GPSurvey Sample Data Tutorial

After you've finished the installation of GPSurvey, you should take some time to familiarizeyourself with its capabilities. We strongly suggest that you take the time now to run through the GPSurvey tutorial. You can either print this document and work with the paper copy during the processing of the sample data, or you can look at it in one window while GPSurvey runs in another. The choice is up to you.

NOTE: The data loading and baseline processing portion of this tutorial is estimated at 45-50 minutes, depending on your computer and background with GPS. The network adjustment portion of this tutorial is estimated at an additional 45-60 minutes.

Before beginning the tutorial, you must:

1. Install the GPSurvey Manager2. Install the WAVE Baseline Processor3. Install the Network Adjustment Option (TRIMNET Plus) -- NOTE: you should install the Happynet Tutorial, which includes Geoid90W, because Geoid90W is used in this tutorial4. Activate your security device for each of these installed modules

Refer to Chapter 1 of the GPSurvey Software User's Guide that is supplied with GPSurvey. Once installation is complete, you should have a GPSurvey Group on the Windows desktop. If you have any problems or questions concerning the installation process, don't hesitate to call Trimble Technical Support. See the GPSurvey Release Notes for the telephone numbers for technical support.

WINDOWS: This tutorial assumes that you are familiar with Windows.

COMMANDS: Commands that require sequential menu selections will be written with a “ / ” to separate the selections. For example: “Select Project / New” should be interpreted to mean click on the Project menu option, then select New.

TAKE A BREAK: If you wish to take a break during the GPSurvey tutorial, you should do so at the recommended places. If you want to turn the computer off, just close any open options within GPSurvey, then exit GPSurvey by closing it in the standard Windows manner (click on the extreme upper left corner, then select Close). If there is another project open when you return to GPSurvey, click on Project / Open to select your sample project.

ON-LINE HELP: While you are in GPSurvey, be sure to try the on-line help for detailed information about any of the options.

Running the GPSurvey Tutorial

BASIC SEQUENCE OF STEPS IN THIS TUTORIAL:

1. Create a Project2. Load data into the project database3. Process the data4. View the processed network5. Adjust the network6. Create ASCII files of adjusted coordinates for export to other packages

1. Create a new project

1. Double-click on the GPSurvey 2.2 icon in the GPSurvey program group2. Click on Project / New3. In Create a New Project dialog box, enter the name of the project: type HMB (we’ll call the project HMB, because it is located in Half Moon Bay, California, US)4. Click on Create

NOTE: If more than one person in your office wants to work on this tutorial, use a unique name for your project -- your own name, for example -- to keep the projects distinguished from each other. You may all use the same sample data; data files will not be lost or corrupted.

2. Load data into the project.

From the main GPSurvey desktop, click on Load / From DAT File. This opens a dialog box which allows you to browse for data files (they have a *.DAT extension), select data files, and begin loading.

We’re going to do three basic things here:

A. Check the loading configurationB. Select which files to loadC. Load each file, reviewing occupations made in the field and making a few changes.

This last step feels tedious to new users, but careful editing at this early stage can prevent a lot of problems later in your project.

A. Check Load configuration

1. Click on the Config... button2. Set Mode of Operation to Quick Edit/Batch Prompt (click on Quick Edit/Batch Prompt)3. Ensure that all six options are checked (click on an unchecked box to toggle this to a checked state)4. Click on OK to return to the Load from DAT File dialog

B. Select files to load

1. In the Directories panel, browse to the gpsurvey \ sample subdirectory2. Click on Add All to select all files for loading

NOTE: At this point, you should see the following files listed in the Files Selected box:

00010530.dat 00020530.dat00030530.dat10120191.dat23280191.dat51400050.dat51400051.dat51400060.dat51400061.dat61250050.dat61250051.dat61250060.dat61250061.dat

C. Load individual files

NOTE: In this tutorial we know where the mistakes have been made in the field, and we’re going to focus on editing only those station names that are not correct. Also, we’re going to enter fixed control coordinates for only one station. But you should ALWAYS review the information in your data files, and whenever possible edit your data when you first load it into the project database. This is the safest way of handling your data.

