Integral Design

It may be helpful to discuss a few details about the initialization and output of the Seeed GPS Module for .NET Gadgeteer.  The first time I tried to use this module, I wasn’t patient enough to let the device initialize and start producing data.

This example uses the Seeed GPS Module and prints to the Debug output window of Visual Studio.  Add the GPS module in the Designer window like this:

Seeed GPS Module in .NET Gadgeteer Designer

The following code simply writes output to the debugger, but don’t expect it to start in thirty seconds.

using Microsoft.SPOT;

using Gadgeteer.Modules.Seeed;
using Gadgeteer.Modules.Sytech;

namespace GPS_CellularRadio
{
    public partial class Program
    {
        // This method is run when the mainboard is powered up or reset.
        void ProgramStarted()
        {
            gps.PositionReceived += new GPS.PositionReceivedHandler(gps_PositionReceived);
            gps.NMEASentenceReceived += new GPS.NMEASentenceReceivedHandler(gps_NMEASentenceReceived);

            button.ButtonPressed += new Button.ButtonEventHandler(button_ButtonPressed);

            Debug.Print("GPS enabled? " + gps.Enabled.ToString());
            Debug.Print("Program Started");
        }

        void button_ButtonPressed(Button sender, Button.ButtonState state)
        {
            if (button.IsLedOn)
                button.TurnLEDOff();
            else
                button.TurnLEDOn();
        }

        void gps_NMEASentenceReceived(GPS sender, string nmeaSentence)
        {
            if(button.IsLedOn)
            Debug.Print("NMEA Sentence: " + nmeaSentence);
        }

        void gps_PositionReceived(GPS sender, GPS.Position position)
        {
            Debug.Print("Latitude: " + position.LatitudeString + "  Longitude: " + position.LongitudeString);
        }
    }
}

The first thing you are likely to see in the output window after the program starts is a series of NMEA Sentences:

The thread '<No Name>' (0x2) has exited with code 0 (0x0).
Using mainboard GHIElectronics-FEZSpider version 1.0
GPS enabled? True
Program Started
NMEA Sentence: $GPTXT,01,01,02,u-blox ag - www.u-blox.com*50
NMEA Sentence: $GPTXT,01,01,02,HW  UBX-G60xx  00040007 FF7FFFFFp*53
NMEA Sentence: $GPTXT,01,01,02,ROM CORE 6.02 (36023) Oct 15 2009 16:52:08*56
NMEA Sentence: $GPTXT,01,01,02,ANTSUPERV=AC SD PDoS SR*20
NMEA Sentence: $GPTXT,01,01,02,ANTSTATUS=DONTKNOW*33
NMEA Sentence: $GPRMC,,V,,,,,,,,,,N*53
NMEA Sentence: $GPVTG,,,,,,,,,N*30
NMEA Sentence: $GPGGA,,,,,,0,00,99.99,,,,,,*48

There are so many of these statements that I added the button to turn them off after a while so you can see the position statements without the continuous stream of NMEA Statements.

        void button_ButtonPressed(Button sender, Button.ButtonState state)
        {
            if (button.IsLedOn)
                button.TurnLEDOff();
            else
                button.TurnLEDOn();
        }

        void gps_NMEASentenceReceived(GPS sender, string nmeaSentence)
        {
            if(button.IsLedOn)
            Debug.Print("NMEA Sentence: " + nmeaSentence);
        }

It may take fifteen minutes after you start the program for PositionRecieved events to start. Then you can push the button to stop the NMEA Statements.  The position statements will look like this:

Latitude: 4740.56880 N  Longitude: 12206.67188 W
Latitude: 4740.56813 N  Longitude: 12206.67063 W
Latitude: 4740.56727 N  Longitude: 12206.66911 W
Latitude: 4740.56681 N  Longitude: 12206.66839 W
Latitude: 4740.56616 N  Longitude: 12206.66734 W
Latitude: 4740.56365 N  Longitude: 12206.66310 W

The key to using the numbers in Bing or Google mapping or Google Earth is noting that North (N) and West are positive from the equator and the Prime Meridian, Greenwich, UK. To use the numbers in Google Maps, separate the last two digits before the decimal point from the earlier digits and put a minus sign before the Latitude if it is below the equator, and a minus sign before the Longitude if the position is west of Greenwich.

47 40.56880,-122 06.67188
47 40.56813,-122 06.67063
47 40.56727,-122 06.66911
47 40.56681,-122 06.66839
47 40.56616,-122 06.66734
47 40.56365,-122 06.66310

Using these coordinates in Bing Maps has the following result:

GPS Coodinate Mapping