在 R 中解码 sl2 文件的声纳视图的探测数据
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【中文标题】在 R 中解码 sl2 文件的声纳视图的探测数据【英文标题】：Decode sounding data for sonar view of sl2 file in R 【发布时间】：2021-08-03 12:45:48 【问题描述】：在阅读了很多关于如何使用 .sl2 Sonar Log 格式分析使用诸如 Lowrance 等娱乐性声纳收集的数据的帖子之后，我能够使用 arabia 包的 read_sl2 函数从 sl2 文件中提取深度数据。
我还稍微修改了函数以提取更多数据并将一些值转换为国际单位。
read_sl2 <- function(path, verbose=TRUE)
f <- file(path.expand(path), "rb")
dat <- readBin(f, "raw", n = file.size(path.expand(path)), endian="little")
close(f)
# read in the header
header <- readBin(dat, what = "raw", n = 10)
format <- readBin(header[1:2], "int", size=2, endian="little", signed=FALSE)
if (!(format %in% 1:3)) stop("Invalid 'format' in header; Likely not an slg/sl2/sl3 file")
ok_formats <- c("slg", "sl2", "sl3")
if (verbose) message("Format: ", ok_formats[format])
version <- readBin(header[3:4], "int", size=2, endian="little", signed=FALSE)
blockSize <- readBin(header[5:6], "int", size=2, endian="little", signed=FALSE)
if (blockSize == 1970)
if (verbose) message("Block size: downscan")
else if (blockSize == 3200)
if (verbose) message("Block size: sidescan")
else
stop("Block size is not 'downscan' or 'sidescan'; Likely not an slg/sl2/sl3 file")
alwaysZero <- readBin(header[7:8], "int", size=2, endian="little", signed=FALSE)
# yep, we're going to build a list the hard/slow way
sl2_lst <- vector("list")
idx <- 1
pos <- 8 # keeping track of our place in the stream
while (pos < length(dat))
# if verbose mode echo a "." every 100 records
if (verbose && ((idx %% 100) == 0)) cat(".")
blockSize <- readBin(dat[(pos+29):(pos+30)], "int", size=2, endian="little", signed=FALSE)
prevBlockSize <- readBin(dat[(pos+31):(pos+32)], "int", size=2, endian="little", signed=FALSE)
packetSize <- readBin(dat[(pos+35):(pos+36)], "int", size=2, endian="little", signed=FALSE)
frameIndex <- readBin(dat[(pos+37):(pos+40)], "int", size=4, endian="little")
dplyr::data_frame(
channel = readBin(dat[(pos+33):(pos+34)], "int", size=2,endian="little", signed=FALSE),
upperLimit = readBin(dat[(pos+41):(pos+44)], "double", size=4, endian="little"),
lowerLimit = readBin(dat[(pos+45):(pos+48)], "double", size=4, endian="little"),
frequency = readBin(dat[(pos+54)], "int", size=1, endian="little", signed=FALSE),
val1 = readBin(dat[(pos+55):(pos+56)], "int", size=2, endian="little"),
val2 = readBin(dat[(pos+57):(pos+60)], "int", size=4, endian="little"),
date = readBin(dat[(pos+61):(pos+64)], "int", size=4, endian="little"),
waterDepth = readBin(dat[(pos+65):(pos+68)], "double", size=4, endian="little"),
keelDepth = readBin(dat[(pos+69):(pos+72)], "double", size=4, endian="little"),
byt1 = readBin(dat[(pos+73)], "int", size=1, endian="little", signed=FALSE),
byt2 = readBin(dat[(pos+74)], "int", size=1, endian="little", signed=FALSE),
val3 = readBin(dat[(pos+75):(pos+76)], "int", size=2, endian="little"),
val4 = readBin(dat[(pos+77):(pos+78)], "int", size=2, endian="little"),
val5 = readBin(dat[(pos+79):(pos+80)], "int", size=2, endian="little"),
val6 = readBin(dat[(pos+81):(pos+84)], "double", size=4, endian="little"),
