Books:

• "GPS for Land Surveyors" by Jan Van Sickle
• "Introduction to Modern Navigation" by S. L. Parry
• "Surveying with GNSS: A Guide for Surveyors and Engineers" by K. P. Lee

Textbooks:

• "Principles of Surveying" by Barry F. Kavanagh
• "Surveying: Principles and Applications" by Barry Kavanagh and R. L. McDonald

Websites:

• GNSS Overview - Trimble
• Understanding GNSS - Leica Geosystems
• Drone Mapping and Surveying - Pix4D
• RTKLIB: Open Source GNSS Software