| Title: | Simple Geographical Operations (with OSGB36) |
|---|---|
| Description: | Methods focused in performing the OSGB36/ETRS89 transformation (Great Britain and the Isle of Man only) by using the Ordnance Survey's OSTN15/OSGM15 transformation model. Calculation of distances and areas from sets of points defined in any of the supported Coordinated Systems is also available. |
| Authors: | Carlos Lozano Ruiz [aut, cre] |
| Maintainer: | Carlos Lozano Ruiz <[email protected]> |
| License: | BSD_2_clause + file LICENSE |
| Version: | 0.9.2 |
| Built: | 2024-11-13 04:27:38 UTC |
| Source: | https://github.com/clozanoruiz/sgo |
The sgo package aims to help with spatial or geographic analysis in Open Source R and derivatives. Its main purpose is to perform OSGB36/ETRS89 transformations using the Ordnance Survey's OSTN15 transformation model for Great Britain and the Isle of Man. It also transforms GPS ellipsoid heights to orthometric (mean sea level) heights on the relevant Ordnance Survey mapping datum, using the National Geoid Model OSGM15.
Most of the functions available in this package will become much less accurate if used outside the coverage of OSTN, therefore it is advised to apply these functions on coordinates within Great Britain, the Isle of Man and any areas of sea less than a few miles off shore.
This package assumes that the Coordinate Reference Systems (CRS) ETRS89 and WGS84 are practically the same within the UK, but this shouldn't be a problem for most civilian use of GPS satellites. If a high-precision transformation between WGS84 and ETRS89 is required then it is recommended to use a different package to do the conversion.
sgo_points: 2D/3D point coordinates
Functions to provide coordinate transformations:
sgo_bng_lonlat: British National Grid (E/N) to Lon/Lat
sgo_lonlat_bng: Lon/Lat to British National Grid (E/N)
sgo_bng_ngr: British National Grid (E/N) to National Grid
References
sgo_ngr_bng: National Grid References to British National
Grid (E/N)
sgo_laea_etrs: ETRS89-LAEA Easting/Northing to ETRS89
sgo_etrs_laea: ETRS89 to ETRS89-LAEA Easting/Northing
sgo_cart_lonlat: 3D Earth Centred Earth Fixed (ECEF)
Cartesian coordinates to polar coordinates
sgo_lonlat_cart: Polar coordinates to 3D ECEF
Cartesian coordinates
sgo_wgs84_en: WGS84 Lon/Lat to Pseudo-Mercator (E/N)
sgo_en_wgs84: Pseudo-Mercator (E/N) to WGS84 Lon/Lat
sgo_transform: Wrapper for all the transformations above
sgo_coordinates: Extract coordinates from a
sgo_points object
sgo_area: Calculate area from an ordered set of points
sgo_distance: Calculate distance(s) between points
The OSTN15 transformation model is used in this package, and it is licensed
under the BSD Licence (http://opensource.org/licenses/bsd-license.php):
© Copyright and database rights Ordnance Survey Limited 2016, © Crown
copyright and database rights Land & Property Services 2016 and/or ©
Ordnance Survey Ireland, 2016. All rights reserved.
Calculates the planar area for a set of points defined in the OS BNG or ETRS89-LAEA. An accurate approximation of the geodetic area is calculated when points are expressed in angular coordinates.
sgo_area(x, interpolate = NULL, ...)sgo_area(x, interpolate = NULL, ...)
x |
A |
interpolate |
Numeric variable. If not |
... |
Currently ignored |
Calculate areas using the Gauss's area formula (https://en.wikipedia.org/wiki/Shoelace_formula).
When using angular coordinates the function performs an approximation of the geodetic area following the methodology discussed in Berk & Ferlan (2018) where the area on the ellipsoid is determined by using a region-adapted equal-area projection (Albers Equal-Area Conic) with one standard parallel. The standard parallel and the projection origin are tied to the moment centroid of the polygon.
Boundary segments can be divided by interpolating vertices on the projected
geodesic to reduce the error introduced by boundary simplification and to
provide an even more accurate area computation for angular coordinates.
For instance, if interpolate = 500 then any segment between adjacent
coordinates whose length is greater than interpolate will be split in
parts no greater than 500 m and new vertices will be added.
The area calculation in this package is best suited for features that would be represented in a large or medium scale (like plots or council boundaries). It will provide much less accurate results for features usually represented at smalle scale (countries, continents, etc.).
Value of the area in squared metres rounded up to the first decimal.
