Rover operation guidelines (SPS985/SPS986 and SPS Modular)
Real-Time Kinematic (RTK) operation provides centimeter-level accuracy by eliminating errors that are present in the GNSS system. For all RTK
The second part of the RTK GNSS system is the rover receiver. The rover receiver is mounted on a pole, vehicle, marine vessel, or in a backpack, and is moved between the points that require measurement or stakeout. The rover receiver is connected to a base station or to a source of RTK corrections such as a VRS system. The connection is provided by:
- an integrated radio
- a cellular modem in the controller
- an external cellular phone that is connected to the receiver either by Bluetooth wireless technology or by means of a cable
The correction stream for some other positioning solutions, such as SBAS, Beacon, and the RTX or OmniSTAR service, is detected by the GNSS or combined GNSS/Beacon antenna itself. No integrated radio or base station is required.
Rover receiver components
The rover receiver has the following components:
- GNSS receiver
- One GNSS antenna
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- Optional items for the different mounting options (see below)
In most rover applications, the receiver operates entirely from its own integrated battery unit. On a vehicle or on a marine vessel, however, an external power supply can be used. Use an external power supply if one is provided. The internal battery then acts as an uninterruptible power supply, covering any external power failures.
Choose a rover receiver according to the needs of the job:
- A GNSS smart antenna incorporates the GNSS receiver, GNSS antenna, receive radio, and the power supply into a single compact unit. A GNSS Smart antenna can be rapidly set up on a pole, vehicle, or backpack. This makes it easy to carry when you are measuring around the jobsite.
- A modular receiver incorporates the receiver, receive radio, and power supply into a single unit. The GNSS antenna and, optionally, the receive radio antenna, is separate from the receiver. When you use an SPS Modular receiver as a rover, you can use optimized components placed in the best locations for your application. For example:
- A small, lightweight rover antenna can be mounted on a pole or backpack; placed in a high, inaccessible location on a marine vessel mast or cabin; or placed on a site vehicle roof or truck bed.
- A rubber duck radio antenna, or an external radio antenna, can be mounted on a vehicle or vessel roof to provide maximum coverage.
An SPS Modular receiver can be placed in a location that is both easily accessible and safe from theft and the weather. The antennas can be placed high on a vehicle or vessel roof, clear of obstructions and able to deliver maximum performance.
Rover receiver setup guidelines
For good rover operation, observe the following setup guidelines:
- Place the GNSS antenna in a location that has a clear line of sight to the sky in all directions. Do not place the antenna near vertical obstructions such as buildings, deep cuttings, site vehicles, towers, or tree canopy. GNSS rovers and the base station receive the same satellite signals from the same satellites. The system needs five common satellites to provide RTK positioning.
- Place the GNSS and radio antennas as high as possible to minimize multipath from the surrounding area. The receiver must have a clear line of sight to the sky at all times during operation.
- GNSS satellites are constantly moving. Because you cannot measure at a specific location now does not mean that you will not be able to measure there later, when satellite coverage at the location improves. Use GNSS planning software to identify the daily best and worst satellite coverage times for your location and then choose measurement times that coincide with optimal GNSS performance. This is especially important when operating in the worst GNSS locations. You can download the Trimble Planning software from the Trimble website (www.trimble.com/planningsoftware_ts.asp).
- The number of GNSS satellites tracked can be higher than the number of GNSS satellites used in the solution for the following reasons:
- The rover only uses satellites that are commonly seen by the base station
- The satellite status is unhealthy
- The satellite is below the elevation mask
- Satellites need a short period of time to be tracked before they are used
- SBAS satellites are not used for RTK positions
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- To get a fixed position solution with centimeter accuracy, initialize the Precision RTK rover receiver. For initialization to take place, the receiver must track at least five satellites that the base station is also tracking. In a dual-satellite constellation operation, for example, GPS and GLONASS, the receiver must track at least six satellites.
