More GPSS Display Program Information

Major Features
General Description / Disclaimer
Download and Installation
The GPS Input
Tips for Laptop Computers

Major Features :

  • Free "demo" version ( limited features, but it works )
    US$ ? fee to fully enable all features ( from July 2005 )
  • SIMULATION mode allows operation without a DF or GPS
  • Runs on a ( Windows ) IBM PC, with a COM port
  • Accepts standard Agrello format DF messages
  • Accepts standard NMEA $GPRMC GPS messages
  • Provides automatic map plotting of multiple DF bearings
    Free maps available on SunningHill website
  • User selectable relative / true DF bearings
    GPS heading used for plotting relative DF bearings
  • Log file allows replay of data after a hunt


    Specifications :

    Computer :
    IBM PC running Windows 95 or later OS Requires one RS232 COM port ( USB ports can be used with an RS232 adapter )
    Modes :
    GPS + DF, GPS alone, or simulation mode
    Baud Rate :
    4800 baud
    Messages :
    NMEA $GPRMC GPS messages Agrello DF messages
    Presentation :
    "Moving map" display Background = map of municipal streets Overlay = GPS position and DF bearing lines ( past and present )


    General Description / Disclaimer :

    The SunningHill GPSS IBM display program is a general purpose GPS map-plotting IBM program that also has DF plotting abilities. Street-level maps for the entire United States ( and many other countries ) are available on Robin's website, along with utilities to create custom maps from user-provided images. The GPSS display program therefore represents perhaps the "ultimate" DF display program for mobile DF hunters.... When employed with the PicoDopp DF, ( which automatically switches between the DF and GPS data sources, at regular intervals ) the GPSS display program provides a "fully automated" DF plotting display... the hunter must merely "drive around" while the display accumulates ( and plots ) DF bearing lines from various locations, eventually revealing the location of the transmitter with a series of intersecting DF bearing lines.

    DISCLAIMER : There is no association or collaboration between Doppler DF Instruments and SunningHill Software. Robin Lovelock ( creator of the GPSS display program ) has recently ( July 2005 ) started charging a US$ ? fee for the keycodes that unlock all the features of the GPSS display program. A "demonstration" version of the GPSS program is still available free of charge on Robin's website. It has some limitations, but it actually works, and you can download and install it now, to try it out. Questions or problems relating to the GPSS display program should be deferred to Robin, and if any discrepancy exists between information presented here ( regarding his program ) and information presented on Robin's website, Robin's version ( obviously ) takes precedence.

    Home page of SunningHill Software :

    Robin's GPSS Download page :

    Robin's DF page :

    Robin's Radio page :


    GPSS Download and Installation :

    The information provided here is not intended to serve as a substitute for Robin's installation instructions... This information is merely provided to serve as an outline of the procedure, to show what is involved in installing and running the GPSS display program...

    The GPSS display program can be downloaded as two self-extracting "executable" files ( = .exe file extensions ) from the GPSS website, at this address :

    Please read the information provided on the SunningHill webpage, so I don't have to repeat it here.

    The two download files ( GPSS55A.exe and GPSS55B.exe ) are about 1.4 Megabytes each. Folks downloading over a company intranet may have firewall problems, because .exe files can be dangerous, and the downloads may be automatically rejected by your company's server computer. If this happens, you will have to figure out some other way to get the downloads, possibly on a home computer. The files are ( barely ) small enough to be installed on two floppy disks, to transport them between computers.

    After a successful download of both the GPSS.exe files, create a new folder in your C: drive named "GPSS" and move the files there.

    Run each of the .exe files, and they will extract and install themselves in that folder.

    Once this is done, find the GPSS.exe file, create a shortcut for it and put the shortcut on the desktop. Double click the shortcut, and the GPSS program should start up.

    The program will search for GPS data on any available COM port, and ( if found ) will report it. It will also start a DF "simulation" display, using data accumulated near Robin's home in SunningHill.

    If you have a GPS reciever, ( and have properly configured it to send NMEA data ) turn it on and hook it up to the computer's COM port... the port that you actually intend to use for normal DF operation. If everything is running properly, the program will detect GPS data and will switch to a ( large scale ) map of the area identified by the GPS, and will show the location of the GPS, on that map.

    At this point, it is time to register the GPSS program. Once registered with Robin Lovelock, ( cost : US$ ? ) you will be given a registration "key" number by Robin, which can be used to kill the simulation and enable normal operation of the program. To register the program, hit "CTRL-R" while it is running, to copy all the required information to the text clipboard, then open NotePad and paste the information into the file. Send the file as an e-mail attachment to Robin Lovelock, at this address :

    Robin will respond with a "key" number which you can install in the registration window of the program, to enable the main features and kill the simulation. This usually takes 24 hours or less. He will also identify other GPSS users near you, and provide a link to download any ( free ) maps that he has made available on his website... these maps are detailed, "street level" maps that allow the GPSS program to perform really well...

    Download the ( zipped ) maps using the link Robin provided in his reply e-mail, and move the zip file to the GPSS folder... unzip them there, and restart the GPSS program... If the GPS input is working, the display should "zoom in" to the exact location indicated by the GPS reciever, showing the local streets and features.

    Now for the PicoDopp DF... disconnect the GPS from the computer and re-connect it to the PicoDopp GPS input. Connect the PicoDopp output to the computer input, apply power to the PicoDopp, and watch the display. If the test jumper is still installed on the PicoDopp MAIN board, the display should show your location and a DF bearing line extending outwards from that location. Adjusting the calibration trimpot on the PicoDopp board should change the bearing displayed on the screen.

    If all these things are achieved, the GPSS program is ready to use... there are a few more thing to do, but essentially everything is running properly.


    The GPS Input :

    The GPS must be configured to generate NMEA messages at 4800 baud. This usually requires some ( one-time ) user "set-up" work.

    The GPSS display program uses the NMEA $GPRMC sentence, which contains all the necessary information to plot the user's location. The PicoDopp DF searches for this particular message, and ( if found ) repeats every 5th message to the display computer. ( = about once every 5 seconds )

    Some GPS units may require a special cable to obtain the RS232 data... I use a Garmin eTrex, which requires such a ( special ) plug, which is molded directly into the data output cable.

    Tips for Laptop Computers :

    The following tips do not apply directly to the GPSS display program, but they may be useful if the user has difficulty getting the COM port to work... these tips were originally discovered while using the original MsDOS PicoDopp display program on a laptop.

    Laptop computers can sometimes pose special problems for the display program. They usually have only one COM port, ( = COM1 ) and it is usually dedicated to an external mouse. It is sometimes necessary to defeat the mouse function in the Windows CONTROL PANEL, to enable its use by the display program.

    It may also be necessary to close and re-open the COM port in the CONTROL PANEL, ( even if the mouse does not employ it ) in order to enable it for use by the display program. This action causes the Windows operating system to send a fresh batch of "startup code" to the COM port, which erases any prior commitments for the COM port.

    For laptop computers, the numeric arrow keys are usually "shared" with alphabetical keys on the keyboard. These keys are sometimes employed as an alternative for an external mouse, by using the Windows MouseKeys function. If this is true, then keystrokes to these keys will be routed to the mouse driver software, ( instead of the display program ) which will make vehicle heading updates ( and cursor operation ) impossible.

    The MouseKeys function is found in the Windows CONTROL PANEL, in the ACCESIBILITY OPTIONS folder, under the MOUSE tab. Defeating the MouseKeys function will cause the operating system to route numeric arrow keystrokes to the display program, to enable their use for vehicle heading updates and cursor operation.