diff --git a/README.md b/README.md index b4e7700..a8ae1f7 100644 --- a/README.md +++ b/README.md @@ -47,6 +47,30 @@ individual site navigation files into one. The archive for the daily file can be downloaded from: https://cddis.nasa.gov/archive/gnss/data/daily/. Access to this site requires registration, which is free. +After registration, automated downloads can be done in a script by adding +the following entry to one's netrc file (filling in the appropriate values +for username and password): +```bash +echo machine urs.earthdata.nasa.gov login password >> ~/.netrc +chmod 600 ~/.netrc +``` + +and then including the following code (or similar) in a script: + +```bash +day=$(date +%j) +year=$(date +%Y) +yr=$(date +%y) +RINEX_NAV_FILE="brdc${day}0.${yr}n" +curl \ + --cookie-jar /tmp/cookie \ + --netrc \ + --location \ + --output "${RINEX_NAV_FILE}.gz" "https://cddis.nasa.gov/archive/gnss/data/daily/${year}/brdc/${RINEX_NAV_FILE}.gz" \ +uncompress --force --keep "${RINEX_NAV_FILE}.gz" +ls -al "${RINEX_NAV_FILE}" +``` + These files are then used to generate the simulated pseudorange and Doppler for the GPS satellites in view. This simulated range data is then used to generate the digitized I/Q samples for the GPS signal.