fast static networks manual

Planning, Processing and Adjusting Fast Static GNSS networks

Trimble Business Centre v2 GNSS processing and analysing software

September 2011

Copyright

http://creativecommons.org/licenses/by/3.0/au/ State of Queensland (department of Transport and Main Roads) 2013 Feedback Please send your feedback regarding this document to: [email protected]

TBG Fast Static Manual vO.3.doc

Document control sheet

Contact for enquiries and proposed changes If you have any questions regarding this document or if you have a suggestion for improvements, please contact:

Project manager: Neville Janssen (Principal Surveyor) Phone: (07) 3834 2052

Version history

Version no. Date Changed by Nature of amendment

Draft N.M.Janssen Start of Initial draft.

0.1 30103/2010 G.J.Friske Completion of procedure

0.2 03/06/2010 N.M.Janssen Minor changes pages 17 & 27

0.3 22/09/2011 G.J.Friske Update to TMR template

Document Sign-off:

The following officers have approved this document.

Branch/Unit Manager (accountable for representing the BranchlUnit delivering the project)

Name Neville Janssen

Position Pri~rveyor

Signature fhwl Date --=1t'9/""'O"-!/...c"'----__ _ Sponsor (ac~ountable for representing the organisatlon(s) delivering the project)

Name Tony Kirchner

Position Director (Geospatial Technologies)

Signature Date f-/IO//( I (

Project customer (accountable for ensuring the stated benefit(s) of the project to the business have been measured and achieved) Name Position

Signature

Tony Kirchner Director (Geospatial Technologies)

1-9.1~. I

Department of Transport and Main Roads Version 0.3 22/09/2011

Date 4-//0 / I I ~,.r-=-t/~~~-

Page 2 of 44

TBC Fast Static Manual_v0.3.doc

Department of Transport and Main Roads Version 0.3 22/09/2011 Page 3 of 44

Contents

Introduction and Background Information............................................................. 4

1 Planning Software Utility............................................................................. 5 1.1 Simple Planning ............................................................................................. 5 1.2 Advanced Planning ........................................................................................ 7

2 Trimble Business Centre (TBC) for Fast Static Networks ........................ 8 2.1 Create & Setup New Project .......................................................................... 8 2.2 Download data ............................................................................................... 9 2.2.1 Download 4700 Base Receivers ................................................................................9 2.2.2 Download R8 Receivers.............................................................................................9 2.2.3 Download and Import Not Using ActiveSync............................................................10 2.3 Receiver Raw Data Check-in ....................................................................... 12 2.4 Import .Dat files............................................................................................ 14

3 Processing Baseline Data ......................................................................... 16 3.1 Baseline Processing .................................................................................... 16 3.1.1 Plan View General Nav & Info...............................................................................16 3.1.2 Seeding Primary Control Point .................................................................................16 3.1.3 Independent Baselines.............................................................................................18 3.1.4 Disable Trivial, Unwanted or Bad Baselines.............................................................19 3.1.5 Filter Poor Data ........................................................................................................20 3.1.6 Process Baselines....................................................................................................22 3.1.7 Baseline Loop Closure .............................................................................................23

4 Step 4 Network Adjustment ................................................................... 24 4.1 Minimally Constrained Network Adjustment................................................. 24 4.1.1 Adjust Network .........................................................................................................24 4.1.2 View and Interpret Network Adjustment Report .......................................................26 4.2 Constrained Network Adjustment................................................................. 27 4.2.1 Set Coordinates........................................................................................................27 4.2.2 Adjust Network .........................................................................................................29 4.2.3 Network Adjustment Report .....................................................................................29

5 Adjusted Coordinate Report & Export ..................................................... 30 5.1 Adjusted Coordinate Report......................................................................... 30 5.2 Export Adjusted Point Coordinates .............................................................. 31 5.2.1 Export Style Setup....................................................................................................31 5.2.2 Export to 12d Model .................................................................................................32



Introduction and Background Information

This procedure has been created to assist Trimble GNSS users to utilize Trimble Business Centre adjustment software to plan, download, process and adjust a GNSS Fast Static network.

Users of this procedure are urged to be familiar with the Intergovernmental Committee on Surveying and Mapping's (ICSM) publication Standards and Practices for Control Surveys (SP1) v1.7. SP1 is available in pdf format from the ICSM website, http://www.icsm.gov.au

SP1 documents Standards of Accuracy and best practice guidelines for Surveys and Reduction. This includes network design, independent baselines, connections to existing network, network adjustment and assigning Class and Order.

The Main Roads publication GPS Control Surveys v1.2 is also recommended as a source of network design, field procedure and network adjustment guidelines.

