Re: [R] code to convert 3D geographical coordinates to Cartesian?

2012-12-31 Thread Tom Roche 

summary: I'm looking for packaged, tested code to convert geographical
coordinates (e.g., longitude, latitude, elevation) to Cartesian
coordinates (x,y,z) in 3-space. I know of R code for 2-space and for
spherical <-> Cartesian. This can be extended (I attach a quick kludge
extending pracma::sph2cart), but a proper extension is non-trivial.

details:

https://stat.ethz.ch/pipermail/r-help/2012-December/332658.html
 Is there packaged code to convert geographical coordinates (e.g.,
 longitude, latitude, elevation) to Cartesian coordinates in 
 3-space? [Since] there's certainly scope for error, [I'd] prefer
 to use tested, well-used code if available.

https://stat.ethz.ch/pipermail/r-help/2012-December/332666.html
>>> Have you checked the spatial stats task view on CRAN?

https://stat.ethz.ch/pipermail/r-help/2012-December/332667.html
>> I have, and can't believe that functionality this fundamental is not
>> API. But I have looked at several packages and am not seeing it.

https://stat.ethz.ch/pipermail/r-help/2012-December/332671.html
(rearranged)
> How did you search?

> install.packages("sos")
> require(sos)
>  > findFn("latitude longitude cartesian")

Thanks! I didn't know about that search mechanism. I was googling via
rseek.org and reading .pdf for packages that looked useful.
Unfortunately

> sphereplot::sph2car "Transforms 3D spherical coordinates to cartesian
> coordinates"

Note this does spherical <-> Cartesian, not geographical <-> Cartesian.
That can be extended (see a quick hack following my .sig to end of post,
extending Borchers' implementation), but the extension is {non-trivial,
error-prone}. Hence my hope to find code that is much better
tested/known/used.

> GEOmap::Lll2xyz "List Lat-Lon to cartesian XYZ"

GEOmap::Lll2xyz (and all the functions I saw in GEOmap) are 2D-input:
they take arguments=(lat, lon), not (lat, lon, elev). Again, this could
be extended; but, again, the same caveats apply.

> You have a very different notion of what would be considered core  
> capabilities in a statistics program than I have.

Geospatial information comes in a wide variety of formats. Doing
*geospatial* statistics with *real-world data* requires the ability to
transform those various formats. I consider geospatiality to be a core
competency for R, and geographical <-> Cartesian transforms to be
fundamental to that: YMMV.

thanks again, Tom Roche 
--sample hack follows to end of post--

# Convert geographic coordinates (lon, lat, elevation) to
# Cartesian coordinates (x, y, z) relative to earth center.
geo2cart <- function(lon.lat.elev) {
  stopifnot(is.numeric(lon.lat.elev))
  library(pracma) # for sph2cart
  return(sph2cart(geo2sph(lat.lon.elev)))
} # end function geo2cart(lon.lat.elev)

# Convert geographic coordinates (lon, lat, elevation) to
# spherical coordinates (azimuth/Θ, polar angle/φ, radial distance/r),
# relative to earth center
geo2sph <- function(lon.lat.elev) {
  stopifnot(is.numeric(lon.lat.elev))

  # Use convention of package=pracma: see 
http://cran.r-project.org/web/packages/pracma/
  # same as described @ http://en.wikipedia.org/wiki/File:3D_Spherical_2.svg
  # to convert
  # * longitude -> azimuth (Θ)
  # * latitude -> polar angle (φ)
  # * elevation -> radial distance from earth center (r)
  if (is.vector(lon.lat.elev) && length(lon.lat.elev) == 3) {
theta <- lon2azi(lon.lat.elev[1])
phi <- lat2pol(lon.lat.elev[2])
r <- elev2rdist(lon.lat.elev[3])
m <- 1
  } else if (is.matrix(lon.lat.elev) && ncol(lon.lat.elev) == 3) {
theta <- lon2azi(lon.lat.elev[,1])
phi <- lat2pol(lon.lat.elev[,2])
r <- elev2rdist(lon.lat.elev[,3])
m <- nrow(lon.lat.elev)
  } else {
stop('geo2sph: ERROR: input must be a vector of length 3 or a matrix with 3 
columns.')
  }

  if (m == 1) {
tpr <- c(theta, phi, r)
  } else {
tpr <- cbind(theta, phi, r)
  }
  return(tpr)
} # end function geo2sph(lon.lat.elev)