Sandi Berk & Miran Ferlan, 2018. Accurate area determination in the cadaster: case study of Slovenia. Cartography and Geographic Information Science, 45:1, 1-17. DOI: 10.1080/15230406.2016.1217789
Snyder, J.P. 1987. Map Projections — A Working Manual. US Geological Survey Professional Paper, no. 1395. Washington, DC: US Government Printing Office. DOI: 10.3133/pp1395
lon <- c(-6.43698696, -6.43166843, -6.42706831, -6.42102546, -6.42248238, -6.42639092, -6.42998435, -6.43321409) lat <- c(58.21740316, 58.21930597, 58.22014035, 58.22034112, 58.21849188, 58.21853606, 58.21824033, 58.21748949) A <- sgo_area(sgo_points(list(lon, lat), epsg=4326))lon <- c(-6.43698696, -6.43166843, -6.42706831, -6.42102546, -6.42248238, -6.42639092, -6.42998435, -6.43321409) lat <- c(58.21740316, 58.21930597, 58.22014035, 58.22034112, 58.21849188, 58.21853606, 58.21824033, 58.21748949) A <- sgo_area(sgo_points(list(lon, lat), epsg=4326))
Converts Ordnance Survey grid reference easting/northing coordinates to GCS longitude/latitude (SW corner of grid square).
sgo_bng_lonlat(x, to = 4258, OSTN = TRUE, OD = FALSE)sgo_bng_lonlat(x, to = 4258, OSTN = TRUE, OD = FALSE)
x |
A |
to |
Numeric. Sets the |
OSTN |
Logical variable indicating whether use OSTN15 transformation when TRUE or a less accurate but slightly faster single Helmert transformation when FALSE. |
OD |
Logical variable. When TRUE, and the output contains a
column with heights, then a new column is added to the result indicating the
ordnance datum (OD) used on each point. It is ignored when |
The UK Ordnance Survey defined 'OSGB36' as the datum for the UK, based on the 'Airy 1830' ellipsoid. However, in 2014, they deprecated OSGB36 in favour of ETRS89 for longitude/latitude coordinates. Thus, when converting to longitude/latitude the OSGB36 datum should be always converted to ETRS89 (or WGS84).
According to the Transformations and OSGM15 User Guide, p. 8: "...ETRS89 is a precise version of the better known WGS84 reference system optimised for use in Europe; however, for most purposes it can be considered equivalent to WGS84." and "For all navigation, mapping, GIS, and engineering applications within the tectonically stable parts of Europe (including UK and Ireland), the term ETRS89 should be taken as synonymous with WGS84." This means that ETRS89 and WGS84 datums will be considered equivalent by this routine.
If, for historical reasons, longitude/latitude coordinates must have the old
OSGB36 datum, then the parameter to must be set to 4277.
Note: Grid references rounded to whole metres will give latitude/longitude that are accurate to about 5 decimal places: in Great Britain, 1/100000 of a degree of latitude is about 70cm and 1/100000 of a degree of longitude is about 1m. All those coordinates outside the rectangle covered by OSTN15 will be automatically computed using the small Helmert transformation. Such coordinates will be accurate up to about +/-5 metres. Converting from BNG to lon/lat coordinates is slower than the other way around, due to the iterative nature of the algorithm that is built into OSTN15.
An object of class sgo_points whose coordinates are defined as
Longitude/Latitude.If OD=TRUE a column named height.datum is
added to the resulting object.
Ordnance Survey Limited, 2018. Transformations and OSGM15 user guide
sgo_points, sgo_lonlat_bng,
sgo_coordinates, sgo_transform.
p <- sgo_points(list(651409.903, 313177.270), epsg=27700) p.89 <- sgo_bng_lonlat(p) #ETRS89 lon/lat p.36 <- sgo_bng_lonlat(p, to=4277) #OSGB36 lon/latp <- sgo_points(list(651409.903, 313177.270), epsg=27700) p.89 <- sgo_bng_lonlat(p) #ETRS89 lon/lat p.36 <- sgo_bng_lonlat(p, to=4277) #OSGB36 lon/lat
Converts BNG Easting/Northing coordinates to National Grid References
sgo_bng_ngr(x, digits = 10)sgo_bng_ngr(x, digits = 10)
x |
A |
digits |
Numeric. It defines the precision of the resulting grid references. |
All resulting grid references will have 10 digits (1m × 1m square) by
default. In order to reduce the output precision change the digits parameter
accordingly. When digits=0, it returns the numeric format of the grid
references.
Note that National Grid references are truncated instead of being rounded when converting to less precise references (as the OS system demands). By doing so, the grid reference refers to the lower left corner of the relevant square - to ensure the more precise polygon will remain within the boundaries of the less precise polygon.
