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 :
Settings (control panel/Regional settings) : Ajust
the value for decimal separator (.) and list
separator (,)
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.
Data input/output for GRCP
Raw data :
•Country map (lowest adm. Level, ASC
format)
•Administrative data (CSV format)
•Survey data (geolocalised, CSV format)
GAMS script
Zondat.gms (compile)
Preparation
(GRCP-WS)
1
Compile
2
Input files (GRCP) :
• Locatm.grd (map)
•Administrative data (gams tables)
•Locat.grd (survey points)
•Variables (*.grd, *.gcd)
3
Run GRCP
Output files (GRCP) :
• *.grd, *gcd
• *grdm, *gcdm (maps)
• *.csv, *.txt
Maps (Images) :
• *.gif, *.jpg, *.png, *.bmp
4
Plotting (GRCP-WS)
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.
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 (!)
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.
Use function “Maps-> ASC to
variable”
Example: Population density
Projection of data given at
administrative level on the map
Data aggregated at any
administrative level
can easily be
projected on the map.
1. Load data
2. Projection/From
adm. To map
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.
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
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
GAMS program
To perform statistical operation on the data in GRCP, the
user has to write and execute a GAMS program.
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)
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)
KERNM
Interpolation
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.
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.
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
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)