# Filter and convert longitudes to radians.
# Much-too-simple tests:
# > lon2azi(c(seq(0, 180), seq(-179, -1)))/pi
# > lon2azi(c(0:359))
lon2azi <- function(lon) {
  library(pracma) # for deg2rad

  stopifnot(is.numeric(lon))
  # only handle vectors
  if (!is.vector(lon)) {
lon.vec <- c(lon) 
  } else {
lon.vec <- lon
  }

  # only take -180 <= lon.vec <= 180
  # TODO: better error messages
  stopifnot(length(lon.vec[lon.vec < -180]) == 0)
  stopifnot(length(lon.vec[lon.vec > 180]) == 0)

  # Convert to azimuth=Θ in radians.
  # Convert to 0 <= lon.vec <= 360 (hmm ...) e.g., -179 -> 181.
  lon.vec[lon.vec < 0] <- 360.0 + lon.vec[lon.vec < 0]
  theta.vec <- deg2rad(lon.vec)

  if (!is.vector(lon)) {
return(theta.vec[1])
  } else {
return(theta.vec)
  }
} # end function lon2azi(lon)

# Filter and convert latitudes to radians.
# Much-too-simple tests:
# > lat2pol(c(seq(90, 0), seq(-1, -90)))/pi
# > lat2pol(c(-100:100))
lat2pol <- function(lat) {
  library(pracma) # for deg2rad

  stopifnot(is.num

Re: [R] code to convert 3D geographical coordinates to Cartesian?

2012-12-31 Thread David Winsemius 


On Dec 30, 2012, at 8:14 PM, Tom Roche wrote:



https://stat.ethz.ch/pipermail/r-help/2012-December/332658.html

Is there packaged code to convert geographical coordinates (e.g.,
longitude, latitude, elevation) to Cartesian coordinates in 3-space?

...

Net: the task seems straightforward enough, but there's certainly
scope for error, so I'd prefer to use tested, well-used code if
available.


https://stat.ethz.ch/pipermail/r-help/2012-December/332666.html

Have you checked the spatial stats task view on CRAN?



http://cran.r-project.org/web/views/Spatial.html


I have, and can't believe that functionality this fundamental is not
API.


You have a very different notion of what would be considered core  
capabilities in a statistics program than I have.



But I have looked at several packages and am not seeing it. I
suspect that either it's so low-level that it's just not exposed as  
API,

or just that there is API but I'm not seeing it in the package docs
("hidden in plain sight"). Hence I ask


Am I missing something?


How did you search?

install.packages("sos")
require(sos)
> findFn("latitude longitude cartesian")

Two different packages with functions that sound as though they might  
be useful.


sphereplot::sph2car  "Transforms 3D spherical coordinates to cartesian  
coordinates"


GEOmap::Lll2xyz "List Lat-Lon to cartesian XYZ"


--
David.

David Winsemius, MD
Alameda, CA, USA

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Re: [R] code to convert 3D geographical coordinates to Cartesian?

2012-12-30 Thread Tom Roche 

https://stat.ethz.ch/pipermail/r-help/2012-December/332658.html
>> Is there packaged code to convert geographical coordinates (e.g.,
>> longitude, latitude, elevation) to Cartesian coordinates in 3-space?
...
>> Net: the task seems straightforward enough, but there's certainly
>> scope for error, so I'd prefer to use tested, well-used code if
>> available.

https://stat.ethz.ch/pipermail/r-help/2012-December/332666.html
> Have you checked the spatial stats task view on CRAN?

