# Presentation: 577205

## OPUS:Online Positioning User Service 

**OPUS****:****Online Positioning User Service **

- http://www.ngs.noaa.gov/OPUS/
- ngs.opus@noaa.gov

## 				WHAT IS OPUS?

**O**n-line **P**ositioning                                                     **U**ser **S**ervice

- Fast & easy access     to the NSRS (**National Spatial Reference System)**  for GPS users

**Notes:**
Now I would like to spend the remainder of our time talking about OPUS the ON-line Positioning User Server.

This program provides faster and easier access 
to the National Spatial Reference System.

I’m probably the number one fan of OPUS

I submit over a 150 runs a month 
to check the stability of the cooperative  base stations.

I find it very easy to use and very accurate.

## Areas Covered by OPUS

## 			How Does OPUS Work?

-   Data submitted through NGS web page

-   Processed automatically with  NGS computers & software

-   Position with respect to 3 suitable CORS (or IGS sites if 1) no NAD 83 positions are available and 2) the host country has an agreement with NGS. In these international cases, ITRF coordinates only are returned, and there are no state plane or US grid coordinates

-   Solution via email (usually in minutes)

**Notes:**
OPUS works by Submitting data through the NGS Web page

It is Processed automatically with respect to 3 CORS

3 independent single base line solutions are performed in the ITRF (International Terrestrial Reference Frame) using the PAGES software and then averaged together. 

The Same thing but different is done for the Nad83 computations.  

You can read all about it under the “discussion” button on the OPUS home page

If everything is working as it should you can usually expect results in just a few minutes.

## 				OPUS Guidelines

-   Dual-frequency data (L1/L2)

-   [recommended] Minimum 2 hrs of data (maximum 48—only cross midnight once)

-   No kinematic or Rapid Static yet
- (OPUS-RS is under development)

-   No Glonass.  Galileo will be discussed
-     as the constellation becomes available

-   Accurate height requires:
-  correct antenna type
-  correct antenna height

**Notes:**
Some of the OPUS Guidelines are 

the data must be dual frequency (for now)

it should be at least 2 hours in duration

No kinematic or rapid static

No glonass

You  must supply the correct antenna type and height,
or I wouldn’t bet on the results of the vertical component

And the file name should be the standard 8.3 CORS naming convention.

## 		How Does OPUS Compute Position?

- 3 single baselines computed

- 3 positions averaged —
- simple mean (equal weights)

- Differences between positions include any errors in CORS coordinates

## Time-series plots, 60-day and long-term

- web page

- 60-day time series

- Long-term time series

- The time series plots provide a means of evaluating the small changes in position of a CORS.

## 		How Does OPUS Pick Base Stations?

- 		How Does OPUS Pick Base Stations?

- Estimate position for remote station
- Compute distance to every available CORS
- Sort CORS by increasing distance
- Select the 5 closest CORS
- Look at 1st 3 CORS with TEQC program. Criteria:
- 		●   data cover time span for remote station
- 		●   > 80% of data available
- 	 	●   low multipath
- 	 	●   if not, replace with 4th CORS (then 5th)
- 6. 	Start single baseline solutions using 1st 3 CORS
- 	 	●   check solution quality
- 		●   if bad solution, replace CORS with 4th (then 5th)

## 	CORS Selection (example = CORV solved from CHZZ, NEWP, P376)

- 	CORS Selection (example = CORV solved from CHZZ, NEWP, P376)

**Notes:**
**OPUS uses 3 CORS to compute a position.  
It tries to find the best CORS which may not necessarily be the closest.  
Quality of data, quantity of data and distance all go into the selection process.  
I believe OPUS will test as many as 50 stations  to find the 3 best suited CORS

## Quick Link to OPUS from NGS Home Page

- www.ngs.noaa.gov

## Using the OPUS Web Page

**Notes:**
This is the OPUS home page and to the left are helpful links.
Everything you want to know about OPUS is right here.

“OPUS explained” is at the top and there are guidelines,
Discussions on  precisions, and
descriptions of processing techniques
There’s a link to NGS’ antenna calibration page, an F.A.Q. page and more.

