Difference between revisions of "Digital terrain analysis with RHydro"

Latest revision as of 09:12, 28 August 2009

The digital terrain analysis tools are now merged with the topmodel package. A revised guide can be found at R wiki

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-This is an example using the DEM supplied with the package. Load the package and the DEM (we also need the package topmodel for the make.classes() function):
+The digital terrain analysis tools are now merged with the topmodel package. A revised guide can be found at [http://wiki.r-project.org/rwiki/doku.php?id=guides:tutorials:hydrological_data_analysis:dta|the R wiki]
-  library(topmodel)
-  library(RHydro)
-  data(huagrahuma.dem)
-Fill depression and look at the difference between the original and filled map:
-  dem.filled <- sinkfind(huagrahuma.dem, cellsize=25, degree=0.1)
-  library(lattice)
-  levelplot(dem.filled)
-  difference <- dem.filled - huagrahuma.dem
-  max(difference)
-  min(difference)
-  levelplot(difference)
-Topographic index calculation:
-  topidx <- atb(dem.filled, cellsize=25)
-  class(topidx)
-  str(topidx)
-  levelplot(topidx$atb)
-  levelplot(topidx$area)
-If you want, you can compare with the analysis on the non-filled DEM that contains obvious artefacts
-  old <- atb(huagrahuma.dem, cellsize=25)
-  levelplot(old$area)
-  levelplot(topidx$area - old$area)
-Have a look at the potential outlet:
-  outlet(topidx$area,c(28,8),2)
-We know from manual catchment delineation (on a topographic map) that the area of the catchment is around 2.4 km2, so the following cells are likely to contain the outlet: c(28,8); c(29,8); c(29,9). Just try them out with the subcatch() function and take the one you like.
-  catchment <- subcatch(dem.filled, c(29,8))
-  image(catchment)
-  catchment[catchment == 0] <- NA
-  flowlength <- flowlength(dem.filled, c(29,8))
-Headwater cells are identified on the basis of a topographic index
-or an accumulation area threshold. This is an “intuitive” choice:
-  rivers <- river(dem.filled,topidx$atb,topidx$area,cellsize=25,thatb=12.35,tharea=10000)
-  image(rivers)
-Play around with the values of thatb and tharea and look at the impact…
-Mask the rivers and topographic index maps outside the catchment:
-  rivers <- rivers * catchment
-  topidxmap <- topidx$atb * catchment
-And make topographic index classes which can be used with topmodel.
-  classes <- make.classes(topidxmap,16)
-  plot(classes)
-The object ''classes'' can be used as input for [[topmodel]]

Difference between revisions of "Digital terrain analysis with RHydro"

Latest revision as of 09:12, 28 August 2009

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