A list with at least one column named 'ngr'.
sgo <- sgo_points(list(x=247455, y=706338, name="Ben Venue"), coords=c("x", "y"), epsg=27700) grid10 <- sgo_bng_ngr(sgo) grid8 <- sgo_bng_ngr(sgo, digits=8) #and notice the truncating, not rounding, of grid8 regarding grid10.sgo <- sgo_points(list(x=247455, y=706338, name="Ben Venue"), coords=c("x", "y"), epsg=27700) grid10 <- sgo_bng_ngr(sgo) grid8 <- sgo_bng_ngr(sgo, digits=8) #and notice the truncating, not rounding, of grid8 regarding grid10.
Converts a GCS expressed Earth-centered Earth-fixed (ECEF) cartesian coordinate to Longitude and Latitude and Ellipsoid Height.
sgo_cart_lonlat(x)sgo_cart_lonlat(x)
x |
A |
Currently converts from EPSGs 4936 and 4978 to 4937 and
4979
An object of class sgo_points with polar coordinates (Longitude,
Latitude and Ellipsoid Height).
p <- sgo_points(list(3487823.234, -305433.201, 5313739.634), epsg=4936) p.xyz <- sgo_cart_lonlat(p) #Cartesian coordinatesp <- sgo_points(list(3487823.234, -305433.201, 5313739.634), epsg=4936) p.xyz <- sgo_cart_lonlat(p) #Cartesian coordinates
sgo_points objectExtract the coordinates of an sgo_points object expressed as a matrix.
sgo_coordinates(x, names.xyz = NULL, as.latlon = FALSE, ll.format=NULL)sgo_coordinates(x, names.xyz = NULL, as.latlon = FALSE, ll.format=NULL)
x |
An instance of |
names.xyz |
Character vector. New names for the columns x, y and
possibly z of the object |
as.latlon |
Logical variable. When |
ll.format |
Character variable. Applies a format to the returned
coordinates when |
A matrix with 2 or 3 named columns.
p <- sgo_points(list(57.47777, -4.22472), epsg=4326) coords <- sgo_coordinates(p)p <- sgo_points(list(57.47777, -4.22472), epsg=4326) coords <- sgo_coordinates(p)
Calculates the distance between OS National Grid Reference points. Points with angular coordinates will use the Harvesine or Vicenty formulae.
sgo_distance(x, y, by.element = FALSE, which = ifelse(isTRUE(x$epsg==27700 || x$epsg==7405), "BNG", "Vicenty"), grid.true.distance = ifelse(isTRUE(x$epsg==27700 || x$epsg==7405), TRUE, FALSE), iterations = 100L)sgo_distance(x, y, by.element = FALSE, which = ifelse(isTRUE(x$epsg==27700 || x$epsg==7405), "BNG", "Vicenty"), grid.true.distance = ifelse(isTRUE(x$epsg==27700 || x$epsg==7405), TRUE, FALSE), iterations = 100L)
x |
A |
y |
A |
by.element |
Logical variable. If |
which |
Character vector. For geodetic coordinates one of
|
grid.true.distance |
Logical variable. Currently only used for BNG
coordinates. If |
iterations |
Numeric variable. Maximum number of iterations used in the Vicenty method. |
This function can use two different methods when working with geodetic
coordinates: When which = "Vicenty" the Vincenty's formula is used to
calculate the geodesics (distance) on an ellipsoid to an accuracy of up to
a millimetre. If such accuracy is not needed, which can also
accept the string "Harvesine" which calculates the great-circle distance
between two points on a sphere. Harvesines are faster to compute than the
Vicenty distances but can result in an error of up to 0.5%.
When working with (BNG) planar coordinates the Local Scale Factor is the
scale distortion inherent in the map projection at a point. When
grid.true.distance is TRUE the function computes a line
scale factor using Simpson's Rule to achieve greater accuracy and
approximate the distance to the true geodesic distance. When it is
FALSE the Euclidean distance in the plane is calculated.
Note: Considering F as the scale factor, we have that
S (True distance) = s (grid distance) / F
For most purposes the scale factor can be taken as constant for distances up
to 20km (errors not exceeding 1 or 2 parts er million) and equal to the mid
point of the line. For longer lines, this routine computes a scale factor for
both ends (F1 and F2) and the mid point (Fm) and then uses the Simpson's
Rule:
F = 1/6(F1 + 4Fm + F2)
If by.element is FALSE sgo_distance returns a dense
numeric matrix of dimension length(x) by length(y). Otherwise it returns a
numeric vector of length x or y, the shorter one being
recycled. Distances involving empty geometries are NA.
All distances are returned in metres.
