User's Manual

be sent to the application in the form of a NMEA message,

where other applications require the GPS data be sent as a SiRF

Binary message. Most mapping and navigation applications can

use the NMEA message. This setting is configured with the

NMEA/SiRF Binary radio buttons on the GPS page.

• Elev. Mask: displays the current elevation mask. This is the

minimum angle above the horizon that a satellite must be located

before it is used and is represented on the sky plot by a red

circle. This setting is useful when using the GPS in areas where

there might be obstructions to the view of low flying satellites

(e.g. around buildings or trees). A typical elevation mask setting

is between 5 and 15 degrees to eliminate those satellites from

being used to calculate a position. The purpose for this setting is

to increase the accuracy of the GPS. However, by using this

setting, you are reducing the total number of satellites that can

be tracked and used by your GPS receiver. The idea is to

eliminate those satellites that may degrade the accuracy of your

GPS receiver. This is configured in the Masks section of the

GPS page.

• Masks: Displays the current PDOP and HDOP mask values as

configured in the Masks section of the GPS page. If the

measured Dilution of Precision (DOP) value exceeds the value

set for the corresponding mask, the resulting calculated position

will be ignored. In general, as the value of the DOP decreases,

the accuracy of the GPS position increases. DOP values greater

than six usually indicate the GPS position data is of poor quality

(due to poor satellite geometry) and the resulting positions are

less accurate. NOTE: DOPs can not be displayed in Binary

Mode, however, the DOP masks are still in effect.

Satellite Icons

• Unused: A GPS satellite whose signal is being received, but not

being used for position calculations.

• Used: A GPS satellite that is being used to calculate your

current position.

• SBAS: A Satellite Based Augmentation System (SBAS)

satellite, which can be used for error corrections. (See the DGPS

page for more information.)