General
Data can be imported with already in R implemented functions such as
read.table(), read.csv() or from other
packages functions (e.g. {readr} and {data.table}).
Just make sure that the import produces a matrix or data.frame like
object with each measurement stored in a row, and columns representing
dip directions, dip angles, plunge, etc.
For example your .txt file is tab-separated and may look
like this:
| Dip direction | Dip | |
|---|---|---|
| 1 | 120 | 50 |
| 2 | 60 | 12 |
| 3 | 287 | 82 |
you could import the file like
imported_data <- read.table(
"path/to/my/file.xt",
header = TRUE,
sep = "",
row.names = 1
)You can also use
file.choose()to open the explorer window and navigate to your file.
This imports the tab-separated file as an "data.frame"
object with the first column representing the row names, and the two
other columns the headers of the table. Say these measurements represent
plane measurements (e.g. bedding or fault plane orientation), we just
need to coerce that data.frame into a "Plane" object:
my_planes <- as.Plane(imported_data)If you want a "Line" object, coerce the data.frame using
as.Line(). For "Pair" (line-on-plane) and
"Fault" (line-on-plane with sense of motion) objects,
you’ll need a four and five-column table, respectively, representing dip
directions, dip angle, trend, and plunge and sense measurements. Then
use as.Pair() or as.Fault() to parse the
object into {structr}.
Note that the dip direction is the preferred notation for plane measurements in {structr} as it undoubtly indicates the orientation by using only 2 parameters.
Some helpers
There are several other conventions for the notation of plane and line orientations from compass measurements. Here are some functions for you to correctly convert your measurements into the notation required for the use in {structr}.
Right-hand rule
To converts strike measurements into dip directions using right-hand rule:
strike_measurements <- c(270, 315, 0, 45, 90, 135, 180, 225, 270)
rhr2dd(strike_measurements)
#> [1] 0 45 90 135 180 225 270 315 0
# or from dip direction to strike (using right-hand rule):
dip_directions <- c(0, 45, 90, 135, 180, 225, 270, 315, 360)
dd2rhr(dip_directions)
#> [1] 270 315 0 45 90 135 180 225 270Quadrant notation
Sometimes, strike notation doesn’t follow the right hand rule.
Instead the quadrant of the dip direction is indicated by a Cardinal
letter, i.e. “N”, “E”, “S”, and “W”. In that case you can use the
function quadrant2dd()
strike_direction <- c(270, 315, 0, 45, 90, 135, 180, 225, 270) # strike in left-hand-rule
dip_quadrtant <- c("N", "E", "E", "S", "S", "W", "W", "N", "N") # dip quadrant
quadrant2dd(strike_direction, dip_quadrtant)
#> [1] 0 45 90 135 180 225 270 315 0If your table contains the strike and dip-quadrant measurement in a
single column, e.g. “270N”, you can conveniently split the column into
two by using split_strike()
split_strike("270N")
#> $measurement
#> 270N
#> 270
#>
#> $direction
#> 270N
#> "N"Fault notation
Fault (and Pair) measurements are usually a combination of Plane and
Ray or Line measurements. Then they can be defined using the
Fault() and Pair() functions. However,
sometimes the Line or Ray component is given by the rake angle, which is
the angle between the fault strike and the lineation. Unfortunately,
there are several different ways how to indicate the proper orientation
of the lineation.
Fault plane and rake (or pitch)
This is the standard notation. Here, the rake is the angle between lineation and the right-handrule strike of the fault plane. The angle is measured on the fault plane, clockwise from the strike, where down-plunging is positive. Rake values range between 0 and 360° (or −180° and 180°).
If your datra follows this convention, use the function
Fault_from_rake()
fault_plane <- Plane(c(120, 120, 100, 0), c(60, 60, 50, 40))
fault_pitch <- c(84.7202, -10, 30, 180)
Fault_from_rake(fault_plane, rake = fault_pitch)
#> Fault object (n = 4):
#> dip_direction dip azimuth plunge sense
#> [1,] 120 60 109.52858 5.958159e+01 1
#> [2,] 120 60 204.96163 8.649165e+00 -1
#> [3,] 100 50 30.36057 2.252101e+01 1
#> [4,] 0 40 90.00000 1.487542e-14 1Fault plane, rake angle and plunge quadrant
Here, the rake angle is measured in the fault plane between the strike given by either right or left-hand rule and the lineation. The angle is recorded in a clockwise sense (looking down upon the fault plane) and has a range from 0 to 180%deg;. The quadrant of plunge indicates the direction of the strike from which the rake angle is measured.
