS to calculate areas or perimeters The third one is a route finding task. GIS allow for the optimising of any specific route The fourth question requires to the GIS to identify the location where certain specific conditions may be meet The question five allows for the spatial differences to be shown and calculated between any given time period: spatio-temporel analysis Question six allows for more sophisticated geographic pattern to be displayed The last question is related to simulation


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Here is a movie, using ArcView GIS to answer a question. The results are shown on a map highlighted in yellow.

Demo: This demo is in the file gisdemo.avi 1 - Display the Roads layer 2 - Select one type of Soil 3 - Display the wet lands 4 - Select the wetlands which are completely contained in an area having the selected type of soil


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Why use Geographic Information Systems in Natural Resources?

•Increasing understanding of the complexity of ecosystems

•Appreciation for the influence of spatial factors.

•Need for fast and efficient manipulation of large data sets.

•Outputs in a form easy to understand by a wide variety of professionals

•GIS can reveal time trends and spatial patterns of the resources distribution.

•Formulation of hypothesis and elaboration of predicting models that will aid in a final process of Decision-Making.(More details in doc “Why use GIS in Natural Resources? “)


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GIS Components

A GIS comprises of a collection of integrated computer hardware and software which together is used for inputting, storing, manipulating, analysing and presenting a variety of geographical data. It is also useful to include in this definition the requisite geographical database and skilled GIS personnel. A GIS can then represent a set of working practices, management structures and data organise so as to utilise the spatial data handling functions of a software/hardware package.


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Part 2 - Data collection

Data Collection for a Marine Fisheries Resources GIS

Data to be collected

- Resource and Habitat

- Fishing Zone

- Fishing Vessels and Gears

- Ports

- Infrastructures

- Coast

- Human activities (socio-economic data)


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Methods (1)

- Interviews, questionnaires, form filling(Cf. Doc Maltese form for Inventory of commercial Fishing Units)

- Photography, measurements,meteorological data gathering, trawl surveys

- Electronic automatic measurement devices and distance measuringinstruments

- Multimedia devices (video, sounds, ....)

- Data loggers


In practice, interviewing fishermen is often the only means of obtaining certain sorts of data. The disadvantage is that the data obtained could be very subjective and could be rarely converted in a mappable or statistical form Data collected through a questionnaire and standard form, since presented as structured and methodically administered, are easier to transfer to a structured electronic format for management and analysis Trawl surveys are used as a major source of information on species distributions and abundance. To obtained valid data, trawl surveys must be designed seriously in a way which ensure the acquisition of statistically valid information. Now days, data loggers are often automatic devices which are placed in some location where data needs to be constantly and regularly gathered (weather variables, water quality, etc...)


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Trawl Survey : Fishing Log FormThe acquisition of data for a marine Fisheries Resources GIS

Data Collection

Data Collection: Sampling Station during a trawl survey. The location is given by:

• The latitude and the longitude, with an accuracy of one minute. • A sector code showing the geographical sub region a station belongs

to. The sector code is specific to the survey. The code may indicate the stratum issued from the stratification plan used for the survey (Coastal divisions, main fishing areas, etc). The sectors are used for the analysis of the data, computing statistics on the stations belonging to each stratum and analysing the difference between each stratum.


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IR-RIMJIETTAL-LAMPUKI

The acquisition of data for a marine Fisheries Resources GISData Collection

Data Collection: Fishing Zones: sectors delimited using compass


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Methods (2)

- Global Positioning System (GPS)

- Acoustic Sonar devices :- underwater mapping- location of fish schools or other under water objects

- Satellite remote sensing- water temperature, waves height and direction, sediment or

phytoplanckton concentration

- Aerial photography - more detail on land use or on sea-based activities

Recently, digital cameras have been developed, which authorise a direct acquisition in digital format of aerial photography into a GIS. The problem of aerial photography is that there could be many sources of distortion that may be corrected using stereoscopic aerial photography


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In Review: Triangulating

1. Position is calculated from distance measurements (ranges) to satellites.

2. Mathematically we need four satellite ranges to determine exact position.

3. Three ranges are enough if we reject ridiculous answers or use other tricks.

4. Another range is required for technical reasons ....

Devices which allow the user to very accurately establish his location on the earth ‘s surface

Global Positioning System

With the use of GPS, it is now possible for fishing or survey vessels to accurately determine where trawl hauls were made, where underwater obstacle occur, where water quality samples were taken, etc... The future => remote surveillance systems Learn More about How GPS works at http://www.trimble.com/gps/howgps/gpsfram1.htm


