functions.R 7.01 KB
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calc_sensor_ratio <- function(sensor_size_x, sensor_size_y) {
  ratio <- sensor_size_x / sensor_size_y
  return(ratio)
}


calc_lens_angle_of_view <- function(sensor_size, lens_focal_length) {
  angle_of_view <- 2 * atan(sensor_size / (2 * lens_focal_length))
  return(angle_of_view)
}

calc_IFOV <- function(flight_height, size, sensor_recorded_pixels, focal_length) {
  return((size/sensor_recorded_pixels) * flight_height / focal_length)
}

calc_IFOV_mm <- function(flight_height, size, sensor_recorded_pixels, focal_length) {
  return(1000 *calc_IFOV(flight_height, size, sensor_recorded_pixels, focal_length))
}

calc_FOV <- function(flight_height, size, focal_length) {
  return((size) * flight_height / focal_length)
}

calc_flight_height <- function(ifov, size, sensor_recorded_pixels, focal_length) {
  return(ifov / (size/sensor_recorded_pixels) *focal_length)
}

calc_hyperfocal_distance <- function(focal_length, aperture, circle_of_confusion) {
  return((focal_length^2)/(aperture*circle_of_confusion) + focal_length)
}

calc_focal_dist <- function(focal_length, aperture, circle_of_confusion, flight_height) {
  hyperfocal_distance <- calc_hyperfocal_distance(focal_length, aperture, circle_of_confusion)
  
  focus_dist <- (hyperfocal_distance * sqrt(flight_height))/(sqrt(hyperfocal_distance + flight_height))
  
  focus_dist <- (-hyperfocal_distance^2 + sqrt(hyperfocal_distance^4 + 4 * hyperfocal_distance^2 * flight_height^2))/(2 * flight_height)
  
  focus_dist <- ifelse(focus_dist > hyperfocal_distance, hyperfocal_distance, focus_dist)
  return(focus_dist)
}

calc_depth_of_field_near <- function(focal_length, aperture, circle_of_confusion, object_distance) {
  hyperfocal_distance <- calc_hyperfocal_distance(focal_length, aperture, circle_of_confusion)
  return(object_distance / ( (object_distance - focal_length) / (hyperfocal_distance - focal_length) + 1))
}

calc_depth_of_field_far <- function(focal_length, aperture, circle_of_confusion, object_distance) {
  hyperfocal_distance <- calc_hyperfocal_distance(focal_length, aperture, circle_of_confusion)
  if(object_distance <= hyperfocal_distance) {return(object_distance / ( (focal_length - object_distance) / (hyperfocal_distance - focal_length) + 1))}
  else {return(Inf)}
}

calc_exposure_value <- function(aperture, shutter_speed, iso=100) {
  return(log2((100/iso)*(aperture^2)/(1/shutter_speed)))
}

calc_aperture <- function(exposure_value, shutter_speed, iso=100) {
  return((1/10) * sqrt(iso) * sqrt(1/shutter_speed) * sqrt(2^exposure_value))
}

calc_shutter_speed <- function(exposure_value, aperture, iso=100) {
  return(1/((25 * aperture^2 * 2^(2-exposure_value))/(iso)))
}

calc_iso <- function(exposure_value, aperture, shutter_speed) {
  return((25 * aperture^2 * 2^(2-exposure_value))/(1/shutter_speed))
}

calc_flight_speed <- function(IFOV, blur, shutter_speed) {
  return(((IFOV)*blur) / (1/shutter_speed))
}

calc_distance_exposure_station <- function(end_lap, FOV_x) {
  return(FOV_x - ((end_lap/100) * FOV_x))
}

calc_spacing_flight_lines <- function(side_lap, FOV_y) {
  return(FOV_y - (side_lap/100) * FOV_y)
}

calc_percent_exposure_station <- function(end_lap_size, FOV_x) {
  return(100 - (end_lap_size/ FOV_x)*100)
}

calc_percent_flight_lines <- function(side_lap_size, FOV_y) {
  return(100 - (side_lap_size/ FOV_y)*100)
}

calc_image_recording_speed <- function(flight_speed, distance_exposure_stations) {
  return(flight_speed / distance_exposure_stations)
}

