Environment variable DISPLAY should be set up properly. Refer to X11 user guide.
Then you have to activate the settings defined in ~/.Xdefaults by the command
Run a program solve_reset if you don't have solve scratch files. NB: Scratch files should also be re-created after each Solve upgrade! You should also be sure that your environment variable WORK_DIR has been set before running solve_reset: echo $WORK_DIR . Usage of solve_reset:
Solve requires hpterm window with size not less than 80x24 characters.
Solve consists of a set of programs which call each other. In order to launch interactive Solve enter a command
Solve scratch files contains information about one or more sessions. To learn the status of scratch files hit the key X from the main Solve menu. Solve reports the database name, version number, total number of observations (including no-detection), band and status.
Interactive Solve allows the user to fulfill the following operations:
NB: If you load the experiment from the superfile then you are unable to update the database. Superfiles are loaded much faster than databases; they are used for BATCH runs and for special solutions.
Option (G) in the OPTIN menu invokes program SDBH, which loads the experiment in the scratch area. Option (X) inquires about the current status of scratch area.
Then hit (K) -- get database. SDBH asks you to enter the name of the database and version number. If you omit the version number then the newest version will be taken. Then Solve will display history records. If you are not interested in reading all history records you can hit S in order to skip them. When you reach SDBH Options menu, hit G to initiate data retrieval process. If you are going to analyze the experiment for the first time you need to load two databases: X-band (first) and S-band (second). Be sure that the current status of SDBH is Will keep current data when adding new before loading the second database. Keep in mind: X-band and S-band databases should have been processed by the same version of CALC with exactly the same a priori values.
Calibrations are set separately for each database. Check that calibration setup is exactly the same for both databases! Look at the database name at the upper right corner of calibration status setup. You can switch X-band and S-band databases by hitting (N) and (P) in "Database calibration setup" and "Flyby Station-Dependent Calibrations Status" menus. Atmosphere partials are always the same for both databases.
Check "Observation Dependent Calibration Status". Hit (+) in OPTIN menu. Calibrations "Pol Tide", "WobXCont", "WobYCont", "EarthTid", "Ocean" "PTideOld", "Axis 2" should be set up.
Check once more your parameterization. Only clock polynomials of the 0,1,2 order should be setup. All other parameters should not be activated. Then run LSQ solution by hitting (Q). Look at the listing of the solution. Check once more that only clock polynomials are in the solution.
Check wrms. It should not exceed 1 microseconds. If the wrms exceeds that value it means that you have troubles, e.g. there are several very strong outliers.
Check clock offsets and rates (CL 0) and (CL 1). If there are stations with clock offsets greater by modulo than 10-4 sec -- 100 000 nsec and/or the stations with clock rate greater by modulo than 10-9 -- 100 000 D-14, you should apply an a priori clock model for that station. The number of digits in a float number presentation is not enough to handle the case when adjustments to clock parameters are too large. Rounding errors may corrupt results. To overcome this problem, an a priori clock model is added to the theoretical delays and delay rates. If you notice that clock offsets and clock rates exceed the limit for all stations, it means that the clock reference station itself has anomalous clock offset or rate. Change the clock reference station in that case. You can find preliminary values for a clock model from the correlation report if it is available.
Find all stations with anomalous clock offset and/or rate. Write down the values of clock and rate for these stations. Solve supports an a priori clock model for up to 4 stations. Go back to OPTIN menu. Then go to the last page of SETFL. Then hit (<). You will see the menu of SET_ACM program. Follow the SET_ACM manual [2]. Make one more LSQ solutions after applying a priori clock model. Clock parameters for the stations with applied clock model should be about zero.
