Task Sometimes you have incomplete coverage over a region with gaps that need filling. In other cases you may have recorded data for a set of points but intend to analyse surfaces. There are several techniques of spatial interpolation that can estimate data values over a whole region. Your task is examine some of these techniques and identify conditions for their appropriate use. Complete the ArcGIS exercise and find out about a range of interpolation techniques.

Interpolating Raster Surfaces
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Source: ESRI Virtual Campus. Interpolating raster surfaces with ArcGIS Spatial Analyst, Module 4 of Learning ArcGIS 9 Spatial Analyst. <http://training.esri.com/gateway/index.cfm> URL last accessed 10-10-2006.

Creating Vector Surfaces
[ URL ]

Source: ESRI Virtual Campus. Creating 3D data, Module 4 Part A of Learning ArcGIS 9 3D Analyst. <http://training.esri.com/gateway/index.cfm> URL last accessed 10-10-2006.

Spatial Interpolation
[ pdf ]
Source: Longley et al., 2001. Chapter 13 Section 4.4 pp. 295-299.

Updated source: Longley PA, Goodchild MF, Maguire DJ and Rhind DW, 2005. Chapter 14.4.4 in Geographic Information Systems & Science. New York: Wiley. pp. 333-339.

Interpolation
[ URL ]
Source: Sárközy F, 1998. GIS functions - interpolation, Periodica Polytechnica Civil Engineering. <http://www.agt.bme.hu/public_e/funcint/funcint.html> URL last accessed 09-01-2007.
Data Structures for Surfaces Source: Wise S, 2002. Ch 9 in GIS Basics. London: Taylor and Francis. pp 133 - 154. Pay special attention to sections 9.2 and 9.3.
Task Most GIS store vector and raster data but very few, if any, have analytical functions that can combine data of different types in a model. All too often you will find yourself having to convert data to one or other data model. Furthermore, the sequencing and frequency of converting data can affect the outputs of subsequent analyses and so you should know something of these techniques. Your tasks are to explore rasterisation and vectorisation techniques and to assess their weaknesses.

ArcGIS Spatial Analyst
[ URL ]

Source: ESRI Virtual Campus. Interpolating raster surfaces with ArcGIS Spatial Analyst, Module 1 of Learning ArcGIS 9 Spatial Analyst. <http://training.esri.com/gateway/index.cfm> URL last accessed 10-10-2006.

Converting Between Spatial Data Models
[ ppt ]
Source: Trodd N, 2005.

Converting Surfaces
[ URL ]

Source: ESRI Virtual Campus. Converting 3D data, Module 4 Part C of Learning ArcGIS 9 3D Analyst. <http://training.esri.com/gateway/index.cfm> URL last accessed 10-10-2006.

Task If you are handling raster data then you need to realign the grid structures so that grid cells correspond to the same areas on the ground. This may require a reorientation of the grid, change in spatial resolution and a recalculation of values. Your task is to investigate techniques for resampling raster data and identify effects that might have a consequence on later analyses.
Spatial Resampling
[ URL ]
Source: Ellis F, 2001. Spatial resampling, in GIS Self Learning Tool, University of Melbourne. <http://www.sli.unimelb.edu.au/gisweb/RSAModule/RSASelect.htm> URL last accessed 08-01-2007.
Task Before you undertake any spatial analysis you must decide on the size of units, their spatial support, at which you your models will operate and aggregate data to these units. Note that it is a fallacy to think that you can disaggregate data to create smaller units that have a valid meaning without ancillary information. Your task is to look at techniques to generalise line entities.
Line Generalisation
[ URL ]
Source: Ellis F, 2001. Line generalisation, in GIS Self Learning Tool, University of Melbourne. <http://www.sli.unimelb.edu.au/gisweb/LGmodule/LGModule.htm> URL last accessed 08-01-2007.