Comparison of Copernicus Time Series of NDVI V1 and V2 in Valderejo Test Site

• Agustin.Lobo@ictja.csic.es
• 20150310

Introduction

• NDVI V1 and V2 (available at http://land.copernicus.vgt.vito.be/PDF/portal/Application.html#Home) both available for 2013.
  
• Valderejo IC3 Climadat site (-3.213993, 42.878605) http://goo.gl/maps/hvkiy

Requirements

require(ggplot2)
require(lubridate)
require(scales)

1. Data

• V1: VN2013VGTm is the melted (long format) of VN2013VGT which in turn is a crop() of the annual brick of NDVI 2013 for Europe (see Val2013VGT_log.R).
  
• V2: VN2013m (equivalent for V2, see Val2013_log.R; note hdf5 is different than that of GEOV1 )

head(VN2013VGTm,3)

##   ID       Date DOY  NDVI   QF QF0
## 1  1 2013-01-03   3 0.836 <NA>  NA
## 2  2 2013-01-03   3 0.840 <NA>  NA
## 3  3 2013-01-03   3 0.828 <NA>  NA

head(VN2013m[1:3,],3)

##   ID       Date DOY  NDVI   QF QF0
## 1  1 2013-01-01   1 0.808 <NA>  NA
## 2  2 2013-01-01   1 0.808 <NA>  NA
## 3  3 2013-01-01   1 0.796 <NA>  NA

• ID: pixel ID
• Date: Date
• DOY: day of the year
• NDVI
  
• QF: quallity flag
• QF0:

2. Plot

Define time limits and label positioning

fini <- ymd("20130101")
ffin <- ymd("20140101")
datebreaks <- seq(fini, ffin, by="3 month")

Time series for the 18 pixels (grid) of Valderejo (X axis DOY)

ggplot() + 
  geom_point(data=VN2013VGTm,aes(x=DOY,y=NDVI)) +
  geom_line(data=VN2013VGTm,aes(x=DOY,y=NDVI,group=ID),col="red") +
  geom_point(data=VN2013m,aes(x=DOY,y=NDVI)) +
  geom_line(data=VN2013m,aes(x=DOY,y=NDVI,group=ID),col="green") +  
  facet_wrap(~ID,nrow=3,ncol=6) + 
  ggtitle("Valderejo 2013 NDVI V1 (red) and NDVI V2 (green) compared")

#ggsave("Val2013V1_V2comparedDOY.jpeg")

Time series for the 18 pixels of Valderejo (individual observations + mean)

ggplot() + 
  geom_point(data=VN2013VGTm, aes(x=Date,y=NDVI),col="red") +
  geom_point(data=VN2013m, aes(x=Date,y=NDVI),col="blue") +
  stat_summary(data=VN2013VGTm,aes(x=Date,y=NDVI),fun.data ="mean_sdl", mult=1, 
               geom = "smooth",colour="red") +
  stat_summary(data=VN2013m,   aes(x=Date,y=NDVI),fun.data ="mean_sdl", mult=1, 
               geom = "smooth",colour="blue") +
  scale_x_datetime(breaks = date_breaks("1 month"),
                   labels = date_format("%m")) +
  xlab("") + ylab("NDVI") +
  #theme(axis.text.x = element_text(angle = 45, hjust = 1)) +
  ggtitle("Valderejo 2013 V1 (red) and V2 (blue) compared")

#ggsave("Val2013V1_V2compared_median.bmp")