| Configuration Tested: | Garmin GPS 12XL
Power: 4 x AA alkaline batteries.
Firmware: 2.04 |
| Data Logger: | Limited internal data logging. |
| Data Input/Output Port: | RS-232 with 4-Pin male connector. |
| Supplied RTCM Cable: | None. |
| Optional Cables | - Garmin 5-pin female to unterminated end.
- If supplied with a computer interface cable, will require a NULL MODEM to switch pins 2 and 3.
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| Cable & Connectors Used in BMGS Testing: | - Purchased the Garmin 4-pin female to unterminated end cable and had the supplier add a DB9F connector so that it was specifically wired for connection to the CDGPS.
- A number of optional cables are available from Garmin and their distributors.
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| Antenna: | - Integrated/internal GPS antenna provided (optional, external GPS antenna is available).
- In one configuration the Global Surveyor was placed inside a small backpack to which the DGPS antenna was attached to a 2' PVC pipe. The Garmin 12XL GPS receiver with integrated/internal antenna was hand-held.
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| RTCM Reception Indication: | - When RTCM/DGPS corrections are received, the "3D NAV" message on the Satellite Status page or screen changes to "3D DIFF" (or "2D DIFF" if insufficient satellites are in view for 3D positioning).
- When RTCM data is unavailable the warning: Message! Press Page, is flashed to the screen. Upon pressing the Page button the user is provided the following message if RTCM was not available: No RTCM Input.
- It appears that the Garmin GPS 12XL does not recognize other RTCM messages (i.e., Type-2, Type-3, etc.) that are being transmitted by the Global Surveyor Service, as such, the above warning message occurs regularly, even though RTCM data has not been lost.
- It appears that the RTCM Age setting, which not a setting available to the user, is approximately 60 seconds. In other words, if the RTCM data is "lost" for a period of time, the Garmin 12XL will continue to use the old RTCM corrections for approx 60 seconds noting that you are still receiveing DGPS corrections.
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| Post Mission Data Access: | - No data viewing/analysis software is provided. Optional software is available from Garmin and/or other sources.
- The Averaging function only averages the horizontal coordinates, not the vertical component. Aside from Garmin's Figure-Of-Merit (FOM) indicator, no Quality Control information is available while in Average-mode (i.e., once Averaging, the user is "locked" onto that particular menu until averaging is completed).
- If one requires the vertical coordinate, it can only be viewed in real-time, on a fix-by-fix basis, on the Position screen.
- One can collect horizontal positions while moving (i.e. dynamic) to a track Log using the Tack Setup. This enables the user to log 1024 horizontal positions, which can eventually be uploaded to the computer using some of the available software.
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| General Notes: | - No indication in User's Manual or on receiver screens indicating the satellite elevation mask setting, signal-to-noise-ratio (SNR) setting, or DOP tracking/logging.
- The vertical coordinate in the manual is noted as "Altitude" and the manual gives no indication whether this is MSL or Ellipsoidal. The Global Surveyor tests indicate that this vertical coordinate is orthometric.
- RTCM Type-16 messages are echoed to the screen if these are transmitted.
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