> http://cran.r-project.org/web/views/Spatial.html

I have, and can't believe that functionality this fundamental is not
API. But I have looked at several packages and am not seeing it. I
suspect that either it's so low-level that it's just not exposed as API,
or just that there is API but I'm not seeing it in the package docs
("hidden in plain sight"). Hence I ask

>> Am I missing something?

TIA, Tom Roche 

__
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Re: [R] code to convert 3D geographical coordinates to Cartesian?

2012-12-30 Thread Bert Gunter 
Have you checked the spatial stats task view on CRAN?

http://cran.r-project.org/web/views/Spatial.html

-- Bert

On Sun, Dec 30, 2012 at 6:49 PM, Tom Roche  wrote:

>
> Is there packaged code to convert geographical coordinates (e.g.,
> longitude, latitude, elevation) to Cartesian coordinates in 3-space?
> I can see how to do this using
>
> 1. a spherical-to-Cartesian conversion like pracma::sph2cart(tpr)
>
> http://cran.r-project.org/web/packages/pracma/
>
> 2. a geographical-to-spherical conversion. This seems to involve (in
>roughly increasing order of difficulty or error-prone-ness)
>
> * converting longitude (units=°) to an azimuthal angle (units=rad)
>
> * converting latitude (units=°) to a polar angle (aka inclination)
>   (units=rad)
>
> * converting elevation (usually, distance above mean sea level) to
>   radial distance (i.e., distance from earth center). Ideally this
>   should be done using a user-chosen coordinate reference system and
>   ellipsoid/geoid (i.e., PROJ.4-style), hence my hope that some package
>   (of which I'm currently unaware) has already coded this The Right Way.
>   For now, for the atmospheric model with which I need to work, I
>   believe I can just assume a spherical earth with r=6370 km, and just
>   add that to the elevation.
>
> 3. composition of the two (e.g., sph2cart(geo2sph(lat.lon.elev))),
>noting that package=pracma uses the mathematics convention that
>azimuth=Θ and polar angle=φ (vs the reverse physics convention).
>
> Net: the task seems straightforward enough, but there's certainly scope
> for error, so I'd prefer to use tested, well-used code if available.
> Am I missing something?
>
> TIA, Tom Roche 
>
> __
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>



-- 

Bert Gunter
Genentech Nonclinical Biostatistics

Internal Contact Info:
Phone: 467-7374
Website:
http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm

[[alternative HTML version deleted]]

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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

[R] code to convert 3D geographical coordinates to Cartesian?

2012-12-30 Thread Tom Roche 

Is there packaged code to convert geographical coordinates (e.g.,
longitude, latitude, elevation) to Cartesian coordinates in 3-space?
I can see how to do this using

1. a spherical-to-Cartesian conversion like pracma::sph2cart(tpr) 

http://cran.r-project.org/web/packages/pracma/

2. a geographical-to-spherical conversion. This seems to involve (in
   roughly increasing order of difficulty or error-prone-ness)

* converting longitude (units=°) to an azimuthal angle (units=rad)

* converting latitude (units=°) to a polar angle (aka inclination)
  (units=rad)

* converting elevation (usually, distance above mean sea level) to
  radial distance (i.e., distance from earth center). Ideally this
  should be done using a user-chosen coordinate reference system and
  ellipsoid/geoid (i.e., PROJ.4-style), hence my hope that some package
  (of which I'm currently unaware) has already coded this The Right Way.
  For now, for the atmospheric model with which I need to work, I
  believe I can just assume a spherical earth with r=6370 km, and just
  add that to the elevation.

3. composition of the two (e.g., sph2cart(geo2sph(lat.lon.elev))),
   noting that package=pracma uses the mathematics convention that
   azimuth=Θ and polar angle=φ (vs the reverse physics convention).

Net: the task seems straightforward enough, but there's certainly scope
for error, so I'd prefer to use tested, well-used code if available.
Am I missing something?

TIA, Tom Roche 

__
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.