gnacad -in calibration.N4 -format geo++ -out custom.ATX -format antex Use -list on the output to verify headers. Task 3: Compare Two Antennas Before a field campaign, you might compare your rover antenna ( LEIAR25) against a reference ( JAV_RINGANT ).
gnacad -version If you see a version number and date, you are ready. This section mimics the structure of an ideal gnacad tutorial pdf . We will cover the three most common tasks. Task 1: View an ANTEX File (Visualization) You have an ANTEX file igs20.atx . You want to see the phase center variations for a specific antenna, say TRM59800.00 .
GNACAD is a niche but powerful software tool used primarily to visualize, analyze, and format antenna calibration data, specifically for files from the calibration system. It is the industry standard for handling Antenna Exchange Format (ANTEX) files, which contain the absolute phase center variations (PCV) for GNSS antennas. gnacad tutorial pdf
Pair your GNACAD skills with a RTKLIB or PPP (Precise Point Positioning) tutorial. Accurate antennas + robust software = millimeter-level GNSS. About the Author: This guide was compiled from open-source documentation, Geo++ technical notes, and 10+ years of high-precision GNSS surveying experience. Last updated: 2025. Permission is granted to print this article as a personal PDF for offline use.
gnacad -antex igs20.atx -merge custom.atx -out combined.atx For a CORS network with 50 antennas, use a batch script: gnacad -in calibration
Introduction: What is GNACAD? In the world of high-precision surveying, geodesy, and GNSS (Global Navigation Satellite Systems), the accuracy of your data is only as good as the calibration of your equipment. While many professionals are familiar with rover antennas and base station setups, fewer understand the critical role of antenna phase center calibration . This is where GNACAD enters the conversation.
gnacad -antex igs20.atx -plot TRM59800.00 -gnuplot This generates a .gp file. Run gnuplot on it to see a polar heatmap. Geo++ calibration systems output .N4 or .M12 files. To use them in standard GNSS software (Bernese, GIPSY, RTKLIB), you must convert to ANTEX. This section mimics the structure of an ideal
gnacad -antex igs20.atx -list -type TRM59800.00 A text table of North, East, Up offsets (L1/L2) plus PCV values per elevation.