GPS Base

This command allows you to configure SurvPC with conventional GPS (GNSS) equipment with the purchase of the optional GPS drivers.

• Instrument Connect: (button). Common across the GPS interface is the Instrument Connect button that attempts to connect SurvPC to the instrument selected in the Current tab via the communication parameters established in the Comms tab. This action is similar to that of ✅ but leaves the GPS Base interface open so that other parameters can be viewed or set.

The tabs shown are configured based on the selected instrument with the most common consisting of:

• Current
• Comms
• Receiver
• RTK

Note: It is recommended to go left to right through the tabs, from Current to Comms to Receiver to RTK, to ensure that all settings are correct, especially when configuring a new receiver for the first time.

Base Setup

Upon the tapping of ✅ from any tab within GPS Base, additional steps will display to help determine the most accurate location of the Base receiver. The Base needs a specific coordinate to use as its stationary position so that it can transmit corrections to the connected rover(s). The location can be established one of several ways:

Note: To the extent possible, it is advisable to establish the Base over a known position as this provides additional accuracy checks if the site needs to be revisited in the future. A method that can be used to establish a more accurate base position would be to:

1. Initially collect raw static data with the GPS Raw Only command, then,
2. Post-process the data using tools such as Carlson SurveyGNSS or OPUS, then,
3. Use the result when establishing the base location.

From New Position

• Read from GPS: Commonly referred to as Get Here or Find Me, this method users a version of the Average GNSS routine to establish the base receiver's position and use it as its "true" position:
  

  

  Note: Common practice is to allow the Base enough time from initial power-up to "find itself" (usually a minute or two). It does so by downloading any updated almanac information and/or resolving ambiguities.

  • Min. Measurement Count: Indicate the minimum number of readings that must be met to determine the calculated position of the base.
  • Time in Minutes: Indicate the shortest amount of time that must be satisfied before results are determined.
  • Standard Deviation (H/V): Indicate the maximum amount of Horizontal and Vertical standard deviation of the readings.
  • Tolerances: Configure any additional Tolerances.
  • Monitor/Skyplot: Check/review the current receiver readings as provided by Monitor/Skyplot.

  After the results have been obtained, the results are displayed:

  

  Note: Depending on the number of readings used to establish the base position (more is better), the true position of the receiver can be off up to the published Autonomous accuracy of the receiver (generally no more than 2 meters). For this reason, a Points Localization is commonly used after the configuration of the GPS Rover.

  • Resume: Permits additional readings to be used in the Base position.
  • Edit: Allows the horizontal and/or vertical components of measurements to be toggled for use in the Base position:
    

    

  Accepting the results of the Base setup then flows to the Base Configuration step.

• Enter Lat/Lon: Requires you to enter the latitude and longitude for the position of the base antenna:
  

  

  Note: This is useful if you are setting up over a monument whose latitude and longitude is known (e.g. a location as the result of post-processing or perhaps that from a NGS Survey Mark Query.

  Accepting the results then flows to the Base Configuration step.

• Enter Grid System Coordinates: Requires you to enter the grid system Northing and Easting for the point that the base is occupying:
  

  

  Note: This is useful if you are setting up over a monument whose coordinates you know.

  Accepting the results then flows to the Base Configuration step.

From Known Position

• Repeat Last Setup: This option re-uses the most recent base setup and is useful where a site is revisited on successive days. Processing then flows to the Base Configuration step.
• Previously Surveyed Point: This requires you to enter the coordinates, on the configured coordinate system, of a known, surveyed point:
  

  

  Note: The known point must be found in the raw file in a form that includes its Latitude/Longitude (a previous GPS measurement).

  Accepting the results then flows to the Base Configuration step.

• Use Local Coordinates: If you have performed a localization, a local coordinate can be specified:
  

  

  • Scale to Ground: When enabled, the presumed grid elevation will be scaled to the ground elevation.

  Note: If a localization is not yet associated with the job, the standard File Selector dialog box is displayed prompting for the localization to apply.

  Accepting the results then flows to the Base Configuration step.

• Read From File: This option launches the standard File Selector dialog box that allows you to specify a saved base configuration file. This is useful when returning the Base to a previously configured location.

Base Configuration

Once the Base location has been established, data is presented for confirmation:

• RTK Broadcast ID: Assign a meaningful broadcast ID (usually a point number associated with the Base location) whose information is recorded in the raw file.
• Store in Point List: Allows you to store the Base location to the point list of the job.
• Continue with Base Setup:
  • Answering Yes will continue to the Save Base prompt.
  • Answering No will return to the initial Base Setup so an alternate method can be explored.

Save Base Reference File

It is recommended that the Base information be saved so that it can be used with the Read From File option if additional visits to the job are needed.

• Answering Yes will launch the standard File Selector dialog box where the Base reference (*.ref) can be stored.

  Note: The Base Antenna Height information is not stored in the reference file. Therefore, the antenna height does not necessarily have to be the same from setup to setup.

• Answering No will simply complete the Base configuration.