Thaddeus Vincenty, 1975. Direct and Inverse Solutions of Geodesics on the Ellipsoid with application of nested equations. Survey Review, 23:176, 88-93, DOI: 10.1179/sre.1975.23.176.88
p1 <- sgo_points(list(-3.9369, 56.1165), epsg=4326) lon <- c(-4.25181,-3.18827) lat <- c(55.86424, 55.95325) pts <- sgo_points(list(longitude=lon, latitude=lat), epsg=4326) p1.to.pts <- sgo_distance(p1, pts, by.element = TRUE) ## Perimeter of a polygon defined as a series of ordered points: lon <- c(-6.43698696, -6.43166843, -6.42706831, -6.42102546, -6.42248238, -6.42639092, -6.42998435, -6.43321409) lat <- c(58.21740316, 58.21930597, 58.22014035, 58.22034112, 58.21849188, 58.21853606, 58.21824033, 58.21748949) pol <- sgo_points(list(lon, lat), epsg=4326) # Create a copy of the polygon with its coordinates shifted one position # so that we can calculate easily the distance between vertices coords <- sgo_coordinates(pol) pol.shift.one <- sgo_points(rbind(coords[-1, ], coords[1, ]), epsg=pol$epsg) perimeter <- sum(sgo_distance(pol, pol.shift.one, by.element=TRUE))p1 <- sgo_points(list(-3.9369, 56.1165), epsg=4326) lon <- c(-4.25181,-3.18827) lat <- c(55.86424, 55.95325) pts <- sgo_points(list(longitude=lon, latitude=lat), epsg=4326) p1.to.pts <- sgo_distance(p1, pts, by.element = TRUE) ## Perimeter of a polygon defined as a series of ordered points: lon <- c(-6.43698696, -6.43166843, -6.42706831, -6.42102546, -6.42248238, -6.42639092, -6.42998435, -6.43321409) lat <- c(58.21740316, 58.21930597, 58.22014035, 58.22034112, 58.21849188, 58.21853606, 58.21824033, 58.21748949) pol <- sgo_points(list(lon, lat), epsg=4326) # Create a copy of the polygon with its coordinates shifted one position # so that we can calculate easily the distance between vertices coords <- sgo_coordinates(pol) pol.shift.one <- sgo_points(rbind(coords[-1, ], coords[1, ]), epsg=pol$epsg) perimeter <- sum(sgo_distance(pol, pol.shift.one, by.element=TRUE))
Converts Pseudo - Mercator coordinates to WGS84 (EPSG=4326)
sgo_en_wgs84(x, to = 4326)sgo_en_wgs84(x, to = 4326)
x |
A |
to |
Numeric. Sets the |
Currently converts ONLY from EPSG 3857 to 4326 (Longitude/Latitude).
An object of class sgo_points whose coordinates are defined as
Longitude/Latitude.
IOGP Publication 373-7-2 - Geomatics Guidance Note number 7, part 2 (October 2020). https://epsg.org/guidance-notes.html
p <- sgo_points(list(-11169055.58, 2810000.00), epsg=3857) res <- sgo_en_wgs84(p)p <- sgo_points(list(-11169055.58, 2810000.00), epsg=3857) res <- sgo_en_wgs84(p)
Converts ETRS89 geodetic coordinates to ETRS89-LAEA Easting/Northing (EPSG:3035)
sgo_etrs_laea(x)sgo_etrs_laea(x)
x |
A |
ETRS89-LAEA (EPSG:3035) is a CRS for pan-European statistical mapping at all scales or other purposes where true area representation is required.
An object of class sgo_points whose coordinates are defined as
Easting/Northing in the EPSG:3035 Projected Coordinate System.
IOGP Publication 373-7-2 - Geomatics Guidance Note number 7, part 2 (October 2020). https://epsg.org/guidance-notes.html)
p <- sgo_points(list(-3.9369, 56.1165), epsg=4258) prj <- sgo_etrs_laea(p)p <- sgo_points(list(-3.9369, 56.1165), epsg=4258) prj <- sgo_etrs_laea(p)
Converts ETRS89-LAEA Easting/Northing to ETRS89 geodetic coordinates (EPSG:4258)
sgo_laea_etrs(x)sgo_laea_etrs(x)
x |
A |
ETRS89-LAEA (EPSG:3035) is a CRS for pan-European statistical mapping at all scales or other purposes where true area representation is required.
An object of class sgo_points whose coordinates are defined as
Longitude/Latitude in the ETRS89 Coordinate Reference System.
IOGP Publication 373-7-2 - Geomatics Guidance Note number 7, part 2 (October 2020). https://epsg.org/guidance-notes.html
prj <- sgo_points(list(3962799.45, 2999718.85), epsg=3035) p <- sgo_laea_etrs(prj)prj <- sgo_points(list(3962799.45, 2999718.85), epsg=3035) p <- sgo_laea_etrs(prj)
Converts a geodetic coordinate system to BNG (projected) Easting/Northing coordinates. It also transforms GPS ellipsoid heights to orthometric (mean sea level) heights on the relevant Ordnance Survey mapping datum, using the National Geoid Model OSGM15.