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Acoustic Sonar Systems

Two Main Purposes:- under water Mapping- locate fish or other underwater objects

Transducer Mechanical Vibrations Echo sounder

SidescanSonar System

Computer


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Satellite Remote Sensing Systems

Measure of marine parameters :- Water temperatures,- Wave height and direction- bathymetry- ocean currents and water colour

�Sediment concentration�Phytoplankton standing stock�Turbidity patterns�Current speed and direction�Light attenuation coefficients

Example:A wind field map of western Pacific oceanArrows show wind direction and velocity, which is colour coded for emphasis: blue 14 m/s; land is shown in black


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Data acquisition of already formatted datafor a Marine Fisheries Resources GIS

International Organizations responsible for Collecting Marine data :

•NOAA: National Oceanographic and Atmospheric Administration of the USAURL: http://www.noaa.gov/

•IOC : International Oceanographic CommissionURL: http://ioc.unesco.org/iocweb/default.htm

•BODC: British Oceanographic Data CentreURL: http://www.bodc.ac.uk/

Hydrographic Maps and Charts produced by national maritime authorityTypically show coastline, bathymetry (isobaths), isolated depth sounding, obstacles, navigation buoys and light and other relevant navigational information

Scale : from 1:50 000 upwards to 1:10 000 000

Topographic Mapsproduced by national agencies

Scale: from large scales (1:1 250 to 1:25000) up to small scales (> 1:200 000)

Thematic MapsUsually derived from Topographic maps


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Part 3 - Maps

Models are simplifications - not miniature versions of the reality.

Maps are a type of geographic model.

Maps must be abstraction from reality.

Map as Model: The Abstraction of Reality

Purpose of Cartography

Cartography is the art and science of mapmaking.

Communication is the traditional objective.

Analysis has become an important objective with the development of GIS.

(More details in "Informes& Estudios COPEMED no 4. P.3 )


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Analog Map vs. Digital Map

An analog map is a printed drawing on a piece of paper or a scanned image of a map. It is static.

A digital map is a data set stored in a computer in digital form (not as a picture.) It is not static, and the flexibility of digital maps is vastly greater than paper maps. Inherent in this concept is the point that data on which the map is based is available to examine or question.

Analysis capabilities are much greater with digital maps, and reporting outputs are available in more formats, and faster. (more details in doc. “Analog Map vs. Digital Map“)...


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Map scale defines the amount of reduction of reality.Scale is expressed in three primary ways

1.Verbal Scale : "one inch equal (represents) to 63,360 inches""eight inches equal 1 mile"

2.Representative fraction (RF): “1:2,000” Expressed as an ratio in the same units means that one inch (or one meter) on the map represents2,000 inches (or meters) on the ground.

3.Graphic scale (bar) : Remains accurate after mechanical enlargement of map, printed ratio or printed scale will be wrong after "zooming" the page on the copy machine.

Map Scale

(more details in doc. “Map Scale.“)...


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• Scale defines the precision of the location and the level ofdetail

1. Be care when using small scale maps as input and then enlarging

2. Rule of Thumb: It is always better to reduce a map after analysis than to enlarge it for analysis.

Map Scale: Small vs. Large• Small scale refers to the RF ratio. A 1:250,000 scale is small

compared to a 1:2,000.The ratio is small and the amount of reduction is large, producing a map of a large area.

• Large scale means less reduction and a map covering a small area.

Map Scale


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Map Scale


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Legend

The reference area on a map that lists the colours, symbols, line patterns, shadings and other annotation used on the map, and their meanings.The legend often includes the map's title, scale, origin, orientation and otherinformation.


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Level Description Example

Nominal Names/labels Port of St Julian’s BayOrdinal Ordered/Rank Large, smallInterval Measured Miles, feetRatio Measured Density

Ratio is an interval measure with an absolute starting point.Example :

% of sand in a Soil is a ratio (0 means that there is no sand)temperature is an interval (since zero temperature varies according to the units of measurement).

Spatial Measurement Levels

(more details in doc. “Spatial Measurement Levels: nominal, ordinal, interval, and ratio.“)...


