Package 'geoprofiler'

Draw a profile line or a point to retrieve coordinates

Description

Opens a plot window showing the the map with the data, where the user can click profile coordinates.

Usage

get_coordinates(x, n = 1, type = "o", col = "#B63679FF", ...)

draw_profile(x, n = 10, ...)

Arguments

x	sf object
n	the maximum number of points to locate. Valid values start at 1.
type	One of "n", "p", "l" or "o". If "p" or "o" the points are plotted; if "l" or "o" they are joined by lines.
col	color of line or point
...	additional graphics parameters used if type != "n" for plotting the locations.

Value

sf object of the profile.

---

Extract End Points of a Line

Description

Extract End Points of a Line

Usage

line_ends(x)

Arguments

x	sf line object

Value

sf point object

Examples

p1 <- data.frame(lon = -90.8, lat = 48.6) |>
  sf::st_as_sf(coords = c("lon", "lat"), crs = "WGS84")
profile_points(p1,
  profile.azimuth = 135, profile.length = 10000,
  crs = sf::st_crs("EPSG:26915")
) |>
  profile_line() |>
  line_ends()

---

Example sf data set

Description

example dataset

Usage

data('locations_example')

Format

An object of class sf

Examples

data("locations_example")
head(locations_example)

---

Distance Between Points

Description

This uses the haversine formula (by default) to calculate the great-circle distance between two points, i.e., the shortest distance over the earth's surface.

Usage

point_distance(a, b, ...)

Arguments

a	lon, lat coordinate of point 1
b	lon, lat coordinate of point 2
...	parameters passed to tectonicr::dist_greatcircle()

Value

units object giving the distance

Examples

berlin <- c(13.4, 52.517) # lon, lat
tokyo <- c(139.767, 35.7) # lon, lat
point_distance(berlin, tokyo)

---

Azimuth Between Profile Points

Description

Azimuth Between Profile Points

Usage

profile_azimuth(x)

Arguments

x	sf point object. First point marks the start point.

Details

If only two points are given, the azimuth is calculated using triangulation from the tectonicr package. If more than two points are given, the azimuth is calculated using linear interpolation in the coordinate reference frame given by profile.

Value

Azimuth as units object

See Also

profile_length()

Examples

p1 <- data.frame(lon = -90.8, lat = 48.6) |>
  sf::st_as_sf(coords = c("lon", "lat"), crs = "WGS84")

profile_points(p1,
  profile.azimuth = 135, profile.length = 10000,
  crs = sf::st_crs("EPSG:26915")
) |>
  profile_azimuth()

---

Profile Coordinates

Description

Project points on a cross section given by a starting point and the direction

Usage

profile_coords(x, profile, azimuth = NULL, drop.units = TRUE)

Arguments

x	'sf' object
profile	'sf' object of the profile or the profile's starting point.
azimuth	numeric. Direction (in degrees) emanating from starting point. Is ignored when profile contains two points or is a LINESTRING.
drop.units	logical. Whether the return should show the units or not.

Value

tibble where X is the distance along the profile line. Y is the distance across the profile line. (units of X and Y depend on coordinate reference system).

Author(s)

Tobias Stephan

Examples

data(locations_example)
p1 <- data.frame(lon = -90.8, lat = 48.6) |>
  sf::st_as_sf(coords = c("lon", "lat"), crs = "WGS84")
profile_crds <- profile_coords(locations_example, profile = p1, azimuth = 135)
head(profile_crds)

# Plot the transformed coordinates
plot(profile_crds)

---

Length of Profile

Description

Length of Profile

Usage

profile_length(x, ...)

Arguments

x	sf line object
...	(optional) passed on to s2::s2_distance()

Value

units object when coordinate system is set.

See Also

profile_azimuth()

Examples

p1 <- data.frame(lon = -90.8, lat = 48.6) |>
  sf::st_as_sf(coords = c("lon", "lat"), crs = "WGS84")
profile_points(p1,
  profile.azimuth = 135, profile.length = 10000,
  crs = sf::st_crs("EPSG:26915")
) |>
  profile_line() |>
  profile_length()

---

Combine Points to a Line

Description

Combine Points to a Line

Usage

profile_line(x)

Arguments

x	sf point object

Value

sf line object

See Also

profile_points()

Examples

p1 <- data.frame(lon = -90.8, lat = 48.6) |>
  sf::st_as_sf(coords = c("lon", "lat"), crs = "WGS84")
profile_points(p1,
  profile.azimuth = 135, profile.length = 10000,
  crs = sf::st_crs("EPSG:26915")
) |>
  profile_line()

---

Profile End Point

Description

Create a end point along a profile line starting at a point with a defined direction and length.