1. Click on the OK button to begin loading data files2. In the Station/Antenna Editor display, click Config...3. In the Check-in Controls dialog, click on Interactive, then click on OK4. In the Station/Antenna Editor display, click on OK5. In the Verify Receiver Configuration 1 dialog, click on OK6. In the Verify Station for Static Occupation 1 dialog, enter the following values forMOON2 (use the tab key to move from one field to another):LAT: 37-26-20.29455 NLONG: 122-26-34.63873 WHeight: -10.682 m (NOTE: this is an ellipsoidal height -- do NOT enter benchmark elevations in this field)Position Quality: Fixed Control Usable GPS: checked7. Click on OK when these values have been entered8. In the Verify Info (antenna info) for Static Occupation 1, click on OK

The file 00010530.dat is now written into the database. The raw, unedited data is retained in the data file for your records, but the project database includes the new position information.

The next file we will load, 00020530.dat, contains two incorrect station names which we will change. This file contains kinematic occupations, with stations Michael, 1001, 1002, 1003, 1004, 1005, and 1006. Each of these stations was occupied twice. However, at the second occupations of 1001 and 1002, the stations were incorrectly named 1007 and 1008. We will change these names.

1. When the Station/Antenna Data Editor display appears, look for station 1007 on the left hand side of the display. You may have to scroll down to find this information.2. Double click on the name 1007. A drop-down list control should appear in this field.3. Open up the list and change station 1007 to 1001 by selecting 1001 from the list.

(NOTE: because station 1001 has been checked in previously, it already exists in the database; therefore, simply click on the scroll bar in the Name field and select 1001)4. Look for station 1008 on the left hand side of the display. You may have to scroll down to find this information5. Double click on the name 1008. A drop-down list control should appear in this field.6. Change Station 1008 to 1002 by selecting 1002 from the list.7. Click OK in the Station/Antenna Data Editor to save the edited information by loading the file into the project database.

For each of the remaining files, review the information in the table, then click OK in the Station/Antenna Data Editor to finish loading the file into the project database. You are encouraged to use the Quick Edit/Batch Prompt Mode for most of your work.

When all the files have been loaded into the project database, the program will close automatically and return to the GPSurvey desktop.

REVIEW

Up to this point, we have done the following:

· Created a project· Loaded data files to the project database· Edited some station information while we loaded the data files

Next, we will perform these tasks:

· Process the baselines· Review the results· Perform some loop closures· Adjust the network· Export final adjusted coordinatesTHIS IS A GOOD PLACE TO TAKE A BREAK.

3. Process the Baselines

The baseline processor is a program within GPSurvey called WAVE (Weighted Ambiguity Vector Estimator). The sequence of steps in the WAVE program is simple:

A. Load the files to be processedB. Set up the parameters for processing OPTIONAL: Edit the network of baselines to be processedC. Process the baselinesD. Review the resultsE. Save the results

We’ll take each one of these in order.

A. Load the files to be processed

From the GPSurvey desktop, click on Process / Baselines to enter WAVE. The first task is to select files to process. Follow these steps:

1. With files listed in the top half of the Load dialog, click on Add All2. With files listed in both sections of the Load dialog, click on OK

All the files (there should be 13) will load automatically into WAVE

Note for customers with the Single Frequency (L1) processing option:

The sample data distrubuted with GPSurvey was collected using dual frequency (L1/L2) receivers. When loading this data into the WAVE baseline processor configured for single frequency processing, you will receive the following warning message:

<FILENAME> contains dual freqency data.If loaded, the L2 data will not be used in processing.Press 'Load' to load this file, 'Skip' to bypass it, or'Suppress' to load this file and suppress subsequent warnings.

At this point single frequency customers should press the 'Suppress' button. This will cause all the data to be loaded into WAVE and to be treated as if it had been collected using single frequency (L1) receivers.

B. Set up the parameters for processing

Follow these steps for nearly automatic processing:

1. Click on Process / SetupNOTE: Verify that Independent Set (default value) is checked for Static Baseline GenerationVerify that only Stop & Go(default value, when kinematic data is present) is checked for Kinematic Processing2. Accept the default parameters for processing and click OK in the Setup dialog -- notice the message in the lower left bar of the computer screen which briefly says “Building network”

If we wished to change the selection of baselines to process (optional), we would go to Edit / Network, but in this tutorial, we will accept the default selection. For information on editing the network for processing, see your WAVE User’s Guide.

