Constellation Data Systems, Inc.
Constellation Data Systems, Inc.

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Some GPS data sources are not in NMEA format. Reading a data source in non-NMEA data format is a rather straight forward task for a software developer skilled in the methods of accessing the serial port. Then Converting non-NMEA data into a NMEA datastream can be rather simple task, or a difficult task depending upon your requirements. Regardless, the task of injecting that data into a NMEA aware application however, is a task which could easily require a developer several man years of effort. The Virtual To Virtual GPS Utility allows easy data injection into a NMEA aware application, resulting in savings of schedule/costs and risk reduction.

Source code for this utility is published, and custom built variations of this utility may be created with the GPS Software Development Kit.


1. Click here to download the Virtual To Virtual GPS Utility User's Guide in PDF format. Read prior to installing and running the utility.
2. Click here to download the Virtual To Virtual GPS Utility Software.
3. Click here to download the VSP Core Software (required to execute the utility).

GPS Product licensing is handled through through the Constellation Data Systems Sales office.

Data Flow Diagram

In the following diagram, a custom windows application (typically a WIN32 application) is shown reading non-NEMA protocol data from a GPS receiver. The source of this data very much depends upon your equipment and interfaces. As an example, your requirements may dictate that you have to convert LORAN C data from and antique WidgetCon receiver on COM1, into a more modern NMEA stream. In such a scenerio, you would create a WIN32 application that reads the LORAN data from COM1, and then converts that into a NMEA stream and writes that data, using the WIN32 communications API to a Virtual Serial Port (shown below hypothetically as COM3).

The Virtual To Virtual GPS component would then transfer that data to COM4, with some added NMEA style timing pacing. It is often the lack of that pacing which causes some 3rd party applications to fault or otherwise misbehave.

Command Line Switches

| Virtual To Virtual GPS Utility v2.31, Rev c
| (c) 2004 Constellation Data Systes, Inc. (CDS)
| All Rights Reserved, Restricted USE, contact CDS for licensing.
Usage: VirtualToVirtualGps Source Destination

Source - Virtual Serial Port onto which NMEA is written.
Destination - Virtual Serial Port from which NMEA is read.

[switches] - Optional settings. All VALUE's are in decimal.

---Suffix 'A' denotes optional settings of VSP 'COMA'---

---Suffix 'B' denotes optional settings of VSP 'COMB'---