Default GAMB setup is as follows:
Steps of manual ambiguities resolution:
Start with the first of the baselines which contains the reference station which you select from the list of baselines by moving the cursor there and click in the left mouse button. When the plot of residuals appears we may see several vertical lines with observations separated by n * the ambiguity spacing which is indicated in the second dialog window from the top (for example 50, 100 or 200 nsec, this is the so-called ambiguity spacing). Move the mouse pointer onto the dialog window field 'Shift All ambiguities', click the left mouse button and move the cursor to the vertical line of residuals which is closest to 0. Sometimes there may not even be any residuals at this ambiguity level. The vertical position of the cursor does not matter, only the horizontal. Press the left mouse button and all residuals are shifted to that ambiguity level. Click 'CNPLT baseline page' and select the next baseline containing the reference station. Repeat the ambiguity shifting for all baselines with the reference station and run the solution again. Do not bother to look at the non-independent baselines at this stage.
Hit (X) at the OPTIN menu and select the setup as follows:
Include in "Solution Generate residuals"
To start the computation of S/X ionosphere contribution, return to the main OPTIN page and invoke the program IONO by hitting ([). The program lists the databases which reside in the scratch files. We do not calibrate the S-band database. Normally everything is set up properly and you just type (P) to continue.
The next step is to inspect residuals. Set estimation of baseline-dependent clocks: hit (C) from the menu of the last SETFL page. Menu of the program BCLOK will be displayed. First set all baselines by hitting (W), then deselect a clock reference station by hitting the station code.
Make a solution by hitting (Q). Look at the listing. Normally the total wrms should be in the range [500, 1500] psec. If it exceeds 2000 psec, it means that probably either ambiguity resolution was not successful or there are clock breaks at one or more stations.
You should check estimates of baseline-dependent clocks. If the estimates exceed 1 nsec, it is an indication of remaining permanent ambiguities at that baseline, i.e there are no jumps in ambiguities among observations at all baselines but all observations at some baselines have incorrect ambiguities what causes triangle misclosures to be a multiple of the ambiguity spacing. You have to get rid of permanent ambiguities.
Set solution type X-band only or S-band only
on the last SETFL page in accordance with the band affected by permanent
ambiguities. Make a solution. Look at the list of baseline-dependent clocks.
Find the first baseline with the estimate of the baseline-dependent clocks
to be a multiple of group delay ambiguity spacing. Make plot of residuals of
that baseline by hitting (P) at the OPTIN menu. Then use the function
Set amb. shift. Set the correct sign of ambiguities: the sign should
be the same as the sign of the baseline-dependent clock adjustments if the
order of stations in the baseline both in the listing and in CNPLT is the same.
The sign is opposite if the order of stations in the listing and in CNPLT is
different. Then use the function Shift multi pts. CNPLT will ask you
to point to the Starting point and then the End point. Click
at the point in the very bottom of the plot in order to mark the "Starting
point", then click the point in the very top of the plot in order to mark the
"end point". Then you make a solution once more. Repeat this procedure if
needed with the next baseline. Don't forget to set the solution type back to
G-GXS combination after all these manipulations.
Sometime you have observations with ambiguities less than the group delay
ambiguity spacing. These are sub-ambiguities and they are caused by a wring
choice of maximum in the delay resolution function. There is no way to resolve
sub-ambiguities in Solve. You have to suppress all observations with
sub-ambiguities. It is still possible to recover at least part of such
observations by running the program mk4fit for those observations, but this
topic goes beyond this manual.
If you find a jump in the plot of residuals you may try to insert a clock
break. Be sure that it is not a jump in ambiguities at X- or S-band. In order
to insert a clock break hit (E) in the main OPTIN menu, then
list station's pages by hitting (N) or (P) till you find the
station where you are going to insert clock breaks. Then hit (*) several
times until you see a line insert. Then hit (C) and enter
the time tag of the clock break. Then a new epoch for clock polynomial appears
at the SETFL page for that station. Set the first three flags to 1 for the new
clock break. Then make a new solution and check the listing and residual plots.
Keep in mind that there should be enough observations between the start of
the session, clock break(s) and the end of the session. There should be no less
than 4 observations, otherwise your solution will be unstable or singular.
If it seems to you that the session has many clock breaks, it may indicate
another serious problems unrelated to clock behavior.