C. Process the baselines

1. Click on Process / Baselines to begin the processing; processing may take 10-20 minutes, depending on the speed and configuration of your computer2. When the Static Processing status box appears, click on Results / Solution Summary to view results as they are generated.

D. Review the results

The Solution Summary lists the results of the processing for each baseline and kinematic segment. In this tutorial, you’ll see solutions numbered 1-16, 17.1-17.7, 18-19, 20.1-20.7, 21, 22.1-22.7, 23-24, 25.1-25.7. Don’t worry about the numbering scheme here -- we’re more interested in the quality of the results. Also, you can double-click on individual baselines to view detailed summaries, but for now, we want to focus on two quality indicators:

· Ratio -- generally > 1.5, with higher numbers preferred· Reference Variance -- ideal is around 1.0, but < 1.0 is fine; up to 10 may be acceptable for kinematic and single-frequency data (that is, a range of 2-10 is questionable, and > 10 is highly suspect -- however, use loop closures and network adjustment to make the final decision on accepting questionable results)

You are encouraged to view these two values together. When the ratio is low AND the reference variance is high, you have reason to question the results. In a situation like this, you may need to re-process the data with different parameters. Refer to your WAVE manual for more information on troubleshooting.

In this tutorial, most of the solutions are L1 fixed, because one of the setup parameters is to force a L1 final solution for baselines less than 5 km in length, even with dual frequency data. All the ratios are well over 10, which is encouraging. Also, most of the reference variances are ideal, although there are a number which appear to be a little high, particularly the reference variance on one kinematic initialization (>10). If there really is a problem with any of these baselines, we’ll find it in the network adjustment. Loop closures, which can be performed under the View / Network Map option, are also useful in testing questionable baselines.

E. Save the Results

1. From the Solution Summary, click on File / Save 2. In the Save Processing Session dialog, click on OK 3. After the results have been saved, click on File / Exit to return to the GPSurvey desktop

THIS IS A GOOD PLACE TO TAKE A BREAK.

4. VIEW NETWORK MAP

You should be at the GPSurvey desktop at this time. To view a map of the processed results, click on View / Network Map.

Notes on the network map:· FastStatic and static vectors are black lines· Kinematic stop-and-go vectors are light blue lines· Continuous kinematic positions (not processed in this tutorial) are white dots, connected by blue lines

· Kinematic events (not processed in this tutorial) are denoted as X in the continuous kinematic plotZoom

It is possible to zoom in on an area of the network using several easy steps. To zoom in on the vicinity of the kinematic stations in this network:

· Place the cursor (+) west (left) of Morris and north of (above) Moon2· Click down on the left mouse button· With the left mouse button depressed, drag the mouse up and to the right, near Colter· Release the mouse button

Note the scale of the plot in the lower left. You may need to zoom again to view the kinematic stations clearly.

Click on View / Redraw to return to the original scale.

Loop Closures

A “loop closure” is a quick way to check questionable baselines. Each baseline, or vector, is comprised of three components, dx, dy, and dz, which are defined in the earth-centered, earth-fixed Cartesian coordinate system. In a loop closure, baselines between points are added together, until you return to the point of beginning. The algebraic sum of these vectors should be near zero -- if it is more than several centimeters, there is likely a bad baseline (or more than one) in the loop.

Let’s do one loop closure including the baseline Ben - Venice, which had a particularly high reference variance (over 7).

NOTE: You may notice a small number two next to the cursor when you are selecting baselines for loop closures. This number indicates more than one baseline between the two points. You may choose the first baseline which appears or click on NEXT in the baseline ID box to select an alternate baseline.

1. Select Baselines / Closure; this brings up two boxes, one labeled Baseline ID, the other labeled New Closure2. Drag the Baseline ID box out of the way, so you can find BEN--VENICENOTE: the default format of vectors here is dNorth, dEast, and dUp, although you may change this with Baselines / Format3. Click on baseline BEN--VENICE (note it turns green, while whatever vector is closest to the cursor goes to red temporarily)4. Click on BEN--PK5. Click on PK--MOON26. Click on MOON2--MORRIS (drag the boxes out of the way as necessary)NOTE: The small 2 in the cursor indicates more than one baseline between these points; ignore this for now7. Click on MORRIS--COLTER8. Click on COLTER--VENICE9. Note the values of (d)N, (d)E, and (d)U in the Closure box -- each less than 1 cm.This completes the loop. If the baseline between Ben and Venice had been unacceptable, it is highly unlikely the loop closure would have resulted in such small numbers (theoretically, if all is perfect, they should be zero). We’ll proceed directly to the network adjustment and not worry too much more about this baseline.