Enter your email address and Check it twice.
If it isn’t correct you’re not going to get back any results.
Use the browse button to find your data on your pc.
There’s a dropdown menu for the antennas.
OPUS only uses NGS calibrated antennas. 
 So, if you don’t see your antenna on the list and you still proceed ,
you’ll get a warning from OPUS that the antenna phase pattern has not be applied.
Enter in your antenna height,
You can request State plane coordinates.
Now, you can let OPUS choose which base stations to use for the computations or you CAN choose your own.
Then simply hit enter.

## Allowable Data Formats

- Compressed archive of multiple files. Archive must contain RINEX “site123h.04o” or Hatanaka “site123h.04d”

-  Compressed individual files.“Site123h.zip”must
-    contain “site123h.06o” or “site123h.06d”

-  Manufacturer’s native / raw (binary)—uncompressed--as long as UNAVCO’s teqc program can process it

-  RINEX Receiver Independent Exchange--uncompressed

**Notes:**

We have made a few improvements recently
You’ve heard me say that the user is able to select up to 3 base stations
This drop down menu on the OPUS page allows you can choose 1 to 3 CORS that you want used in your solution.
 It is from here that you can also choose cooperative CORS.

And if anyone is still using a modem to upload data 
you will be very pleased to know that OPUS now accepts compressed datasets  and archives of multiple datasets 
Here you must follow the naming convention rules.  

## Select or exclude base stations

-  including Cooperative CORS

- Select state plane coordinate zone

- Extended Output

- Set user profile

- Associate antenna type, antenna height, SPC code, selected base stations and extended option choices with your email address

**Notes:**

We have made a few improvements recently
You’ve heard me say that the user is able to select up to 3 base stations
This drop down menu on the OPUS page allows you can choose 1 to 3 CORS that you want used in your solution.
 It is from here that you can also choose cooperative CORS.

And if anyone is still using a modem to upload data 
you will be very pleased to know that OPUS now accepts compressed datasets  and archives of multiple datasets 
Here you must follow the naming convention rules.  

## OPUS OutputStandard

-  1008   NOTE:  Antenna offsets supplied by the user were zero.  Coordinates
-  1008   returned will be for the antenna reference point (ARP).
-  1008
-                               NGS OPUS SOLUTION REPORT
-                               ========================
-       USER: jeff.olsen@noaa.gov                     DATE: January 13, 2006
- RINEX FILE: corv059f.05o                            TIME: 19:08:14 UTC
-   SOFTWARE: page5  0601.10 master3.pl              START: 2005/02/28  05:00:00
-  EPHEMERIS: igs13121.eph [precise]                  STOP: 2005/02/28  06:59:30
-   NAV FILE: brdc0590.05n                        OBS USED:  4228 /  4314   :  98%
-   ANT NAME: ASH700936B_M    NONE             # FIXED AMB:    25 /    29   :  86%
- ARP HEIGHT: 0.0                              OVERALL RMS: 0.013(m)
-  REF FRAME: NAD_83(CORS96)(EPOCH:2002.0000)            ITRF00 (EPOCH:2005.1596)
-          X:     -2498423.165(m)   0.018(m)          -2498423.872(m)   0.018(m)
-          Y:     -3802822.048(m)   0.021(m)          -3802820.836(m)   0.021(m)
-          Z:      4454737.695(m)   0.024(m)           4454737.792(m)   0.024(m)
-        LAT:   44 35  7.91054      0.002(m)        44 35  7.92698      0.002(m)
-      E LON:  236 41 43.48129      0.014(m)       236 41 43.42434      0.014(m)
-      W LON:  123 18 16.51871      0.014(m)       123 18 16.57566      0.014(m)
-     EL HGT:          107.485(m)   0.034(m)               107.108(m)   0.034(m)
-  ORTHO HGT:          130.010(m)   0.043(m) [Geoid03 NAVD88]
-                         UTM COORDINATES    STATE PLANE COORDINATES
-                          UTM (Zone 10)         SPC (3601 OR N)
- Northing (Y) [meters]     4936954.907           105971.557
- Easting (X)  [meters]      475821.322          2277335.385
- Convergence  [degrees]    -0.21381402          -1.98897497
- Point Scale                0.99960719           0.99994603
- Combined Factor            0.99959034           0.99992918
- US NATIONAL GRID DESIGNATOR: 10TDQ7582136955(NAD 83)
-                               BASE STATIONS USED
- PID       DESIGNATION                        LATITUDE    LONGITUDE DISTANCE(m)
- AH2489 NEWP NEWPORT CORS ARP               N443506.072 W1240342.736   60138.7
- AJ6959 CHZZ CAPE MEARS CORS ARP            N452911.437 W1235841.187  113322.4
- DH4503 P376 EOLARESVR_OR2004 CORS ARP      N445628.313 W1230608.100   42648.2
-                  NEAREST NGS PUBLISHED CONTROL POINT
- AH2486      CORVALLIS CORS ARP             N443507.910 W1231816.519       0.0

