Movatterモバイル変換

sgo: Simple Geographical Operations (with OSGB36).

Description

The sgo package aims to help with spatial or geographic analysis in OpenSource R and derivatives. Its main purpose is to perform OSGB36/ETRS89transformations using the Ordnance Survey's OSTN15 transformation model forGreat Britain and the Isle of Man. It also transforms GPS ellipsoid heightsto orthometric (mean sea level) heights on the relevant Ordnance Surveymapping datum, using the National Geoid Model OSGM15.

Details

Most of the functions available in this package will become much lessaccurate if used outside the coverage of OSTN, therefore it is advised toapply these functions on coordinates within Great Britain, the Isle of Manand any areas of sea less than a few miles off shore.

This package assumes that the Coordinate Reference Systems (CRS) ETRS89 andWGS84 are practically the same within the UK, but this shouldn't be aproblem for most civilian use of GPS satellites. If a high-precisiontransformation between WGS84 and ETRS89 is required then it is recommendedto use a different package to do the conversion.

Object constructors

• sgo_points: 2D/3D point coordinates

Transformation and Conversion functions

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 GridReferences

• sgo_ngr_bng: National Grid References to British NationalGrid (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 ECEFCartesian 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 asgo_points object

Geometric measurements

• sgo_area: Calculate area from an ordered set of points

• sgo_distance: Calculate distance(s) between points

Disclaimer

The OSTN15 transformation model is used in this package, and it is licensedunder the BSD Licence (http://opensource.org/licenses/bsd-license.php):
© Copyright and database rights Ordnance Survey Limited 2016, © Crowncopyright and database rights Land & Property Services 2016 and/or ©Ordnance Survey Ireland, 2016. All rights reserved.

Calculate area from an ordered set of points

Description

Calculates the planar area for a set of points defined in the OS BNG orETRS89-LAEA. An accurate approximation of the geodetic area is calculatedwhen points are expressed in angular coordinates.

Usage

sgo_area(x, interpolate = NULL, ...)

Arguments

Details

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 thegeodetic area following the methodology discussed in Berk & Ferlan (2018)where the area on the ellipsoid is determined by using a region-adaptedequal-area projection (Albers Equal-Area Conic) with one standard parallel.The standard parallel and the projection origin are tied to the momentcentroid of the polygon.

Boundary segments can be divided by interpolating vertices on the projectedgeodesic to reduce the error introduced by boundary simplification and toprovide an even more accurate area computation for angular coordinates.For instance, ifinterpolate = 500 then any segment between adjacentcoordinates whose length is greater thaninterpolate will be split inparts no greater than500 m and new vertices will be added.

The area calculation in this package is best suited for features that wouldbe represented in a large or medium scale (like plots or council boundaries).It will provide much less accurate results for features usually representedat smalle scale (countries, continents, etc.).

Value

Value of the area in squared metres rounded up to the first decimal.

References

Sandi Berk & Miran Ferlan, 2018.Accurate area determination in thecadaster: case study of Slovenia. Cartography and Geographic InformationScience, 45:1, 1-17. DOI: 10.1080/15230406.2016.1217789

Snyder, J.P. 1987.Map Projections — A Working Manual. US GeologicalSurvey Professional Paper, no. 1395. Washington, DC: US Government PrintingOffice. DOI: 10.3133/pp1395

Examples

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))

British National Grid (BNG) Easting/Northing to Geodetic CoordinateSystem (GCS)

Description

Converts Ordnance Survey grid reference easting/northing coordinates to GCSlongitude/latitude (SW corner of grid square).

Usage

sgo_bng_lonlat(x, to = 4258, OSTN = TRUE, OD = FALSE)

Arguments

Details

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 ofETRS89 for longitude/latitude coordinates. Thus, when converting tolongitude/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 referencesystem optimised for use in Europe; however, for most purposes it can beconsidered equivalent to WGS84." and"For all navigation, mapping,GIS, and engineering applications within the tectonically stable parts ofEurope (including UK and Ireland), the term ETRS89 should be taken assynonymous with WGS84." This means that ETRS89 and WGS84 datums will beconsidered equivalent by this routine.

If, for historical reasons, longitude/latitude coordinates must have the oldOSGB36 datum, then the parameterto must be set to 4277.