If you wish to perform other loop closures, click on Reset in the Closure box first.

To close the Network Map and return to the GPSurvey desktop:

· Click on File / Exit

If you see a message asking whether or not to save changes to the database, click on No. If you made a mistake and clicked on Yes, don’t worry, it won’t hurt anything here. You haven’t actually changed any of the data in the database; you only changed the status of baselines for display in the Network Map.

So far, we have accomplished these tasks:

1. Created a project2. Loaded data into the project database3. Processed the data and reviewed the results4. Viewed the processed network as a map and performed a loop closure

We have two main tasks remaining, and you'll see that the first of these is considerably more involved than the second:

1. Adjust the network2. Export the final adjusted coordinates

THIS IS A GOOD PLACE TO TAKE A BREAK

5. ADJUST THE NETWORK

NOTE: The remaining portion of this tutorial will take approximately 45-60 minutes. This portion of the tutorial focuses on network adjustment using the program TRIMNET Plus. For the sake of convenience, this program will be referred to simply as TRIMNET.

Some comments on the network adjustment:

This tutorial does not provide:

· Background information on least squares adjustment · Detailed commentary on the steps and analysis of various screens· Commentary on the many special features within TRIMNET

This tutorial does provide:

· Basic TRIMNET steps which are common to most adjustments· Fully constrained adjustment in NAD83, with geoid height estimates included for optimal orthometric height computations

Some basic facts about TRIMNET:

· There are four basic modules:1. GPS Module -- for importing GPS vectors and basic quality control checks2. Terrestrial Module -- for importing and entering conventional survey data3. Geoid Module -- for estimating geoid separations and improving geoid models (accessed via the Terrestrial Module)4. Network Adjustment Module -- where all the observations are combined and adjusted; this is where you will spend most of your time· The tab key and down arrow key move from one field to another; shift-tab and up arrow key reverses the order; the tutorial specifies which key to use at the appropriate time· The spacebar toggles options within a field · The mouse does not work in TRIMNET

NOTE: TRIMNET allows you to perform fully constrained adjustments in whatever datum you wish to define. It is not a datum/coordinate transformation package. That is, observations may be adjusted in the target datum, enabling you to produce final adjusted coordinates in whatever datum and projection you define.

There are four basic stages to this adjustment:

1. Build the network and check some basic quality indicators -- GPS Network Module2. Perform the minimally constrained adjustment, to check the integrity of the GPS data -- Network Adjustment Module3. Obtain geoid height estimates, which enable us to compute orthometric heights (elevations); this stage involves moving rather quickly through the following sequence:a) Network Adjustment Module b) Terrestrial Module

c) Geoid Module d) Terrestrial Module e) Network Adjustment Module4. Perform fully constrained adjustment -- Network Adjustment Module

Let’s begin the network adjustment now.

· From the GPSurvey desktop, click on Adjust / Network to bring up a menu of TRIMNET Module options. · Double-click on the GPS Network Module icon -- note that after we enter the DOS-based section of Trimnet, your mouse does not apply; the mouse will return to usefulness when we come back to this same menu

1. BUILDING THE NETWORK -- The GPS Network Module

1. With Build Network From Trimvec Directory highlighted, press Enter (“No Vectors Have Been Loaded into Memory” message is normal the first time you enter this module)2. Wait a few seconds, then observe map of vectors on screen; press Esc to return to main menu3. Highlight Summarize Network (use down arrow to move highlight), press Enter· Highlight Redundant Vectors -- observe vector component differences (units are meters) for baselines which were measured more than once (note any differences in exess of about 5 cm -- in this case, all differences are less than 5 cm); press Esc· Highlight Global Network Closures, press Enter -- use the page down key to scroll down and observe the dx, dy, dz columns (units are meters); check for any excessive numbers (5-7 cm in most cases, but what is “excessive” depends on the application); press Esc twice to return to main menu· NOTE: if you ever notice excessive values in the redundant vectors or global network closures screens, record for your own use which solution numbers (far left column) are involved4. Highlight Network Adjustment, press Enter5. At Save Network to Disk Prompt, press “Y” or toggle spacebar for Y to designate Yes, save network to disk; press Enter

NOTE: The previous step automatically passes the network into the Network Adjustment Module. Notice the module name at the upper right portion of the screen.

