Control Surveys

Overview

Control surveys establish the horizontal and vertical framework for other surveying work. Understanding methods, accuracy requirements, and connections to geodetic control is essential.

Learning Objectives

• Establish horizontal and vertical control
• Connect to geodetic reference systems
• Meet accuracy specifications
• Document control survey results

Key Concepts

GNSS Control Methods

Positioning techniques for control:

• Static GPS for highest accuracy
• Rapid static for efficiency
• Network RTK for real-time positions
• OPUS processing for NGS connection
• Observation planning and execution

Conventional Control

Traditional control methods:

• Closed traverses for horizontal control
• Differential leveling for vertical control
• Triangulation and trilateration
• Combined angle and distance networks

Accuracy Standards

Accuracy specifications include:

• FGDC geodetic control standards
• Project-specific requirements
• NGS guidelines for publication
• Local agency standards
• Accuracy vs. precision distinction

Documentation Requirements

Control survey documentation:

• Observation logs and field notes
• Processing reports and results
• Monument descriptions
• Coordinate lists and diagrams
• Accuracy statements

Key Terms

• Static GPS: Extended occupation for high-accuracy positioning
• RTK: Real-Time Kinematic GPS positioning
• Benchmarks: Permanent vertical control points

Practice Questions

1. What observation methods are used for high-accuracy horizontal control?
2. How are GNSS observations connected to the National Spatial Reference System?

Based on CalTrans LS/LSIT Video Exam Preparation Course materials.