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Spatial objects and Spatial Measurement Levels

Interval/ratio: Utilisation of density pattern: number of points / surface unit increase with the value of the attribute Continuous variable: plot of interval limits (example: isobaths) Transformation to ordinal measurement by classification Ordinal: 1 symbol with graduated colour 1 symbol with graduated size Nominal Different symbols Different colours


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Part 4 - Geographic coordinate Systems

To locate entities requires a reference system. The reference system allows:

1. the location of entities,

2. to establish a fixed relationship between the position on the map and the real world

The most basic reference system is the spherical grid.Longitude (measures distance east - west) and

Latitude (measures distance north - south) and measured in degrees

This system do not use any projection, thus it is not accurate to measure distances, but it is useful to identify locations anywhere on the earth surface.

Spatial Location and Reference


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The length of one degree of longitude varies depending upon the latitude, will be 111 km at equator, but converges to 0 at the poles. This system of reference, measures angles from the centre of theearth rather tan distances on the earth surface, it is not a planar coordinate system.

Geographic coordinate systemspherical grid.


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Map Projections and Coordinate systems

Techniques to depict the spherical earth in two dimensions.

"Projection" comes from the idea of shining a light from the centre of the earth and projecting the image of the earth's features on a flat surface.


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Type of projection

Attending to the type of surface the spherical volume is projected, there are three type of projections.

Planar projection


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Shape When the scale of a map at any point on the map is the same in any direction, the projection is conformal. Shape is preserved on conformal projections.

Distance A map is equidistant when its distances are equal in any place from the centerof the projection to any other place on the map. Distances are preserved in equidistant projections.

DirectionA map preserves direction when azimuths (angles from a point on a line to another point) are portrayed correctly in all directions. This projection is called azimuthal.

AreaWhen a map portrays areas over the entire map so that all mapped areas have the same proportional relationship to the areas on the Earth that they represent, the map is an equal-area map. Areas are conserved in equal-area projections.

Projection Characteristics


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For an effective use of distances and spatial relationships in a map it is necessary to know the projection in which it is deployed. Different projections are appropriate for specific tasks depending of what characteristic it preserves. (Area, distance, angle, shape).

Nautical maps are in MERCATOR which is cylindrical and conformal, the shape is preserved, and the distances distort toward poles, while area and direction are not preserved.

For different purposes and depending of the world area we are working with are convenient different projections.

Projection


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Examples of some map projections characteristics


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UTM for Malta areaZone 33 :- central Meridian 15 East-Reference latitude : 36 North


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Part 5 - Create a digital geographical database: data input

WORKFLOW IN A GIS PROJECT


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A. Spatial data: Located features that represents tangible entities of the realworld with a geographic reference (i.e. a pair of coordinates) . For instance a river an island or a boat, that are represented in GIS or in an analog map by spatial elements such as a line, a polygon or a point respectively with its geographical position indicated by pairs of coordinates.

(More details in doc. “Spatial Elements: points, lines, polygon data”)

B. Aspatial data: Descriptive information about the features. Usually qualitative or quantitative attributes of the spatial features. (Salinity, biomass, name, date) and all this kind of information that describe the geographically referenced spatial elements.

TYPE OF INFORMATION IN A GIS DATABASE


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Source Of Geographical Data

• Digital data supplierEx: distributor of remotely sensed data

• Analogue data : graphical representation of the distribution of spatial phenomena

Ex: maps

• Field Survey : record sample values at known locationEx : sampling stations of a trawl survey

CREATE A DIGITAL GEOGRAPHICAL DATABASE


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Acquiring Digital Datasets From A Data Supplier :

Are the data compatible with my application ? We must know :• Currency of the data• Format description• Georeferencing system used • Data collection technique and sampling strategy• Quality• Data classification and interpolation methods used• Size and shape of the individual mapping unit


The data that has been collected will be in numerous formats. Though some of it may be already suitable for immediate input in the GIS, the majority of it will require conversion to a suitable digital format. Data heterogeneity may be also a problem and standardisation time consuming:

• Images: different resolutions, different sensors • Vector: different scales, different legends, different coordinate

systems Each GIS Software uses is own format for data storage, but may includes some importation / exportations procedures. When working with GIS, what we are doing essentially is manipulating models of the real world. Since the map is a simplification of the real world, transformations like generalisation, classification. Data quality is very important and may be controlled through standard procedures for the collection and the transfer.


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Creating Digital Datasets by Manual Inputs


A - Entering spatial data

B - Verification and Edition

C - Entering attribute data

D - Link spatial objects to attributes data


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Georeferencing

All spatial data in a GIS are located with respect to a common frame of reference : same coordinate system

Apart from local studies, use of a geodesic coordinate system : position on the earth’s surface.

