**Garmin and PLGR - the NMEA Datum Issue**

Because your GIS data in Alaska is set to NAD27 datum, you must pay
attention to your GPS unit output and how it handles the datum set on
the receiver itself. The PLGR and Garmin are exactly opposite of each
other. Trimble users disregard -- you have full control over datum on
export.

**Garmin (tested on GPS III+ only)**

[Waypoints and Tracks:]{.underline}

A Garmin downloading points and tracks (in the GARMIN mode) outputs them
all in WGS-84, no matter what the datum on the GPS display is set to.
Software like Waypoint+ or MapSource then allows you to change the datum
to NAD27Alaska for import into ArcView

[Logging on External Device using NMEA:]{.underline}

In order to allow real-time download of tracks recorded on an external
data logging device, you must set the Garmin to NMEA mode. The Garmin
does not use a standard NMEA when it comes to datum's. The NMEA is
normally put to WGS84, but Garmin sets it to the datum you select in the
GPS. Software like GPS Tag (ver. 2.0) will grab the changed datum and
will burn such on your image.

# PLGR (tested on PLGR+96 Fed Version)

[Waypoints (PLGR can only download points):]{.underline}

Downloading waypoints (in the ASCII-OUT mode / SERIAL set to Standard)
the PLGR outputs them all in the datum you choose on display. This is
exactly **opposite** of a Garmin. The output waypoint file will contain
a datum field and this will reflect the datum you chose. The data is
then ready for ArcView Import via "Add Event Theme" or via the AlaskaPak
extension.

[Logging on External Device using NMEA:]{.underline}

In order to allow real-time download of tracks recorded on an external
data logging device, you must set the PLGR to NMEA mode (Set SERIAL to
Custom / OUT set to NMEA. PLGR does use a standard NMEA when it comes to
datum's. The NMEA is put to WGS84 regardless how you set the datum for
display. This is exactly **opposite** of a Garmin.

# INSTRUCTIONS

To test the NMEA outputs yourself, you can use the old trusty
HyperTerminal program that comes with all installations of the Windows
operating system (WIN 3X -- Windows 2000). You will also need a download
cable for your receiver and an available COM port (prefer Com1).

-   Go to Programs/Accessories/Communications/HyperTerminal and open the
    HyperTerminal icon

-   Assign a name and icon to the settings particular to the GPS you
    want to test. For example, if I am testing a Garmin, call the
    Connection: "Garmin-NMEA" and assign an icon.

-   Connect using the COM port of choice

-   Under the Port settings, you must change the "Bits per seconds"
    to 4800. Maintain all other settings:

-   Data Bits: 8

-   Parity: None

-   Stop bits: 1

-   Flow control: Hardware

-   Press OK and Save the settings by going to File/Save.

-   Ensure your Garmin is set to the NMEA format (sets itself to 4800
    Baud automatically)

-   You should now see streaming NMEA information.

> The \$PGRMM data line displays the Datum selected on the Garmin.
> Change the Datum on the Garmin to another choice and you will see the
> Datum change on the screen.

-   If you want to test the PLGR, ensure the PLGR's SERIAL Setting is
    set to "CUSTOM" and the SERIAL OUTPUT is set to "NMEA". Although the
    PLGR does **not** have a defined line in NMEA that specifies the
    DATUM, you can monitor the coordinates being outputted in
    HyperTerminal when changing the display datum on the PLGR. You will
    see no alteration on the DATUM.