AUSGeoid98 is Australia's national geoid model.

AUSGeoid98 consists of a 2' by 2' grid (approximately 3.6km) of geoid-ellipsoid separations (N Values) relative to the GRS80 ellipsoid, which is also used for the new Geocentric Datum of Australia (GDA94). These values are suitable for use with Global Positioning System (GPS) and will improve the achievable accuracy of Australian Height Datum (AHD) height transfer using GPS. (Geoscience Australia website).



1 Planning Software Utility The planning software utility can be used to give an indication of how many satellites could be visible in your site area. If planning for a specific site with obstacles see section 1.2 Advanced Planning after reading section 1.1.

1.1 Simple Planning Get the latest Almanac from the Trimble web site

http://www.trimble.com/gpsdataresources.shtml

The GPS only file has the extention .ssf The GPS and Glonass has a .alm extension Right click on required option, select Save Target As, change Save as type to

All Files, browse to where you want to save the file and Save. Close the download box.

Open Satellite Planning Software Open TRIMBLE BUSINESS CENTRE (TBC) dont open a project, and go to

Tools Planning File Station

Either key in the details of the location or pick it from the Map Set Elevation Cutoff to 150 Set the date, time and duration of likely logging period

Ok



Import the Almanac you have just downloaded. If it was a .ALM file use Almanac Load If it was a .SSF file use Almanac Import SSF

Once loaded you can now view the satellite graphs in Graphs Number of Satellites The different colours represent the different total number of satellites. Ensure the correct satellite systems are checked in the tool bar just above the satellites graph. For most users this should be presently set to GPS & Glonass.

NB: The satellites rise 4 minutes earlier each day. Thus a block of satellites will be roughly a half an hour earlier each week. Other useful graphs include PDOP and SKYPLOT.



1.2 Advanced Planning

If field checks reveal a less than ideal site for GNSS, draw a site obstruction sketch using a compass and clinometer to map the obstructions. These obstructions can be entered into the planning software as obstacles. The resultant satellite visibility graph can be used to determine the best time to observe the particular station or determine that it is unsuitable to include in the network. This procedure follows on from 1.1 Simple Planning.

Go back to File > Station and click on the Obstacles button. Use your cursor (easiest way) hold down and drag around to create a grey mask in

the skyplot. If you have difficulty just Clear All and try again.

Once done select OK and your satellite plots will update to show only the available satellites given the obstructions presented.



2 Trimble Business Centre (TBC) for Fast Static Networks

Trimble Business Center office software is ideal for processing and analyzing satellite and terrestrial survey data recorded in the field. The software provides numerous innovative and unique features, and it is easy to learn and use. (Trimble Release.pdf)

2.1 Create & Setup New Project

Open TBC from the desktop icon or through the Start menu. Close the Welcome to Trimble Business Centre page using the black x on the right. When creating your first project,

Use File > New Project > Metric

Then select Set As Default > OK

Now that metric is set as the default a new project can be created using the New Default Project button, or File > New Project

Save the project using File > Save Project As or the button.

The project settings should now be completed to define the parameters of the project. Select Project > Project Settings or the button

Within the Project Settings window the General Information tab should be highlighted. Fill in the Reference number and Description fields as appropriate.



Select Company Information from the menu list on the left. Fill in as appropriate and repeat for User Information tab.

Select Coordinate System from the menu. Select the Change button which will present two options New System and Recently Used System. If the Recently Used System happens to be correct select its radio button and then Finish.

Otherwise select New System > Next> Coordinate System And Zone > Next > then select Map Grid Australia (GDA) from the left column and relevant zone from the right column

Next > Predefined Geoid model > AUSGEOID98 (Australia) > Finish.

Select Baseline Processing and then Satellites from the menu list. Set the elevation mask to 150 (as recommended by SP1). Ensure both GPS and Glonass satellites are ticked on if your using R8s, or only GPS if 4700s. Glonass will only be highlighted when the TBC dongle is inserted.

From the menu select Default Standard Errors > GNSS. In Default Setup Errors enter a value 0.002 m for both Error in height of antenna and Centring error. In Confidence Level Display use the drop down to select 1-sigma. Select Ok to finish entering project settings.

Appendix A defines how to setup a new default project setting. This allows you to save a default project with your commonly used fields like company and user information, coordinate system and default standard errors already filled out.

2.2 Download data The method of downloading is essentially the same no matter what receiver youre using. R8s are the predominant receiver in use across the state with a few old 4700s still on life support.

If ActiveSync is not working properly, see section 2.2.3.