- OPUS Output*Standard*

**Notes:**
WHAT DOES THE OPUS OUTPUT LOOK LIKE
OPUS was designed to be a one page document that was simple and easy to read.
There’s basically three sections to the it.  
The first part is information about the dataset you submitted and the software used.
Here I would check your antenna name and the height you entered.  
If you don’t have the correct antenna, well, you know.
Over here, you have the number of possible observations vs the number used, you want to be in, say the 90% range.
Next is the number and ratio of fixed ambiguities and again I like to see this number pretty high at least around 80% if not better.
And I like the overall RMS to be under three.
The second part is the meat and potatoes, the coordinates you were looking for.
You have your NAD83 (CORS96) position reported at the 2002.0 epoch and ITRF00 coordinates  at the epoch of the midpoint of your data.
Coordinates are reported in both the Cartesian xyz, and geodetic coordinates systems. 
The Orthometric ht. is based on the current geoid model.
You have your UTM coordinates, your US National Grid Designator, and your State Plane coordinates if you chose that option.
Do you remember I said that OPUS performs 3 independent solutions?  
These numbers to the right of the solution are Peak to Peak errors.  
They are shown for both coordinates systems and may differ between the two.  
Peak to peak errors are the difference between the max and min values of the 3 individual solutions.
These numbers are indicative of the CORS that were used in the processing. 
 If you have large peak to peaks, say over 4 or 5 cm or so, I would try to determine which CORS is the problem by selecting different ones.  
Hopefully in the future we will have a “do not use” menu much as there is a choice menu.
And the third part lists which Base Stations were used in the solution along with their position and the distance from the GPS station being solved for.
The closest published station is shown,  and in this case, it is itself since this is a published CORS.
And of course the ever more popular disclaimer is at the bottom of every solution.
Now I want you to notice that this solution used the precise orbits.

## 			Reading OPUS Output

-  USER: jeff.olsen@noaa.gov                     DATE: January 13, 2006
- RINEX FILE: corv059f.05o                            TIME: 19:08:14 UTC
-   SOFTWARE: page5  0601.10 master3.pl              START: 2005/02/28  05:00:00
-  EPHEMERIS: igs13121.eph [precise]                  STOP: 2005/02/28  06:59:30
-   NAV FILE: brdc0590.05n                        OBS USED:  4228 /  4314   :  98%
-   ANT NAME: ASH700936B_M    NONE             # FIXED AMB:    25 /    29   :  86%
- ARP HEIGHT: 0.0                              OVERALL RMS: 0.013(m)

- 			Reading OPUS Output

-   The version of PAGES software used for processing

-     The antenna type you selected and height of antenna reference point height you entered. Confirm that these are correct.

-     The ephemeris used (OPUS will use the best available):
-  “igs” final post-fit orbit--better than 1 cm (10-14 days wait)
-  “igr” rapid post-fit orbit--better than 2 cm (17 hours wait)
-  “igu” ultra-rapid predicted orbit--better than 20 cm (available
-  immediately)
-      Navigation file used

-   Your email address & observation file. Solution run date & time

**Notes:**
**The next section has your email address, the RINEX file name, the date and time  the run was completed.

**The pages software version is reported.
Next is whether  the precise, the rapid or the  ultra rapid orbit was used in the solution 
and you can see that the rapid orbit was used here.
The antenna name and antenna height you entered are echoed.

## 		Reading OPUS Output con’t.

-  USER: jeff.olsen@noaa.gov                     DATE: January 13, 2006
- RINEX FILE: corv059f.05o                            TIME: 19:08:14 UTC
-   SOFTWARE: page5  0601.10 master3.pl              START: 2005/02/28  05:00:00
-  EPHEMERIS: igs13121.eph [precise]                  STOP: 2005/02/28  06:59:30
-   NAV FILE: brdc0590.05n                        OBS USED:  4228 /  4314   :  98%
-   ANT NAME: ASH700936B_M    NONE             # FIXED AMB:    25 /    29   :  86%
- ARP HEIGHT: 0.0                              OVERALL RMS: 0.013(m)

-   Start & end dates & times of your file

-   Ratio and % of observations used in solution

-   Ratio and % of fixed/total ambiguities

-   Overall RMS of the solution

- 		Reading OPUS Output con’t.

