Process EM38 Survey line

This function processes an EM38 survey line into a data frame, which may be spatial.

em38_surveyline(
  survey_line = NULL,
  hdop_filter = NULL,
  time_filter = NULL,
  fix_filter = NULL
)

Arguments

survey_line

a decoded survey line from n38_decode.

hdop_filter

Numeric, discard GPS data where the Horizontal Dilution of Precision is greater than this number. Defaults to 3 metres. Set to NULL to keep all readings.

time_filter

Numeric, discard readings taken more than n seconds after the last acceptable GPS reading. Usually best to set this to 2-3x GPS aquisition frequency.

fix_filter

Select readings with a minimum quality of GPS fix. Options are:

  1. Autonomous GPS fix.

  2. DGPS fix, using a local DGPS base station or correction service such as WAAS or EGNOS.

  3. Pulse per second (PPS) fix.

  4. real-time kinematic (RTK) fix.

  5. RTK float fix.

  6. estimated (dead reckoning)

  7. manual input mode

  8. simulation mode

  9. WAAS fix.

To filter on multiple options, supply a vector e.g. c(2, 9).

Value

If valid GPS data is present, an `sf` data frame with sfc_POINT geometry. Otherwise, if valid instrument data is present, a data frame. Otherwise, a string explaining failure to process.

Note

Inclusion of comments is yet to be implemented.

Examples

data('n38_demo')
n38_chunks  <- n38_chunk(n38_demo)
n38_decoded <- n38_decode(n38_chunks)
demo_line_1 <- em38_surveyline(n38_decoded[[2]], 3)
demo_line_2 <- em38_surveyline(n38_decoded[[2]], 3, 0.2)