Ashtech Z-Surveyor Service Manual download pdf (Page 33)

Survey Preparation & Execution 25

Surveying

Static Survey

Prior to leaving the office to perform a GPS survey, check the following items:

1. Check through the GPS system to ensure all components are present to

successfully perform the survey.

2. Check to ensure that the batteries are charged.

3. Using the Mission Planning module of the post-processing software, check

the satellite availability for the time period when data is to be collected.

Ensure that satellite geometry is sufficient to support good GPS surveying.

Satellite geometry is measured using a calculated value call Dilution of

Precision (DOP). A number of different DOP values exist, the most common

of which is Position Dilution of Precision (PDOP). The Mission Planning

software will give PDOP values for the time periods in which data is intended

to be collected. Avoid collecting data during periods where PDOP values are

larger than 4 (the lower the number the better). Refer to the documentation

accompanying the post-processing software for more details on PDOP and

how to use the Mission Planning software to determine when data should be

and should not be collected.

Figure 4.2. Inside View of Kit Bag

630045.book Page 25 Sunday, February 11, 2001 11:38 AM

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Ashtech Z-Surveyor Service Manual Page 33