Content
GS08 Network Rover
SmartWorx Lite running on a CS10 Training
The following hand out describes a short practical session, introducing you to the principles of GNSS surveying, and a hands on look at the Leica GS08 Network Rover.
The aim of today‟s practical is for you, in conjunction with a PowerPoint presentation, to understand some of the considerations when using GNSS equipment on site, and to practically “stakeout” a small building plot, having created your own „local coordinate system‟.
The practical is broken down into Tasks, from putting the kit together, to setting out some coordinates.
The equipment you will be using today is the Leica Viva GS08 NetRover. All the components of the Viva NetRover work seamlessly together, creating a lightweight and cable-free GNSS solution. It marries the SmartWorx Viva Lite preparatory software solution, alongside proven hardware and GNSS receiver technology.
The receiver in the CS10 is GLONASS-enabled, adding another 22 satellites to the equation. In an urban-canyon, such as Nottingham City centre, the addition of these ensures we can observe at least 5 GPS and 2 GLONASS satellites, even with a reduced proportion of the sky, greatly aiding our RTK-position.
In a nutshell, the antenna tracks and ranges to satellites on the L1 & L2 carrier frequencies. It relays this information via Bluetooth to the CS10 field controller. The CS10, in unison with its 3.5G internet GPRS-modem, calculates a receiver position using corrected range data for each satellites, supplied by SmartNet over the web.
If you have any questions about the kit, or it is not working, please contact one of the members of staff.
Task 1 – ‘Assembly’
In the box, you will find a CS10 Field Controller, GS08 antenna, and associated ancillaries. Fit the batteries in the controller and antenna, and mount on the pole using the clamp / bracket.
Task 2 – ‘Creating a control job’
Having setup the kit in a so called “SmartRover” configuration, turn the controller and antenna on using the power buttons. The controller will boot-up Windows, from which you can double-click on the SmartWorx Viva Lite icon from the desktop (orange). The main menu (4 icons) will be shown.
Tap ‘Jobs & Data‘, ‘New job‘, and create a job called ‘control’, storing the data to CF-Card or Internal Memory. To add text, use the pop-up touch-screen keyboard, pressing RETURN to store the text.
The ‘Coordinate system‘ (the 3rd tab) should be changed to ‘None‘.
When finished, tap ‘Store‘. This will return you to the main menu.
Task 3 – ‘Adding points to the control job’
From the main menu, tap “Jobs & Data”, then “View & edit data”, and “New..” to add the known control stations for the campus. Tap „Store‟ to save the points, These must be typed in manually, therefore appearing as Ctrl, in the class listing.
Coordinates: Stn1
When finished, press OK or the back button escape back to the main menu
Task 4 – ‘Creating a working job’
Having added the control points into a ‟control‟ job, you must now create a working job, where our
surveyed data will be stored. As before, create a “New job”, calling it “campus survey”. This time
however, the coordinate system needs to be „WGS-84‟. Save the job to the CF-Card or Internal Memory.
Store and continue back to the main menu.
Task 5 – ‘Surveying the control stations’
From the main menu, “Go to Work”, and “Survey”.
Press the Fn (function) key and tab “Conect”, to start the RTK data stream. You will receive an information message, telling you that you are connected and receiving information from SmartNet
(Network RTK RTCMv3.1).
Wait until the navigation wheel tightens to become a cross-hair (every 8sec a double-tick appears, showing that ambiguities have been resolved). Look for a 3DCQ of 15-20mm.
Call the Point ID stn1 (the same ID as our control points), stand over the nail, level the pole with the plate-bubble, and tap Measure.
The instrument will count 10 RTK positions, and will store the point automatically.
Repeat this procedure for all control stations, ensuring the correct point ID is used. You can review the data in “Jobs & Data” and “View & edit job”.
Task 6 – ‘Determine Coordinate System – an introduction’
GPS measured points are always stored based on the global geocentric datum known as WGS 1984. Most surveys require coordinates in a local grid system. For example, based on a country‟s official mapping datum or an arbitrary grid system used in a particular area such as a construction site. To convert the WGS 1984 coordinates into local coordinates a coordinate system must be created. Part of the coordinate system is the transformation used to convert coordinates from the WGS 1984 datum to the local datum. The Determine Coordinate System application allows; the parameters of a new transformation to be determined, and the parameters of an existing transformation to be recomputed.
The control points used for the transformation should surround the area for which the transformation is to be applied. It is not good practice to survey or convert coordinates outside of the area covered by the control points as extrapolation errors can be introduced. Determine Coordinate System is the conventional method of determining a coordinate system. Parameters such as the height mode must be set by the user. One or more control points for both the WGS 1984 and the local datum are needed.
Depending on the number of control points and available information, a Onestep, Twostep or Classic 3D transformation can be used. The type of transformation to be used when determining a coordinate system.
