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# R code to plot latitudinal profiles of mean elevation, along with both
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# RMSE and correlation coefficients comparing fused layers with both the
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# raw ASTER and with the Canada DEM
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#
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# Jim Regetz
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# NCEAS
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# Created on 08-Jun-2011
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library(raster)
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datadir <- "/home/regetz/media/temp/terrain/dem"
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# load elevation rasters
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d.aster <- raster(file.path(datadir, "aster_300straddle.tif"))
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d.srtm <- raster(file.path(datadir, "srtm_150below.tif"))
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d.uncor <- raster(file.path(datadir, "fused_300straddle.tif"))
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d.eramp <- raster(file.path(datadir, "fused_300straddle_rampexp.tif"))
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d.bg <- raster(file.path(datadir, "fused_300straddle_blendgau.tif"))
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d.can <- raster(file.path(datadir, "cdem_300straddle.tif"))
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# extract raster latitudes for later
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lats300 <- yFromRow(d.aster, 1:nrow(d.aster))
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lats150 <- yFromRow(d.srtm, 1:nrow(d.srtm))
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# initialize output pdf device driver
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pdf("elevation-assessment.pdf", height=8, width=11.5)
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#
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# plot latitudinal profiles of mean elevation
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#
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par(mfrow=c(2,2), omi=c(1,1,1,1))
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ylim <- c(550, 575)
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plot(lats300, rowMeans(as.matrix(d.uncor), na.rm=TRUE), type="l",
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xlab="Latitude", ylab="Mean elevation", ylim=ylim)
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text(min(lats300), min(ylim)+0.5, pos=4, font=3, labels="uncorrected")
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abline(v=60, col="red", lty=2)
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mtext(expression(paste("Latitudinal profiles of mean elevation (",
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136*degree, "W to ", 96*degree, "W)")), adj=0, line=2, font=2)
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plot(lats300, rowMeans(as.matrix(d.can), na.rm=TRUE), type="l",
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xlab="Latitude", ylab="Mean elevation", ylim=ylim)
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text(min(lats300), min(ylim)+0.5, pos=4, font=3, labels="Canada DEM")
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abline(v=60, col="red", lty=2)
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plot(lats300, rowMeans(as.matrix(d.eramp), na.rm=TRUE), type="l",
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xlab="Latitude", ylab="Mean elevation", ylim=ylim)
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text(min(lats300), min(ylim)+0.5, pos=4, font=3, labels="exponential ramp")
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abline(v=60, col="red", lty=2)
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plot(lats300, rowMeans(as.matrix(d.bg), na.rm=TRUE), type="l",
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xlab="Latitude", ylab="Mean elevation", ylim=ylim)
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text(min(lats300), min(ylim)+0.5, pos=4, font=3, labels="gaussian blend")
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abline(v=60, col="red", lty=2)
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#
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# plot latitudinal profiles of RMSE
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#
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# simple helper function to calculate row-wise RMSEs
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rmse <- function(r1, r2, na.rm=TRUE, use) {
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diffs <- abs(as.matrix(r1) - as.matrix(r2))
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if (!missing(use)) diffs[!use] <- NA
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sqrt(rowMeans(diffs^2, na.rm=na.rm))
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}
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par(mfrow=c(2,3), omi=c(1,1,1,1))
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ylim <- c(0, 35)
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# ...with respect to ASTER
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plot(lats300, rmse(d.uncor, d.aster), type="l", xlab="Latitude",
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ylab="RMSE", ylim=ylim)
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lines(lats150, rmse(crop(d.uncor, extent(d.srtm)), d.srtm), col="blue")
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legend("topright", legend=c("ASTER", "SRTM"), col=c("black", "blue"),
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lty=c(1, 1), bty="n")
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text(min(lats300), max(ylim)-1, pos=4, font=3, labels="uncorrected")
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abline(v=60, col="red", lty=2)
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mtext(expression(paste(
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"Elevation discrepancies with respect to separate ASTER/SRTM components (",
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136*degree, "W to ", 96*degree, "W)")), adj=0, line=2, font=2)
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plot(lats300, rmse(d.eramp, d.aster), type="l", xlab="Latitude",
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ylab="RMSE", ylim=ylim)
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lines(lats150, rmse(crop(d.eramp, extent(d.srtm)), d.srtm), col="blue")
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legend("topright", legend=c("ASTER", "SRTM"), col=c("black", "blue"),
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lty=c(1, 1), bty="n")
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text(min(lats300), max(ylim)-1, pos=4, font=3, labels="exponential ramp")
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abline(v=60, col="red", lty=2)
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plot(lats300, rmse(d.bg, d.aster), type="l", xlab="Latitude",
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ylab="RMSE", ylim=ylim)
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lines(lats150, rmse(crop(d.bg, extent(d.srtm)), d.srtm), col="blue")
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legend("topright", legend=c("ASTER", "SRTM"), col=c("black", "blue"),
