5/6/2023 0 Comments D.legend grass gis![]() Shallow Water Flow Discharge \((m^3/s)\) with Landcover from NDVI ![]() R.shade shade=relief color=discharge_with_ndvi output=shaded_discharge_with_ndvi brighten=40ĭ.legend raster=discharge_with_ndvi at=60,95,2,3.5 font=Lato-Regular fontsize=14 R.sim.water elevation=elevation dx=dx dy=dy rain_value=50 man=roughness nwalkers=10000 depth=depth_with_ndvi discharge=discharge_with_ndvi R.recode input=ndvi output=roughness rules=roughness.txt With the following values or paste these values To recode class values to Manning’s n valuesĮither create a rules file called roughness.txt To compute NDVI with the red and near infrared channels Normalized Difference Vegetation Index (NDVI)ĭerive roughness from NDVI to simulate shallow overland water flow. Shallow Water Flow with Vegetation Indices Shallow Water Flow Discharge \((m^3/s)\) with Landcover Shallow Water Flow Depth \((m)\) with Landcover R.shade shade=relief color=depth_with_landcover output=shaded_depth_with_landcover brighten=40ĭ.legend raster=depth_with_landcover at=60,95,2,3.5 font=Lato-Regular fontsize=14 R.sim.water elevation=elevation dx=dx dy=dy rain_value=50 man=mannings nwalkers=10000 depth=depth_with_landcover discharge=discharge_with_landcover R.slope.aspect elevation=elevation dx=dx dy=dy R.recode input=classification output=mannings rules=mannings.txt I.maxlik group=imagery_2018 subgroup=imagery_2018 signaturefile=signature output=classification I.cluster group=imagery_2018 subgroup=imagery_2018 signaturefile=signature classes=3 To recode class values to Manning’s n values. ![]() See the appendix at the end of this tutorialįor a list of suggested Manning’s n values. Grass should have a Manning’s n value of 0.368, Recode the resulting map of landcover classesĪs Manning’s roughness coefficients using To classify spectral reflectance based on spectral signatures. ![]() With to calculate spectral signatures for 3 landcover classes To create a new subgroup also named imagery_2018 To add all the channels for the 2018 orthophotograph Interface, name the new imagery group imagery_2018, With red, green, blue, and near infrared channels Landcover can be derived from orthophotography Under the add map elements dropdown menu in the graphical user interface. In the command console or using the add raster legend button To drape the shaded relief map over the skyview factor. Will combine direct and diffuse illumination to better visualize relief. Then drape the relief map over the smoothed digital elevation modelĪlternatively try visualizing relief using diffuse illuminationįrom the skyview factor - the proportion of the sky visibleĪ composite of the shaded relief and skyview factor The light source can be set using the altitude and azimuth settings. Visualize the relief of the terrain using direct illumination with Optionally make the moving window circular with flag -c. Smooth the digital elevation model using the module Has substantial noise that would impact hydrological simulations. Then set a mask to the vector map shoreline with the module Using the various zoom options dropdown orĪnd set the boundaries for the region. Zoom in on the landforms in the southwest of the island.Įither set the computation region from the display Select nyspf_governors_island as your location,Īnd create a new mapset called hydrology. Set the GRASS GIS database directory to grassdata directory, This tutorial uses the Governor’s Island Dataset for GRASS GIS.ĭownload, extract, and move this geospatial dataset Learn more about hydrology in GRASS on theįor hydrological modeling and analysis including: This tutorial introduces hydrological modeling Shallow Water Flow with Vegetation Indices.
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