Some comments on the Network Adjustment Module:

· Adjustment parameters are set up in Adjustment Menu· Adjustment results are displayed under Displays / Adjustment Results· Much of the network adjustment involves going back and forth between these two menu options· Current datum, projection, adjustment status displayed in Status Box· No station weighting will be used in this adjustment, but it can be added under Weighting Strategy / GPS Observations / Station Weighting for your own adjustments, if you wish· Error estimates and error ellipses are displayed at the 1-sigma level (this may be changed, but we won’t change it for this tutorial)2. THE MINIMALLY CONSTRAINED ADJUSTMENT -- Network Adjustment Module

SETUP THE ADJUSTMENT1. Highlight Datum Definition / Change Datum, press Enter2. Highlight NAD83, press Enter; press Esc to return to main menu3. Highlight Adjustment Menu / Coordinate Fix Status; press Enter twice

· Use page down key to advance pages, arrow down to highlight latitude of MOON2· Enter the published Latitude and Longitude of MOON2 and hold these values fixed in the adjustment:A. Type in latitude: 37 26 20.294550 N, then press tab key three times to move to the longitude fieldB. Type in longitude: 122 26 34.638730 W, then press <shift> tab once to move to the Fix column (NOTE: the latitude and longitude values were carried over from the project database, where we entered them as fixed control, but we still need to manually set the FIX status)C.Use space bar to toggle FIX status to YX--NOTE: “Fixed” means the value will not change in the adjustment. To fix a value, you first type in the number, then you toggle the status in the Fix column· Press Enter4. Highlight Adjust Network; press Enter. The strange screen graphics which appear reflect computations happening in the background; just wait a minute or so until all the graphics are complete and the main menu appears again.

Comment: We have just completed the basic steps to begin a minimally constrained adjustment. We are holding only one point fixed right now, so we can focus on the GPS observations -- if there are errors in this adjustment, and we had held several points fixed, it would be too difficult to separate the error in GPS from the error in the control data. So we deal with the GPS first.

It is possible to perform a minimally constrained adjustment without changing the datum (that is, adjusting in WGS-84), and it is possible to adjust without specifying a particular point fixed. But in this tutorial, we have opted to adjust in NAD83 with MOON2 fixed horizontally. This will enable us to generate reasonably good NAD83 latitude and longitude for each point in the network, which we will use to generate geoid height estimates later.

REVIEW THE RESULTS

1. From the main menu, highlight Displays / Adjustment Results / Statistical Summary; press Enter· Note values at the top:· Network Reference Factor = 3.59 (in this tutorial, yours should be close to this)· Chi-Square Test = FAIL· Degrees of Freedom = 90

2. Press Esc to return to Display Adjustment Results menuComment: in a healthy network (no major blunders or bad vectors), the Network Reference Factor is normally less than 10 on the first run. Ideally, it is approximately 1.00, which would indicate the weights of each observation are appropriate. When this value approaches 1.00, the network should pass the chi-square test. We will adjust the weighting strategy after we examine some other screens.3. Highlight Error Ellipses; press Enter -- Note scale in lower right corner of ellipses; scale of 0.10m or more indicates excessive error; press Esc (Tip: lower case letter “z” will escape the error ellipse displays);4. Highlight Histogram; press Enter -- Note any residuals (bar plots) which fall outside the light blue vertical lines (“outliers”); press Esc5. Highlight Observation Adjustment, press Enter -- view residuals here; if outliers showed on the histogram, then the weak observations are highlighted in this display with hatched lines (value in tau column > 1.00); if observations are bad, note Observation number in left column; press Esc6. Highlight Coordinate Adjustment, press Enter -- note the error estimates (“Sigma”) of the computed quantities, which appear in the right hand column; the units are meters. Also, the value in the “Adjust” column is simply the change in value from the previous adjustment to the current adjustment -- these are NOT residuals; press Esc

