shadow (version 0.7.1)

surfaceGrid: Create grid of 3D points covering the 'facades' and 'roofs' of obstacles

Description

The function creates a grid of 3D points covering the given obstacles at specified resolution. Such a grid can later on be used to quantify the shaded / non-shaded proportion of the obstacles surface area.

Usage

surfaceGrid(obstacles, obstacles_height_field, res, offset = 0.01)

Arguments

obstacles

A SpatialPolygonsDataFrame object specifying the obstacles outline

obstacles_height_field

Name of attribute in obstacles with extrusion height for each feature

res

Required grid resolution, in CRS units

offset

Offset between grid points and facade (horizontal distance) or between grid points and roof (vertical distance).

Value

A 3D SpatialPointsDataFrame layer, including all attributes of the original obstacles each surface point corresponds to, followed by six new attributes:

• obs_id Unique consecutive ID for each feature in obstacles

• type Either "facade" or "roof"

• seg_id Unique consecutive ID for each facade segment (only for 'facade' points)

• xy_id Unique consecutive ID for each ground location (only for 'facade' points)

• facade_az The azimuth of the corresponding facade, in decimal degrees (only for 'facade' points)

See Also

Function plotGrid to visualize grid.

Examples

# NOT RUN {
grid = surfaceGrid(
  obstacles = build,
  obstacles_height_field = "BLDG_HT",
  res = 2
)
plot(grid)
plot(grid, pch = 1, lwd = 0.1, col = "black", add = TRUE)

# When 'res/2' is larger then height, facade will be left unsampled
build_small = build
build_small$BLDG_HT = 1
grid = surfaceGrid(
  obstacles = build_small,
  obstacles_height_field = "BLDG_HT",
  res = 2
)
plot(grid)
plot(grid, pch = 1, lwd = 0.1, col = "black", add = TRUE)
table(grid$type)

grid = surfaceGrid(
  obstacles = build_small,
  obstacles_height_field = "BLDG_HT",
  res = 2.00001  # res/2 > h
)
plot(grid)
plot(grid, pch = 1, lwd = 0.1, col = "black", add = TRUE)
table(grid$type)

# When input already contains 'obs_id', 'type', 'seg_id', 'xy_id', 'facade_az' or 'ZZZ'
build2 = build
build2$ZZZ = 1
grid = surfaceGrid(
  obstacles = build2,
  obstacles_height_field = "BLDG_HT",
  res = 2
)

# }