sgo_lonlat_bng(x, to=27700, OSTN=TRUE, OD=FALSE)sgo_lonlat_bng(x, to=27700, OSTN=TRUE, OD=FALSE)
x |
A |
to |
Specifies the EPSG code to convert the coordinates to. It can only
take the following values: |
OSTN |
Logical variable indicating whether use OSTN15 transformation when TRUE or a less accurate but slightly faster single Helmert transformation when FALSE. |
OD |
Logical variable. When TRUE, and the output contains a
column with heights, then a new column is added to the result indicating the
ordnance datum (OD) used on each point. It is ignored when |
The UK Ordnance Survey defined 'OSGB36' as the datum for the UK, based on the
'Airy 1830' ellipsoid. However, in 2014, they deprecated OSGB36 in favour of
ETRS89 for longitude/latitude coordinates. Thus, x should be defined
as ETRS89 (or WGS84) most of the times.
Note: When transforming from EPSG=4277 any height included in the input
will be simply discarded (see sgo_points).
According to the Transformations and OSGM15 User Guide, p. 8: "...ETRS89 is a precise version of the better known WGS84 reference system optimised for use in Europe; however, for most purposes it can be considered equivalent to WGS84." and "For all navigation, mapping, GIS, and engineering applications within the tectonically stable parts of Europe (including UK and Ireland), the term ETRS89 should be taken as synonymous with WGS84." This means that EPSGs with the ETRS89 datum or WGS84 will be considered equivalent by this routine.
Note: All those coordinates outside the rectangle covered by OSTN15
will be automatically computed using the small Helmert transformation. Such
coordinates will be accurate up to about +/-5 metres, therefore the resulting
easting and northing coordinates will be rounded to the metre. Since those
coordinates are outside of the OSTN15 domain the resulting coordinates will
have the resulting height defined as NA.
Similarly, when using OSTN=FALSE on 3D coordinates, the result will
have all the heights defined as NA.
Converting from lon/lat to BNG coordinates is faster than the other way
around, due to the iterative nature of the algorithm that is built into
OSTN15.
An object of class sgo_points whose coordinates are defined as
Easting/Northing (epsg=27700 or 7405). They are adjusted to the SW corner of
1m grid square. If OD=TRUE a column named height.datum is
added to the resulting object.
Ordnance Survey Limited, 2018. Transformations and OSGM15 user guide
sgo_points, sgo_bng_lonlat,
sgo_coordinates, sgo_transform.
lon <- c(-4.25181,-3.18827) lat <- c(55.86424, 55.95325) pts <- sgo_points(list(longitude=lon, latitude=lat), epsg=4326) bng.pts <- sgo_lonlat_bng(pts)lon <- c(-4.25181,-3.18827) lat <- c(55.86424, 55.95325) pts <- sgo_points(list(longitude=lon, latitude=lat), epsg=4326) bng.pts <- sgo_lonlat_bng(pts)
Converts a GCS expressed in Longitude and Latitude (and Ellipsoid Height) to an Earth-centered Earth-fixed (ECEF) cartesian coordinate system.
sgo_lonlat_cart(x)sgo_lonlat_cart(x)
x |
A |
Currently converts from EPSGs 4258 and 4937 to 4936 or
from EPSGs 4326, 4979 to 4978
An object of class sgo_points whose coordinates are defined as a
x, y and z cartesian vector.
p <- sgo_points(list(-5.00355049, 56.7968571), epsg=4326) p.xyz <- sgo_lonlat_cart(p) #Cartesian coordinatesp <- sgo_points(list(-5.00355049, 56.7968571), epsg=4326) p.xyz <- sgo_lonlat_cart(p) #Cartesian coordinates
Converts OS National Grid References to Easting/Northing coordinates
sgo_ngr_bng(x, col = NULL, check.only = FALSE)sgo_ngr_bng(x, col = NULL, check.only = FALSE)
x |
A data.frame, list or vector containing strings describing OS National Grid References, with or without whitespace separators. (e.g. 'SU 387 148'). |
col |
Character string with the name of the 'column' containing the
vector of NGR values, it is required when |
check.only |
Logical parameter. If it is set to TRUE then the routine returns a logical vector indicating which references are correct. |
All entered standard grid references can range from two-digit references up
to 10-digit references (1m × 1m square).
If x is a list with 2 or more vector elements, col can be used
to inform the function which of the elements contains the NGR strings. The
rest of the elements will be appended to the resulting object. See examples.