Note: Grid references rounded to whole metres will givelatitude/longitude that are accurate to about 5 decimal places: in GreatBritain, 1/100000 of a degree of latitude is about 70cm and 1/100000 of adegree of longitude is about 1m.All those coordinates outside the rectangle covered by OSTN15will be automatically computed using the small Helmert transformation. Suchcoordinates will be accurate up to about +/-5 metres.Converting from BNG to lon/lat coordinates is slower than the other wayaround, due to the iterative nature of the algorithm that is built intoOSTN15.

Value

An object of classsgo_points whose coordinates are defined asLongitude/Latitude.IfOD=TRUE a column namedheight.datum isadded to the resulting object.

References

Ordnance Survey Limited, 2018.Transformations and OSGM15 user guide

See Also

sgo_points,sgo_lonlat_bng,sgo_coordinates,sgo_transform.

Examples

p <- sgo_points(list(651409.903, 313177.270), epsg=27700)p.89 <- sgo_bng_lonlat(p) #ETRS89 lon/latp.36 <- sgo_bng_lonlat(p, to=4277) #OSGB36 lon/lat

BNG Easting/Northing to National Grid References (NGR)

Description

Converts BNG Easting/Northing coordinates to National Grid References

Usage

sgo_bng_ngr(x, digits = 10)

Arguments

Details

All resulting grid references will have 10 digits (1m × 1m square) bydefault. In order to reduce the output precision change the digits parameteraccordingly. Whendigits=0, it returns the numeric format of the gridreferences.

Note that National Grid references are truncated instead of being roundedwhen converting to less precise references (as the OS system demands). Bydoing so, the grid reference refers to the lower left corner of the relevantsquare - to ensure the more precise polygon will remain within the boundariesof the less precise polygon.

Value

A list with at least one column named 'ngr'.

See Also

sgo_points,sgo_ngr_bng.

Examples

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.

Geodetic Coordinate System (GCS) in cartesian coordinates to polarcoordinates

Description

Converts a GCS expressed Earth-centered Earth-fixed (ECEF) cartesiancoordinate to Longitude and Latitude and Ellipsoid Height.

Usage

sgo_cart_lonlat(x)

Arguments

Details

Currently converts from EPSGs4936 and4978 to4937 and4979

Value

An object of classsgo_points with polar coordinates (Longitude,Latitude and Ellipsoid Height).

See Also

sgo_points,sgo_bng_lonlat.

Examples

p <- sgo_points(list(3487823.234, -305433.201, 5313739.634), epsg=4936)p.xyz <- sgo_cart_lonlat(p) #Cartesian coordinates

Extracts coordinates from ansgo_points object

Description

Extract the coordinates of ansgo_points object expressed as a matrix.

Usage

sgo_coordinates(x, names.xyz = NULL, as.latlon = FALSE,ll.format=NULL)

Arguments

Value

A matrix with 2 or 3 named columns.

Examples

p <- sgo_points(list(57.47777, -4.22472), epsg=4326)coords <- sgo_coordinates(p)

Calculate distance(s) between points

Description

Calculates the distance between OS National Grid Reference points. Pointswith angular coordinates will use the Harvesine or Vicenty formulae.

Usage

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)

Arguments

Details

This function can use two different methods when working with geodeticcoordinates: Whenwhich = "Vicenty" the Vincenty's formula is used tocalculate the geodesics (distance) on an ellipsoid to an accuracy of up toa millimetre. If such accuracy is not needed,which can alsoaccept the string "Harvesine" which calculates the great-circle distancebetween two points on a sphere. Harvesines are faster to compute than theVicenty distances but can result in an error of up to 0.5%.

When working with (BNG) planar coordinates the Local Scale Factor is thescale distortion inherent in the map projection at a point. Whengrid.true.distance isTRUE the function computes a linescale factor using Simpson's Rule to achieve greater accuracy andapproximate the distance to the true geodesic distance. When it isFALSE the Euclidean distance in the plane is calculated.