**Notes:**
**The start and stop times of your dataset are given.   At this time, opus expects at least 2 hours of data.  And I believe it will accept as much as 48 hours.
The number of  possible observations vs the number used is shown.
Next is the number and ratio of fixed ambiguities.
And then the overall RM S

## 		Guidelines for Good Solution

- 		Guidelines for Good Solution

-   Make sure antenna type and height are correct

-   Review statistics:
-   at least 90% of observations should be used
- OBS USED:  4228 /  4314   :  _98%_
-   at least 50% of the ambiguities should be fixed
- # FIXED AMB:    25 /    29   :  _86%_
-   overall RMS should seldom exceed 0.030 m
- OVERALL RMS: _0.013(m)_

-  In case of bad statistics, try choosing different CORS and re-submit.

**Notes:**
I think 50 % is low.  I like to see that ## in the 80’s and 90’s

And I wouldn’t like to see Peak to Peaks at 5.  I like to keep them under 2 cm for North and East and under 3 for up.

But it depends on what accuracy you need.

## 		Reading OPUS Output con’t.		Solution/Coordinates

-  REF FRAME: NAD_83(CORS96)(EPOCH:2002.0000)            ITRF00 (EPOCH:2005.1596)
-          X:     -2498423.165(m)   0.018(m)          -2498423.872(m)   0.018(m)
-          Y:     -3802822.048(m)   0.021(m)          -3802820.836(m)   0.021(m)
-          Z:      4454737.695(m)   0.024(m)           4454737.792(m)   0.024(m)
-        LAT:   44 35  7.91054      0.002(m)        44 35  7.92698      0.002(m)
-      E LON:  236 41 43.48129      0.014(m)       236 41 43.42434      0.014(m)
-      W LON:  123 18 16.51871      0.014(m)       123 18 16.57566      0.014(m)
-     EL HGT:          107.485(m)   0.034(m)               107.108(m)   0.034(m)
-  ORTHO HGT:          130.010(m)   0.043(m)

-   Reference frames. Epochs

-  Position, xyz

-   Peak-peak errors, xyz (range, max-min)

-   Peak-peak errors may vary between NAD83 & ITRF

-   Orthometric ht. is based on current geoid model

- 		Reading OPUS Output con’t.		*Solution/Coordinates*

- [Geoid03 NAVD88]

-   Position, lat / long / eh / oh

-   Peak-peak for lat/long etc

**Notes:**
Reference Frames & Epoch Date are given.  OPUS reports the ITRF coordinates at the current epoch date,  and the NAD83 are reported at the 2002.0 epoch.
OPUS performs independent solutions for the NAD83 & ITRF2000

**Coordinates are reported in both the Cartesian, xyz and geodetic coordinates systems.  

peak to peak errors are shown for both the NAD83 & ITRF2000 solutions and may differ between the two.  
These values are the difference between max and min error between the 3 individual solutions and are usually the worst in the up component.

The Orthometric ht. is based on the current geoid model which is currently Geoid99

## How Does OPUS Compute Errors?

- E

- W

- S

- N

- 1 σ standard deviation

- peak-to-peak error
-        more conservative
-        ~ 2 σ

- peak-to-peak distances

## 		 	OPUS Output con’t.			Grid Coordinates

-                          UTM (Zone 10)         SPC (3601 OR N)
- Northing (Y) [meters]     4936954.907           105971.557
- Easting (X)  [meters]      475821.322          2277335.385
- Convergence  [degrees]    -0.21381402          -1.98897497
- Point Scale                0.99960719           0.99994603
- Combined Factor            0.99959034           0.99992918
- US NATIONAL GRID DESIGNATOR: 10TDQ7582136955(NAD 83)

-   Universal Transverse Mercator (UTM) coordinates

-   State Plane coordinates (if requested)

