Fellow Surveyors,
Been stuck on this one for a little while now.
I recently converted two .t02 files (each being 1 hour in duration) into RINEX files using a "Convert to RINEX" utility.
Issue now is that I need to merge these two RINEX files into 1 (2 hour observation duration) file. I need to do this as the photogrammetry software (PIX4D) will only let me upload 1 RINEX file to post-process my flights.
I have tried opening them in notepad, and pasting the data manually such that it is one file (not including the header), however this does not work.
Any suggestions!!??
Thanks in advance!
Quentin
Replies
If there is no time gap between the two (or more) RINEX files, you can merge them manually, but there are useful tools to do it.
If you do it manually, you need to take care to the header, and you have to edit manually the "Time of last observation"
Easier way to download GPS Toolkit: http://www.gpstk.org/bin/view/Documentation/WebHome
Use MergeRinObs.exe utility for observation files and MergeRinNav utility for Navigation files (if you have Meteo files, than use MergeRinMet).
These utilities are running from CommandLine window, but easy to use (eg. MergerinObs.exe -i Rinex1.RNX Rinex2.rnx Rinex3.rnx -o Rinex_all.rnx)
Unfortunately the utility is not modifying the Time of last observation row, you have to do it manually - just take a look at the last RINEX file, and copy the row about this variable, and overwrite the adequate row in the merged file.
If you are using your own software, you have to merge the NAV files also. If you are using a 3rd party service for post processing, such as AusPos, Trimble CenterPoint RTX, or OPUS (from NGS), you don't need to merge the Navigation files, they have their own NAV file.
Unfortunately I didn't find any utility for merging Glonass Nav data, I do it manually.
Try to use teqc sw from unavco with "-phc" option. Unfortunately it doesn't have GUI, so I use it with FAR manager.
And one moment, is there any time between two files? If not all will be ok.
Have you seen this resource?
Operation
The program operates in the DOS window. Alternatively, you can simply run "gmerge.exe" with a double click or with "Run..." in your "Start" menu. (I use the DOS window myself.)
Four files are needed for input. One file is generated as output. The names are fixed. The files must be in the subdirectory where you are working.
Input Files:
point1.rnx -- ASCII, RINEX format. This point is treated as a base station by my some of my programs.
point2.rnx -- ASCII, RINEX format. This point is treated as a rover or unknown station by my some of my programs.
pos -- ASCII, special format, described below. This file holds reference coordinates for known stations. For example, one could put coordinates for local CORS stations in this file. If gmerge.exe doesn't find a 4 character ID in the pos file, it will use the coordinate in the RINEX header, instead. But, while gmerge.exe is not picky, it is mandatory to have a pos file.
ant -- ASCII, NGS format, described below. This file holds antenna phase center (ARP/L1/L2) relations and phase center variations with vertical angle. This file is an exact copy of ant_info.003, maintained by the National Geodetic Survey. If gmerge.exe doesn't find an antenna ID in the ant file, it will assume that the L1 (and L2) phase centers are coincident with the Antenna Reference Point (ARP) and that there is no phase center variation with vertical angle. As before, gmerge.exe is not picky, but it is mandatory to have an ant file.
Output File:
gmerge.out -- ASCII, "gmerge" format. This is merged pseudorange and carrier phase, at a common interval and data rate. The header is generated with the best available information on coordinates and antenna properties.
Discussion:
The program is pretty straightforward. It reformats data from two different RINEX inputs. The WGS84 ellipsoid is used; but it can be considered the same as the GRS80 ellipsoid at the sub-millimeter level. Nothing is done about reference frame origins. The ITRF frames are not the same as the NAD 83 frame (to the tune of a couple of meters). So, don't mix and match ITRF and NAD 83 in your "pos" file unless you know what you are doing.
A note on operation: gmerge will preferentially output the P(Y) pseudorange over a C/A pseudorange on L1.
I am in a gradual (very gradual) process of converting my software to work with the gmerge format, instead of directly with RINEX files.
THIS looks like a tool which you might find helpful called MergeRin (haven't tested it..)
also attached is some documentation you might find helpful until someone else comes along with more experience with it.. good luck!