val7 = readBin(dat[(pos+85):(pos+88)], "double", size=4, endian="little"),
val8 = readBin(dat[(pos+89):(pos+92)], "double", size=4, endian="little"),
val9 = readBin(dat[(pos+93):(pos+96)], "double", size=4, endian="little"),
byt3 = readBin(dat[(pos+97)], "int", size=1, endian="little", signed=FALSE),
byt4 = readBin(dat[(pos+98)], "int", size=1, endian="little", signed=FALSE),
byt5 = readBin(dat[(pos+99)], "int", size=1, endian="little", signed=FALSE),
byt6 = readBin(dat[(pos+100)], "int", size=1, endian="little", signed=FALSE),
speedGps_kn = readBin(dat[(pos+101):(pos+104)], "double", size=4, endian="little"),
temperature_c = readBin(dat[(pos+105):(pos+108)], "double", size=4, endian="little"),
lng_enc = readBin(dat[(pos+109):(pos+112)], "integer", size=4, endian="little"),
lat_enc = readBin(dat[(pos+113):(pos+116)], "integer", size=4, endian="little"),
speedWater_kn = readBin(dat[(pos+117):(pos+120)], "double", size=4, endian="little"),
track = readBin(dat[(pos+121):(pos+124)], "double", size=4, endian="little"),
altitude = readBin(dat[(pos+125):(pos+128)], "double", size=4, endian="little"),
heading = readBin(dat[(pos+129):(pos+132)], "double", size=4, endian="little"),
timeOffset = readBin(dat[(pos+141):(pos+144)], "integer", size=4, endian="little"),
sounding = readBin(dat[(pos+145):(pos+148)], size=4, "double", endian="little"),
flags = list(
dat[(pos+133):(pos+134)] %>%
rawToBits() %>%
as.logical() %>%
set_names(
c(
"headingValid", "altitudeValid", sprintf("unk%d", 1:7),
"gpsSpeedValid", "waterTempValid", "unk8", "positionValid",
"unk9", "waterSpeedValid", "trackValid"
)
) %>%
.[c(1:2, 10:11, 13, 15:16)] %>%
as.list() %>%
purrr::flatten_df()
)
) -> sl2_lst[[idx]]
idx <- idx + 1
pos <- pos + (packetSize+145-1)
if (verbose) cat("\n")
dplyr::bind_rows(sl2_lst) %>%
dplyr::mutate(
channel = dplyr::case_when(
channel == 0 ~ "Primary",
channel == 1 ~ "Secondary",
channel == 2 ~ "DSI (Downscan)",
channel == 3 ~ "Left (Sidescan)",
channel == 4 ~ "Right (Sidescan)",
channel == 5 ~ "Composite",
TRUE ~ "Other/invalid"
)
) %>%
dplyr::mutate(
frequency = dplyr::case_when(
frequency == 0 ~ "200 KHz",
frequency == 1 ~ "50 KHz",
frequency == 2 ~ "83 KHz",
frequency == 4 ~ "800 KHz",
frequency == 5 ~ "38 KHz",
frequency == 6 ~ "28 KHz",
frequency == 7 ~ "130-210 KHz",
frequency == 8 ~ "90-150 KHz",
frequency == 9 ~ "40-60 KHz",
frequency == 10~ "25-45 KHz",
TRUE ~ "Other/invalid"
)
) %>%
tidyr::unnest(flags)
data <- read_sl2("myfile.sl2")
#Conversions
#Lat/Lon
PolarEarthRadius = 6356752.3142
RadiansToDegrees = 180.0 / pi
data$longitude <- (data$lng_enc / PolarEarthRadius) * RadiansToDegrees
data$latitude <- ((2.0 * atan(exp(data$lat_enc / PolarEarthRadius))) - (pi / 2.0)) * RadiansToDegrees
#InternationalUnits
FeettoMeter = 0.3048
data$waterDepth_m <- data$waterDepth*FeettoMeter
data$keelDepth_m <- data$keelDepth*FeettoMeter
但是，我不仅对深度感兴趣，而且对整个水柱（所有探测点）的声纳图像感兴趣。
sounding/bounce 数据似乎记录在包的末尾，但我不知道如何解码。 https://wiki.openstreetmap.org/wiki/SL2#:~:text=SL2%20is%20a%20binary%20format,downloaded%20on%20their%20web%20site.
