by Peter Bird, 2002.08.04
A (.gps) geodesy file gives only horizontal-plane velocity components
and error ellipses for each benchmark.
Such files may be displayed in maps created by FiniteMap
or NeoKineMap, and can serve as
essential input to NeoKinema,
and are also used by OrbScore2
in the step of comparing Shells
dynamic finite element model predictions to reality.
If the complete covariance matrix for horizontal velocity components is
available, it is placed in a second associated (.gp2) file.
However, this file is not currently used by OrbScore2 (although it can
be used by NeoKinema).
The .gps format is very like the format of v_nnr.dat by Corne Kreemer but it adds header lines (and optional station names on the right).
Each .gps file will have 3 lines of headers:
File name and source(s)
Fortran FORMAT, in ( ), for reading the data lines that follow the headers
E_lon_deg N_lat_deg v_E_mmpa v_N_mmpa v_E_sigma v_N_sigma correlation frame identifier(s)
with the (obvious) meanings:
E_lon_deg = longitude, in degrees from Greenwich meridian, with East positive
N_lat_deg = latitude, in degrees from equator, with North positive
v_E_mmpa = velocity component to East, in millimeters per year
v_N_mmpa = velocity component to North, in millimeters per year
v_E_sigma = standard deviation (1-sigma) of v_E_mmpa, also in mm/a
v_N_sigma = standard deviation (1-sigma) of v_N_mmpa, also in mm/a
correlation = coefficient of correlation between v_E_mmpa and v_N_mmpa
reference_frame = reference frame for velocity, left-justified, limited to 15 bytes
identifier(s) = optional station name and/or source reference, if a compilation
Thus, the first few lines of v_nnr.dat, converted to .gps format, become:
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Note that this standard allows the significant digits and column widths to
be changed; just make corresponding changes in the Fortran FORMAT of line 2,
and in the abbreviated headers of line 3.
(However, unless there are radical improvements in accuracy, there does not
seem to be any good reason to change.)