An object of class sgo_points whose coordinates are defined as
Easting/Northing when check.only is kept as FALSE. Otherwise, it
returns a logical vector indicating which grid references are correct and
which ones are not.
vec <- c("NN 166 712", "HU38637653") lst <- list(vec) v <- sgo_ngr_bng(vec) l <- sgo_ngr_bng(lst) # any additional column (here 'attr') will be added to the result extra <- list(p=c("NN 166712", "HU38637653"), attr=c("name1","name2")) res <- sgo_ngr_bng(extra, col="p") res # grid references returned by sgo_bng_ngr are within an # element (column) named 'ngr' grid <- sgo_bng_ngr(sgo_points(list(x=247455, y=706338, name="Ben Venue"), coords=c("x","y"), epsg=27700)) bng <- sgo_ngr_bng(grid, col="ngr") # test bad <- c("NN 166 712", "AA 3863 7653") check <- sgo_ngr_bng(bad, check.only=TRUE) #returns a logical vectorvec <- c("NN 166 712", "HU38637653") lst <- list(vec) v <- sgo_ngr_bng(vec) l <- sgo_ngr_bng(lst) # any additional column (here 'attr') will be added to the result extra <- list(p=c("NN 166712", "HU38637653"), attr=c("name1","name2")) res <- sgo_ngr_bng(extra, col="p") res # grid references returned by sgo_bng_ngr are within an # element (column) named 'ngr' grid <- sgo_bng_ngr(sgo_points(list(x=247455, y=706338, name="Ben Venue"), coords=c("x","y"), epsg=27700)) bng <- sgo_ngr_bng(grid, col="ngr") # test bad <- c("NN 166 712", "AA 3863 7653") check <- sgo_ngr_bng(bad, check.only=TRUE) #returns a logical vector
2D or 3D coordinates (and other attributes) of a point or collection of points
sgo_points(x, coords = NULL, epsg = NULL) ## S3 method for class 'sgo_points' print(x, ..., n = 6L) ## S3 method for class 'sgo_points' as.data.frame(x, row.names = NULL, optional = FALSE, ...) ## S3 method for class 'sgo_points' as.list(x, ...)sgo_points(x, coords = NULL, epsg = NULL) ## S3 method for class 'sgo_points' print(x, ..., n = 6L) ## S3 method for class 'sgo_points' as.data.frame(x, row.names = NULL, optional = FALSE, ...) ## S3 method for class 'sgo_points' as.list(x, ...)
x |
A matrix, list or dataframe with at least 2 columns of either
easting/northing or longitude/latitude coordinates per row. A column with
height values is optional.
Please note that the order is important when |
coords |
A vector with the names of the two or three columns containing the X (easting or longitude), Y (northing or latitude) and optionally Z (ellipsoid or orthometric height) coordinates. |
epsg |
Specifies the EPSG code of coordinates to store. It can take any of the following values:
|
... |
Further arguments passed to or from other methods, see print, as.data.frame or as.list . |
n |
Maximum number of features to print. |
row.names |
NULL or a character vector giving the row names for the data frame. Missing values are not allowed. |
optional |
Logical. See as.data.frame |
This object stores 2D or 3D point coordinates and any other column-list of
attributes related to each point. Note that additional column-lists will be
expanded with NA values if they contain less elements than
coordinates.
Currently it only supports the following epsgs:
4258: ETRS89, geodetic coordinate system. The columns in
x must be defined as Longitude and Latitude (sgo also accepts
a third column for ellipsoid heights). The defined datum for this set of
coordinates is ETRS89 (https://epsg.io/4258).
4937: ETRS89, geodetic coordinate system. The columns in
x must be defined as Longitude, Latitude and Ellipsoid Heights
respectively. The defined datum for this set of coordinates is ETRS89
(https://epsg.io/4937).
4936: ETRS89, geodetic coordinate system. The columns in
x must be defined as cartesian coordinates x, y and z. The defined
datum for this set of coordinates is ETRS89 (https://epsg.io/4936).
3035: ETRS-LAEA, projected coordinate system. The
columns in x must be defined as Easting and Northing. The defined
datum for this set of coordinates is ETRS89 (https://epsg.io/3035)
4326: WGS84, geodetic coordinate system. The columns in x
must be defined as Longitude and Latitude (sgo also accepts a
third column for ellipsoid heights). The defined datum for this set of
coordinates is WGS84 (https://epsg.io/4326).
4979: WGS84, geodetic coordinate system. The columns in x
must be defined as Longitude, Latitude and Ellipsoid Height respectively.
The defined datum for this set of coordinates is WGS84 (https://epsg.io/4979)
4978: WGS84, geodetic coordinate system. The columns in x
must be defined as cartesian coordinates x, y and z. The
defined datum for this set of coordinates is WGS84 (https://epsg.io/4978)
4277: OSGB36, geodetic coordinate system. The 2 columns in
x must be defined as Longitude and Latitude values respectively. The
defined datum for this set of coordinates is OSGB 1936
(https://epsg.io/4277). Coordinates defined like this should only be
used for historical reasons and to convert only to or from BNG coordinates.
Height values will be discarded when working with this coordinate
system.