当我在 ReefMaster 等商业软件中读取 sl2 文件时，我能够使用从 sl2 文件中读取的数据查看水柱，所以我猜信息在里面，但我不知道如何解码。
有什么想法吗？
【问题讨论】：
【参考方案1】：我终于自己想通了。
答案不是很漂亮，数据很重，所以函数返回内存分配错误的频率比较高，但是这里是：
read_sound <- function(path, verbose=TRUE)
#Unit transformations
PolarEarthRadius = 6356752.3142
RadiansToDegrees = 180.0 / pi
FeettoMeter = 0.3048
f <- file(path.expand(path), "rb")
dat <- readBin(f, "raw", n = file.size(path.expand(path)), endian="little")
close(f)
# read in the header
header <- readBin(dat, what = "raw", n = 10)
format <- readBin(header[1:2], "int", size=2, endian="little", signed=FALSE)
if (!(format %in% 1:3)) stop("Invalid 'format' in header; Likely not an slg/sl2/sl3 file")
ok_formats <- c("slg", "sl2", "sl3")
if (verbose) message("Format: ", ok_formats[format])
version <- readBin(header[3:4], "int", size=2, endian="little", signed=FALSE)
blockSize <- readBin(header[5:6], "int", size=2, endian="little", signed=FALSE)
if (blockSize == 1970)
if (verbose) message("Block size: downscan")
else if (blockSize == 3200)
if (verbose) message("Block size: sidescan")
else
stop("Block size is not 'downscan' or 'sidescan'; Likely not an slg/sl2/sl3 file")
alwaysZero <- readBin(header[7:8], "int", size=2, endian="little", signed=FALSE)
# yep, we're going to build a list the hard/slow way
sound_list <- vector("list")
idx <- 1
pos <- 8 # keeping track of our place in the stream
while (pos < length(dat))
# if verbose mode echo a "." every 100 records
if (verbose && ((idx %% 100) == 0)) cat(".")
blockSize <- readBin(dat[(pos+29):(pos+30)], "int", size=2, endian="little", signed=FALSE)
prevBlockSize <- readBin(dat[(pos+31):(pos+32)], "int", size=2, endian="little", signed=FALSE)
packetSize <- readBin(dat[(pos+35):(pos+36)], "int", size=2, endian="little", signed=FALSE)
frameIndex <- readBin(dat[(pos+37):(pos+40)], "int", size=4, endian="little")
upperLimit = readBin(dat[(pos+41):(pos+44)], "double", size=4, endian="little")*FeettoMeter
lowerLimit = readBin(dat[(pos+45):(pos+48)], "double", size=4, endian="little")*FeettoMeter
dplyr::tibble(
sounding = readBin(dat[(pos+145):(pos+145+packetSize)], n=packetSize, "integer", size=1, endian="little"),
sounddepth = round(seq(upperLimit,lowerLimit,length.out = length(sounding)),2),
longitude = readBin(dat[(pos+109):(pos+112)], "integer", size=4, endian="little")*RadiansToDegrees/PolarEarthRadius,
latitude = (2*atan(readBin(dat[(pos+113):(pos+116)], "integer", size=4, endian="little")/ PolarEarthRadius)-(pi/2))*RadiansToDegrees,
waterDepth_m = readBin(dat[(pos+65):(pos+68)], "double", size=4, endian="little")*FeettoMeter,
ping = idx
)-> sound_list[[idx]]
idx <- idx + 1
pos <- pos + (packetSize+145-1)
sound <- bind_rows(sound_list)
sound$sounding <- ifelse(sound$sounding<0, sound$sounding+256, sound$sounding) #The data is decoded adding +256 to negative values
sound$ID <- cumsum(!duplicated(sound[3:4]))
sound <- aggregate(. ~ sounddepth+ID, sound, mean)
return(sound)
【讨论】：
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