GNSS Data Collection Methods
Static/FastStatic GNSS data
The following distinctions exist between the data collected during a Static survey session and FastStatic survey session.
For Static sessions, the receiver is assumed to:
- Remain stationary over a single point
- Collect data for a longer period of time than for FastStatic (30 minutes to several hours)
For FastStatic sessions, the receiver is assumed to:
- Collect data at several points during a session,
- Remain stationary while collecting data at each point
- Not collect data while the receiver is moving between points
- Collect data for a shorter period of time than for a static session
The most important distinction between Static and FastStatic is the minimum time required for the receiver to record data (the occupation time).
Static occupation times can range from 30 minutes to several hours or more in length for applications requiring the highest levels of precision and repeatability.
In general, longer baselines require longer occupation times. As occupation times increase, so does the confidence in the computed result. The time required to remain on station depends on the satellite constellation. The occupation time decreases as the number of satellites in view increases. Occupation times also depend on the length of the baseline being observed. Longer baselines, in general, require longer occupation times, regardless of the satellite constellation.
Static and FastStatic survey methods offer the highest possible GNSS precisions. Best results are usually achieved when you plan in advance to use Static and FastStatic data collection sessions in conjunction with one another.
Kinematic vs. Static\FastStatic data
The distinction between a Kinematic survey session and Static or FastStatic sessions is the mobile or roving action of the receiver while data is collected; receivers generally do not remain stationary while collecting kinematic data.
Another important distinction between Kinematic and Static/FastStatic survey methods is the occupation time. In Kinematic surveying, the station occupation time is dramatically shortened (after initialization). It can vary from minutes down to seconds, depending on the application. This allows for a highly productive survey; many data points can be collected in a short period of time.
However, this increased productivity has a disadvantage: the attainable precisions are lower than with the Static/FastStatic methods and the shorter occupations are more susceptible to multipath because of the smaller amount of data. The precisions associated with Kinematic surveying limit its use to GNSS applications where high precision is not a requirement.
Kinematic surveying requires an initialization step to solve for the unknown integer ambiguity in the GNSS signal when lock on the satellite is acquired. This ambiguity must be solved for during processing to obtain the high precision results required for survey applications.
Once initialization occurs, you can use short occupations at survey points. During processing, the initialization is applied to subsequent solutions. Therefore, once initialization occurs you only need an occupation time with enough data to obtain the new position.
Roving and continuous kinematic data
Continuous kinematic surveying lets you perform these operations:
- Map topographic features, such as profiles, cross sections, and contours
- Map the paths of moving vehicles, such as airplanes or boats
Continuous kinematic surveying has the same restrictions as Stop & Go Kinematic surveying. In Continuous Kinematic surveys, however, the baseline processor can solve for the receiver’s position not only when it is stationary, but also for each GNSS observation made while the rover is moving. Topographic surveys, for example, can be performed by logging data continuously over a project area, provided proper attention is paid to antenna heights.
Note: The baseline processor automatically assigns point IDs toeach of the continuous points.