27700: British National Grid, projected coordinate system. The
columns in x must be defined as Easting and Northing (sgo also
accepts a third column for orthometric heights). The defined datum for this
set of coordinates is OSGB 1936 (https://epsg.io/27700).
7405: British National Grid, projected coordinate system. The
columns in x must be defined as Easting, Northing and ODN Orthometric
height respectively (sgo accepts heights from other datums like
Orkney, Lerwick, Stornoway, Douglas, St.Marys and 'Newlyn offshore').
The defined datum for this set of coordinates is OSGB 1936
(https://epsg.io/7405).
3857: WGS 84 / Pseudo-Mercator, projected coordinate system. The
columns in x must be defined as Easting and Northing. The defined
datum for this set of coordinates is WGS84 (https://epsg.io/3857)
An object of class sgo_points. This object is a actually a list with
class sgo_points and at least 5 elements (or 6 elements if it is 3D):
x: A numeric vector containing easting or longitude coordinates.
y: A numeric vector with northing or latitude coordintes.
z: A numeric vector with height values when the object is 3D.
epsg: A scalar value with the EPSG code of the current
Geographic Coordinate System (GCS).
datum: A string describing the geodetic datum that defines the
GCS of the object. Currently can take the values "OSGB36", "WGS84" or
"ETRS89"
dimension: A string describing whether the object is 2D or 3D.
It can take the values "XY" or "XYZ".
sgo_coordinates, sgo_transform.
# lists: p1 <- sgo_points(list(-3.9369, 56.1165), epsg=4326) lon <- c(-4.25181,-3.18827) lat <- c(55.86424, 55.95325) p2 <- sgo_points(list(longitude=lon, latitude=lat), epsg=4326) #p3 will fill up the list 'desc' with NA's to have the same number of #elements as coordinates in the list: p3 <- sgo_points(list(longitude=lon, latitude=lat, desc="c1"), coords=c("longitude", "latitude"), epsg=4326) # dataframe: ln <- c(-4.22472, -2.09908) lt <- c(57.47777, 57.14965) n <- c("Inverness", "Aberdeen") df <- data.frame(n, ln, lt, stringsAsFactors = FALSE) p4 <- sgo_points(df, coords=c("ln", "lt"), epsg=4326) # plotting on a map: if (require(maps)) { map('world', regions=('uk'), xlim=c(-9, 0), ylim=c(54.5, 60.9)) points(x=p1$x, y=p1$y, pch=0, col="green") #Stirling points(p4, pch=0, col="red") text(p4, labels=p4$n, pos=1, cex=0.9) }# lists: p1 <- sgo_points(list(-3.9369, 56.1165), epsg=4326) lon <- c(-4.25181,-3.18827) lat <- c(55.86424, 55.95325) p2 <- sgo_points(list(longitude=lon, latitude=lat), epsg=4326) #p3 will fill up the list 'desc' with NA's to have the same number of #elements as coordinates in the list: p3 <- sgo_points(list(longitude=lon, latitude=lat, desc="c1"), coords=c("longitude", "latitude"), epsg=4326) # dataframe: ln <- c(-4.22472, -2.09908) lt <- c(57.47777, 57.14965) n <- c("Inverness", "Aberdeen") df <- data.frame(n, ln, lt, stringsAsFactors = FALSE) p4 <- sgo_points(df, coords=c("ln", "lt"), epsg=4326) # plotting on a map: if (require(maps)) { map('world', regions=('uk'), xlim=c(-9, 0), ylim=c(54.5, 60.9)) points(x=p1$x, y=p1$y, pch=0, col="green") #Stirling points(p4, pch=0, col="red") text(p4, labels=p4$n, pos=1, cex=0.9) }
Changes the geodetic coordinate system of a set of points using a single Helmert transformation.
sgo_set_gcs(x, to = NULL)sgo_set_gcs(x, to = NULL)
x |
A |
to |
Specifies the EPSG code to convert the coordinates to. Currently it
can take any of the following values: |
Changes the geodetic coordinate system of a set of points. Note that the precision of various datums will vary, and the original WGS-84 is not defined to be accurate to better than ±1 metre. Most transformations shouldn't be assumed to be accurate to better than a meter; between OSGB36 and WGS84 somewhat less - the lost of accuracy can be up to ±5m when using single Helmert transformations.
Input points with a projected coordinate system (e.g. 27700, 7405, 3035 or 3857) are not allowed.
Warning This function is mainly for internal use of the program. Since it relies on a single Helmert transformation it is not recommended to call it directly. Use any other of the transformation functions available (sgo-package).
