Trajectory level plots in
This function plots back trajectories on a
leaflet map. This function
requires that data are imported using the
trajLevelMap( data, longitude = "lon", latitude = "lat", pollutant, control = "default", smooth = FALSE, statistic = "frequency", percentile = 90, lon.inc = 1, lat.inc = 1, min.bin = 1, .combine = NA, sigma = 1.5, cols = "default", alpha = 0.5, tile.border = NA, provider = "OpenStreetMap" )
Data frame, the result of importing a trajectory file using
- latitude, longitude
The decimal latitude/longitude.
Pollutant to be plotted. By default the trajectory height is used.
Used for splitting the trajectories into different groups which can be selected between using a "layer control" menu. Passed to
Should the trajectory surface be smoothed? Defaults to
FALSE. Note that, when
smooth = TRUE, no popup information will be available.
Statistic to use for
trajLevel(). By default, the function will plot the trajectory frequencies (
statistic = "frequency"). As an alternative way of viewing trajectory frequencies, the argument
method = "hexbin"can be used. In this case hexagonal binning of the trajectory points (i.e., a point every three hours along each back trajectory). The plot then shows the trajectory frequencies uses hexagonal binning.
There are also various ways of plotting concentrations.
It is possible to set
statistic = "difference". In this case trajectories where the associated concentration is greater than
percentileare compared with the the full set of trajectories to understand the differences in frequencies of the origin of air masses. The comparison is made by comparing the percentage change in gridded frequencies. For example, such a plot could show that the top 10\ tend to originate from air-mass origins to the east.
statistic = "pscf"then a Potential Source Contribution Function map is produced. This statistic method interacts with
statistic = "cwt"then concentration weighted trajectories are plotted.
statistic = "sqtba"then Simplified Quantitative Transport Bias Analysis is undertaken. This statistic method interacts with
The percentile concentration of
pollutantagainst which the all trajectories are compared.
- lon.inc, lat.inc
The longitude and latitude intervals to be used for binning data.
The minimum number of unique points in a grid cell. Counts below
min.binare set as missing.
When statistic is "SQTBA" it is possible to combine lots of receptor locations to derive a single map.
.combineidentifies the column that differentiates different sites (commonly a column named
"site"). Note that individual site maps are normalised first by dividing by their mean value.
For the SQTBA approach
sigmadetermines the amount of back trajectory spread based on the Gaussian plume equation. Values in the literature suggest 5.4 km after one hour. However, testing suggests lower values reveal source regions more effectively while not introducing too much noise.
Colours to be used for plotting. Options include "default", "increment", "heat", "turbo" and
RColorBrewercolours — see the
openair::openColours()function for more details. For user defined the user can supply a list of colour names recognised by R (type
grDevices::colours()to see the full list). An example would be
cols = c("yellow", "green", "blue").
Opacity of the tiles. Must be between
Colour to use for the border of binned tiles. Defaults to
NA, which draws no border.
The base map to be used. See http://leaflet-extras.github.io/leaflet-providers/preview/ for a list of all base maps that can be used.