Usage

profile_points(
  start,
  profile.azimuth,
  profile.length,
  crs = st_crs(start),
  return.sf = TRUE
)

Arguments

start	sf point object.
profile.azimuth	numeric or units object. Direction of profile in degrees if numeric.
profile.length	numeric or units object.
crs	Coordinate reference system. Should be parsed by sf::st_crs().
return.sf	logical. Should the profile points be returned as a sf object (TRUE, the default) object or as a data.frame.

Value

class depends on return.sf.

Note

Use metric values (meters, kilometers, etc) in case of a projected coordinate reference frame, and degree when geographical coordinate reference frame.

Examples

p1 <- data.frame(lon = -90.8, lat = 48.6) |>
  sf::st_as_sf(coords = c("lon", "lat"), crs = "WGS84")
profile_points(p1,
  profile.azimuth = 135, profile.length = units::set_units(10, "km"),
  crs = sf::st_crs("EPSG:26915")
)

---

Example raster data set

Description

example dataset

Usage

data('raster_example')

Format

An object of class matrix

Examples

data("raster_example")
head(raster_example)

---

Swath Elevation Profile Statistics

Description

Calculate swath-profile values perpendicular to a straight baseline. The distance between samples and the number of samples can be specified, see arguments k and dist. Values of the swath-profile are extracted from a given raster file, see argument raster. CRS of raster and points have to be the same.

Usage

swath_profile(
  profile,
  raster,
  k = 1,
  dist,
  crs = terra::crs(raster),
  method = c("bilinear", "simple")
)

Arguments

profile	either a sf object or a matrix(ncol=2, nrow=2) with x and y coordinates of beginning and end point of the baseline; each point in one row column 1 x coordinates (or longitudes) column 2 y coordinates (latitudes)
raster	Raster file ("SpatRaster" object as loaded by terra::rast())
k	integer. number of lines on each side of the baseline
dist	numeric. distance between lines. Unit depends on reference system specified by crs (see note).
crs	character. coordinate reference system. Both the raster and the profile are transformed into this CRS. Uses the CRS of raster by default.
method	character. method for extraction of raw data, see terra::extract(): default value: "bilinear"

Details

The final width of the swath is: $2k \times \text{dist}$.

Value

list.

swath

matrix. Statistics of the raster measured along the lines

data

list of numeric vector containing the data extracted from the raster along each line

lines

swath lines as "sf" objects

Note

The unit of dist depends on the coordinate reference system specified in crs (which uses the coordinate system of raster by default). This means, a geographic coordinates system (e.g. WGS84) assumes units in degrees, while a projected coordinate system (e.g. UTM) assumes meters.

Source

The algorithm is a modified version of "swathR" by Vincent Haburaj (https://github.com/jjvhab/swathR).

See Also

swath_stats()

Examples

# Create a random raster
r <- terra::rast(ncol = 10, nrow = 10, xmin = -150, xmax = -80, ymin = 20, ymax = 60, crs = "WGS84")
terra::values(r) <- runif(terra::ncell(r))

# Create a random profile
profile <- data.frame(lon = c(-140, -90), lat = c(55, 25)) |>
  sf::st_as_sf(coords = c("lon", "lat"), crs = "WGS84")
swath_profile(profile, r, k = 2, dist = 1)

---

Summary Statistics on Swath Elevation Profile

Description

Statistics of the elevation data across a swath profile.

Usage

swath_stats(x, profile.length = 1)

Arguments

x	list. The return object of swath_profile()
profile.length	numeric or units object. If NULL the fractional distance is returned, i.e. 0 at start and 1 at the end of the profile.

Value

data.frame

See Also

swath_profile()

Examples

# Create a random raster
r <- terra::rast(ncol = 10, nrow = 10, xmin = -150, xmax = -80, ymin = 20, ymax = 60)
terra::values(r) <- runif(terra::ncell(r))

# Create a random profile
profile <- data.frame(lon = c(-140, -90), lat = c(55, 25)) |>
  sf::st_as_sf(coords = c("lon", "lat"), crs = "WGS84")
swath <- swath_profile(profile, r, k = 5, dist = 10)

swath_stats(swath, profile.length = profile_length(profile_line(profile)))

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