1. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment1 Lecture 4. Grid-based modelling Outline – introduction – linking models to GIS – basics of cartographic modelling – modelling in GRID

2. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment2 Introduction GIS provides: –comprehensive set of tools for environmental data management –limited spatial analysis functionality –but does provides framework of application limited spatial analysis functionality may be addressed by linking models into GIS

3. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment3 Spatial modelling issues Model problems: –most models do not provide tools for data management and display, etc. –many models are aspatial GIS provides: –framework of application –allows user to add spatial dimension (if not already built into the model)

4. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment4 GIS-able models Types of models applicable to integration with GIS include: –certain aspatial models black box models lumped models –all spatial models distributed models –temporal models

5. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment5 Linking models to GIS Two basic methods of integrating models into the GIS framework: –soft or loose coupling models and GIS are linked via file transfer –hard or tight coupling models and GIS are linked directly through sharing common database model programmed using GIS macros and functions

6. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment6 Creating the link How models are integrated into a GIS depends on: –the type model itself –the flexibility of the GIS as a modelling environment –the time and resources available Fuzzy boundary between loose and tight coupling

7. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment7 Loose coupling External data transfer G.I.S MODEL GIS database

8. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment8 Tight coupling GIS database Internal data transfer G.I.S MODEL

9. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment9 Example GIS-based gas dispersion model –requirements: an emergency planning decision support system is required for accident planning involving releases of chlorine gas from chemical plants a dense gas dispersion model needs to be linked to a GIS to enable predictions of gas dispersion to be integrated with environmental data to assist in emergency planning procedures –loose or tight coupling?

10. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment10 Questions… Which model? Which GIS? Which data? What level of coupling?

11. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment11 Loose coupling approach 1.identify point of release (POR) and conditions of release (COR) 2.input POR and COR variables to model via keyboard input 3.run model 4.pass model results to GIS via file exchange 5.create model results data layer in GIS 6.integrate (overlay) with other data layers

12. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment12 Tight coupling approach 1.identify POR and COR 2.run model create POR and COR layers model accesses GIS database directly for inputs at every increment of the model run to update basis for predictions model creates new data layer in GIS database describing results 3.integrate (overlay) model results with other data layers

13. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment13 Integrating GASTAR with Arc/Info

14. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment14 Modelling testing Testing models –verifying model output can present certain problems for the user –especially true if : the model is complicated two or more models are used the data used is complex or of dubious accuracy or both! long timescales are involved the model is of the black box variety or if the user is unfamiliar with its workings

15. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment15 Example RUNMOD –a lumped catchment model of the hydrological cycle lumped input: precipitation lumped storage: soil store, groundwater store, channel store lumped output: evapotranspiration, runoff –parameters governing infiltration, through flow, percolation, etc. can be altered to improve modelled outputs compared to measured outputs –this is a process known as calibration

16. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment16 Questions… What are the advantages of model calibration? How could this particular model be integrated into a GIS framework?

17. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment17 Modelling guidelines In order to ensure that model results are as close to reality as possible the following guidelines apply: –ensure data quality –beware of making too many assumptions –match model complexity with process complexity –compare predicted results with empirical data where possible and adjust model parameters and constants to improve goodness of fit –use results with care!

18. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment18 Basics of cartographic modelling Mathematics applied to raster maps –often referred to as map algebra or ‘mapematics’ –e.g. combination of maps by: addition subtraction multiplication division, etc. –operations on single or multiple layers

19. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment19 A definition “A generic means of expressing and organising the methods by which spatial variables and spatial operations are selected and used to develop a GIS model”

20. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment20 A simple example… 5 4 7 Input 1 6 4 4 6 6 6 6 4 4 4 4 3 3 3 3 33 23 22 2 2 2 2 1 1 1 1 2 5 7766 77 135 6108 5 5 Input 2 Output + =

21. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment21 Question… How determine topological relationships? i.e. Boolean: AND, NOT, OR, XOR What is the arithmetic equivalent?

22. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment22 Building spatial models It is (in theory) surprisingly simple: – algebraic combination of: OPERATORS and FUNCTIONS rules and relationships inputs (and outputs) – interfaces run at the command line/menu interface batch file embedded in system macro/script ‘hard’ programmed into system

23. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment23 Problems in model building knowledge –systems and processes –relationships and rules compatability –input data available –outputs required quality issues –data quality (accuracy, appropriateness, etc.) –model assumptions and generalisation –confidence and communication

24. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment24 Modelling in Arc/Info GRID Four basic categories of functions in map algebra: – local – focal – zonal – global Operate on user specified input grid(s) to produce an output grid, the cell values in which are a function of a value or values in the input grid(s)

25. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment25 Local functions Output value of each cell is a function of the corresponding input value at each location – value NOT location determines result – e.g. arithmetic operations and reclassification – full list of local functions in GRID is enormous Trigonometric, exponential and logarithmic Reclassification and selection Logical expressions in GRID Operands and logical operators Connectors Statistical Other local functions

26. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment26 Local functions 25 16 5 4 7 49 input output = sqr(input)

27. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment27 Some examples input output = tan(input) output = reclass(input)output = log2(input)

28. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment28 Focal functions Output value of each cell location is a function of the value of the input cells in the specified neighbourhood of each location Type of neighbourhood function – various types of neighbourhood: 3 x 3 cell or other – calculate mean, SD, sum, range, max, min, etc.

29. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment29 Focal functions 5 4 7 16 11 input output = focalsum(input)

30. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment30 Some examples input output = focalmean(input, 20) output = focalstd(input)output = focalvariety(input)

31. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment31 Neighbourhood filters Type of focal function –used for processing of remotely sensed image data – change value of target cell based on values of a set of neighbouring pixels within the filter – size, shape and characteristics of filter? – filtering of raster data supervised using established classes unsupervised based on values of other pixels within specified filter and using certain rules (diversity, frequency, average, minimum, maximum, etc.)

32. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment32 Supervised classification 1 2 3 4 5 1 2 Old classNew class 134 245 124 112 122 112

33. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment33 134 245 124 diversity modal minimum maximum mean Unsupervised classification 5 4 1 5 3

34. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment34 Zonal functions Output value at each location depends on the values of all the input cells in an input value grid that shares the same input value zone Type of complex neighbourhood function – use complex neighbourhoods or zones – calculate mean, SD, sum, range, max, min, etc.

35. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment35 Zonal functions 5 4 7 input output = zonalsum(zone, input) zone Zone 1 Zone 2 9 9 9 9 9 9 9 9 777 7 77 7 7

36. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment36 Some examples input output = zonalthickness(input_zone) Input_zone 535.54 766.62 127 160 output = zonalmax(input_zone, input) output = zonalperimeter(input_zone) 6280 10800

37. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment37 Global functions Output value of each location is potentially a function of all the cells in the input grid – e.g. distance functions, surfaces, interpolation, etc. – Again, full list of global functions in GRID is enormous euclidean distance functions weighted distance functions surface functions hydrologic and groundwater functions multivariate.

38. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment38 Global functions 5 4 7 input output = trend(input) 9 8 7 6 8 7 6 6 7 6 5 54 4 5 6

39. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment39 Distance functions Simple distance functions – calculate the linear distance of a cell from a target cell(s) such as point, line or area – use different distance decay functions linear non-linear (curvilinear, stepped, exponential, root, etc.) – use target weighted functions – use cost surfaces

40. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment40 Some examples inputsource output = eucdistance(source)output = eucdirection(source)output = costdistance(source, input)

41. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment41 COSTPATH example

42. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment42 Conclusions Linking/building models to GIS Idea of maths with maps – surprisingly simple, flexible and powerful technique – basis of all raster GIS Fundamental to spatial interpolation, distance and neighbourhood functions

43. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment43 Workshop Constructing models in Arc/Info GRID –Demonstration of GRID functions Focal functions Local functions Global functions Zonal functions AML for GRID

44. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment44 Practical Facilities location using Arc/Info GRID Task: Locate suitable sites for a wind farm in the Yorkshire Wolds Data: The following datasets are provided… –Digital elevation model (50m resolution 1:50,000 OS Panorama data) –Contour data (10m interval 1:50,000 OS Panorama data) –ITE land cover map (25m resolution) –Roads (1:250,000 Meridian data) –Wind speed data

45. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment45 Practical Steps: 1.Formulate a location model based on available data and requirements for a wind farm 2.Pre-process data to create model input layers as required 3.Run model 4.Identify best location(s)

46. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment46 Siting wind turbines

47. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment47 Practical Experience at simple cartographic model building Experience with spatial modelling functions within Arc/Info GRID Familiarity with locational models and wind farm siting in particular

48. GEOG5060 GIS & Environment Lecture 4 GEOG5060 - GIS and Environment48 Next week… Terrain modelling 1: the basics –DEMs and DTMs –Derived variables –Example applications Workshop: Terrain modelling in Arc/Info and Grid Practical:Using DEMs