2.2.1 Download 4700 Base Receivers

To be completed at a later stage. Section 2.4 Import .DAT files may be of help as an interim measure.

2.2.2 Download R8 Receivers

There are a number of ways depending on whether ActiveSync works on your computer or not, and where youve logged the data to. If ActiveSync doesnt work see Section 2.2.3.

Logged to Receiver

With a Bluetooth connection between the receiver and TSc2, select Instrument from the main Survey Controller screen. Select Receiver Files and then Import from Receiver. From the subsequent list of files, select the required files by ticking beside them on the far left of the screen. Select Import at bottom right and then Start. The file will transfer and then select OK. Now follow the Logged to TSc2 steps below.

Logged to TSc2

Method 1: With the required TBC project open, connect the TSc2 via USB to the computer. After a good few seconds a window should open on the far right of TBC screen. The device type is listed as seen below.



Use the + button beside Survey Controller symbol to drop down the list of known files. The GNSS files are in the Other Files drop down list. When a single file is highlighted the files details will display at the bottom of the window. If the file was transferred from the receiver to TSc2, the time and date reflect this and not the time of logging.

Highlight the required files using control key and mouse left button. Use the button to import the files into TBC. The files will be individually imported after which the Receiver Raw Data Check In window will pop up (vide Section 2.3).

2.2.3 Download and Import Not Using ActiveSync

This method is a workaround because of consistent trouble with ActiveSync on some computers.

2.2.3.1 Transfer Files Logged to Receiver to TSc2

With a Bluetooth connection between the receiver and TSc2, select Instrument from the main Survey Controller screen. Select Receiver Files and then Import from Receiver. From the subsequent list of files, select the required files by ticking beside them on the far left of the screen. Select Import at bottom right and then Start. The file will transfer and then select OK.



2.2.3.2 Transfer from TSc2 to USB Memory Device

Once all required files are on the TSc2, transfer them onto a USB memory stick.

1. Insert a USB memory stick in the bottom of the TSc2.

2. In Trimble Survey Controller select Files > Windows Explorer which will take you straight to Trimble Data;

3. Single File Locate file, press and hold stylus on name, a progressive circle of dots precedes a new window, select copy (jump to step 5)

4. Multiple Files - find and highlight all the required files > hold Control button down and tap on screen over each file. Select > Menu at bottom right of screen > Edit > Copy.

5. Up in the title bar select Trimble Data > Hard Disk > Menu > Edit > Paste

Files will be transferred from TSc2 to the USB. To return to Trimble Data select Hard Disk in the title bar and the Trimble Data. When all required files are on the USB, insert the USB in the computer and either transfer files into GNSS folder or leave them where they are.

2.2.3.3 Import into TBC

In an active project select File > Import which will open an Import window on right of screen.

Use the button to browse to where the files are located;

If only 1 file is highlighted its details appear at bottom of the window (in grey). Be aware the time is transfer time not logging start time.

Highlight all relevant files; Select Import Proceed to Section 2.3



2.3 Receiver Raw Data Check-in

Check that all the Point IDs are correct and have been called the same name every time the point has been logged. An incorrect Point ID can be changed simply by clicking into the box and changing it. The file names need to be written on the GPS Static Log sheets. Check the start and end times to ensure logging durations are as required. If there are any unwanted setups, un-tick them on the left.



Check that the antenna types, method of measuring and measured heights are correct by selecting the Antenna tab. Any data in blue can be edited. The Manufacturer, Type and Method can all be changed using the drop down arrow which appears when you hover over a field.

The Receiver tab contains information on the Receiver Manufacturer, Type and Serial Number. If the Survey Styles in your hand controller are setup correctly you shouldnt need to go into this tab.

When all is correct select OK and the network will appear in the Plan View.

Go to Section 3: Baseline Processing



2.4 Import .Dat files

TBC does not create .dat files as part of its process like TGO did but you may wish to import a .dat file from an old project. Care should be taken as any old .dat file will only have GPS satellites, no Glonass.

With a new project created as per 2.1 or an existing project open, .dat files can be imported by;

File > Import or use button. The Import window will open to right of screen. Use button to browse to and select relevant folder where the dat file is. Select OK. The Import window will be populated.

Select all relevant .dat files Import



The Receiver Raw Data Check In window will pop up. Check the details like Point ID, Start and End Times are correct for each dat file to be imported. Ensure only relevant files have Import ticked on.

Select the Antenna tab. Check that antenna manufacturer type, Method (spot measured to) and Height (of antenna) are correct.

When confident all details are correct select OK. The imported points will appear in the plan view.