- To maintain a fixed position solution, the rover must continuously track at least four satellites that the base station is also tracking. The radio link between the base and rover receivers must also be maintained.
- Loss of the satellite signals or loss of the radio link will result in a loss of centimeter position accuracy. If the radio link is lost and you have the purchased Trimble xFill service, xFill takes over, which allows for centimeter precisions.
- From Fixed, the receiver changes to Float or Autonomous mode:
- In Float mode, the rover has connection to the base station through a radio, but has not yet initialized.
- In Autonomous mode, the rover has lost radio contact with the base station receiver, and is working by itself with the available GNSS signals.
- On a vehicle or marine vessel, place the GNSS antenna in a location as free from shock and vibration as possible. For the SPS Modular receivers, a single magnetic mount is normally sufficient to hold the antenna in a suitable location, whereas for the larger smart antenna, a triple magnetic mount is normally recommended. Good alternatives include a 5/8" thread bolt in a suitable location on the roof or bull bars, or a door-mounted pole bracket.
The GNSS receiver and its cabling should be installed in accordance with all national and local electrical codes, regulations, and practices. The receiver and cabling should be installed where they will not become energized as a result of falling nearby power lines, nor be mounted where they are subjected to over-voltage transients, particularly lightning. Such installations require additional protective means that are detailed in national and local electrical codes.
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To mount a
To mount the
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- (SPS985/SPS986) Make sure that the rover receiver does not lose power. The Batteries for the SPS985/SPS986 smart antenna can be changed when flat. If you do not use the rover receiver very often, ensure that it is charged at least every three months. For vehicle operation or marine vessel operation, Trimble recommends that you use an external power source so that the internal battery can be saved for times when the receiver is being used off the vehicle or vessel.
- Do not locate the receiver or antenna within 400 meters (about 1,300 ft) of powerful radar, television, cellular communications tower, or other transmitters or GNSS antennas. Low-power transmitters, such as those in cellular phones and two-way radios, normally do not interfere with receiver operations. Cellular communication towers can interfere with the radio and can interfere with GNSS signals entering the receiver. This does not harm the receiver, but it can prevent the receiver electronics from functioning correctly.
- Do not use the rover receiver directly beneath or close to overhead power lines or electrical generation facilities. The electromagnetic fields associated with these utilities can interfere with GNSS receiver operation. Other sources of electromagnetic interference include:
- gasoline engines (spark plugs)
- televisions and computer monitors
- alternators and generators
- electric motors
- equipment with DC-to-AC converters
- fluorescent lights
- switching power supplies
- Trimble recommends that, wherever possible, all GNSS receiver equipment is protected from rain or water. Although, the receivers are designed to withstand all wet weather conditions, keeping the receivers dry prolongs the life of the equipment and reduces the effects of corrosion on ports and connectors. If the equipment gets wet, use a clean dry cloth to dry the equipment and then leave the equipment open to the air to dry. Do not lock wet equipment in a transport case for prolonged periods. Wherever possible, avoid exposing the GNSS receiver to corrosive liquids and salt water.
- If you are using the rover receiver in open spaces, Trimble recommends that you stop work during electrical storms where the risk of lightning strike is high.
- Where cables are involved, Trimble recommends that you use cable ties to secure the cables to the rod or other equipment to avoid inadvertent snagging while moving about the jobsite. Be careful not to kink, twist, or unnecessarily extend cables, and avoid trapping them in vehicle doors or windows. Damage to cables can reduce the performance of GNSS equipment.
Internal radio setup for rover operations
The internal receive only radio of the receiver is delivered with the transmit (Tx) radio frequencies preprogrammed into the receiver. To add receive (Rx) radio frequencies to 450 MHz radios, use the WinFlash utility or web interface (see Adding UHF Internal Radio Frequencies). Network channels can be selected for the 900 MHz radios.
Once the radio frequencies are configured, use the controller or receiver to select channel frequencies during base station or rover setup operations.