calc_flight_duration <- function(distance_area_x, FOV_x, distance_area_y, FOV_y, spacing_flight_lines, flight_speed) {
  distance <- 1 * (distance_area_x + ceiling(FOV_x / (2 * spacing_flight_lines))) * 2 * spacing_flight_lines + (distance_area_x/spacing_flight_lines) * (distance_area_y+ FOV_y)
  duration <- (distance / flight_speed) / 60
  return(duration)
}

calc_min_flight_height_coded_gcp <- function(diameter_coded, size_x, sensor_recorded_pixels_x, focal_length) {
  ifov <- diameter_coded / 80
  height <- calc_flight_height(ifov, size_x, sensor_recorded_pixels_x, focal_length)
  return(height)
}

calc_max_flight_height_coded_gcp <- function(diameter_coded, size_x, sensor_recorded_pixels_x, focal_length) {
  ifov <- diameter_coded / 15
  height <- calc_flight_height(ifov, size_x, sensor_recorded_pixels_x, focal_length)
  return(height)
}

calc_min_flight_height_noncoded_gcp <- function(diameter_coded, size_x, sensor_recorded_pixels_x, focal_length) {
  ifov <- diameter_coded / 110
  height <- calc_flight_height(ifov, size_x, sensor_recorded_pixels_x, focal_length)
  return(height)
}

calc_max_flight_height_noncoded_gcp <- function(diameter_coded, size_x, sensor_recorded_pixels_x, focal_length) {
  ifov <- diameter_coded / 24
  height <- calc_flight_height(ifov, size_x, sensor_recorded_pixels_x, focal_length)
  return(height)
}

calc_pixel_freq <- function(plot_size, spacing, no_of_lanes, position_precision_sd, sensor_res, gsd, use_uniform=FALSE) {
  
  pixels <- 1:sensor_res
  # Positions of plots, pixel position as index, TRUE as value if plot present, else FALSE
  plot_positions <- ifelse(seq(1, sensor_res + no_of_lanes*spacing/gsd) %% round(plot_size/gsd) + round(plot_size/(gsd*2))  == round(plot_size/(gsd)), TRUE, FALSE)
  
  # Get camera views on plots
  sensor_views <- rollapply(data=plot_positions, width=sensor_res, by=round(spacing/gsd), FUN = function(x) x)
  
  # Calculate frequency of plots at specific sensor position
  sensor_position_freq <- apply(sensor_views, MARGIN=c(2), sum)
  # Normalize
  sensor_position_freq <- sensor_position_freq / sum(sensor_position_freq)
  
  # Normal distribution for each sensor pixel
  if(!use_uniform) {
    pixel_distribution <- mapply(pixels, FUN=function(z) {dnorm(x=pixels, sd=position_precision_sd/gsd, mean=z)})
  } else {
    pixel_distribution <- mapply(pixels, FUN=function(z) {dunif(x=pixels, min=z-(position_precision_sd/gsd), max=z+(position_precision_sd/gsd))})
  }
  # Sweep over columns and multiply with occurance frequency of sensor at this position
  pixel_distribution_sens <- sweep(pixel_distribution, MARGIN=2, sensor_position_freq, '*')
  # Sum up result
  pixel_frequency <- rowSums(pixel_distribution_sens)
  # Normalize
  pixel_frequency <- pixel_frequency / sum(pixel_frequency)

  pixel_frequency_data <- data.frame(x=1:sensor_res, freq=pixel_frequency)
  
  return(pixel_frequency_data)
}

calc_pixel_freq_xy <- function(plot_size_x, plot_size_y, spacing_x, spacing_y, no_of_lanes_x, no_of_lanes_y, sensor_res_x, sensor_res_y, position_precision_sd, gsd) {
  
  pixel_frequency_data_x <- calc_pixel_freq(plot_size_x, spacing_x, no_of_lanes_x, position_precision_sd, sensor_res_x, gsd)
  pixel_frequency_data_y <- calc_pixel_freq(plot_size_y, spacing_y, no_of_lanes_y, position_precision_sd, sensor_res_y, gsd, use_uniform = TRUE)
  
  pixel_frequency_data_xy <- unlist(pixel_frequency_data_y[,'freq']) %o% unlist(pixel_frequency_data_x[,'freq'])
  pixel_frequency_data_xy <- (pixel_frequency_data_xy / max(pixel_frequency_data_xy))
  return(list(pixel_frequency_data_xy, pixel_frequency_data_x, pixel_frequency_data_y))
}


long2UTM <- function(long) {
  (floor((long + 180)/6) %% 60) + 1
}