3 Processing Baseline Data

3.1 Baseline Processing Baseline processing produces a vector (baseline) between two occupations with data time overlap. The baselines form the basis of the network which will be adjusted further on in this procedure.

3.1.1 Plan View General Nav & Info Once the baselines are onscreen the points and baselines can be interrogated and edited.

Left click on a point will display the point name and all the baselines to and from it (see below in 3.1.2). Move over the point name and select using left click. Now right click anywhere.

The Point Derivation Report lists all GNSS sessions at the selected point. One session is used as a reference position and the difference in the raw XYZ coordinates for all other sessions are listed. This could help determine if a particular session could be a problem and needs to be checked for bad data like cyclic slips using the Session Editor.

3.1.2 Seeding Primary Control Point A control station of known coordinates (seed) needs to be set to control the baseline processing. The highest Class and Order control mark for horizontal and vertical accuracy should be seeded. In some cases this may require different stations to be seeded for horizontal and vertical. A Least Squares Adjustment works best when the adjustments required are minimal. Inaccurate starting coordinates adversely affect the accuracy of the baseline results Therefore seeding the best quality survey mark helps to achieve this aim. A minimal constrained network adjustment should be computed on the ellipsoid associated with the datum on which the observations were acquired.(vide SP1 v1.7 section 2.2.1 Class)

Will revert to the previous selected point or baseline Clear Selection clears the selection Selection Explorer is not helpful Will delete the point or baseline currently selected Centre places the selected point in the middle of the Plan View Add coordinate allows you to add a coordinate Point Derivation (see below) Properties allows you to change the point name and displays the

current coordinate values



For Main Roads this essentially requires the minimally constrained adjustment (and therefore this seed point) be completed on GDA94 ellipsoidal coordinates. AHD heights are transformed to Ellipsoidal heights using geoid-ellipsoid separations (N value).

h = H + N

where:

h = height of the terrain above the ellipsoid

H = height of the terrain above the geoid (AHD height)

N = geoid-ellipsoid separation (N value)

Select the mark to be seeded by left clicking on its circular symbol.

From the pop-up select the named point

Right button anywhere on screen

Select Add Coordinate from the new pop-up



In the Add Coordinate window enter the GDA94 Latitude, Longitude and ellipsoidal height;

The seeded marks symbol should change to a triangle with a solid dot inside if edited for both horizontal and vertical. If edited for horizontal it will be a triangle. If only for vertical the symbol will be a square.

3.1.3 Independent Baselines

If the fieldwork has been completed using a maximum of two receivers at any one time you should be able to skip this step.

However, if three or more receivers have been used concurrently some trivial baselines will need to be disabled. Baselines are calculated from observed point data and therefore when for e.g. three receivers are used concurrently the three resultant baselines form a mathematically perfect triangle which bias the adjustment and make results better than they really are. Only two of these baselines are independent, the third is trivial and needs to be disabled. A correctly observed network would observe this third baseline at a different time.

In the one session, observing with n receivers, the total number of baselines that can be computed is n(n-1)/2. However, only n-1 of those baselines are independent. Vide SP1 v1.7 Part B section 2.6.6.2 Independent Baselines (page B-19) for more information.

When more than 2 receivers are utilised it is vital to the success of a network and ease of processing that the Baselines to field is completed on the GPS Log sheet.

change the coordinate type to Global

edit the Latitude and Longitude to the values from the PM report (or other source)

edit the Height to the calculated h value Select the button and change the

quality from Unknown to Control for both horz and vert (if applicable)

Check the Grid coordinates and Elevation are correct from the PM report (may be a small rounding error of 1-2mm)

Select OK



3.1.4 Disable Trivial, Unwanted or Bad Baselines There are two ways to explore baselines. The best way is presented below.

(The other way is View > Project explorer or use link at the left of screen beside the Plan View tab. Then use the + drop down on Sessions.)

To explore baselines, use View > New Time Based View or use button. All baselines will be displayed. This is where the Baselines to section on the GPS Survey Log Sheet earns its money. In larger projects using multiple receivers it is common to have read a number of baselines between two marks, only one of which was meant to be read and thus required.

An unwanted baseline like B61 above could be either deleted or disabled. B61 has so little overlap it is no potential use therefore deleting is the best and tidiest option. However if it had a large overlap of time it would be best to disable in case its needed later. If the network has problems you may be able to re-evaluate which baselines you use, always remembering the independent baseline rules.

To delete a baseline, in the Time Based View window above, right click on the baseline and select Delete. If the wrong one is chosen, Edit > Undo will bring it back.

To disable a baseline highlight one of the duplicate baselines (B61), right click and select Session Editor.

