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Introduction to GRCP

Introduction to GRCP. Boualem RABTA Center for World Food Studies (SOW-VU) Vrije Universiteit - Amsterdam. Requirements. Install GRCP (to work comfortably with large maps, a minimum amount of RAM and disk space required) Install and configure GAMS :

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Introduction to GRCP

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  1. Introduction to GRCP Boualem RABTA Center for World Food Studies (SOW-VU) VrijeUniversiteit - Amsterdam

  2. Requirements Install GRCP (to work comfortably with large maps, a minimum amount of RAM and disk space required) Install and configure GAMS : Settings (control panel/Regional settings) : Ajust the value for decimal separator (.) and list separator (,)

  3. About GRCP • GRCP is a software for joint processing of surveys (and censuses) and maps. • Data from different sources can be put together and represented on the map and geographical information (from maps) can be appended to the survey. • Statistical procedures are available to address issues such as prediction (regression, classification), association (Polling) and causality (matching). • Results are produced in tables, extensively commented listing files and may also be plotted on the map.

  4. Data input/output for GRCP • Input files (GRCP) : • Locatm.grd (map) • Administrative data (gams tables) • Locat.grd (survey points) • Variables (*.grd, *.gcd) • Raw data : • Country map (lowest adm. Level, ASC format) • Administrative data (CSV format) • Survey data (geolocalised, CSV format) Preparation (GRCP-WS) Compile GAMS script Zondat.gms (compile) Run GRCP • Output files (GRCP) : • *.grd, *gcd • *grdm, *gcdm (maps) • *.csv, *.txt 1 3 2 4 • Maps (Images) : • *.gif, *.jpg, *.png, *.bmp Plotting (GRCP-WS)

  5. Importing GIS data to GRCP Raw data: • Map at the lowest administrative level in ArcView ASCII fromat (e.g. GIS_CN.asc) • Codes and names for administrative levels (ML, R, PV, CN) in CSV format (ML_name.csv, R_name.csv, PV_name.csv, CN_name.csv) • Association CN->PV->R in CSV format (CN_PV.csv) Use function ‘’Maps->Create locatm from ASC’’ in the interface (indicate the location of the map and the administrative data). The map will be converted to GRCP Format (locatm.grd, *.gms) At this level, the map can be plotted at any administrative level and boundaries can be shown as well.

  6. Importing Survey data Raw data: • Survey table in CSV format (e.g. survey.csv) Identify georeference of every observation a) Georeference is already available (GPS coordinates) b) Georeference needs to be constructed • From information on settlement (village, town) • From information on administrative subdivisions, rural/urban 1- Create the survey frame (locat.grd): Open the data file in GRCP (Survey->Load survey data) and then use function ‘’Survey->generate variable files’’ 2- Extract the variables from the dataset (Survey->generate variable files) distinguish between categorical and real variables. At this stage, the survey points can be shown on the map and some data might be plotted as well (!)

  7. Projection from maps to survey It is also possible to extract information from maps in Arcview ASCII fromat (e.g. population density, climate, rainfall, soil…) and to append it to the survey so it can be used for analysis. Usefunction “Maps-> ASC to variable” Example: Population density

  8. Projection of data given at administrative level on the map Data aggregated at any administrative level can easily be projected on the map. • Load data • Projection/From adm. To map

  9. File structure (on disk) The software shows a simplified view of the files tree. The disk structure of a GRCP folder looks like the following: Folder for real-valued files (*.grd) Folder for all for categorical files (*.gcd) with corresponding header file (*.hdr) Folder for GAMS scripts Folder for all for categorical files (*.gcd) without corresponding header file (*.hdr). Real-valued files can also be put here.

  10. Files format The map frame (locatm.grd) and the survey frame (locat.grd) The locatm.grd file Geographic location of the observations in the survey The locat.grd file X X X X

  11. Files format General rules: 1) All variables that correspond to the survey frame have extensions with three characters. Examples: *.gcd, *.grd 2) All variables that correspond to the map frame have extensions with four characters , where an “m” is added to indicate that this is a “map” file. Examples: *.gcdm, *.grdm (The only exception is the map frame itself (locatm.grd)) Input files for Polling: The main statistical tool of Polling is the computation of conditional frequencies, which works purely on categorical data. -> The main file format is *.gcd -> All real-valued files (*.grd) will have to be categorized -> Every *.gcd file needs a header file, with extension *.hdr Output files Output files have a multitude of different extensions (explained later) Examples: *.gcd, *.grd, *.hdr, *.gcdm, *.grdm, *.hdrm, *.txt, *.csv, *.hrr, *.sas

  12. GAMS program To performstatisticaloperationon the data in GRCP, the user has to write and execute a GAMS program.

  13. Available functions in polling include : CROSS Input: *.gcd Output: *.hdr (header file for categories) *.hrr (header file for weights) *.gcdm (projection of categories on the map) *.grdm (projection of weights on the map) *.hdrm (header file for categories on the map) SLICE Input: *.grd Output: *.gcd (categories) *.hdr (header file for categories) *.hrr (header file for weights) *.gcdm (projection of categories on the map) *.grdm (projection of weights on the map) KERNM Interpolation ZONDIR Input: All activated files Output(data): *.gcd (categories) *.hdr (header file for categories) *.grd (weight file) *.hrr (header file for weights) *.gcdm (projection of categories on the map) *.grdm (projection of weights on the map) Output(results): *.txt (main results) *.csv (excerpts from main results file) *.sas (SAS program for mapping in SAS)

  14. Projection from map to survey For each survey observation, values of the map at that location (eg, population, elevation, soil quality, climate,…) is appended as attribute. $BATINCLUDE ..\LIBRARY\MAPTOSUR.gms VAR1 Takes a gcdm (map) file (VAR1) and generates gcd (survey) file. Takes a grdm (map) file (VAR1) and generates grd (survey) file.

  15. Interpolation data collected within specific sites in an area of interest can be extended spatially to sites where no sample collection has taken place. Surface interpolation functions create a continuous surface from discrete set of measured points through the input of data collected at a number of sample points.

  16. On classified data mollifier/nearest neighbor interpolation is applied. KERNM specifies the interpolation parameters to be used by CROSS, SLICE and ZONDIR commands. SET ZVARM ' File names and description real valued variables' / LATM 'Latitude ' LONM 'Longitude ' VOIDM1 VOIDM2 /; * Specify rule and kernel window size for mapping on grid SCALAR RULEM,THETAM; THETAM = 0.6; * kernel window size RULEM = 0 ; * {0=no projection 1=mollifier 2=nearest neighbor 3=fast nearest neighbor(define thetam as pixels)} $BATINCLUDE ..\LIBRARY\KERNM.gms ZVARM RULEM THETAM Then, we may use CROSS, SLICE and ZONDIR

  17. Plotting options Colors: GRCP uses 10 colors for the data, 4 colors for administrative boundaries, 1 color for nodata values and 1 color for ML area. Color schemes can be loaded and modified. Legend/Title : Position as well as font size for legends and titles can be adjusted. Survey points : can be plotted as layer on top of other maps. They can also plotted as maps with administrative boundaries and ML background. The size and shape can be modified. Maps : the pixel size can be adjusted (small maps)

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