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lty=c(1, 1), bty="n")
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text(min(lats300), max(ylim)-1, pos=4, font=3, labels="gaussian blend")
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abline(v=60, col="red", lty=2)
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# ...with respect to CDEM
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plot(lats300, rmse(d.uncor, d.can), type="l", xlab="Latitude",
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ylab="RMSE", ylim=ylim)
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text(min(lats300), max(ylim)-1, pos=4, font=3, labels="uncorrected")
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abline(v=60, col="red", lty=2)
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mtext(expression(paste(
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"Elevation discrepancies with respect to Canada DEM (",
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136*degree, "W to ", 96*degree, "W)")), adj=0, line=2, font=2)
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plot(lats300, rmse(d.eramp, d.can), type="l", xlab="Latitude",
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ylab="RMSE", ylim=ylim)
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text(min(lats300), max(ylim)-1, pos=4, font=3, labels="exponential ramp")
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abline(v=60, col="red", lty=2)
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plot(lats300, rmse(d.bg, d.can), type="l", xlab="Latitude",
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ylab="RMSE", ylim=ylim)
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text(min(lats300), max(ylim)-1, pos=4, font=3, labels="gaussian blend")
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abline(v=60, col="red", lty=2)
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#
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# plot latitudinal profiles of correlation coefficients
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#
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# simple helper function to calculate row-wise correlation coefficients
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corByLat <- function(r1, r2, rows) {
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if (missing(rows)) {
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rows <- 1:nrow(r1)
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}
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m1 <- as.matrix(r1)
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m2 <- as.matrix(r2)
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sapply(rows, function(row) cor(m1[row,], m2[row,],
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use="pairwise.complete.obs"))
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}
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par(mfrow=c(2,3), omi=c(1,1,1,1))
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ylim <- c(0.99, 1)
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# ...with respect to ASTER
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plot(lats300, corByLat(d.uncor, d.aster), type="l", xlab="Latitude",
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ylab="Correlation", ylim=ylim)
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lines(lats150, corByLat(crop(d.uncor, extent(d.srtm)), d.srtm), col="blue")
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legend("bottomright", legend=c("ASTER", "SRTM"), col=c("black", "blue"),
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lty=c(1, 1), bty="n")
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text(min(lats300), min(ylim), pos=4, font=3, labels="uncorrected")
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abline(v=60, col="red", lty=2)
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mtext(expression(paste(
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"Elevation correlations with respect to separate ASTER/SRTM components (",
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136*degree, "W to ", 96*degree, "W)")), adj=0, line=2, font=2)
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plot(lats300, corByLat(d.eramp, d.aster), type="l", xlab="Latitude",
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ylab="Correlation", ylim=ylim)
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lines(lats150, corByLat(crop(d.eramp, extent(d.srtm)), d.srtm), col="blue")
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legend("bottomright", legend=c("ASTER", "SRTM"), col=c("black", "blue"),
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lty=c(1, 1), bty="n")
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text(min(lats300), min(ylim), pos=4, font=3, labels="exponential ramp")
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abline(v=60, col="red", lty=2)
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plot(lats300, corByLat(d.bg, d.aster), type="l", xlab="Latitude",
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ylab="Correlation", ylim=ylim)
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lines(lats150, corByLat(crop(d.bg, extent(d.srtm)), d.srtm), col="blue")
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legend("bottomright", legend=c("ASTER", "SRTM"), col=c("black", "blue"),
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lty=c(1, 1), bty="n")
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text(min(lats300), min(ylim), pos=4, font=3, labels="gaussian blend")
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abline(v=60, col="red", lty=2)
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# ...with respect to CDEM
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plot(lats300, corByLat(d.uncor, d.can), type="l", xlab="Latitude",
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ylab="Correlation", ylim=ylim)
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text(min(lats300), min(ylim), pos=4, font=3, labels="uncorrected")
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abline(v=60, col="red", lty=2)
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mtext(expression(paste(
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"Elevation correlations with respect to Canada DEM (",
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136*degree, "W to ", 96*degree, "W)")), adj=0, line=2, font=2)
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plot(lats300, corByLat(d.eramp, d.can), type="l", xlab="Latitude",
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ylab="Correlation", ylim=ylim)
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text(min(lats300), min(ylim), pos=4, font=3, labels="exponential ramp")
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abline(v=60, col="red", lty=2)
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plot(lats300, corByLat(d.bg, d.can), type="l", xlab="Latitude",
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ylab="Correlation", ylim=ylim)
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text(min(lats300), min(ylim), pos=4, font=3, labels="gaussian blend")
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abline(v=60, col="red", lty=2)
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# close pdf device driver
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dev.off()
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