Comment: the screens listed above are the primary screens to review after each adjustment. The general sequence is:· Adjust network· Note error ellipses and histogram as they quickly scroll by· Review Statistical Summary· If histogram shows outliers, review Observation Adjustment· Review Coordinate Adjustment for post-adjustment error estimates· Re-adjust if necessary, changing weights or disabling observations first

Re-Adjust the Network

1. From Display Adjustment Results menu, press Esc twice to reach main blue menu2. Highlight Adjustment Menu / Weighting Strategy / GPS Observations / Scalar; press Enter· Current Strategy field should be set to “all GPS solutions”· Use down arrow to highlight Current Value Set field· Use space bar to toggle value to alternative; press Enter, then press Esc to green Adjustment Menu3. Highlight Adjust Network; press Enter

Review Results

1. Highlight Displays / Adjustment Results / Statistical Summary; press Enter2. Review Statistical Summary· Note Network Reference Factor = 1· Note Chi-Square = Pass· Note Weighting Strategies listed near bottom of display: Alternative Scalar Applied Globally = 3.59; press Esc

3. Highlight Observation Adjustment, press Enter· Note residuals -- these are all within an acceptable limit (“acceptable” for other networks depends on your job requirements)4. Press Esc three times to main blue menuComplete minimally constrained adjustment

1. Highlight Adjustment Menu / Weighting Strategy / GPS Observations / Scalar; press Enter2. Use down arrow to highlight Current Value Set, use space bar to toggle to user-defined; press Enter3. In the User-Defined Global Scalar box, enter the value found at the bottom of the Statistical Summary (it was 3.59, which we’ll round up to 3.6 in this case); press Enter; press Esc twice to green Adjustment menu; 4. Highlight Adjust Network; press Enter 5. Highlight Save Network to Disk; press Enter

NOTE: When you exit the Network Adjustment Module, you are given a prompt to save network to disk. But when you have completed certain stages of the adjustment, it is a good idea to save the network to disk, even if you are not exiting the program. In this case, use the menu option to save (as we just did in step 5).

Comment: you would normally review the adjustment results after this last adjustment, but there will be very little change in the results this time. We can consider the minimally constrained adjustment complete at this point. That is, we feel confident that the GPS observations are acceptable.

Disabling Observations

NOTE: do not disable anything in this tutorial. The steps are outlined here only as an example.

We did not need to disable any observations in this network. However, if you find outliers in your own networks (not uncommon), you will likely need to disable them. Use the Adjustment Menu / Observation Disable/Enable option to do this. When you are in this menu, remember the following items:1. Use the spacebar to toggle N to Y, which means “Yes, Disable this observation”2. Be sure to disable ALL THREE COMPONENTS of a baseline vector (that is, disable the gpsaz, gpsht, and gpsdis), even if only one of them was an offending observation -- that is, disable the entire vector, not just one-third of it3. After you specify the observations to disable, press Enter; this puts you back in the green Adjustment Menu; select Adjust Network

3. IMPORTING GEOID HEIGHT ESTIMATES -- The Terrestrial and Geoid Modules

Overview of What’s Next

· Go to Terrestrial Module to carry over lat/long from adjustment· Check one setting in Terrestrial Module· Go to Geoid Module, create file with geoid height estimates· Take file of geoid heights to Terrestrial Module, build “terrestrial network”· Combine terrestrial observations (geoid heights) with GPS observations· Compute fully constrained adjustment