Start date and time at left Blue bar is the session duration at the

first mark

Green: session duration at the 2nd mark Look for duplicate, trivial or unwanted

baselines

e.g. B61 is unwanted due to short time overlap and is also a duplicate (B60)

See below on how to check and disable



Back in the Time-Based View window, highlight the trivial baseline (B61), right click and select Disable Baselines.

Repeat this step for all trivial or unwanted baselines. The disabled baseline will be greyed out in the Time Based View list. This procedure can also be used for bad baselines.

3.1.5 Filter Poor Data Poor satellite data can be cut-out or entire satellites disabled to potentially improve the resultant solution. Care needs to be taken as what data to cut and to ensure too much data is not cut. You could easily spend a lot of time improving the data, only to end up with a worse solution. Any pre-processing filtering should only cut obviously very bad data or satellites. You can always come back and edit after baseline processing if warranted to help a baseline to pass. It is recommended that the baselines are processed before looking to filter poor data.

Navigate to the Session editor for a baseline through either the Time Based View > right click on baseline > Session Editor or Project Explorer > right click on baseline > Session Editor as above in 3.1.2.

In some instances an entire satellite may need to be disabled due to having only logged a very short period of data or the data may be poor. This can done by left clicking on the satellite number or right clicking anywhere on the whole satellite row, selecting Disable Satellite from the resultant window.

The same two procedures can be used to re-enable a satellite (use Enable Satellite).

Using the date, start (top far left) and end (top far right) times work out if this baseline is the correct one to disable

This is an obvious baseline for disabling

Select OK



To edit out suspect or bad data, make a window around the required data by holding the left button down and dragging to the opposite corner. Be careful to stay within the upper and lower grey lines which separate the satellites, or else both satellites will be selected. The satellite number, start and finish time of the Selected Time Slot is displayed at the bottom of the Session Editor window.

A number of windows can be created on the one satellite. When moving over or selecting data, the date and time of the current mouse pointer position is displayed at the top middle of the window.

To remove a single time slot, right click on the relevant time slot. Select Remove Time Slots. To remove multiple time slots, right click anywhere on the satellite data Select All Time Slots > Remove Time Slots.

After finishing all editing and disabling, select Apply Time Edits > OK

Repeat for all required satellites.

From & to station and baseline number are listed in top panel

Date, start and end time of session are shown

Satellite numbers are listed down the left side. G for GPS & R for Glonass

E.g. G3 has no logged common data

R18 has some cyclic slips in L1 (blue) which may require cutting later

R20 has poor data and is disabled (greyed out).

Left click on the satellite number to disable the entire satellite

Ok when finished



3.1.6 Process Baselines Ensure no baselines or points are actively selected onscreen (only the highlighted will be processed), then select Survey > Process Baselines or use button.

The process baselines window displays the baselines processed and relevant information.

Fixed - This denotes that the processor was able to resolve the integer ambiguity with enough confidence to select one set of integers over another.

Float - This denotes that the processor was unable to resolve the integer ambiguity with enough confidence to select one set of integers over another.

RMS - Used to express the accuracy of point measurement. It is the radius of the error circle within which approximately 70% of position fixes are found. It can be expressed in distance units or in wavelength cycles. Smaller values for RMS are considered better.

Ratio - This shows the ratio of the variance of the second best solution divided by the variance of the best solution. The baseline processor compares the two solutions with the lowest variance. Only fixed solutions have ratios.

If a baseline is particularly bad and is not critical to the network you could tick it off in the panel above. However if you do this, the baseline will not exist in the project. A better option would be to disable the baseline or the satellite data can be checked and edited in the Session editor as in 3.1.3. Note any baseline solutions that had higher horizontal and/or vertical precisions, high RMS or low Ratios for checking later.

Save the processed baselines. You could at this stage look at the Baseline processing report (Reports > Baseline Processing Report) but it doesnt really tell you anything new.



3.1.7 Baseline Loop Closure

Looking at the loop closures can give you another indication of the quality and fit of your network within itself. It can help identify bad vetors.

Select Survey > GNSS Loop Closure or use the button. The resultant summary will open in Internet Explorer and will summarise the number of loops assessed and the number that passed. It will also detail the pass/fail criteria, the best, worse and average loop miscloses. The standard error is also displayed.

Just because a loop doesnt pass doesnt mean you have a problem. Assessment is needed as to what accuracy the network is required to have.

(To change the loop closure criteria use Reports > Report Options > GNSS Loop Closure Report from the Reports list. Expand the Report Setting section in the Settings group. Edit the report settings as needed and OK.)