If you have a station with too few good observations (less than 5 at each
baseline), or you have a station with postfit residual scatter larger than
5 nsec you can deselect it. But it is a last resort. In general you should try
to keep as many stations/baselines as possible in the initial and intermediary
solutions, and to leave the final decision to the time of the final solution.
An analyst is able to select/deselect station/baseline in any time during
further solutions including batch runs, however the data should be edited
properly, otherwise selecting the baselines which have been suppressed during
the initial solution might degrade the solution due to the presence of
outliers.
Settings for intermediary solution:
Now the time came to start outlier elimination/restoration. Go to the main
OPTIN page and then hit (\). You will see the menu of program ELIM/MILE
for outliers elimination/restoration. There is extensive user documentation
about ELIM/MILE:
Set the first line to elimination by hitting (T).
Eventually hit (P) for going ahead. ELIM will suppress outliers.
In order to quit ELIM with saving results hit (S).
Check your solution.
If you have a poor or bad solution you have to find the reason. First, check
a) calibration; b) parameterization; c) clock breaks. Then examine the
residuals. Check clock breaks and the resolution of group delay ambiguities.
If you are sure that there is a malicious station which spoils the entire
experiment you may try to deselect this station.
If you find that your intermediary solution is good, or at least you find the
reason why it is poor, you can move to the final solution.
Then update weights upon ELIM completion. Hit (W) on the
ELIM menu. You will see UPWEI menu. Set floor to 10.0 psec by hitting
(L) and then hit (I). Then go back ELIM by hitting
(O) in UPWEI menu and execute outliers elimination once more.
If you notice that chi/ndg went noticeably away from 1.0 (e.g. below
0.95), update weights once more.
Look at the Clock Constraint Statistics at the
bottom part of the listing. Look at the station which produces
minimal RMS. If this station is not a station a) with clock
break orb) which observed less than 75% of total time, you
can take it is a new clock reference station. NB: if
you changed the clock reference station you have to reset
flags for estimation of baseline dependent clocks anew. Make
a new solution and look at the results. If NRMS becomes smaller
for many stations you made a better choice. You may repeat
this procedure several times. In general the choice of clock
reference station influences results only marginally except
the case when the station with anomalous clock behavior was
taken as a clock reference station.
Look at the Clock Constraint Statistics at the
bottom part of the listing. If NRMS has the share more than
1.30 for some station(s), it is necessary to investigate
the reason.
Look at the plot of segmented parameters. Call program MDLPL
by hitting (/) on the main OPTIN menu. Information
about usage of MDLPL you can find in the
manual of MDLPL_PLUS [8].
Look at the estimates of clock function modeled by linear
spline. Clock function describes behavior of the H-maser and
instrumental noise. If you see a smooth curve with
a quasi-diurnal or a quasi-semidiurnal period you should not
worry. A noisy, saw-like curve is an indication of strong
instrumental errors.
You can raise the value of sigma of the constraints imposed
on the clock of an individual station (to make constraint
less strong): go to the last page of the SETFL menu, then
hit (") key. Key (*) toggles modes: site
dependent constraints versus session dependent constraints
(common for all stations). Set site dependent
constraints, position the cursor on the value of the
constraint for the station of interest, then hit the space bar.
SETFL will ask you to enter the value.
If you have a smooth curve of clock function you can set
a sigma of constraint which results in NRMS of the clock
function with share of about 1.00 (constraint sigma is about
the same as the RMS of clock the function). If you have
a saw-teeth-like, noisy clock function, then a stiffer
constraint (less sigma of constraint) should be imposed:
a constraint which results in the NRMS of clock function with
share in the range [1.5, 2.0].
As a rule of thumb baseline-dependent clocks should remain
only for the baselines which produce adjustments exceeding
3 formal uncertainties. Significant baseline-dependent
clocks may occur when some channels at station(s) were dropped
in final fringing. Estimates of baseline-dependent clocks
which exceed 1 nsec indicate incorrectly resolved group
delay ambiguities or sub-ambiguities. Reset the flags of
estimation of baseline-dependent clocks by invoking BCLOK
from the last page of the SETFL menu by hitting (C).