-   US National Grid

- 		 	OPUS Output con’t.			*Grid Coordinates*

**Notes:**

**UTM coordinates are given

**the US National Grid designation is given

**and if you chose the State plane coordinates option that position will be reported

## 		READING OPUS OUTPUT (control)

- PID       DESIGNATION                        LATITUDE    LONGITUDE DISTANCE(m)
- AH2489 NEWP NEWPORT CORS ARP               N443506.072 W1240342.736   60138.7
- AJ6959 CHZZ CAPE MEARS CORS ARP            N452911.437 W1235841.187  113322.4
- DH4503 P376 EOLARESVR_OR2004 CORS ARP      N445628.313 W1230608.100   42648.2
-                  NEAREST NGS PUBLISHED CONTROL POINT
- AH2486      CORVALLIS CORS ARP             N443507.910 W1231816.519       0.0
- This position and the above vector components were computed without any
- knowledge by the National Geodetic Survey regarding the equipment or
- field operating procedures used.

- 		READING OPUS OUTPUT (control)

- Disclaimer

-   Base Stations--NAD83 position--distance away

-   The closest published station in the NGS data base
-     In case you didn’t know it was there

**Notes:**

**It lists which  Base Stations were used in the solution along with their position and the distance from the GPS station being solved for

**The closest published station is given,  and in this case, it is itself since this is a published CORS.  Usually you’ll see one of the published FBN’s here.

**And of course the ever more important disclaimer is at the bottom of every solution or as Mark would say the COT ‘cover our tushies”.

## 		How Can I Improve My Results?

- 		How Can I Improve My Results?

- Consider observing a longer session

-  Data sets of at least
-    four hours have been
-    shown to produce
-    more reliable results

- Avoid conditions that perturb the GPS signal—unsettled weather, solar flares, multipath (nearby reflective surfaces)

**Notes:**
Over the past several years 
many test have been performed to
determine how to improve the results of OPUS

Marc and some of his close friends performed a test to 
study the solution repeatability  as a function of base line length between 26 and 300 km.  
This study showed that relative position errors 
were basically the same in this range 
which is attributed to the quality of the orbits.
But it was found that the duration of your session does matter. 
Data sets of at least four hours have been shown to produce more reliable results particularly in heights.

##   Distribution of Horizontal Offset from Accepted Values 

-   0.8 cm N-S RMS
-   1.4 cm E-W RMS

-  > 200 CORS
-  2  hours of data

**Notes:**
A year or so ago,
Tests were performed to determine OPUS’ ability to reproduce know values.  
More than 200 CORS stations with 2 hour datasets 
were used for the test 
since the CORS positions are well known

This scatter plot shows the horizontal distribution from published values at 
 8 mm North-South RMS
14 mm East-West RMS

68% of obs fall with in 8mm NS

## 	Distribution of Vertical Offset from Accepted Values 

-  1.9 cm RMS
-  All mean offsets
-   < 1 mm

-  > 200 CORS
-  2  hours of data

**Notes:**
The vertical distribution from published Values was
 less than 2 cm Vertical RMS.
All mean offsets were   < 1 mm.
The graph shows the distribution from the known values,
 the published values that are in our database. 
This is a note from Gerry Mader,
 It is important to point out that we submitted 
many many datasets of 2 hours for each site 
and though the distribution was 1.9 cm, 
the average value was only 1 mm off from the published value.  
And this was true for each and every site.  
so, though a single opus run may have been a cm or two off from the published, 
the mean of all of them was within 1 mm. 

## 		Error Messages and Warnings

- Resolution of the example messages below depends on circumstances. If there is a problem with software or hardware on the NGS side, sometimes just re-submitting the data file later is successful. If there is a problem with your data file, reobservation may be necessary.

- “The OPUS positioning software is only available for use  for datasets taken/recorded in one of the areas determined to be valid for OPUS A solution will not be performed on  the dataset submitted.
- The time span of the submitted dataset is too short.   OPUS needs a minimum of one hours worth of data to begin  processing.
- The dataset submitted to OPUS does not meet the RINEX standard.   Please re-submit the data in RINEX 2.0 or 2.1 standard.   Aborting...
- The dataset submitted to OPUS contained too many data gaps or a large number of sampling interval changes.  Aborting...
- WARNING!  No antenna type selected.  An antenna pattern will not be applied.
- The observations to slip ratio is too low.  There were an unusually high number of cycle slips in the dataset.  Aborting...
- ERROR!  Opus terminated abnormally in one of the processing modules.

