RHTDP

RHTDP provides R bindings to the NGS Horizontal Time-Dependent Positioning utility, v3.2.5, written by Richard Snay, Chris Pearson, and Jarir Saleh of NGS. HTDP allows users to transform positional coordinates across time and between spatial reference frames.

RHTDP is a work-in-progress; currently only crustal displacement and velocity calculations are implemented. Transformations between reference frames are planned, as well as integration with the sp package.

Installation

# Development version from GitHub:
# install.packages("devtools")
devtools::install_github("jbuonagurio/RHTDP")

Usage

Following exercises 1 and 2 in the HTDP User's Guide, the following example estimates the displacement that occurred at point 'beta' during the Loma Prieta earthquake (M=7.1) of October 18, 1989. The NAD_83(2011/CORS96/2007) reference frame is used (iopt=1).

beta <- matrix(data=c(-121.7722, 36.6698), nrow=1)
t0 <- as.Date("1989-10-16")
t1 <- as.Date("1989-10-18")
displace(beta, t0, t1, 1)

R output:

            de         dn           du        ve       vn        vu
1 -0.001449719 0.07401263 -0.004262457 -25.82612 37.15177 -1.329391

HTDP displacement:

 HTDP (VERSION v3.2.5    ) OUTPUT

 DISPLACEMENTS IN METERS RELATIVE TO NAD_83(2011/CORS96/2007)
 FROM 10-16-1989 TO 10-18-1989 (month-day-year)
 FROM 1989.789 TO 1989.795 (decimal years)

NAME OF SITE             LATITUDE          LONGITUDE            NORTH    EAST    UP 
beta                     36 40 11.28000 N  121 46 19.92000 W    0.074  -0.001  -0.004

HTDP velocity:

 HTDP (VERSION v3.2.5    ) OUTPUT

VELOCITIES IN MM/YR RELATIVE TO NAD_83(2011/CORS96/2007)


          beta                    
LATITUDE   =  36 40 11.28000 N  NORTH VELOCITY =  37.15 mm/yr
LONGITUDE  = 121 46 19.92000 W  EAST VELOCITY  = -25.83 mm/yr
ELLIPS. HT. =      0.000 m      UP VELOCITY    =  -1.33 mm/yr
X = -2696934.816 m              X VELOCITY     =  -9.71 mm/yr
Y = -4354426.684 m              Y VELOCITY     =  33.37 mm/yr
Z =  3788064.740 m              Z VELOCITY     =  29.01 mm/yr

Supported values for iopt are below; see the User's Guide for more information. Alternatively, use the iopt() function to list these within R. Note that option 4 (WGS_72) has been removed.

Key	Reference Frame
1	NAD_83(2011/CORS96/2007) (North American plate fixed)
2	NAD_83(PA11/PACP00) (Pacific plate fixed)
3	NAD_83(MA11/MARP00) (Mariana plate fixed)
5	WGS_84(transit) (NAD_83(2011) used)
6	WGS_84(G730) (ITRF91 used)
7	WGS_84(G873) (ITRF94 used)
8	WGS_84(G1150) (ITRF2000 used)
9	WGS_84(G1674) (ITRF2008 used)
10	WGS_84(G1762) (IGb08 used)
11	SIO/MIT_92 (ITRF91 used)
12	ITRF88
13	ITRF89
14	ITRF90 or (PNEOS90/NEOS90)
15	ITRF91
16	ITRF92
17	ITRF93
18	ITRF94
19	ITRF96
20	ITRF97 or IGS97
21	ITRF2000 or IGS00/IGb00
22	ITRF2005 or IGS05
23	ITRF2008 or IGS08/IGb08

Warning

HTDP exclusively uses 14-parameter transformations between reference frames. If you require rigorous transformations between various realizations of NAD83, use NADCON/GEOCON/GEOCON11.

Chuck Ghilani of Penn State has an excellent presentation covering the recommended transformation process between different epochs and datums.