4 Step 4 Network Adjustment

TBC Help defines a Network Adjustment as a Solution of simultaneous equations designed to achieve closure in a survey network by minimizing the sum of the weighted squares of the residuals of the observations.

4.1 Minimally Constrained Network Adjustment

A minimally constrained adjustment is the first step of the network adjustment procedure

(Vide SP1 v1.7 Section 2.6.9 Processing Baselines and/or GPS Control Surveys Manual,

Section 2.2.8 for more information).

4.1.1 Adjust Network

As a survey mark was seeded in Baseline Processing the process is very simple. Ensure no baselines are highlighted.

Use Survey > Adjust Network or the button. The Adjust Network launches on the right of screen. It will show the Point ID of the Fixed Seed Coordinate. The 2D and h boxes should already be ticked. If not, tick them. If you entered an AHD height tick the e box instead of the h (spheroidal) box.

After the network adjusts, the Plan View will display the horizontal error ellipses and vertical residual at each point. The Adjust Network window will display the results i.e. Reference factor; Chi Square test; and Degrees of Freedom.

Select the Adjust button An unresolved computation error box

may appear. This will because there are flagged observations. Select Yes



If the Chi Square test failed, select the Weighting tab.

In the example above, 1.29 is the Ref Factor from the last adjustment. The goal is to get it to 1.00. Selecting the * button multiplies the Ref Factor by the scalar (i.e. 1.29 x 1.00 = 1.29). After re-adjusting the network, the Ref Factor will be 1.00 and the Scalar will be 1.29. The scalar value is an error estimate used to scale precisions to the desired level of confidence.

In the Plan View (or the Project Explorer) select points and vectors to review their errors and residuals in the Results tab. Investigate and resolve the points with the largest ellipses first.

Reference Factor shows the standard error of unit weight

Chi Square test (95%) is a test of the sum of the weight squares of the residuals, the number of degrees of freedom and a critical probability of 95 percent or greater.

Degrees of Freedom shows the remaining degrees of freedom, which are a measure of the redundancy in a network.

The Ref Factor & Scalar values are different

Select the * button The Scalar value will change to the

same value as the Ref. Factor

Select Adjust from bottom of window Select the results tab. The Ref Factor

will now be 1.00 and the Chi Square test will have passed.



If you select a vector, the window will show the baseline vectors from and to Point ID and its vector number (PV76). The Orientation, Ellipsoidal Distance and Diff Height residuals are listed. These may be useful to someone.

4.1.2 View and Interpret Network Adjustment Report View the network adjustment results by selecting Reports > Network Adjustment Report

The error ellipse semi-major axis component is the main point of interest in the report. The error ellipse is a graphical representation of the magnitude and direction of the error of network-adjusted points. Further on, the Adjusted GPS Observations section can be used to find the shortest baseline in the network. This information should now be used to calculate if the network meets the required CLASS (vide SP1 section 2.2.1 Class, page A-6 for further information).

If all is well proceed to the next step, Constrained Network Adjustment. If the minimally constrained adjustment has revealed problems, go back and further evaluate the network design and interrogate the satellite data.

These values are not the error ellipse values used to determine CLASS

However they are a good indication and need to be close to the required error ellipse values

If not, issues in the network will need to be addressed



4.2 Constrained Network Adjustment The final step is a fully constrained Least Squares adjustment. The process is basically the same as the above Minimally Constrained Adjustment. Error ellipses are calculated and allow the network to be allocated an accuracy ORDER.

ORDER is a function of the CLASS of a survey, the conformity of the new survey data with an existing network coordinate set AND the precision of any transformation process required to convert results from one datum to another. (Vide SP1 section 2.6.10.3 Constrained Adjustment p: B-25)

The basic workflow is:

1. Set Coordinates on multiple base stations

2. Adjust Fully Constrained Network

3. View Network Adjustment Report

There are a couple of ways to approach the constraining of control points.

Constrain All - All known horizontal and vertical values of sufficient accuracy could be constrained and the network adjusted.

One at a Time - The other option is to constrain one known value at a time and then adjust. This process is repeated until all values are constrained. This way can make it easier to identify which constrained value is the problem when the adjustment has issues. It is recommended that all horizontal marks are individually constrained and then the vertical values mark by mark.

Carefully selecting control points in the network planning stage will help to eliminate many potential sources of problems. Always try to select horizontal control points that have been adjusted in the same network.

4.2.1 Set Coordinates The process is exactly the same as when constraining the seed point (Section 3.2.1) except this time Grid coordinates, MGA94 and AHDd will be added.

Select the mark to be seeded by left clicking on its circular symbol.