**Notes:**
The OPUS positioning software is only available for use  for datasets taken/recorded in one of the areas determined to be valid for OPUS A solution will not be performed on  the dataset submitted.
The time span of the submitted dataset is too short.   OPUS needs a minimum of one hours worth of data to begin  processing.

The dataset submitted to OPUS does not meet the RINEX standard.   Please re-submit the data in RINEX 2.0 or 2.1 standard.   Aborting...
The dataset submitted to OPUS contained too many data gaps or a large number of sampling interval changes.  Aborting...
WARNING!  No antenna type selected.  An antenna pattern will not be applied.

The observations to slip ratio is too low.  There were an unusually high number of cycle slips in the dataset.  Aborting...

ERROR!  Opus terminated abnormally in one of the processing modules.
A copy of the output has been forwarded to the OPUS software group.  If the dataset can be processed, the results will be mailed shortly.   Aborting...

## How do I get help?

-   Study the Guidelines
-     under “Using OPUS”

- Submit specific questions, comments or  suggestions using “Contact OPUS” link

- Study the answers
-   under “FAQs”

**Notes:**
HOW DO YOU GET HELP

 First use the Links on the OPUS Web page
there are guidelines for  successful use
descriptions of processing techniques
discussions of guidelines
insight to expected precision
an explanation of each line in the report
a FAQ page
and more

**If you still have questions or have a comment or suggestion you can submit an email to OPUS itself.

## OPUS-DB (OPUS-DataBase)

- Observation log

**OPUS-DB**** (OPUS-DataBase)**

- description form

- photo(s)

- NGS website:
- OPUS-DB

- NGS DATABASE

- NGS magic

**Notes:**
In contrast, OPUS-DB is very streamlined; all the work takes place on the NGS-side of the internet

Of course, that puts the burden of effort on NGS.

## “OPUS DB” (Submitting OPUS Results) close to release

**OPUS solutions meeting certain**** **_[criteria](http://www.ngs.noaa.gov/CORS-Proxy/OPUS/OpusNewReg.jsp)_** and accompanied by metadata describing the site may be eligible for publication on Data Sheets from the NGS Integrated Data Base (IDB).  Users submitting to the IDB must be registered with NGS to receive a user ID and password and agree to the terms of this publication. Please review the **_[procedures](http://www.ngs.noaa.gov/OPUS/OPUS_03.html)__ _**for IDB submission.**

- “OPUS DB” (Submitting OPUS Results) close to release

- The numerical criteria for an OPUS solution
-         to be accepted for publication are:
- NGS calibrated GPS antenna
- minimum 4 hour data span
- minimum 90% observations used
- minimum 80% fixed ambiguities
- maximum 0.02m horizontal peak-to-peak
- maximum 0.04m vertical peak-to-peak

## Demonstration

**Demonstration**
**Application II**

**Notes:**
We are responsible for maintaining the National Spatial Reference System...as I mentioned earlier....the national reference base for position, height, distance and direction.  

This reference system gives GPS coordinates their integrity – information essential to ensuring the reliability of our communications, transportation, and defense systems.

## CONTROLLING A BRIDGE SURVEY

- The accompanying slides were presented
- at the
- 2002 CORS Forum
- by
- Gary Thompson
- of the
- North Carolina Geodetic Survey.

## Using OPUS to control Bridges

**Using OPUS to control Bridges**

- On a typical bridge job, NCDOT
- Sets an azimuth pair (           )
- Uses approximately 6-7 control panels (     )
- Controls the site with 2 receivers

## P1

- P2

- P3

- P4

- P5

- P6

## B9999-1

- B9999-2

- P1

- P2

- P3

- P4

- P5

- P6

## Field Work is now complete.

- The following steps need to be taken to finish the process:

## Office Process

- Download the Raw Data and RTK dc files
- Convert both blocks of raw data to RINEX format using Trimble’s utility
- Upload the files to: _[http://](http://www.ngs.noaa.gov/OPUS/)__[www.ngs.noaa.gov](http://www.ngs.noaa.gov/OPUS/)__[/OPUS/](http://www.ngs.noaa.gov/OPUS/)_
- Receive the results from OPUS via email  in minutes

## Continued...

- Import the dc file into Trimble Geomatics Office
- Update the initial base position for the first base to the coordinates provided by OPUS1
- After a recompute, everything in the dc file should be corrected relative to the first base location (OPUS1)

## Continued ...

- The position for OPUS2 is only used for comparison to what was derived from OPUS1
- Coordinates can now be utilized as needed

## OPUS & RTK 

**OPUS & RTK **
**Savings to NCDOT**

*****	The cell phone listed in the OPUS & RTK surveying comparison was not 	used in the survey work, but was available for contacting the office.

