Kerotest Shannon Portafuse III, Руководство оператора

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Kerotest Manufacturing – SHANNON & PAF III OPERATORS MANUAL - REV 3
Page 48 of 60
Position Accuracy
GPS accuracy is affected by a number of factors, including satellite positions, noise in the radio signal,
atmospheric conditions, and natural barriers to the signal. Noise can create an error between 1 to 10 meters
and results from static or interference from something near the receiver or something on the same frequency.
Objects such as mountains, buildings, or even clouds in between the satellite and the receiver can also
produce error, sometimes up to 30 meters. The most accurate determination of position occurs when the
satellite and receiver have a clear view of each other and no other objects interfere.
THE SMART SCANNER™ WAS NEVER DESIGNED TO GIVE A POSITION ACCURATE ENO UGH TO GO FIND A
FITTING AND DIG IT UP. IT IS PROVIDED TO ALLOW THE USER TO DETERMINE THE GENERAL LOCATION
WHERE THE FITTING CAN BE FOUND.
Position Error Indicator
The Position Error Indicator gives the operator an indication of how much confidence they should place in the
accuracy of the current position reading.
Value Rating Description
1 Ideal
This is the highest possible confidence level to be used for applications
demanding the highest possible precision at all times.
1-2 Excellent
At this confidence level, positional measurements are considered accurate
enough to meet all but the most sensitive applications.
2-5 Good
Represents a level that marks the minimum appropriate for making business
decisions. Positional measurements could be used to make reliable in-route
navigation suggestions to the user.
5-10 Moderate
Positional measurements could be used for calculations, but the fix quality
could still be improved. A more open view of the sky is recommended.
10-20 Fair
Represents a low confidence level. Positional measurements should be
discarded or used only to indicate a very rough estimate of the current
location.
>20 Poor
At this level, measurements are inaccurate by as much as 300 meters with a 6
meter accurate device (50 DOP × 6 meters) and should be discarded.
As a general rule, confidence indications above a Value of 2 should not be used although the SMART Scanner™
will not prohibit the operator from using any reading.
Although it is beyond the scope of discussion for this manual, the number we refer to as the Position Error
Indicator is actually the “Horizontal Dilution of Precision” value (HDOP) rounded to the nearest integer for
those with a more advanced knowledge of GPS terminology.