From the pop-up select the named point

Right button anywhere on screen

Select Add Coordinate from the new pop-up



In the Add Coordinate window to right of screen enter the MGA94 Easting and Northing; and the AHDd height value.

Repeat for all points to be constrained (if using the Constrain All method).

Ensure Coordinate Type is Grid

edit the Easting and Northing to the values from the PM report (or other source)

edit the Height (if appropriate) to the PM Report AHDd value

Select the button and change the quality from Unknown to Control

for both horz and vert (if applicable)

Check the Global coordinates are correct from the PM report (may be minute rounding error)

Select OK



4.2.2 Adjust Network

Use Survey > Adjust Network or the button. The Adjust Network launches on the right of screen. It will show the Point ID of the constrained marks. The 2D, h and e boxes should already be ticked as appropriate. If not, tick the correct ones. AHDd height the e box should be ticked instead of the h (spheroidal) box.

As in the Minimally Constrained Adjustment, select the Results tab to see if the Chi Square test passed.

Select the Weighting tab and then select the * button to set the Scalar value to the Ref Factor value.

Select Adjust to re-adjust the network with the new scalar value. In the Results tab the Reference Factor should be 1.00 and the Chi Square test should Pass.

In the Plan View (or the Project Explorer) select points and vectors to review their errors and residuals in the Results tab. Investigate and resolve the points with the largest ellipses first.

4.2.3 Network Adjustment Report View the network adjustment results by selecting Reports > Network Adjustment Report.

The top section contains Project Information and Coordinate Information. Adjustment Settings are listed next.

The next section contains the Adjusted Grid Coordinates. Of interest are the errors in Easting, Northing and Elevation. These are the same values that are displayed in the Plan View graphically. Check values in the Fixed column are the correct constraints.

The Adjusted Geodetic Coordinates are listed together with the Height error.

Of most interest is the Error Ellipse Components section. The semi-major axis component is used to assess ORDER. If the network fits well to the existing known constraint values the semi-major ellipse value should be small and therefore the ORDER should calculate to a high value.

The Adjusted GPS Observations can be used to find the Azimuth, change in height and the ellipsoidal distance. It also lists error and residual values.

The Covariance Terms shows the change in elevation, horizontal precision ratio and 3D precision ratio. Covariance is a measure of the correlation of errors between two observations or derived quantities.

Print this report as a PDF with an appropriate name to keep as a record of the adjustment.

PM114990 was the seed point PM101560 has known Horz values

only

PM48460, PM84648 & PM132543 have Vert values only

After checking all is correct, select Adjust at the bottom of panel



5 Adjusted Coordinate Report & Export

5.1 Adjusted Coordinate Report

There are two different reports that can be generated listing the networks Adjusted Coordinate values.

The first way is selecting Reports > Point List which opens a window in TBC as below.

This report can be saved as a PDF or Excel file by using the drop down arrow on the button in the Point List window title bar. Excel is not recommended. PDF is perfect for including in the eFB.

The 2nd way is Reports > Point List (HTML) which opens the same report as above in your default web browser. This report can be saved as a web page or txt file. It can also be printed to a PDF.



5.2 Export Adjusted Point Coordinates Initially a new style has to be setup to allow easy integration of the adjusted control points into 12d Model. Once setup, the new style can be used every time.

5.2.1 Export Style Setup A style can be setup to make it easy to import a correctly formatted ascii DAT file into 12d Model.

File > Export Format Editor

With the top P,E,N,elev, Code option highlighted, select Copy and a new Definition name of Copy of P, E, N, elev, Code will be added to be bottom of the list. Edit the name to Output to 12d and select Next.

If you usually import ascii comma delimited files into 12d, select Next. If you prefer Fixed Width select that option and then Next.



Whichever option Type option you selected in the last step change the Default file extension to .dat and ensure all of the options are as you like them. Select Next > Finish.

5.2.2 Export to 12d Model

Use either File > Export or button to activate the Export option. From the File Format list select Output to 12d option.

Select Output to 12d format

Select Options tab (see below Select Points window)

Edit the filename as desired



The Data Selected back in the initial window should be the number of points in your project (i.e 11 in this case). Select Export at the bottom of the window. The DAT file will be created in the folder below where the project VCE file sits. If your field data didnt have a Code/Name, PFSC will need to be added. Comments should also be added. The format should end up Pt Number, Easting, Northing, Height, Code, Comment as below. Edit out the GPS control points if they arent required in the 12d project.

