Ionospheric Propagation Error Correction
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Solution Overview
Problem
Current satellite-based navigation systems, such as GNSS, face significant errors due to ionospheric propagation effects, particularly higher-order errors that are not accurately accounted for, leading to position ambiguities and inaccuracies, especially when only two frequencies are available.
Innovation Solution
A method to determine and correct higher-order propagation errors in electromagnetic waves by measuring and modeling the electron content and density of the ionosphere using signals at different carrier frequencies, allowing for precise error correction without the need for additional measuring devices or routes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dual-frequency measurements are used to correct first-order ionospheric errors, then distance errors are reduced to centimeter level, but higher-order residual errors (proportional to 1/f^3) remain at several centimeters
Solution Approach 1:
The patent changes the mathematical model parameters by introducing higher-order terms (m=3, 4, 5) in the frequency expansion of the ionospheric refractive index. This allows the system to account for higher-order dispersion effects that were previously neglected, reducing residual errors from several centimeters to sub-centimeter level while maintaining reliability with only two frequency measurements.
Solution Approach 2:
The patent performs preliminary calculations by pre-computing the higher-order error terms using the available dual-frequency measurements. The higher-order correction terms are calculated in advance and stored, allowing them to be applied quickly during position determination without requiring additional real-time measurements or complex computational processes.
2Measurement precision
If additional measuring devices and measuring routes are added to improve error determination, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent enables the existing dual-frequency measurement system to self-correct higher-order errors using only the two available frequency measurements. The system utilizes the frequency difference between the two signals to compute higher-order correction terms without requiring additional receivers, satellites, or measurement routes, thereby maintaining system simplicity while improving precision.
Solution Approach 2:
The patent makes the dual-frequency measurement system universal by enabling it to perform both first-order and higher-order error corrections simultaneously. The same two frequency measurements serve multiple purposes: they provide the basis for both the primary ionospheric correction and the higher-order residual error correction, eliminating the need for separate measurement systems for different correction levels.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables more accurate position determination by reducing residual errors to less than 2 mm, improving the reliability and precision of satellite-based navigation applications, especially in real-time kinematic methods and remote sensing.
Implementation Method 1
The interaction is dispersive, i.e. strongly frequency dependent (proportional 1/f2). The refractive index n is not equal to 1, which leads to an extended beam path or transit time error.
Implementation Method 2
The measured phase is determined by the phase length where n denotes the ionospheric refractive index and s the ray path. The propagation path with the minimum phase length can be found according to Fermat's principle.
Implementation Method 3
The invention can also be used for correction, for example in remote sensing using radar, for example in correcting Faraday rotation effects in L-band radar.
Data Source
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AI summary
The invention relates to a method for determining an error in the propagation of electromagnetic waves in an atmosphere (ION) containing electrically charged particles, wherein a first signal is evaluated, the first signal being transmitted through the atmosphere by means of a first electromagnetic wave (S1 according to 53) and wherein the first electromagnetic wave has a first oscillation frequency, wherein at least a second signal is evaluated, the second signal being transmitted through the atmosphere by means of a second electromagnetic wave (S1 according to 53) and wherein the second electromagnetic wave has a second oscillation frequency that differs from the first oscillation frequency. From the first signal and from the second signal, a measure of the content and/or density of the electrically charged particles (charge measure) is determined (device 53).The charge measure is used (device 54) to determine a term of a propagation path of a third electromagnetic wave (S1 to 54) or a term of a quantity equivalent to the propagation path (e.g., a propagation time), wherein the term depends not only on the charge measure but also on the oscillation frequency and on a magnetic correction parameter to account for the influence of a planet's magnetic field, wherein the magnetic correction parameter is determined as a function of the elevation angle and the azimuth angle of the beam path from a transmitter (S1 - S4) of the first and second electromagnetic waves to a receiver (54) on the planet's surface. Device 53 can provide Device 53 with the charge measure so that Device 54 can, for example, correct the distance between satellite S1 and Device 54 determined from the third electromagnetic wave.