Invoke ELIM by hitting (\) from the main OPTIN menu.
Hit (W) in the ELIM menu in order to invoke UPWEI.
Then hit (D) (Display current weights). A list of
UPWEI statistics will be displayed on your screen. You can
navigate this list by using (Cursor_Up),
(Cursor_Down), (Page_Up) and (Page_Down)
keys. Hitting (Q) allows you to leave the mode of
displaying statistics and return to the UPWEI menu.
Examine chi-sq/ndg column in the source section. Chi-sq/ndg
is the ratio of the sum of the squares of the weighted
residuals over the used observations of the specific source
to its mathematical expectation. Values of chi-sq/ndg which are
significantly greater than 1.0 indicates problems related
to this source: wrong a priori position of the source,
significant contribution of source structure, pointing errors
and so on. These sources are good candidates for coordinate
adjustments. Chi-sq/ndg statistics is not representative if
the source had less than 3-5 good observations and we should
not try to adjust positions of such sources unless we have
another evidence that a priori coordinates of this source were
poor or the source has a noticeable apparent proper motion.
We should try to estimate positions of the sources with
chi-sq/ndg > 1.5 under condition that the number of
observations is higher than 5.
Write down the names of the sources with large chi/ndg. Leave
UPWEI display statistic mode by hitting (Q),
then leave UPWEI by hitting (O) and hit (O)
once more to leave ELIM.
Then hit (S) in the main OPTIN menu and you will see
an another SETFL menu for setting source coordinates
estimation flags. List the menu by hitting keys (B)
and (P), find the sources with positions which you
decided to adjust. Set to 1 in the field Right
ascension and 1 in the field declination, e.g.
Run a solution. Look at the bottom of the listing. Leave
estimation flag set for the sources with estimates greater
than 3 sigmas in declination or in right ascension. If you
have sources which produced adjustments which are less than
2.5-3.0 sigmas -- unset the flag for coordinate estimation for
those sources.
Call MDLPL program by hitting (/) from the main
OPTIN menu. Then hit (R) in the main MDLPL_PLUS menu.
Examine the plot residuals + clock function. If you
don't see a break in the plot of residuals where you have
inserted clocks breaks and you find in the listing that
adjustments to clock breaks are insignificant, remove clock
break(s). On contrary, if you see a noticeable jump in the
plot of a postfit residuals + clock function you
should try to insert a new clock break at the epoch of the
jump.
Update weights after ELIM completion. Hit (W) at the ELIM
menu. You will see UPWEI menu. Set floor to 10.0 psec by hitting
(L) and then hit (I). Then go back to ELIM by hitting
(O).
Now hit (T) to set restoration mode. Set cutoff the limit of
outlier detection to 4.0 sigma (or 3.5 sigma if the session has more than
5000 observations) and then proceed with restoration of the observations
which were previously suppressed by hitting the key (P).
Then set elimination mode, set the cutoff limit to 3 sigma and
eliminate outliers once more. After outliers elimination update weights
and proceed with outliers elimination once more.
Set user partial program CABLE_PART: hit (<) on the main
OPTIN menu and then enter the name of the program: CABLE_PART. Run
a solution. Cable cal admittance will be computed for all stations in
this mode. Admittance about 1.0 means that the cable cal is OK,
admittance -1.0 means that the cable cal is OK but its sign is wrong.
Values around zero indicates that cable cal is probably wrong. If you
find that estimation of cable cal admittance improves fit by more than
2-3% (wrms is less, chi/ndg becomes less) you can decide to set the flag
"not calibrate for cable cal" for some stations permanently. However
as a rule of thumb you should leave cable calibration unless you have
clear evidence that cable calibration at certain stations degrades fit.