This is easily imported into 12d by using Survey > User > File Input > Read xyz Text Files > Read pn,x,y,z,code,comment (comma delimited)

Select General tab Layer should be by Points Tick on the 2 options as shown Select Ok and youll be back in the

initial window



Appendix A Defining a new Default Project Settings This section details how to setup a new default project setting allowing you to save a default project with your commonly used fields like company and user information, coordinate system and default standard errors already filled out. Company and User Information is important metadata especially if networks are submitted to DERM.

Select File > New Project > Metric Template > OK

Project > Project Settings > fill out the following information tabs as appropriate


Department of Transport and Main Roads Generic OnQ Lite template Page 35 of 44

Complete the Coordinate System information with the most commonly worked in Zone. In the future, when using this template in a different Zone remember to change the Zone to the correct one in Project > Project Settings.

Set the Elevation Mask to 15 deg as specified in SP1. Check that all GPS and Glonass satellites are ticked on. If Glonass arent highlighted try inserting the dongle. Youll have to start from scratch if this was the case.



Set the GNSS Default Setup Errors to 0.002m for both Height of Antenna and Centring Error.

Use the drop down menu to set the Confidence Level Display to 1-sigma.

Select OK



File > Save Project As Template > give the new Project Settings a template name > Save

File > Close Project

File > New Project > Select the new template (in the example TMR Fast Static GJF) > Set As Default > OK

Now when you navigate to Project > Project Settings it should contain all the information that you entered previously for Company Information etc.



Appendix B - Precise Ephemeris Ephemeris is a set of parameters used by a global satellite receiver to predict the location of a satellite and its clock behaviour. The broadcast ephemeris that is usually used is a projection of the satellites location and its clock behaviour. The precise ephemeris is post-processed and when used, results in better accuracies. There is usually a 12 to 18 day wait for the precise ephemeris to become available. Precise ephemeris for GPS and GLONASS satellites is published every Thursday.

It is recommended if you need to use the precise ephemeris that you contact Geospatial Technologies and ask the Survey section to download the relevant GPS weeks ephemeris.

If you are competent and have internet access you could follow the process yourself.

1. National Geodetic Survey website

Open your internet browser and get onto www.ngs.noaa.gov/orbits



2. Understand the file naming convention

In the screen-dump above select number 1. GPS Orbit File Naming Convention which will provide the information below.

3. Determine GPS week

Find the date/s of your observations and determine the GPS week on the left of table. Remember the precise ephemeris takes 12 -18 days to be uploaded so yesterdays obs cant be precise processed yet.



4. Download GPS Precise Ephemeris

In the window shown in Step 1, select IGS Product Information under Section 5. Locate the GPS Satellite Ephemerides/Satellite & Station Clocks section in purple, scroll down to Final and then square across and select the CDDIS (US MD) option.

From the following window locate the link ftp://cddis/gsfc.nasa.gov (vide the mouse hand as below) and select it.



In the following window select pub option (always the best option).

Followed by GPS > Products (ftp://cddis.gsfc.nasa.gov/pub/gps/gps/products ) > find the relevant GPS week (e.g. 1574) and select it > locate and select the correct igs sp3 format file (as below igs15744.sp3.Z ). Save the Z zip file to the location of your choice.

Do NOT save the ephemeris file in the same directory as the GNSS files that you want to import as it makes TBC very unhappy.



5. Download GLONASS Precise ephemeris

Basically its a repeat of Step 4 except your selecting GLONASS options instead of GPS.

Use this shortcut ftp://cddis.gsfc.nasa.gov/glonass/products

Find and select the relevant GPS week (e.g. 1574) > locate and select the correct igl sp3 format file (as below igl15744.sp3.Z ). Save the Z zip file to the location of your choice.

Do NOT save the ephemeris file in the same directory as the GNSS files that you want to import as it makes TBC very unhappy.



6. Import files into TBC

With a project open in TBC select File > Import > use the button to browse to the folder where the .Z zip files are > Import

The .sp3 files are extracted to the TBC projects folder.

To make the project use the precise ephemeris when processing baselines, select

Project > Project Settings > Baseline Processing > General > left mouse on Automatic (Ephemeris type) > select Precise > OK.

Proceed with processing baselines as per usual.



Appendix B Known Issues

Delete that does not really delete

If for some reason you delete a point or all points and baselines in a project you cannot re-import the same files back into the same TBC project unless you follow the following procedure.

Select Project Explorer or > Imported Sessions drop down > select required files to delete > right button Delete

Ephemeris File

Do NOT have an ephemeris file in the same directory as the GNSS files that you want to import as it makes TBC very unhappy.

fast static networks manual

Documents

project manager

download data

fast static networks

tbc fast static

main roads version

project customer accountable

version history version

baseline processing