Pre-planning a Survey

GPS or GNSS (global navigation satellite system) Surveys require Planning and Preparation.

The Quality, Accuracy and Precision of a Survey depend on Timing and Accurate Survey Control.

In this investigation we will attempt to itemize and explain the importance of each activity required to ensure success.

TIMING

In preparation of a GNSS Survey; select the time of the day when the satellite constellations are best suited to the type of survey to be performed.

Browse GPS Planning Online (use Internet Explorer with Microsoft Silverlight)

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Select Settings tab and Pick a point on the map nearest your location.

Set the Visible Interval and Time Span to the available hours for the survey.

Select Today or set the date to the future when planning surveys at a future date

Select the Satellite Library tab, tick the constellations enabled on the receivers in use.

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Select Number of Satellites tab – In the Philippines the number of Satellites in View is rarely below 15 (GPS/Glonass/Beidou/Galilleo). If the GNSS receivers used are Beidou enabled there will always be more than 20 satellites available for use in a Survey.

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Select DOP‘s tab, this is the important graph for successful Surveying. If accurate levels Height or Z values) are required select the time span when the VDOP is favorable. For standard, topographical or engineering design are required utilize the time span when the PDOP is below 4.0.

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Print the DOP‘s and Number of Satellites graphs and take these with you to the field for reference. This information will assist and give meaning to the Warning screens popping up on SurvCE while conducting the Survey.

NOTE: It is very important to select a time of the day when the constellation is best to establish survey control. This effects the survey project accuracy relative to the real world.