Note: Considering F as the scale factor, we have thatS (True distance) = s (grid distance) / F
For most purposes the scale factor can be taken as constant for distances upto 20km (errors not exceeding 1 or 2 parts er million) and equal to the midpoint of the line. For longer lines, this routine computes a scale factor forboth ends (F1 and F2) and the mid point (Fm) and then uses the Simpson'sRule:
F = 1/6(F1 + 4Fm + F2)

Value

Ifby.element isFALSEsgo_distance returns a densenumeric matrix of dimension length(x) by length(y). Otherwise it returns anumeric vector of lengthx ory, the shorter one beingrecycled. Distances involving empty geometries areNA.All distances are returned in metres.

References

Thaddeus Vincenty, 1975.Direct and Inverse Solutions of Geodesics onthe Ellipsoid with application of nested equations. Survey Review, 23:176,88-93, DOI: 10.1179/sre.1975.23.176.88

Examples

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 verticescoords <- 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))

Pseudo - Mercator to WGS84 Longitude/Latitude

Description

Converts Pseudo - Mercator coordinates to WGS84 (EPSG=4326)

Usage

sgo_en_wgs84(x, to = 4326)

Arguments

Details

Currently converts ONLY from EPSG 3857 to 4326 (Longitude/Latitude).

Value

An object of classsgo_points whose coordinates are defined asLongitude/Latitude.

References

IOGP Publication 373-7-2 - Geomatics Guidance Note number 7,part 2 (October 2020). https://epsg.org/guidance-notes.html

See Also

sgo_points,sgo_wgs84_en.

Examples

p <- sgo_points(list(-11169055.58, 2810000.00), epsg=3857)res <- sgo_en_wgs84(p)

ETRS89 to ETRS89-LAEA Easting/Northing

Description

Converts ETRS89 geodetic coordinates to ETRS89-LAEA Easting/Northing(EPSG:3035)

Usage

sgo_etrs_laea(x)

Arguments

Details

ETRS89-LAEA (EPSG:3035) is a CRS for pan-European statistical mapping at allscales or other purposes where true area representation is required.

Value

An object of classsgo_points whose coordinates are defined asEasting/Northing in the EPSG:3035 Projected Coordinate System.

References

IOGP Publication 373-7-2 - Geomatics Guidance Note number 7,part 2 (October 2020). https://epsg.org/guidance-notes.html)

See Also

sgo_points,sgo_area.

Examples

p <- sgo_points(list(-3.9369, 56.1165), epsg=4258)prj <- sgo_etrs_laea(p)

ETRS89-LAEA Easting/Northing to ETRS89 geodetic coordinates

Description

Converts ETRS89-LAEA Easting/Northing to ETRS89 geodetic coordinates(EPSG:4258)

Usage

sgo_laea_etrs(x)

Arguments

Details

ETRS89-LAEA (EPSG:3035) is a CRS for pan-European statistical mapping at allscales or other purposes where true area representation is required.

Value

An object of classsgo_points whose coordinates are defined asLongitude/Latitude in the ETRS89 Coordinate Reference System.

References

IOGP Publication 373-7-2 - Geomatics Guidance Note number 7,part 2 (October 2020). https://epsg.org/guidance-notes.html

See Also

sgo_points,sgo_area.

Examples

prj <- sgo_points(list(3962799.45, 2999718.85), epsg=3035)p <- sgo_laea_etrs(prj)

GCS to BNG Easting/Northing

Description

Converts a geodetic coordinate system to BNG (projected) Easting/Northingcoordinates. It also transforms GPS ellipsoid heights to orthometric(mean sea level) heights on the relevant Ordnance Survey mapping datum, usingthe National Geoid Model OSGM15.

Usage

sgo_lonlat_bng(x, to=27700, OSTN=TRUE, OD=FALSE)

Arguments

Details

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 ofETRS89 for longitude/latitude coordinates. Thus,x should be definedas ETRS89 (or WGS84) most of the times.

Note: When transforming from EPSG=4277 any height included in the inputwill be simply discarded (seesgo_points).

According to the Transformations and OSGM15 User Guide, p. 8:"...ETRS89 is a precise version of the better known WGS84 referencesystem optimised for use in Europe; however, for most purposes it can beconsidered equivalent to WGS84." and"For all navigation, mapping,GIS, and engineering applications within the tectonically stable parts ofEurope (including UK and Ireland), the term ETRS89 should be taken assynonymous with WGS84." This means that EPSGs with the ETRS89 datum orWGS84 will be considered equivalent by this routine.

