[R-sig-Geo] R code for rainfall isohyet map

[Stefano Sofia]

Dear R-sig-geo list users,
given n meteorological automatic stations with rain gouge, I need to produce an image with the isohyets of the rainfall values of my region (Italy, Marche region, on the Adriatic Sea in front of Croatia).
For each station the available coordinates are in Gauss Boaga, Long and Lat in degrees, minutes and seconds and Long and Lat in degrees and decimals.
In the code below reported Long and Lat in degrees and decimals have been used.

This is an example of the input file called in the code "pointfile.csv":

Station_code, Rainfall_value, GaussBoaga_EST, GaussBoaga_NORD, Long_degrees, Long_minutes, Long_seconds, Lat_degrees, Lat_minutes, Lat_seconds, Long_Cent, Lat_Cent
1056, 11.8, 2328427, 4851813, 12, 37, 7.45291, 43, 47, 40.09906, 12.618737, 43.794472

The code below reported (with the precious support of Micha Silver) does compile, but the final image reports some numerical values (isohjet_map.png).
Would please somebody be able and help me to see where the code can be improved?

Thank you for your help
Stefano

Code:

library(automap)
library(ggplot2)
library(gstat)
library(rasterVis)
library(rgdal)

## READ INPUT FILE
rain_data <- read.csv(file="pointfile.csv")
str(rain_data)

point_coords <- rain_data[c("Long_Cent","Lat_Cent")]
coordinates(rain_data) <- point_coords
p4str <- CRS("+init=epsg:4326")
proj4string(rain_data) <- p4str

## CONVERTION TO UTM
p4str_UTM <- CRS("+init=epsg:32633")
rain_data_UTM <- spTransform(rain_data, p4str_UTM)

## CHECK THAT THIS IS A SPDF IN THE UTM COORDINATE SYSTEM
str(rain_data_UTM)

## CREATE GRID FOR KRIGING OUTPUT, USING THE EXTENT OF THE RAIN DATA SPDF
minx <-  rain_data_UTM at bbox[1,1]
maxx <- rain_data_UTM at bbox[1,2]
miny <- rain_data_UTM at bbox[2,1]
maxy <- rain_data_UTM at bbox[2,2]
## EACH PIXEL WILL BE 1000 METERS
pixel <- 1000
grd <- expand.grid(x=seq(minx, maxx, by=pixel), y=seq(miny, maxy, by=pixel))
coordinates(grd) <- ~x+y
gridded(grd) <- TRUE
proj4string(grd) <- p4str_UTM

## KRIGING, USING AUTOKRIGE WHICH CREATES A BEST GUESS VARIOGRAM
OK_rain <- autoKrige(Rainfall_value ~ 1, rain_data_UTM, grd)

## TRASFORM TO RASTER
rain_rast <- raster(OK_rain$krige_output)

## READ THE MARCHE BOUNDARY SHAPEFILE
Marche_shape <- readOGR(dsn="Lim_reg_2012_wgs32633.shp", layer="Lim_reg_2012_wgs32633")

##PLOT
png(file="isohyet_map.png")
gplot(rain_rast) + geom_tile(aes(fill=factor(value),alpha=0.8)) + geom_polygon(data=Marche_shape, aes(x=long, y=lat, group=group), fill=NA, color="grey50", size=1) + coord_equal()
dev.off()




         (oo)
--oOO--( )--OOo----------------
Stefano Sofia PhD
Area Meteorologica e  Area nivologica - Centro Funzionale
Servizio Protezione Civile - Regione Marche
Via del Colle Ameno 5
60126 Torrette di Ancona, Ancona
Uff: 071 806 7743
E-mail: stefano.sofia at regione.marche.it
---Oo---------oO----------------

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