GNSS Solutions Tutorial

This is a quick guide on Ashtech's GNSS Solutions version 3, a GPS, GLONASS and SBAS professional processing software.
It is quite simple to operate but keep in mind that you need to know the basics of GPS positioning theory before you can solve a network because there are not many ways of checking the achieved positional accuracy effectively so you have to rely on doing the GPS measurements and processing procedures 100% right. 

First up, in the GNSS Solutions install folder there is a MAIN.ini file. This file allows you to perform changes to some global settings used by all projects such as the "elevation cut-off angle". You may want to make a backup copy of it before tampering with its contents.

Right click on it, select "Open with..." and use a simple text editor like Windows Notepad. Make the changes necessary to your work and save the .ini file again with the same extension. 

In case you are working with a file format different to Rinex, GNSS Solutions is accompanied by Rinex Converter, a tool that allows you to convert your files. This may be opened either from inside the GNSS Solutions by going to Tools -> Rinex Converter from the menu bar or finding the executable file directly from the Start Menu.

In order to convert your files, you need to define the directory where your raw gps data is situated. To do this, click on the "Input dir" button.
Then you have to set the output directory where the converted data will be saved. Click on the "Output dir" button and browse to a folder.
It is strongly suggested that you do not use the "=" between the two buttons as using the same directory for both input and output may cause problems later on with organizing your files.

Now you may edit the metadata of the new files by clicking on the "Additional Info" button. There, you can edit information such as the observer name, antenna height and type or even the receiver's serial number. This is useful if you are following a set of standards for your Rinex files or you want everything in order. Information on antenna height and receiver type can also be changed later in the processing program but keep in mind that any changes you make in GNSS Solutions will not be written in the Rinex file.

You may edit additional conversion options such as "GPS", "GLONASS" or "SBAS" data to be included in the resulting file by clicking on the check boxes on the lower half of the window.
Select the files you want to convert from the left part of the screen (Shift+Click or Ctrl+Click to select multiple files) and press on the large, vertigal "BEGIN" button to begin the conversion. After it is done, press "OK" to continue.

With your Rinex files ready, open GNSS Solutions and click on "Create a new project" on the welcome screen. Alternatively, go to File -> New to start a new project.

On the next screen, name your project anyway you like in the "Project name" field and then press on the "Modify Default Settings" button. This is needed to set a series of very important parameters. If you decide to review them later on, go to Project -> Edit Settings from the menu bar.

 The "Region" tab allows you to set your Spatial Reference System, Time Zone and Linear Units. In case your coordinate system is not displayed, select the "New" option from the drop-down menu. You may also click on the "..." button to review your Datum parameters.

Choosing the "Precise Ephemeris" tab will give you the option of downloading Precise Orbit Files from an internet service if the positional accuracy you are aiming for requires it.

Finally, the "Miscellaneous tab" allows you to set horizontal and vertical desired accuracy and adjustment parameters. Modify them to better suit your project and click on the "OK" button.  

Now choose the way you want to import your files. If you are using stored Rinex files, press "Import Raw Data from Files or Promark/ProFlex devices" or press F4 on your keyboard. If you want to connect a compatible Magellan GPS receiver directly to your PC, GNSS Solutions can download the data for you if you select "Download Raw Data from Z-Max or ProMark3" or just press F3.

Browse to your Rinex files and select them. You will be taken to the "Importing GPS Data" screen. On the upper half labeled "Raw Data" you can review your Site codes, Antenna Height information, Height Type, Antenna Type and Receiver Type. Modify them to match your field notes and make sure everything is in order.

On the lower half labeled "Control Points" you have the option of choosing one of those points to act as a Control Point if you have its data. Edit the East, North and Height (ellipsoid or orthometric depending on your datum) and press the "OK" button and choose the "to import" subcommand to continue.

Your Logged Points and Control Points will now appear on a map. Points with common observation times will be connected with dotted red lines, a sign that the baseline has not been processed yet.
You will notice that the GNSS Solutions interface is split into 5 sections.
Toolbar: The standard windows menu bar containing all commands.
Workspace: Shortcuts to most of the commands found in the menu bar for ease of access.
Survey View and Time View: A graphical representation of your network and a representation of the observation times.
Workbook: Here you can see information on the raw data and baselines as well as processing and adjustment information once these procedures have been completed.
Output: All processes will be reported in this non-editable text box as they are executed. Watch it for errors.

If you want to review your observation times, click on the "Time View" tab below the map to switch to a graphic view.

Before continuing, you should go to Project -> Process Options to edit your processing settings. From here you may change the observation mode, delete baselines, exclude satellites or change the elevation mask angle. When you are done, click "OK" choosing the "To Save" subcommand.

Press F5 to process your baselines. If you have selected the option, GNSS Solutions will look for an active internet connection to download the precise ephemeris files now. 

After the processing has been completed, the baselines will turn a green color meaning that they are successfully solved and are within the horizontal and vertical accuracy limits set at the creation of the project. A solid red baseline means that the solution is over the accuracy.Right-click on the baseline and select "Properties" to investigate further. If you spot the error, change the Process Options and solve your network again, otherwise you may have to repeat your measurements. 

Notice the vertical line and black circle over midpoint of each baseline. The vertical line measures estimated vertical accuracy and the circles are horizontal error eclipses. You may compare them to the legend on the lower right part of the Survey View to see how well you did or you can see the process results directly in the Workbook below. 

Press F7 to adjust your network. This should be done only if you have have performed observations on a point from 2 different control points and thus you can use least squares adjustment. Notice that the error eclipses move on the points themselves to represent the adjustment. The adjustment results can be found in the Output panel or in the Workbook.

To finish your Project, press F9 to generate a text report on the baseline processing and the network adjustment by the name of "Land Survey Overview".