Note: All those coordinates outside the rectangle covered by OSTN15will be automatically computed using the small Helmert transformation. Suchcoordinates will be accurate up to about +/-5 metres, therefore the resultingeasting and northing coordinates will be rounded to the metre. Since thosecoordinates are outside of the OSTN15 domain the resulting coordinates willhave the resulting height defined asNA.Similarly, when usingOSTN=FALSE on 3D coordinates, the result willhave all the heights defined asNA.Converting from lon/lat to BNG coordinates is faster than the other wayaround, due to the iterative nature of the algorithm that is built intoOSTN15.

Value

An object of classsgo_points whose coordinates are defined asEasting/Northing (epsg=27700 or 7405). They are adjusted to the SW corner of1m grid square. IfOD=TRUE a column namedheight.datum isadded to the resulting object.

References

Ordnance Survey Limited, 2018.Transformations and OSGM15 user guide

See Also

sgo_points,sgo_bng_lonlat,sgo_coordinates,sgo_transform.

Examples

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)

Geodetic Coordinate System (GCS) in polar coordinates to cartesiancoordinates

Description

Converts a GCS expressed in Longitude and Latitude(and Ellipsoid Height) to an Earth-centered Earth-fixed (ECEF) cartesiancoordinate system.

Usage

sgo_lonlat_cart(x)

Arguments

Details

Currently converts from EPSGs4258 and4937 to4936 orfrom EPSGs4326,4979 to4978

Value

An object of classsgo_points whose coordinates are defined as ax, y and z cartesian vector.

See Also

sgo_points,sgo_lonlat_bng.

Examples

p <- sgo_points(list(-5.00355049, 56.7968571), epsg=4326)p.xyz <- sgo_lonlat_cart(p) #Cartesian coordinates

NGR to BNG Easting/Northing

Description

Converts OS National Grid References to Easting/Northing coordinates

Usage

sgo_ngr_bng(x, col = NULL, check.only = FALSE)

Arguments

Details

All entered standard grid references can range from two-digit references upto 10-digit references (1m × 1m square).Ifx is a list with 2 or more vector elements,col can be usedto inform the function which of the elements contains the NGR strings. Therest of the elements will be appended to the resulting object. See examples.

Value

An object of classsgo_points whose coordinates are defined asEasting/Northing whencheck.only is kept as FALSE. Otherwise, itreturns a logical vector indicating which grid references are correct andwhich ones are not.

See Also

sgo_points,sgo_bng_ngr.

Examples

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 resultextra <- 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")# testbad <- c("NN 166 712", "AA 3863 7653")check <- sgo_ngr_bng(bad, check.only=TRUE) #returns a logical vector

Object containing 2D or 3D point coordinates

Description

2D or 3D coordinates (and other attributes) of a point or collection ofpoints

Usage

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, ...)

Arguments

Details

This object stores 2D or 3D point coordinates and any other column-list ofattributes related to each point. Note that additional column-lists will beexpanded withNA values if they contain less elements thancoordinates.Currently it only supports the followingepsgs:

• 4258: ETRS89, geodetic coordinate system. The columns inx must be defined as Longitude and Latitude (sgo also acceptsa third column for ellipsoid heights). The defined datum for this set ofcoordinates is ETRS89 (https://epsg.io/4258).

• 4937: ETRS89, geodetic coordinate system. The columns inx must be defined as Longitude, Latitude and Ellipsoid Heightsrespectively. The defined datum for this set of coordinates is ETRS89(https://epsg.io/4937).

• 4936: ETRS89, geodetic coordinate system. The columns inx must be defined as cartesian coordinates x, y and z. The defineddatum for this set of coordinates is ETRS89 (https://epsg.io/4936).

• 3035: ETRS-LAEA, projected coordinate system. Thecolumns inx must be defined as Easting and Northing. The defineddatum for this set of coordinates is ETRS89 (https://epsg.io/3035)

• 4326: WGS84, geodetic coordinate system. The columns inxmust be defined as Longitude and Latitude (sgo also accepts athird column for ellipsoid heights). The defined datum for this set ofcoordinates is WGS84 (https://epsg.io/4326).

