Data Handling And Management, Including Use Of Gis

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Data handling and management, including use of GIS Introduction • • • • • • • • Data D t Handling H dli Data Management g What is a GIS? Map Projections Types of data Verification Mapping Thematic Mapping Data Handling • With increasingly bigger and complicated g of datasets,, the need for management data is essential • Data needs to be structured – Simple list (MS Excel) – Database Management System – DBMS (MS Access) Simple List - MS Excel • • • • • Easy to use Easy to initially input the data (No set up) Easy to produce graphical output Limited in size (256 columns 65536 rows) All related data stored in one worksheet or table – No links between worksheets or tables – Large storage issue • Difficult to interrogate the data • Only y a single g user can access the data at any one time DBMS – MS Access • • • • Requires some training to use Requires setting up Easy to input data once set up Rules can be applied to data and enforced automatically. Removes errors and inconsistencies • Tables are linked (related) – Multiple table interrogation – Smaller storage • Multiple users can access the data simultaneously • Accumulation of very large databases may require the use of sequel server Excel Data Management • One table with all data needed • Large table • Lots L t off column l h headings di • Lots ots of o replication ep cat o • Simple to use B dN Bed Name Species Bed Location Local Authority (LA) LA Address 1 LA Address 2 LA Address 3 LA Address 4 Testing Lab (TL) TL Address 1 TL Address 2 TL Address 3 TL Address 4 Date Test Result Qualifier Result Units Notes Access Data Management • S Severall T Tables bl allll related to each other • Only y a few fields need to be entered t each eac new e e entry ty with • No replicates • Knowledge Kno ledge required to use Bed ID Bed Name Species ID Bed Location LA ID Lab ID Bed ID Date Test ID Result Qualifier Result Notes Test ID Test Type Units Species ID Species Latin Species Common LA ID Local Authority (LA) LA Address 1 LA Address 2 LA Address 3 LA Address 4 Lab ID Testing Lab (TL) TL Address 1 TL Address 2 TL Address 3 TL Address 4 What is a Geographic Information System? • Definition of GIS “a p powerful set of tools for collecting, g, storing, g, retrieval at will, transforming and displaying spatial p data from the real world” (Burrough 1986) a system for capturing capturing, storing storing, checking checking, “a manipulating, analysing and displaying data which are spatially referenced to the earth” earth (Department of Environment, UK 1987) Data requires a) Their position with respect to a known coordinate system b) Their attributes that are unrelated to position ((such as species, names, colour etc.)) c) Their spatial interrelations with each other which describes how they are linked together Examples of Data • • • • • • Maps Bivalve mollusc beds Sampling results Point discharges Rivers High/Low water lines Map Projections • Map projections are attempts to portray portion of the the surface of the earth or a p earth on a flat surface. • This leads to distortions of conformity conformity, distance, direction, scale, and area. • Because of this it is essential to know what projection (Coordinate System) your data is in. Example p Projections j British National Grid Lat/long OSGB36 British National Grid On an OSGB36 projection Lat/Long OSGB36 50°36’16”N 50 36 16 N 02°26’58”W British National Grid SY68197848 •Big difference in the look of the maps Different Coordinate nomenclature •Different Lat/Long OSGB36 50 36 16 N 50°36’16”N 02°26’58”W •Little Little difference in the look of the maps •Same Coordinate nomenclature Lat/Long WGS84 50°36’16”N 02 26 58 W 02°26’58”W • The same set of Coordinates plots in different locations depending on the projection •Always report the projection with the Coordinates Variations of recording data • A set of Coordinates can be written in numerous ways all referring to the same location • DD°MM’SS” DD MM SS • DD°MM.mm’ • DD.dddd° DD dddd° 02 26 58 W 02°26’58”W 02°26.97’W 02 4495°W 02.4495°W • No matter what system is used always be consistent!!!! Latitude and Longitude Greenwich Meridian 0° Longitude 0 12°34’56”N 65°43’21”W 12°34’56”N 65°43’21”E Lines of L i d Latitude Equator 0° Latitude 12°34’56”S 12 34 56 S 65°43’21”E 65 43 21 E Liness of Longiitude 12°34’56”S 12 34 56 S 65°43’21”W 65 43 21 W Accuracy of position • When stating coordinates you should be give an accuracy y of 10m able to g – 12°30’59’’.9 – 12 12°30’ 30 .99 99 – 12°.5124 Accuracy of position • Degree Accuracy of position • Degree • Minute Accuracy of position • Degree • Minute • Second Accuracy of position • Degree • Minute • Second Mapping • Electronic mapping Accuracy of position • Degree • Minute • Second Mapping • Electronic mapping • Paper Map Accuracy of position • Degree • Minute • Second Mapping • Electronic mapping • Paper map • Aerial photo Types of Data • There are only three types of data used in g a GIS these being: – Points e g Sampling locations e.g. – Lines e.g. High Water Line – Regions e.g. Shellfish beds Modelling the Data • There are two methods of modelling data RASTER Point Line Region •Simple data structure •The data are only as accurate as the resolution of the grid •A pixel can only represent one entity •No data attributed to a pixel •Large volume of storage needed VECTOR •Complex data structure •Good representation of data •The data are fixed to a point no matter the scale •The data can be built up in layers, allows overlapping overlapping. •Objects can have data attributed to them Mapping • A GIS takes data and either adds it to a y or creates a layer y to display p y the data layer • The layers can then be stacked and ordered • Data within the layers can be interrogated, manipulated and changed • This allows data to be visualised with respect to other datasets Sampling Points High Water Line Points Lines Populated Areas g Regions Bivalve Mollusc Beds Base Map (Raster Image) Base Layer Points Lines Regions g Base Layer Verification • The verification process is carried out at y step p from obtaining g the data to the every final output of the data. • Starting from confirming the projection/coordinate system • Through to plotting the data and visually inspecting it to see if it conforms to expectations e.g. is it in the sea Thematic mapping • A map displaying selected kinds of g to specific p themes information relating such as population, pollution level, species etc • Maps can display individual points or representations off data between points on a scale Map with Graphs Digital Elevation Model 900 height measurements Digital Elevation Model 900 height measurements Digital Elevation Model Conclusions • Output is only as good as the input – Rubbish In  Rubbish Out • Verification at every step • Knowledge and understanding off the data is vital • Must know Projection and Coordinate system Thank you