An object of class 'sgo_points'.
lon <- c(-4.25181,-3.18827) lat <- c(55.86424, 55.95325) p <- sgo_points(list(longitude=lon, latitude=lat), epsg=4326) # warning: a single Helmert transformation is used in the next transformation p2 <- sgo_set_gcs(p, to=4277) # if higher precision is required to transform between OSGB36 lon/lat and # ETRS89/WGS84 lon/lat then use the OSTN15 transformation (will be slower): # Transform from WGS84 lon/lat coordinates to EPSG:4277 using OSTN15 p2 <- sgo_transform(p, to=4277)lon <- c(-4.25181,-3.18827) lat <- c(55.86424, 55.95325) p <- sgo_points(list(longitude=lon, latitude=lat), epsg=4326) # warning: a single Helmert transformation is used in the next transformation p2 <- sgo_set_gcs(p, to=4277) # if higher precision is required to transform between OSGB36 lon/lat and # ETRS89/WGS84 lon/lat then use the OSTN15 transformation (will be slower): # Transform from WGS84 lon/lat coordinates to EPSG:4277 using OSTN15 p2 <- sgo_transform(p, to=4277)
Transforms the coordinate system of a set of points to any supported coordinate system.
sgo_transform(x, to = NULL, ...)sgo_transform(x, to = NULL, ...)
x |
A |
to |
Specifies the EPSG code to convert the coordinates to. See
|
... |
Additional parameters passed to internal functions. Currently it
supports the additional arguments seen in |
This function is a wrapper of specific transformation functions
(sgo_bng_lonlat, sgo_en_wgs84,
sgo_lonlat_bng, sgo_wgs84_en,
sgo_laea_etrs, sgo_etrs_laea,
sgo_cart_lonlat, sgo_lonlat_cart) that transforms
the coordinate system of a set of points to any of the supported coordinate
systems.
Please note that this package assumes that the Coordinate Reference Systems (CRS) ETRS89 and WGS84 are the same within the UK, but this shouldn't be a problem for most civilian use of GPS satellites. If a high-precision transformation between WGS84 and ETRS89 is required then it is recommended to use a different package to do the conversion.
According to the Transformations and OSGM15 User Guide, p. 8: "...ETRS89 is a precise version of the better known WGS84 reference system optimised for use in Europe; however, for most purposes it can be considered equivalent to WGS84." and "For all navigation, mapping, GIS, and engineering applications within the tectonically stable parts of Europe (including UK and Ireland), the term ETRS89 should be taken as synonymous with WGS84.".
Warning: Coordinates defined in the Geodetic Coordinate System EPSG:4277 (with datum OSGB 1936) should only be used to convert to or from BNG coordinates and for historical reasons only.
An object of class 'sgo_points'.
sgo_points, sgo_coordinates,
sgo_set_gcs, sgo_bng_ngr
ln <- c(-4.22472, -2.09908) lt <- c(57.47777, 57.14965) n <- c("Inverness", "Aberdeen") df <- data.frame(n, ln, lt, stringsAsFactors = FALSE) locations <- sgo_points(df, coords=c("ln", "lt"), epsg=4326) locations.bng <- sgo_transform(locations, to=27700) locations.osgb36 <- sgo_transform(locations, to=4277) locations.ngr <- sgo_bng_ngr(sgo_transform(locations, to=27700)) locations.wgs84EN <- sgo_transform(locations.bng, to=3857)ln <- c(-4.22472, -2.09908) lt <- c(57.47777, 57.14965) n <- c("Inverness", "Aberdeen") df <- data.frame(n, ln, lt, stringsAsFactors = FALSE) locations <- sgo_points(df, coords=c("ln", "lt"), epsg=4326) locations.bng <- sgo_transform(locations, to=27700) locations.osgb36 <- sgo_transform(locations, to=4277) locations.ngr <- sgo_bng_ngr(sgo_transform(locations, to=27700)) locations.wgs84EN <- sgo_transform(locations.bng, to=3857)
Converts WGS84 coordinates to Easting/Northing (Pseudo-Mercator)
sgo_wgs84_en(x, to = 3857)sgo_wgs84_en(x, to = 3857)
x |
A |
to |
Numeric. Sets the |
This routine also accepts source data expressed in ETRS89 coordinates (EPSG=4258 or 4937) as it is considered the difference between those two GCS is far less than the accuracy available when working with Pseudo-Mercator coordinates.
The results can be used in maps where Pseudo-Mercator coordinates are needed. Usually, those include Google, Bing, OpenStreetMap and several other webmap applications.
An object of class sgo_points whose coordinates are defined as
Easting/Northing.
IOGP Publication 373-7-2 - Geomatics Guidance Note number 7, part 2 (October 2020). https://epsg.org/guidance-notes.html
p <- sgo_points(list(-3.9369, 56.1165), epsg=4326) res <- sgo_wgs84_en(p)p <- sgo_points(list(-3.9369, 56.1165), epsg=4326) res <- sgo_wgs84_en(p)