Don't forget to deactivate CABLE_PART program and to set the flag
cable cal for all stations except the ones which it degrades
fit. In order to deactivate user partial program CABLE_PART hit
(<) from the main OPTIN menu again and them hit Return
key in reply on Enter name of user partial program
(Return if none):.
Proceed to the next menu. Hit (D) unless you didn't resolve phase
delay ambiguities:
If you resolved phase delay ambiguities then you need to hit (B),
then hit (6) and then (7) in order to set Reweighting to
Both and to set all other items to Yes.
Then proceed to the next menu and hit the space bar. An editor will be
invoked and it asks you to edit the file with name /tmp/HIST{Solve_initials}.
You can write your comments about this experiment in the history file.
NB: lines should not exceed 78 characters. When you finish editing,
leave the editor and proceed. The contents of the file
/tmp/HIST{Solve_initials} will be added to the history list of the next version
of the databases.
NB: The Catalogue system prohibits you from making two database
updates of the same experiment repeatedly. It is assumed that you load the new
experiment after database update. If you decided to continue to analyze the
same database and you would like to save your settings after you have done
the database update it is till possible. Use program CATLG in order to remove
the last database version. (But check that the version number of the database
which you are deleting is larger than the database version which is loaded
in Solve!)
Last update: 01-MAY-2000 12:23:00
Manual re-distribution of permanent group delay ambiguities
First you have to decide which band is affected by permanent ambiguities.
If baseline-dependent clocks has an adjustment by a multiple of the group delay
ambiguity spacing at X-band -- then X-band. A permanent ambiguity at S-band
will contribute by fX/fS = 12 times less.
Thus, if you see baseline-dependent clock estimates less than one group delay
ambiguity spacing but still larger than 1 nsec, it is an indication that
there are S-band permanent ambiguities.
Inspection of residuals
Now you have to inspect residuals baseline by baseline. The purpose is
to check quality of data, check whether the ambiguities were resolved correctly
and check whether clock breaks have to be inserted. Call program CNPLT
by hitting (P) from the OPTIN menu. (NB: CNPLT conflicts with
some X-applications which grabs colors, like Netscape. You should close such
applications before running CNPLT.)
Intermediary solution
Intermediary solution is carried out upon completion of the initial solution
when the experiment is analyzed the first time. The purpose of the intermediary
solution is to remove strong outliers at the earlier steps. The intermediary
solution has incomplete parameterization. Such a parameterization facilitates
suppression of outliers or observations which look like as outliers.
Now make a solution by hitting (Q). Look at the listing. Check
parameterization: you should estimate a) station positions (except the
reference station), b) clocks; c) atmosphere path delay; d) baseline-dependent
clocks and nothing more.
Set the following menu items for outliers elimination in the intermediary
solution:
(Q) Quality code limit: 5 (D) Update residuals
(-) Singularity check (') Change suppression method
(V) Verbosity level: 1 (N) Confirm each action: no
Final solution
Final solution is carried out either during the first analysis of the
experiment or during re-analysis of the data. It is assumed that initial and
intermediary solutions have already been made. The final solution may be done
for different purposes. One of the objectives is to obtain a so-called quick
solution. The purpose of a quick solution:
min_obs for one source: 2
min_obs for one station: 5
min_obs for one baseline: 4
Database update
Some parameters related to the solution, such as group and phase delay
ambiguities, suppression status, clock and atmosphere parameterization,
baseline-dependent clock status, reweighting parameters can be saved in the
database. Database update is the last step of analysis. As a result a new
version of the database will be created. Hit (U) in the main OPTIN menu
in order to invoke program NEWDB for updating the database. The program NEWDB
will ask you which database you are going to update. As a rule of thumb you
don't need to the update S-band database. GAMB and IONO add 21 items (lcodes)
used in analysis from the S-band related database to the X-band related
database.
NB: If the database update completed abnormally (e.g, lack of disk
space) you should remove the entry of the new database version by using CATLG.
(But check that the version number of the database which you are
deleting is larger than the database version which is loaded in Solve!)
References
Some user documentation related to Solve.
This document was prepared by
Leonid Petrov