Onestep
Transforms coordinates directly from WGS 1984 to local grid and vice versa without knowledge about the local ellipsoid or the map projection.
- The WGS 1984 coordinates are projected onto a temporary Transverse Mercator Projection. The central meridian of this projection passes through the centre of gravity of the common control points.
- The results of (1) are preliminary grid coordinates for the WGS 1984 points.
- These preliminary grid coordinates are matched with the local grid control points. The Easting and Northing shifts, the rotation and the scale factor between these two sets of points are then computed. This process is known as a classic 2D transformation.
- The height transformation is a single dimension height approximation.
As an example, see the conversion, numerically:
| Point ID | WGS-84 | Local-grid | |
| Stn1 | 52°12‟23.15” N, 0°17‟38.40” W, 66m | 7-param => | 695.000, 855.000, 19.530 |
| Stn2 | 52°12‟22.05” N, 0°17‟38.23” W, 66m | 688.477, 816.383, 19.613 | |
| Stn3 | 52°12‟23.65” N, 0°17‟39.08” W, 66m | 657.421, 855.085, 19.252 | |
| Stn4 | 52°12‟22.53” N, 0°17‟39.14” W, 66m | 656.911, 817.723, 19.453 |
Task 6 – ‘Determine Coordinate System’
As described, WGS-84 lats & longs are of no practical use on construction sites; surveyors like flat-earth projection models, in Easting, Northing and height.
Therefore, we are going to create our own “Notts Trent Uni Grid”, which applies for our small site, converting WGS-84 ellipsoidal to E/N/h values. We have stored our known site control, and have measured the stations in WGS-84; now we allow the kit to create a 7-parameter transformation and a new local-coordinate-system.
From the main menu, ‘Go to Work‘, ‘Survey+..‘ and ‘Determine coord sys‘.
Follow the screen-shots below to create your own grid.
Task 6 cont – ‘Determine Coordinate System’
Use the ‘Auto‘ function to match the stations. Remember we named them all the same Point ID so that they can be synchronised by name. Match by position (P) & height (H), and tap ‘Calc‘.
You will have a set of residuals, showing you ‘how good‘ your transformation was. If it is within 0.010m in E/N, tap ‘OK‘ to finish the application. Your new grid will have been stored.
Task 7 – ‘Creating a stakeout job’
From the main menu, go to ‘Jobs & Data‘, ‘New job‘, and create a new job called ‘stakeout‘, storing the data to CF-Card or Internal Memory.
The ‘Coord system‘ (the 3rd tab) should say ‘Notts Trent Uni Grid‘. When finished, hit ‘Store‘.
Task 8a – ‘Adding points to the stakeout job’
From ‘Jobs & Data‘, tap ‘View & edit data‘, and tap ‘New..‘ to add the desired stakeout points for the new building on the campus. These must be typed in manually, therefore appearing as Ctrl, in the class listing. See below for point coordinates.
For large numbers of points, Excel or Text spreadsheets can be imported, as well as DXF AutoCAD draw-ings and MxGenio road string data.
Stakeout pt 1:
Task 8b – ‘Creating a stakeout job—adding points from Excel (ASCII data format)’
As well as entering points manually, coordinates can be uploaded from ASCII files such as .txt and .csv. In excel, create 5 columns with Point ID, Easting, Northing, Height & Code if applicable.
Save this spreadsheet as a .csv (comma separated) file and paste it into the Data folder on an SD-Card.
Task 8c – ‘Creating a stakeout job – adding points from AutoCAD (.DXF data format)’
Leica Viva SmartWorx is capable of converting a CAD file into DBX data, for use in setting out and DTM-stakeout tasks.
Save the cad file as a .DXF and paste it into the Data folder on an SD-Card.
Task 9 – ‘Stakeout’
Armed with your newly created local grid, ‘Go to Work‘, ‘Stakeout‘, setting the Control job as stakeout. Pick one of the points to set out, and allow the on-screen arrows to guide you to the nail i.e. stake each point out. When you are within 0.5m of the point, the display will change to a bulls-eye. Mark the ground with chalk. Move to the next point by toggling left and right on the Point ID line, or use the map screen to tap on a point to select it.
Once complete, press ‘Fn‘ and ‘DISCONNECT‘, ending your RTCM SmartNet data flow.
Task 10 – ‘Summary’
You have entered fixpoint data, surveyed with GNSS, stored digital data, created a local coordinate system, and set out a tennis court. In order to receive Network-Real-Time-Kinematic corrections, you have connected to the internet (via a GSM/GPRS data enabled sim card), dialled in to the SmartNet commercial RTK service, and resolved your receiver ambiguities, to generate 20mm 3D-positions on your own local grid.
As covered in the PowerPoint, you can see the limitations of real-time GNSS, because it is dependant on many factors, most significantly a connection to mobile-internet and an open, unobstructed sky. However, the speed of data collection and the freedom of movement around the site make this technique very efficient when large volumes of data are required.
