# Quick exploration and file listing-based comparison of the CGIAR SRTM

# tiles available in the following places:

#

#   - those downloaded by Ming

#       jupiter.nceas.ucsb.edu:~organisms/SRTM_90m_ASCII_v4.1/

#

#   - those downloaded by Rick

#       jupiter.nceas.ucsb.edu:~organisms/CgiarSrtmAll/5_5x5_ascii/

#

#   - those currently available at CGIAR (ASCII format)

#       ftp://srtm.csi.cgiar.org/SRTM_v41/SRTM_Data_ArcASCII/

#

# Note that in addition to the comparisons made below, I also noticed

# that a few timestamps on zips Ming downloaded are newer than the

# timestamps on the CGIAR ftp site. It appears that these are bad zips

# on the CGIAR site; in subsequent email exchange with Ming, he said he

# believes he replaced them by downloading the corresponding GeoTIFFs

# from CGIAR and converting them to ASCII.

#

# Jim Regetz

# NCEAS

# Created on 21-May-2011

# list of tiles Ming downloaded onto jupiter

cmd <- "cd ~organisms/SRTM_90m_ASCII_v4.1 && ls -l srtm_*zip"

files <- system(cmd, intern=TRUE)

jup.v4.1 <- with(read.table(textConnection(files)), data.frame(tile=V8,

    size=V5, date=as.Date(V6, format="%Y-%m-%d"), time=V7))

# list of tiles Rick downloaded onto jupiter

cmd <- "cd ~organisms/CgiarSrtmAll/5_5x5_ascii && ls -l srtm_*zip"

files <- system(cmd, intern=TRUE)

jup.5_5x5 <- with(read.table(textConnection(files)), data.frame(tile=V8,

    size=V5, date=as.Date(V6, format="%Y-%m-%d"), time=V7))

# current list of tiles at CGIAR ftp site

cmd <- "curl ftp://srtm.csi.cgiar.org/SRTM_v41/SRTM_Data_ArcASCII/"

files <- system(cmd, intern=TRUE)

cgiar <- with(read.table(textConnection(files)), data.frame(tile=V4,

    size=V3, date=as.Date(V1, format="%m-%d-%y"), time=V2))

# list CGIAR tiles not found in jup.5_5x5

setdiff(cgiar$tile, jup.5_5x5$tile)

##  "srtm_32_05.zip" "srtm_68_03.zip"

# list jup.5_5x5 tiles not found in CGIAR (none!)

setdiff(jup.5_5x5$tile, cgiar$tile)

##  character(0)

# list CGIAR tiles not found in jup.v4.1

setdiff(cgiar$tile, jup.v4.1$tile)

##  "srtm_65_01.zip" "srtm_65_05.zip" "srtm_65_06.zip" "srtm_65_07.zip"

##  "srtm_65_08.zip" "srtm_65_10.zip" "srtm_65_11.zip" "srtm_65_13.zip"

##  "srtm_65_15.zip" "srtm_65_16.zip"

# list jup.v4.1 tiles not found in CGIAR (none!)

setdiff(jup.v4.1$tile, cgiar$tile)

##  character(0)

# show that all common tiles between CGIAR and jup.v4.1 have the same file

# size

common <- merge(cgiar, jup.v4.1, by="tile")

identical(common$size.x, common$size.y)

##  [1] TRUE

# but note that three files in jup.v4.1 have different (newer, as it

# turns out) timestamps

identical(common$date.x, common$date.y)

##  [1] FALSE

common$tile[common$date.x!=common$date.y]

##  "srtm_19_06.zip" "srtm_21_14.zip" "srtm_42_14.zip"