1. From the main blue menu of the Network Adjustment Module, highlight Terrestrial Network Module; press Enter2. Type “Y” at prompt to save to disk; press Enter (will take a few seconds to bring up the Terrestrial Module) -- message in Terrestrial Module “Successful Link to stations from Network Adjustment Module” is normal the first time you enter this module3. With Observations highlighted, press Enter4. Highlight Default Observation Parameters, press Enter5. Using the UP arrow key, highlight the field at the bottom of the screen called “Compute Correlations for Geoid Model”; use the spacebar to toggle value to “yes”; press Enter; press Esc to return to main menu of Terrestrial Observations Module6. Highlight Geoid Module; press Enter; answer “Y” at Save Network to Disk prompt; press Enter7. Highlight Load Geoid Model / Geoid90 West; press Enter NOTE: the orthometric heights derived later in this tutorial are based on Geoid90W; you can also use Geoid93W, but your results will be slightly different. If you still wish to use Geoid93, follow these steps (there is no harm done if you already loaded Geoid90W, because the following steps will override this):· Highlight Import New Geoid Model / Use Existing Global GGF File; press Enter· Highlight Geoid93W.GGF; press Enter· In Define New Imported Geoid Model screen, press Enter (it is NOT necessary to type in any other information)· Note the new model listed in the Status box as “Current Model”8. Estimate Geoid Heights / Create DCO File; press Enter; press Esc to main Geoid Module menu9. Highlight Terrestrial Observations Module, press Enter10. In Terrestrial Observations Module, highlight Observations / Access DCO Files / Load Observations from File / GEOIDMOD.DCO; press Enter; press Esc three times to main Terrestrial Observations Module menu11. Highlight Computation Utilities / Compute Network; press Enter; press Esc three times to main menu12. Highlight Network Adjustment Module; press Enter; type “Y” at prompt before exiting; press Enter13. To re-enter Network Adjustment Module with new data (geoid height estimates), you MUST load BOTH the Current Network Adjustment and the Terrestrial Network -- use spacebar to toggle status to Load; press Enter

+---------------------------------------------------------------------------+ LOAD NETWORK ADJUSTMENT MODULE +--------------------------------------------------------------------------+ ¦ ¦ Current Adjustment Network: load ¦ ¦ GPS Network: do not load ¦ ¦ Terrestrial Network: load ¦ +--------------------------------------------------------------------------+ F1=Help ESC=Return to Control Module +--------------------------------------------------------------------------+

Minimally Constrained Adjustment with Orthometric Height

Now that we have geoid height estimates in the network, we can compute orthometric heights for each point. Before we fully constrain the adjustment, we will quickly check to see if our elevation data is within reason. We will do this by adding one orthometric height to our minimally constrained adjustment (an elevation at MOON2).

We will also change coordinate systems from geographic to something more convenient; in this case, the desired system is called California State Plane Coordinate System Zone III. Note that the datum, NAD83, was selected earlier. If the minimally constrained adjustment had been performed in WGS-84, then this would be the time to specify the target datum as well.

· Highlight Change Coordinate System / NAD83 State Plane Coordinates; press Enter· Highlight 403 California Zone 3; press Enter; press Esc to return to main blue menu· Highlight Adjustment Menu / Coordinate Fix Status; press Enter twice· Highlight the Orth (h) field of MOON2 (use page down, down arrow, and tab keys)· Type in the published value for the ortho height: 22.262· Highlight the FIX status field for MOON2, toggle (with the spacebar) the status to YX-h; press Enter· Highlight Adjust Network, press Enter

Review Results

1. Highlight Displays / Adjustment Results / Statistical Summary; press Enter· Note there’s no change in the Network Reference Factor, which is to be expected (this is still a minimally constrained adjustment); press Esc2. Highlight Coordinate Adjustment; press Enter3. Using the control information listed here, compare the computed Ortho Heights on remaining vertical control

Published data for control points:Station N E Ortho height Ortho height (published) (published) (published) (COMPUTED)

MOON2 605992.373 1828075.584 22.262 FIXED PK 614319.815 1822282.301 32.774 32.770 BEN 111.541 111.557COLTER 609124.319 1829722.748 22.910 22.935

The vertical control appears to be in agreement, and the horizontal control also is very close. We can fully constrain this network now, with the expectation that the adjustment will continue to look healthy.