• 4979: WGS84, geodetic coordinate system. The columns inxmust 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 inxmust be defined as cartesian coordinates x, y and z. Thedefined datum for this set of coordinates is WGS84 (https://epsg.io/4978)

• 4277: OSGB36, geodetic coordinate system. The 2 columns inx must be defined as Longitude and Latitude values respectively. Thedefined datum for this set of coordinates is OSGB 1936(https://epsg.io/4277).Coordinates defined like this should only beused for historical reasons and to convert only to or from BNG coordinates.Height values will be discarded when working with this coordinatesystem.

• 27700: British National Grid, projected coordinate system. Thecolumns inx must be defined as Easting and Northing (sgo alsoaccepts a third column for orthometric heights). The defined datum for thisset of coordinates is OSGB 1936 (https://epsg.io/27700).

• 7405: British National Grid, projected coordinate system. Thecolumns inx must be defined as Easting, Northing and ODN Orthometricheight respectively (sgo accepts heights from other datums likeOrkney, 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. Thecolumns inx must be defined as Easting and Northing. The defineddatum for this set of coordinates is WGS84 (https://epsg.io/3857)

Value

An object of classsgo_points. This object is a actually a list withclasssgo_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 currentGeographic Coordinate System (GCS).

• datum: A string describing the geodetic datum that defines theGCS 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".

See Also

sgo_coordinates,sgo_transform.

Examples

# 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)}

Set GCS of a set of points

Description

Changes the geodetic coordinate system of a set of points using a singleHelmert transformation.

Usage

sgo_set_gcs(x, to = NULL)

Arguments

Details

Changes the geodetic coordinate system of a set of points. Note that theprecision of various datums will vary, and the original WGS-84 is not definedto be accurate to better than ±1 metre. Most transformations shouldn't beassumed to be accurate to better than a meter; between OSGB36 and WGS84somewhat less - the lost of accuracy can be up to ±5m when using singleHelmert transformations.

Input points with a projected coordinate system (e.g. 27700, 7405, 3035 or3857) are not allowed.

WarningThis function is mainly for internal use of the program. Since it relies on asingle Helmert transformation it is not recommended to call it directly. Useany other of the transformation functions available (sgo-package).

Value

An object of class 'sgo_points'.

See Also

sgo_points,sgo_transform.

Examples

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 transformationp2 <- 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 OSTN15p2 <- sgo_transform(p, to=4277)

Coordinate transformation of a set of points

Description

Transforms the coordinate system of a set of points to any supportedcoordinate system.

Usage

sgo_transform(x, to = NULL, ...)

Arguments

Details

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 transformsthe coordinate system of a set of points to any of the supported coordinatesystems.

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 aproblem for most civilian use of GPS satellites. If a high-precisiontransformation between WGS84 and ETRS89 is required then it is recommendedto 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 referencesystem optimised for use in Europe; however, for most purposes it can beconsidered equivalent to WGS84." and"For all navigation, mapping,GIS, and engineering applications within the tectonically stable parts ofEurope (including UK and Ireland), the term ETRS89 should be taken assynonymous with WGS84.".

Warning:Coordinates defined in the Geodetic Coordinate SystemEPSG:4277 (with datum OSGB 1936) should only be used to convert to or fromBNG coordinates and for historical reasons only.

Value

An object of class 'sgo_points'.

See Also

sgo_points,sgo_coordinates,sgo_set_gcs,sgo_bng_ngr

Examples

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)

WGS84 to Easting Northing (Pseudo - Mercator)

Description

Converts WGS84 coordinates to Easting/Northing (Pseudo-Mercator)

Usage

sgo_wgs84_en(x, to = 3857)

Arguments

Details

This routine also accepts source data expressed in ETRS89 coordinates(EPSG=4258 or 4937) as it is considered the difference between those two GCSis far less than the accuracy available when working with Pseudo-Mercatorcoordinates.

The results can be used in maps where Pseudo-Mercator coordinates are needed.Usually, those include Google, Bing, OpenStreetMap and several other webmapapplications.

Value

An object of classsgo_points whose coordinates are defined asEasting/Northing.

References

IOGP Publication 373-7-2 - Geomatics Guidance Note number 7,part 2 (October 2020). https://epsg.org/guidance-notes.html

See Also

sgo_points,sgo_en_wgs84.

Examples

p <- sgo_points(list(-3.9369, 56.1165), epsg=4326)res <- sgo_wgs84_en(p)