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# Quick exploration and file listing-based comparison of the CGIAR SRTM
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# tiles available in the following places:
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#
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# - those downloaded by Ming
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5
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# jupiter.nceas.ucsb.edu:~organisms/SRTM_90m_ASCII_v4.1/
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#
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# - those downloaded by Rick
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# jupiter.nceas.ucsb.edu:~organisms/CgiarSrtmAll/5_5x5_ascii/
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#
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# - those currently available at CGIAR (ASCII format)
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# ftp://srtm.csi.cgiar.org/SRTM_v41/SRTM_Data_ArcASCII/
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#
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# Note that in addition to the comparisons made below, I also noticed
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14
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# that a few timestamps on zips Ming downloaded are newer than the
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15
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# timestamps on the CGIAR ftp site. It appears that these are bad zips
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# on the CGIAR site; in subsequent email exchange with Ming, he said he
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# believes he replaced them by downloading the corresponding GeoTIFFs
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# from CGIAR and converting them to ASCII.
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19
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#
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20
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# Jim Regetz
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21
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# NCEAS
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22
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# Created on 21-May-2011
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23
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# list of tiles Ming downloaded onto jupiter
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cmd <- "cd ~organisms/SRTM_90m_ASCII_v4.1 && ls -l srtm_*zip"
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files <- system(cmd, intern=TRUE)
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jup.v4.1 <- with(read.table(textConnection(files)), data.frame(tile=V8,
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size=V5, date=as.Date(V6, format="%Y-%m-%d"), time=V7))
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29
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# list of tiles Rick downloaded onto jupiter
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cmd <- "cd ~organisms/CgiarSrtmAll/5_5x5_ascii && ls -l srtm_*zip"
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files <- system(cmd, intern=TRUE)
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jup.5_5x5 <- with(read.table(textConnection(files)), data.frame(tile=V8,
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size=V5, date=as.Date(V6, format="%Y-%m-%d"), time=V7))
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35
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# current list of tiles at CGIAR ftp site
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cmd <- "curl ftp://srtm.csi.cgiar.org/SRTM_v41/SRTM_Data_ArcASCII/"
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files <- system(cmd, intern=TRUE)
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cgiar <- with(read.table(textConnection(files)), data.frame(tile=V4,
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size=V3, date=as.Date(V1, format="%m-%d-%y"), time=V2))
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41
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42
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# list CGIAR tiles not found in jup.5_5x5
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setdiff(cgiar$tile, jup.5_5x5$tile)
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## "srtm_32_05.zip" "srtm_68_03.zip"
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45
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46
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# list jup.5_5x5 tiles not found in CGIAR (none!)
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47
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setdiff(jup.5_5x5$tile, cgiar$tile)
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48
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## character(0)
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49
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50
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# list CGIAR tiles not found in jup.v4.1
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setdiff(cgiar$tile, jup.v4.1$tile)
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## "srtm_65_01.zip" "srtm_65_05.zip" "srtm_65_06.zip" "srtm_65_07.zip"
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## "srtm_65_08.zip" "srtm_65_10.zip" "srtm_65_11.zip" "srtm_65_13.zip"
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54
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## "srtm_65_15.zip" "srtm_65_16.zip"
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55
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56
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# list jup.v4.1 tiles not found in CGIAR (none!)
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setdiff(jup.v4.1$tile, cgiar$tile)
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58
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## character(0)
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59
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60
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# show that all common tiles between CGIAR and jup.v4.1 have the same file
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61
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# size
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common <- merge(cgiar, jup.v4.1, by="tile")
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63
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identical(common$size.x, common$size.y)
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64
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## [1] TRUE
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65
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66
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# but note that three files in jup.v4.1 have different (newer, as it
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67
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# turns out) timestamps
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68
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identical(common$date.x, common$date.y)
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69
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## [1] FALSE
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common$tile[common$date.x!=common$date.y]
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## "srtm_19_06.zip" "srtm_21_14.zip" "srtm_42_14.zip"
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72
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