Skip to content

Latest commit

 

History

History
142 lines (109 loc) · 5.83 KB

viewscape.md

File metadata and controls

142 lines (109 loc) · 5.83 KB

Viewscape

This vignette provides a basic overview of the functions in R package viewscape.

The basic viewshed analysis can be accessed through calling the compute_viewshed. The two needed objects to compute the viewshed are a digital surface model (DSM) and a viewpoint.

1. Compute viewshed

library(viewscape)

1.1 Compute single viewshed

#Load in DSM
test_dsm <- terra::rast(system.file("test_dsm.tif", 
                        package ="viewscape"))

#Load in the viewpoint
test_viewpoint <- sf::read_sf(system.file("test_viewpoint.shp", 
                                          package = "viewscape"))

#Compute viewshed
output <- viewscape::compute_viewshed(dsm = test_dsm, 
                                      viewpoints = test_viewpoint, 
                                      offset_viewpoint = 6, 
                                      r = 1600,
                                      method = 'plane')

# overlap viewshed on DSM
output_r <- viewscape::visualize_viewshed(output, outputtype = 'raster')
terra::plot(test_dsm, axes=FALSE, box=FALSE, legend = FALSE)
terra::plot(output_r, add=TRUE, col = "red", axes=FALSE, box=FALSE, legend = FALSE)
terra::plot(test_viewpoint, add = TRUE, col = "blue", axes=FALSE, box=FALSE, legend = FALSE)

1.2 Subset viewshed using by specifying the field of view

sector <- viewscape::fov_mask(output, c(40,160))
terra::plot(test_dsm, axes=FALSE, box=FALSE, legend = FALSE)
terra::plot(viewscape::visualize_viewshed(sector, outputtype = 'raster'),
        axes=FALSE, box=FALSE, legend = FALSE, add = TRUE, col = "red")
terra::plot(test_viewpoint, add = TRUE, col = "blue", axes=FALSE, box=FALSE, legend = FALSE)

1.3 Compute the viewshed for multiple viewpoints

#Load in DSM
test_dsm <- terra::rast(system.file("test_dsm.tif", 
                        package ="viewscape"))

# Load points (.shp file)
test_viewpoints <- sf::read_sf(system.file("test_viewpoints.shp", 
                                           package = "viewscape"))

# Compute viewsheds
output <- viewscape::compute_viewshed(dsm = test_dsm, 
                                      viewpoints = test_viewpoints, 
                                      offset_viewpoint = 6, 
                                      parallel = TRUE, 
                                      workers = 8)

# plot all viewsheds on DSM
par(mfrow=c(3,3))
for(i in 1:length(output)) {
  each <- output[[i]]
  raster_data <- viewscape::visualize_viewshed(each, outputtype="raster")
  raster::plot(test_dsm, axes=FALSE, box=FALSE, legend = FALSE)
  raster::plot(raster_data, add=TRUE, col = "red", axes=FALSE, box=FALSE, legend = FALSE)
}

2. Calculate viewscape metrics

2.1 Calculate the metrics of viewshed

The calculate_viewmetrics function is designed to compute a set of configuration metrics based on a given viewshed object and optionally, digital surface models (DSM) and digital terrain models (DTM) for terrain analysis. The function calculates various metrics that describe the visibility characteristics of a landscape from a specific viewpoint.

# Load DTM
test_dtm <- terra::rast(system.file("test_dtm.tif", 
                                    package ="viewscape"))

# Load canopy raster
test_canopy <- terra::rast(system.file("test_canopy.tif", 
                                       package ="viewscape"))

# Load building footprints raster
test_building <- terra::rast(system.file("test_building.tif", 
                                         package ="viewscape"))

# calculate metrics given the viewshed
test_metrics <- viewscape::calculate_viewmetrics(output[[1]], 
                                                 test_dsm, 
                                                 test_dtm, 
                                                 list(test_canopy, test_building))
test_metrics

2.2 Calculate land use/cover diversity

calculate_diversity calculates the proportion of each type of land use/ cover within a viewshed to get the Shannon Diversity Index.

# load landuse raster
test_landuse <- terra::rast(system.file("test_landuse.tif",
                                        package ="viewscape"))


i# the Shannon Diversity Index (SDI)

## [1] 8

test_diversity <- viewscape::calculate_diversity(output[[1]],
                                                 test_landuse, 
                                                 proportion = TRUE)
# SDI and The proportion of each type of land use
test_diversity

## $SDI
## [1] 0.636
## 
## $Proportion
##                    1          2           3          4          5            6
## type       0.0000000 3.00000000 4.000000000 5.00000000 7.00000000 8.0000000000
## proportion 0.8315693 0.04011499 0.001502679 0.03913498 0.08715536 0.0005226708

2.3 calculate a single feature

calculate_feature is to calculate the proportion of a feature (including trees, buildings, parking, and roads) within the viewshed. This function can be applied to

# load landuse raster
test_canopy <- terra::rast(system.file("test_canopy.tif",
                                       package ="viewscape"))
# calculate the percentage of each type of land use  
test_canopy_proportion <- viewscape::calculate_feature(viewshed = output[[1]], 
                                                       feature = test_canopy,
                                                       type = 2,
                                                       exclude_value=0)
test_canopy_proportion