Locations are projected from an ellipsoid onto a plan surface : orthogonal Cartesian coordinates

Positioning systems : use of GPS, which use satellites to define the geographical position and altitude anywhere of the earth’s surface.



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1. VECTOR DATA MODELS Features on the Earth’s surface are mapped on flat, two-dimensional maps as points, lines, and areas. An x,y (Cartesian) coordinate system is used to reference map locations to ground locations.Each point is recorded as a single x,y location. Lines (arcs) are recorded as a series of ordered x, y, coordinates. Areas are recorded as a series of x,y coordinates defining arcs that enclose an area.

(6, 3.5)

(3,6)

(7, 7.5)(2.5, 4.5)

(3, 3.5)

(3, 1)

(1, 5)

(1, 6)

(7,4)

Island

Track

Buoy

Polygon

Line

PointVectorial representation of spatial elements

REPRESENTATION OF SPATIAL INFORMATION

In the vector data structure points, lines and polygons are all recorded in terms of the geographic x and y coordinates. The vector data structure is thus concerned with boundaries


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VECTOR DATA MODEL

Each spatial object (point, line or polygon) will have a unique identifier


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In this model, the total surface of the map is divided into equal size square cells (known as pixels). Each cell contains a value of an attribute that may represent different things depending of the layer we are working with. The main characteristic of these cells is that exactly match with cells in other layers what enables overlaying operations.

RASTER DATA MODEL

The Raster data structure is concerned not with boundaries but whit the space between boundaries. All areas of the map must be allocated an attribute or a value coding for this attribute. It is sometimes called the grid model because data is stored in a matrix of cells, which themselves may be called pixels. These cells are usually square but they may be rectangular, triangular, etc...


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RASTER VECTORIAL

Memory requirements + -Database management - +Continuous variables + -Discrete variables - +Between layers analysis + -One layer analysis - +Graphic output - +

VECTOR VERSUS RASTER DATA MODEL

See more details in Doc "A Comparison of Raster and Vector Data Models"


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ENTERING SPATIAL DATA BY MANUAL IMPUTS

• Import objects coordinates from field survey datasets

• Input devices : semi-automatize spatial data input

Digitizer Scanner

Vector

Scannerization

Vectorization

Points- identifier- X, Y

Polylines- Identifier- Starting Node- Intermediate points- Ending Point

Use of snapping distance to connect nodes together

Raster

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SPATIAL DATA INPUT :IDENTIFY AND CORRECT ERRORS

• Positional error • Missing Entities • Improper placement • Disordered entities

=> Produce a print out=> Use of integrated GIS functions to check or correct errors


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VECTOR -> RASTER : RASTERISATION

RASTER -> VECTOR : VECTORISATION

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DATA CONVERSION : VECTOR / RASTER CONVERSIONS


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• From Cartesian to projected system.

• From One projection system to another projection.

• Basic issues - data expression

Degrees, minutes, seconds (DMS)

Decimal degrees (DD) =degrees + minutes/60 + seconds/3600

DATA CONVERSION : PROJECTION AND COORDINATES UNIT CHANGES


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Aspatial data or attributesThe supplementary information along with the spatial data that constitutes

the GIS database. Attributes can be either quantitative or qualitative, and refers always to the located features. They can be analysed independently by using non-spatial arithmetic operators.


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• Link spatial objects to attributes dataUse of a common unique identifier shared by the spatial element and its attributes

1 xxx yyy zz

2 ggg ddd dd

Spatial data attribute data file

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Id. Attr1 Attr2 Attr3 ...VECTOR

RASTER

ENTERING ATTRIBUTE DATA AND LINK TO SPATIAL OBJECTS

• Entering Attribute data : - manually entered- imported (using standard format : TXT, CSV, ASCII, ...)


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ATTRIBUTE ERRORS: VECTOR DATA

� you can plot the data using the attribute to verify as legend

� you can list the tabular data and see the entities missing attributes.

Attribute error

1.Miss-labelled or miss-identified attributes

2. Typing errors in data entry

3.Involve misspelling and coding


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Missing attributes can sometimes be seen as holes in the data set

Incorrect Attributes can be identified as abnormal attributes when examining 3-dimensional view of surface data oralong margins of different attributes.

ATTRIBUTE ERRORS IN RASTER DATA

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