## HOW IS THE ANTENNA HEIGHT MEASURED?

**Notes:**
I promised we would talk more about antenna heights.

The height of the antenna is measure vertically from the from the mark, to the Antenna Reference Point which is almost always the center of the bottom-most, permanently attached piece o f the antenna.  

Some antennas have a short pipe or extension to them.  

If in doubt you can find photo’s and diagrams of each antenna (that we have calibrated) at the URL shown. 

So if you leave the antenna height as “0” this will be the height  OPUS returns.

## WHY DO I NEED THE ANTENNA TYPE?

**Notes:**
This is a close up of the last slide.  You can see where the ARP is.  

When you enter the correct Antenna type OPUS knows the antenna offsets and passes them to the software to determine the ARP

NGS uses the ARP rather than the phase center.  The ARP is a known point on the antenna whereas the phase center varies depending on the elevation angle from the antenna to the satellite.

## Antenna Calibration Facility in Corbin, Virginia 

- Antenna Calibration Facility in Corbin, Virginia

**Notes:**
We have a facility in Corbin where we do the antenna calibrations.  

The concept here is that we “know” the antenna phase pattern of on of the pairs here.  
And the signals coming from the satellites would be the same since they are so close.

So we can determine the phase pattern of the other antenna.

This next slide explains it better.

## .

- SV 14

- SV 14

- SV 20

- SV 20

- Antenna
- Type A

- Antenna
- Type B

**Antenna Phase Center Variation**

**Notes:**
Here we have two antennas.  We know the antenna phase pattern of the antenna on the left.  And we know that both antennas are receiving the same signal at the same  angle .

You say ah that makes perfect sense.

## .

- SV 14

- SV 14

- SV 20

- SV 20

- Antenna
- Type A

- Antenna
- Type B

- Different
- Phase Patterns

**Note that SV elevation and varying phase patterns affect signal interpretation differently**

**Antenna Phase Center Variation**

**Notes:**
But where the problem comes in is that different types of antennas have different phase pattern.   

This is the point in space where the antenna thinks it is receiving the signal.  And it is different for the L1 & the L2.

So the satellites elevation and the varying phase patterns affect signal interpretation.

## ELECTRONIC PHASE CENTER

**ELECTRONIC PHASE CENTER**

**Elevation Angle (deg.)**

**Phase Center Variation (mm)**

**Notes:**
This shows the difference in vertical position of the L1 Phase Center as the satellite gains altitude. 

You can see the phase pattern changes by 15 mm as the satellite climbs in its orbit

## Recent Solutions

**Notes:**
Another fairly new fun feature is a recent solutions plot 
It plots the locations of all the solutions OPUS has performed for the day.  

There is also a map for the previous days solutions.

*****The yellow triangle represents the last computation performed.  
So if your into it
 once you’ve submitted an OPUS run
you can watch this map 
which refreshes about ever 30 seconds or so, 
to see your VERY OWN SOLUTION magically APPEAR 
and know that that triangle is yours.

## Files processed during even-numbered months, 2002-2005

**Notes:**
1012 users in July

## OPUS usage for one month

## Total OPUS usage during 2005

## ONGOING CORS RESEARCH

- 	* Exploring the use of NTRIP to stream GPS data from selected CORS via the Internet.
- 	* Developing OPUS-GIS which will process a few minutes of GPS code range data (for sub-meter accuracy)
- 	* Developing OPUS-RS (rapid static) that will enable users to obtain positional coordinates with cm-level accuracy using only 15 minutes of GPS carrier phase data

## 	“OPUS  Projects”—under long-term development

- OPUS files identified as belonging to a project are directed to appropriate directories
- Project data submission organized
- Reports sent to project managers
- Station data checked and edited as needed
- PAGES GPS processing accomplished
- ADJUST run