New Mexico Tech
Earth and Environmental Science

ERTH 455 / GEOP 555 - Geodetic Methods

Lab 4: gd2p.pl: static position estimation

"I like my crust deformed."
UNAVCO bumper sticker

Note that you DO have to work on redoubt today!

Introduction

Last week you went through the exercise of determining a position from pseudoranges; basically by hand. Today we will start using GIPSY/OASIS (GPS Inferred Positioning SYstem and Orbit Analysis SImulation Software) for precise positioning. GIPSY is a collection of many programs and scripts to analyze GPS data (and other data).

Note that today focuses on setting you up for processing of GPS data. The processing will remain quite arbitrary and next week we'll move toward improving on this!


source: NASA/JPL

It is possible to string the programs together in a way that highly customizes your processing. Obviously, that requires intimate familiarity with the tools so that you know exactly what you're doing. gd2p.pl (GNSS data 2 Position) is a higher level interface to GIPSY that allows you to process data for a single GPS/GLONASS receiver. It implements the typical GIPSY workflow for kinematic and static positioning.

The command

		$> gd2p.pl -h | more
	
gives you full help and examples for this interface to GIPSY.
		$> gd2p.pl -h_sub 
	
Gives a list of subtopics.
		$> gd2p.pl -h_examples 
	
Gives a list of examples for different processing strategies.

In this lab, we can only cover some basics, I highly recommend that you take some time and explore this tool!

Setting things up: sta_info database and data files

Gipsy comes with a database, called sta_info that is composed of several ASCII files; some we need to add information to be able to estimate positions for new stations. In my lab I keep 1 master copy of this database that contains the information for all the stations that we process. Here, however, you will start out by creating your own copy.

These files are fixed format files! They have to match the format description EXACTLY! Character by character, don't use tabs, no shortcuts or everything goes down the drain. I've warned you!

From the documentation:

sta_id 

This file is the interface between the station identifiers in the
database and the outside world.  In this file, a given station name is
associated with a station identifier and a station number.  A given
station identifier and station number can be associated with more than
one station name.  This is allowed so that multiple names for the same
station can be handled.  The station number is currently not used, but
may be implemented in the future when all stations receive official GPS
numbers.  The following are examples of a few records:

 PENT   801 The following aliases for PENT were inserted on 9-May-1992 by fhw
 PENT   801 PENTICTON  
 PENT   801 Penticton  
 PENT   801 Penticton 1977 
 PENT   801 PGCQ   
 PENT   801 A station somewhere in Canada
 GOLD  1437 DSS10
 GOLD  1437 SPC10
 GOLD  1437 Goldstone Rogue Antenna
 SDAD   202 USC&GS HORIZNOTAL CONTROL MARK SOLEDAD PEAK 1932 RM1
 JPLM  7272 JPLMESA

where PENT, GOLD, and SDAD are all station identifiers, 801, 1437, and
202 are the station numbers and the character strings are station names.
These station names are the known aliases for this particular station
and are case sensitive.  The record format is:

(1x,a4,i6,1x,a60) 

sta_pos

This file associates the station identifier with the station coordinates
at some epoch and the station velocity.  An example of a record is:

 JPLM 1992 07 01 00:00:00.00 1000001.00   -2493304.0630  -4655215.5490   3565497.3390 -3.20000000e-02 1.90000000e-02 6.00000000e-03 Mon Nov  9 15:07:31 PST 1992 itrf91 1992.5

(The record is stored on one line.)  The fields are:  The station
identifier; the epoch of the station coordinates (year, month, day,
hours, minutes and seconds); the duration of the station coordinates
(days); the station coordinates at the epoch (meters); the station
velocities (meters/year); and a comment.  The comment field could
contain the reference system of the coordinates.  The record format is:

(1x,a4,1x,i4,4(1x,i2)1x,f5.2,1x,f10.2,1x,3f15.4,1x,3e15.8,1x,a30)


sta_svec

This file associates the station identifier with the site vector and
antenna type at some epoch.  An example of a record is:

 JPLM JPLM 1992 06 00 00:00:00.00  31536000.00 ROGUE          0.0000     0.0000    0.0000     0.1630 l 1992 07 06


(The record is stored on one line.)  The fields are:  the "to" station
identifier; the "from" station identifier, the epoch of the site vector
(year, month, day, hours, minutes and seconds); the duration (seconds),
that the site vector is valid from the epoch; the antenna type,
corresponding to one of the antenna types in the pcenter file; the
station site vector; the antenna height; the site vector coordinate
system flag, where c indicates Cartesian coordinates (XYZ) and l
indicates local east-north-up coordinates (ENU); the date that the site
vector was issued; and a comment.  The record format is:


(1x,a4,1x,a4,1x,i4,4(1x,i2)1x,f5.2,1x,f12.2,1x,a9,1x,4f11.4,1x,a1,1x,i4,1x,i2,1x,i2)

(In this particular example, the "to" and "from" station identifiers are
the same.  This indicates that the site vector and antenna height in
this record are for the offset between the JPLM antenna and the JPLM
monument.)
	

Now for the data.

Task 1: Update sta_info

Your first task is to add ABBZ to the database.

sta_id

sta_pos

sta_svec

rg <at> nmt <dot> edu | Last modified: September 13 2017 19:50.