4. FULLY CONSTRAINED ADJUSTMENT

1. From Coordinate Adjustment display screen, press Esc three times to main blue menu2. Highlight Adjustment Menu / Coordinate Fix Status; press Enter twice3. Enter control information as listed above (type in N, E, and Ortho Height values labeled “published”); set FIX status (highlight each field, then toggle with the spacebar) as shown here:

MOON2 YX-hPK YX-hBEN - - - hCOLTER YX-h

4. Press Enter after all information has been entered5. Highlight Adjust Network; press Enter6. Highlight Displays / Adjustment Results / Statistical Summary; press Enter· Note Network Reference Factor (still approximately 1)· Page down to bottom, note Reference Factor for Geoid Model: 0.02 (approx.)· Note message at very bottom of Statistical Summary: Variance in geoid model vs. Noise in vertical GPS observations; we prefer to see Variance in geoid model < Noise in vertical GPS observations, if possible

COMMENT: the information on the Geoid Model (particularly the Reference Factor) suggests we grossly overestimated the pre-adjustment amount of error in the geoid separations -- we can amend this with the weighting strategy

7. Review Coordinate Adjustment values (4-5 cm for heights)8. Review Observation Adjustment values -- note values at the top, which are a result of fully constraining the network; note sigmas for Deflections in Latitude and Longitude, which are currently much higher than the actual deflections -- this is not optimal9. Press Esc three times to main blue menu

SCALE GEOID MODEL, RE-ADJUST NETWORK

Note: This next series of steps is not always necessary. But we want to improve the statistics on our adjustment, so we’ll change the weighting strategy with our geoid height estimates.

1. Highlight Adjustment Menu / Weighting Strategy / Geoid Model / Scalar; press Enter2. Use down arrow key to highlight Current Value Set field; use spacebar to toggle to alternative; press Enter; press Esc3. Highlight Adjust Network, press Enter4. Highlight Displays / Adjustment Results / Statistical Summary; press EnterNote: the Geoid Model Reference Factor still looks extremely low (reflecting overestimated pre-adjustment errors for the geoid separations), but the Variance of the Geoid Model is now even less than the noise in the GPS, which is good5. Press Esc6. Highlight Observation Adjustment, press Enter; · Note: sigmas on deflections of lat and long are now much lower than the actual deflections, which is good· Note: review residuals one last time -- THIS IS REALLY THE MOST IMPORTANT CONSIDERATION -- none of the residuals are excessive· Press Esc7. Highlight Coordinate Adjustment, press Enter· Note: error estimates on heights has dropped considerably; all error estimates are less than 1 cm, which is very good, particularly for the kinematic points, where less precise field techniques were used 8. Press Esc three times to main blue menu9. Highlight Save Network to Disk, press Enter 10. Press Esc, type “Y” at the Save to Disk prompt (redundant in this case, but a good habit anyway)UPDATE PROJECT DATABASE WITH ADJUSTED COORDINATES

These steps will update the project database records with the new, adjusted coordinates. The necessary point records already exist, but the coordinate records will be updated.

1. At the TRIMNET Network Adjustment Windows menu, your mouse is once again operational; double-click on Database Connection2. In Database Connection dialog, with Update Database selected, click on OK 3. In Point records dialog, click on OK4. In Coord records dialog, click on OK5. In TRIMNET menu, double-click on Exit to Project Manager

COMMENT: your network adjustment is now complete. Note that the steps followed here offer a generalized approach to network adjustment, but each adjustment is unique. You may not always need to perform each step outlined here, and you may need to add some other steps. For more information, Trimble training classes are highly recommended.

EXPORTING COORDINATES

Adjusted coordinates may be printed out from two places, both in the Utilities menu. The Adj Coords option provides predefined file formats for exporting final coordinates, and it allows you to edit these formats to create your own custom format. The Project Report option lists adjusted coordinates in a single, predefined format which may be written to a text file. We will use the Project Report option in this tutorial.

· Click on Utilities / Project Report · Click on Station Summary and Adjusted Coordinates· Click on the Preview button to review the coordinates· Click on the Text File... button to write the station summary with adjusted coordinates to a text file

NOTE: Reference Coordinates are not adjusted. They may be very close to adjusted coordinates, or they may be several meters different, depending upon the source (C/A code positioning, for example). Avoid using Reference Coordinates when optimal precision is required.

SUMMARY

This completes the GPSurvey tutorial with fully constrained network adjustment. If you have questions about this tutorial, please call our Technical Assistance Center. Remember that we are always interested in your comments and suggestions concerning GPSurvey. Please send your feedback to:

Trimble NavigationSurveying and Mapping Software Development645 North Mary AvenueSunnyvale, CA 94088ENT: the information on the Geoid Model (particularly the Reference Factor) suggests we

grossly overestimate