106 lines
3.3 KiB
Plaintext
106 lines
3.3 KiB
Plaintext
---
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title: "HW4"
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subtitle: "Software Defined Radio"
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output: pdf_document
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date: "`r Sys.Date()`"
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---
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```{r setup, include=FALSE}
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knitr::opts_chunk$set(echo = TRUE)
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```
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# Assignment
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Write an R script to calculate the output of the Klobuchar model.
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Provide a GUI means for entering input data, and the name and the
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path to navigation message file with coefficients of the Klobuchar
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model. Load the coefficients of the Klobuchar model from the given
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RINEX n file using a dedicated function in the R script. Provide a
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feature to calculate the value of the ionospheric delay of the GPS
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signal during 24 hours of a given day, in 1-minute increments, with
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the given coefficients of the ionospheric model. Verify the correctness
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of the algorithm implementation with a given numerical example. After
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that, conduct a 24-hour simulation of the GPS ionospheric delay in 1-
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minute increments for the position $\varphi_u$ = 45.33709°, $\lambda_u$ = 14.42496°, $E$
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= 90°, $A$ = 180°. Store the estimated 24-hour simulation data set in a
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dedicated file on the local disc.
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The problem description, method, R script and implementation results
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should be presented in a single HTML document, which should be
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sent to the subject teacher's e-mail by May 21, 2026 at 23:59 CEST.
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```{r select-file}
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library(rstudioapi)
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rinex_file <- rstudioapi::selectFile()
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```
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```{r read-file}
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# Function to extract Klobuchar parameters from a RINEX navigation file
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extract_klobuchar_parameters <- function(rinex_file) {
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ion_alpha <- numeric(4)
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ion_beta <- numeric(4)
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# Read the file line by line
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con <- file(rinex_file, "r")
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while (length(line <- readLines(con, n = 1)) > 0) {
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if (grepl("ION ALPHA", line, fixed = TRUE)) {
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# Extract the 4 numeric values from the line
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ion_alpha <- unlist(strsplit(line, "\\s+"))[2:5]
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}
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if (grepl("ION BETA", line, fixed = TRUE)) {
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# Extract the 4 numeric values from the line
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ion_beta <- unlist(strsplit(line, "\\s+"))[2:5]
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}
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# Stop reading if we've reached the end of the header (END OF HEADER)
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if (grepl("END OF HEADER", line, fixed = TRUE)) {
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break
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}
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}
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close(con)
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# Return the parameters as a named list
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list(
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ION_ALPHA = ion_alpha,
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ION_BETA = ion_beta
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)
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}
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klobuchar_params <- extract_klobuchar_parameters(rinex_file)
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print(klobuchar_params)
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```
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```{r select-date}
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# TODO
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selected_date <- as.Date("2000-1-1")
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```
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## Klobuchar calculation
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1. Calculate earth-centered angle
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What are R_E and h?
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$$ \psi = \pi/2 - E - \arcsin(\frac{R_E}{R_E + h} \cos(E)) $$
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2. Compute the latitude of the IPP (ionospheric pierce point)
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$$ \phi_I = \arcsin( sin \varphi_u \cos \psi + \cos\varphi_u \sin\psi \cos A )$$
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3. Compute the longitude of the IPP
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$$ \lambda_I= \lambda_u + \frac{\psi \sin A}{\cos \phi_I}$$
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4. Find the geomagnetic latitude of the IPP
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What is phi_P?
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$$ \phi_m = \arcsin(\sin\phi_I \sin\phi_P + \cos\phi_I \cos\phi_P \cos(\lambda_I - \lambda_P)) $$
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5. Find the local time at the IPP
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$$ t = 43200 \lambda_I / \pi + t_{GPS} $$
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$\lambda_I$ in radians, $t$ in seconds.
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where $0 \leq t \leq 86 400$. Therefore:
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If $t \geq 86 400$, subtract $86 400$. If $t < 0$, add $86 400$.
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6. Compute the amplitude of ionospheric delay
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$$ A_I = \sum_{n=0}^{3} \alpha_n(\phi_m/\pi)^n $$
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If $A_I < 0$, then $A_I =0$.
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```{r simulate}
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# input constants
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lat = 45.33709 # phi
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lon = 14.42496 # lambda
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E = 90
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A = 180
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``` |