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Chapter 1

Introduction and Installation

 

 

1.3Processing Modes and Solutions

Processing Solutions

Fixed static solution

This solution is available when sufficient cycle slip-free data is obtainable. This algorithm starts with the float solution, and using this as a starting position (seed), it searches for the nearby integer combinations. Then, it calculates RMS (root mean squared) fits for these integer intersections. The intersection list sorts around this value. In single frequency, fixed static solution requires at least 10 to 15 minutes of continuous static data, and more on longer baselines. Dual frequency receivers require less then half of that time.

Fixed solutions are not reliable on baselines longer than 15 km for single frequency and 30 km for dual frequency. For data sets with multiple static sessions, fixed solutions can be solved for all static periods.

Kinematic Ambiguity Resolution (KAR) solution

This solution searches ambiguities after a serious loss of lock and is useful for precise kinematic processing because it achieves centimeter level accuracies.

This is the on-the-fly (OTF) algorithm. This technique requires that 5 or more satellites be in view and is helped considerably by L2 (dual frequency) phase measurements. KAR can be useful for single frequency receivers if there are enough satellites present for 20 to 30 minutes. KAR is generally engaged at start - up, or after periods of, extremely poor geometry or loss of lock. For dual frequency, it can be used for reliable initialization if baseline lengths are less than 30 km. Single frequency can also be initialized in this manner, but static methods are more reliable.

Float solution

This solution is less accurate than fixed or KAR solutions, but it is the best alternative for longer baselines that are often not solvable.

The types of solutions are described in the shaded box. The following are the types of processing modes:

Static

Static processing involves the determination of a three-dimensional baseline between two stations. There are two types of static solutions are supported by GrafNav: a float solution and a fixed solution. They are discussed in the shaded box.

Kinematic

Kinematic processing is initialized either with a static survey, from a known point or using Kinematic Ambiguity Resolution (KAR). Following initialization, the antenna-mounted vehicle moves from station to station. In some cases, it may be possible to remove the antenna and place it over the desired point. However, in other cases such as an aircraft, positions can be interpolated.

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GrafNav / GrafNet 8.10 User Guide Rev 4

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