Monitor/Skyplot

Some of the non-obvious items are described below:

• Status: Indicates the overall confidence in the current position. The Status is shown as either (ordered in increasing precision and accuracy):
  • AUTONOMOUS: No radio communication between base and rover, not precise, not accurate.
  • DGPS: Corrections from differential sources such as WAAS or SBAS.
  • FLOAT: Communication has been established, but ambiguities have not been resolved.
  • FIXED: Position has been resolved, highly precise, accurate.
  • SUREFIXED: Position has been resolved and confirmed with a secondary GNSS solution, highly precise, highly accurate.

    Note: This solution type is receiver-specific.

• Satellites: Indicates the number of SVs being used in the solution over the total number of SVs signals being received.

  Note: This is governed by several factors, including:

  1. The types of constellations the receiver is able to receive
  2. The Elevation Mask specified for the receiver
  3. The Constellation Configuration specified for the receiver
  4. The Message Type being used by the receiver
• Latency: Latency refers to the time delay between when a GPS receiver receives signals from satellites and when it calculates and provides a position fix. Essentially, the age of the correction coming from the GPS Base or RTK network.

  Note: In most situations, a latency of 1 or 2 seconds can be expected. Most of today's modern receivers can "hold" a fix for longer periods so latency values higher than these normal values is not an immediate cause for concern. However, as the age of the solution begins to increase, the solution Status will start to devolve.

• xDOP: The various Dilutions of Precision provide a measure of the geometric strength of the satellite configuration visible to a receiver, influencing the accuracy of position calculations. Values are dimensionless and commonly range between 1 and 3, values < 1 are considered ideal. Lower DOP values indicate better geometric conditions and typically result in more accurate position fixes. Various DOPs can include:
  • HDOP (Horizontal): HDOP considers only the horizontal dimension of position (latitude and longitude) and provides a measure of the accuracy in determining the receiver's planar location.
  • VDOP (Vertical): VDOP considers only the vertical dimension of position (altitude) and provides a measure of the accuracy in determining the receiver's altitude.
  • TDOP (Time): TDOP considers the accuracy of the receiver's clock synchronization with the satellite clocks. It provides a measure of the accuracy in determining the receiver's time.
  • PDOP (Position): A combination of HDOP and PDOP. PDOP considers the 3D dimensions of position (latitude, longitude and elevation) and provides a measure of the accuracy in determining the receiver's overall position.
  • GDOP (Geometric): GDOP takes into account all the dimensions of position, including latitude, longitude, altitude, and time. It provides a comprehensive measure of the geometric strength of the satellite constellation.
• Hrms: The Horizontal Root Mean Square value is a statistical measure of the magnitude of horizontal readings. It is effectively conveying the potential horizontal error.
• Vrms: The Vertical Root Mean Square value is a statistical measure of the magnitude of elevation readings. It is effectively conveying the potential vertical error.

Additional information (but not inclusive) is the following:

• the current geodetic position
• the Geoid and Geoid Shift (also known as the Geoid Separation Distance)
• the applied Localization
• the current Projection

A summary of the SVs in use vs. visible for each of the constellations supported by the receiver is displayed at the top of the dialog box.

Note: The gray ring around the outer edge of the circle represents the current Elevation Mask.

Note: The gray ring around the outer edge of the circle represents the current Elevation Mask.

Arrows next to the satellites will indicate if the satellite is rising or falling in the sky, by the associated arrow. Click on any satellite number to see individual satellite details, including the precise signal/noise ratio:

Tapping outside of the constellation map permits you to toggle satellites (or even full constellations) if supported by the receiver:

If a satellite is turned off, it displays with a line through it within the Signal/Noise Ratio graphs. Tapping the Sun tab provides additional solar customization and information:

• PRN: Essentially the satellite reference numbers. * indicates satellite in use for position calculation and ! indicates the satellite is not enabled.
• AZI: Azimuth of the satellite from the receiver position.
• ELV: Elevation of the satellite above the horizon, including rising (>) and falling (<) direction.

Tapping a satellite row also displays the detailed satellite information:

In addition to the geodetic position of the Base, it's local coordinates are also displayed

The distance from the Rover to the Base is displayed and its position can be saved into the current job via the Store button. Additionally, Antenna information (if being broadcast) can be reviewed and/or set.

Used primarily with older equipment, Mission Planning can help select the best times for field surveying to maximize available satellite signals. Its goal was to predict when satellites are most available to reduce wait time, time to fix and the likelihood of inaccurate field measurement due to poor satellite geometry.

Almanac

The almanac file contains the information of future satellite orbit positions. Select either to download the almanac file from the Internet load the almanac from a previously stored .alm file.

Once the preferred almanac file is loaded, the user will be presented with the Mission Planning screen. Tabs include:

• Availability
• Skyplot
• Settings
• Obstructions

Availability Tab

In the Availability tab:

1. the vertical scale at left shows the number of predicted satellites.
2. the vertical scale at right shows the Dilution of Precision values.

Note: The PDOP line, which is brown, is typically given the highest priority and should be less than 3 for better results and measurements with high PDOP values can be flagged through a PDOP Tolerance.

Tap the > (right arrow) key to move to the next day to review the next 24 hours of satellite availability.

Note: Tapping on an area of the Availability graph will switch to the details found in Skyplot for the time period.

Skyplot Tab

In the Skyplot tab, the user will be able to see the various satellites in view for a given time. Colors indicate both the type of constellation and satellites below the specified Elevation Mask (as found in the Settings tab) will appear lighter. The table below shows satellite status.

Tap the > (right arrow) key to move to the next time period to review details for that time period.

Note: Values being displayed are controlled through the Settings tab.

Settings Tab

Use the Settings tab to specify your expected location and Height Above Ellipsoid (HAE) and to modify the configuration of the data.

Note: The Elev Mask setting is independent from that set under the Receiver tab of GPS Base or GPS Rover.

Obstructions Tab

Future satellite availability will depend on how open the sky view will be for signal reception. Obstructions play a large part in satellite signal reception. For example, if you have a high building or a ridge blocking satellite signal reception to the Northwest of the receiver position, this obstruction can be entered here.

Note: Obstructions can be:

• entered manually, and/or
• graphically picked in the window on the left.