If this is the notation used, call the function
Fault_from_rake_quadrant() and set
type="plunge"
dip <- c(5, 10, 15, 30, 40, 55, 65, 75, 90)
dip_dir <- c(180, 225, 270, 315, 360, 0, 45, 90, 135)
rake1 <- c(0, 45, 90, 135, 180, 45, 90, 135, 180)
plunge_quadrant <- c("E", "S", "W", "N", "E", "W", "E", "S", "W")
Fault_from_rake_quadrant(Plane(dip_dir, dip), rake1, plunge_quadrant, type = "plunge")
#> Fault object (n = 9):
#> dip_direction dip azimuth plunge sense
#> [1,] 180 5 90.000000 0.000000e+00 1
#> [2,] 225 10 179.561451 7.053022e+00 1
#> [3,] 270 15 270.000000 1.500000e+01 1
#> [4,] 315 30 4.106605 2.070481e+01 1
#> [5,] 0 40 90.000000 1.487542e-14 1
#> [6,] 0 55 299.837566 3.539626e+01 1
#> [7,] 45 65 45.000000 6.500000e+01 1
#> [8,] 90 75 165.489181 4.307952e+01 1
#> [9,] 135 90 225.000000 7.016709e-15 1Fault plane, rake angle and rake quadrant
Here, the rake is the acute angle measured in the
fault plane between the strike of the fault and the lineation. Starting
from the strike line, the angle is measured in a sense which is down the
dip of the plane. Quadrant of rake indicate the direction of the strike
from which the rake angle is measured, i.e. whether right-hand or
left-hand rule is followed. Angle ranges from 0 to 90 °. Use
sense argument to specify the sense of motion.
If this is the notation used, call the function
Fault_from_rake_quadrant() and set
type="rake"
rake2 <- c(0, 45, 90, 45, 0, 45, 90, 45, 0)
rake_quadrant <- c("E", "S", "S", "E", "E", "W", "N", "S", "W")
Fault_from_rake_quadrant(Plane(dip_dir, dip), rake2, rake_quadrant, type = "rake")
#> Fault object (n = 9):
#> dip_direction dip azimuth plunge sense
#> [1,] 180 5 90.000000 0.000000 1
#> [2,] 225 10 179.561451 7.053022 1
#> [3,] 270 15 270.000000 15.000000 1
#> [4,] 315 30 4.106605 20.704811 1
#> [5,] 0 40 270.000000 0.000000 1
#> [6,] 0 55 299.837566 35.396260 1
#> [7,] 45 65 45.000000 65.000000 1
#> [8,] 90 75 165.489181 43.079517 1
#> [9,] 135 90 45.000000 0.000000 1StraboSpot
The package {structr} can import all the collected field data from your Strabospot project.
The best way is to import the .json file database of the StraboSpot project. Go to your field data My StraboField Data > scroll down to your project > click on Options… > Download Project in Strabo JSON Format
Now you can import the downloaded file via
read_strabo_JSON():
strabo_data <- read_strabo_JSON("path/to/my/file.json")The import function produces a list object with all the
meta data (data), the geographic locations
(spots), the used tags (tags), and all the
plane (planes) and line measurements (lines)
already converted into {structr} data objects.
Additional to descriptions and comments, the meta data
(data) also contains information on the dataset name and
time of measurement.
IMPORTANT: The meta data and the plane and line measurements all share the same row indices. Thus, planes and lines with identical row indices have been measured simultaneously (e.g. as a fault).
This import allows that the connection of simultaneously measured plane and lines (such as faults and their striae) will be preserved. Unfortunately, if you export your StraboSpot field data into a
.csvor.xlsfile, this connection is lost…
Alternatively, the function read_strabo_xls() and
read_strabo_mobile() provide import of .xls
and any character-separated table files (e.g. .csv or
.txt).
Keep in mind that these import options do not properly identify whether your lineation measurements are ray-like or line-like vectors, nor does it combine simultaneously lineation-plane measurements to either pairs or faults. Thus, you’ll need to carefully convert these data dataypes after the import to move forward.
Drill core data
Orientations in drill-cores are usually given by α and β angles
(lineations on a plane additionally have a γ angle) which describe
orientations with respect to the drill orientation. To convert these
angles from the “drillcore coordinate reference system” to our
geographical reference system, you may use the function
drillcore_transformation(). Learn more about it in this tutorial.