Position Determination

Surveying for EngineersERE 371

Position Determination

• Fundamental purpose of surveying

• Important for

• Question remains: “Relative to What?”

Survey Control

• Issue

• Local control can range from

• Control can be either horizontal or vertical or both

Horizontal Control

• Surveys need a network of control points

• Procedure

• Vary methods to match requirements

Vertical Control

• Surveys need a network of control points

• Procedure

• We will emphasize horizontal control

Control Determination – General Procedure

Design

Measurement

Computation and Adjustment

Final Coordinates

Horizontal Control Methods

• Many methods

• Methods covered in ERE 371

Expressing Location

• Issue

• May use standard coordinate system

• May use local coordinate system

Classifying Horizontal Control

• Standards

• Established by Federal Geodetic Control Committee

Specifying Horizontal Control Classes

• Outline requirements for

• Specifications for establishing horizontal control vary

Traditional Land-based Horizontal Control Standards

Survey Category

Allowable Error Ratio

Example Applications

First Order 1:100,000 Framework of national control

Second OrderClass I Class II

1:50,0001:20,000

Tie national framework to local surveysMajor engineering projects

Third OrderClass IClass II

1:10,0001:5,000

Local mapping and engineering projectsLocalized projects

Traditional Land-based Horizontal Control Standards

• Additional requirements specified

• Example requirements for first order

Space-based Control Standards

Survey Category

Allowable Error Ratio

Example Applications

AA 1:100,000,000 Global-regional geodynamics

A 1:10,000,000 U.S. Primary reference

B 1:1,000,000 U.S. Secondary reference

C-1C-2-IC-2-IIC-3

1:100,0001:50,0001:20,0001:10,000

Similar to Land-basedClassificationEngineering, mapping, propertyEngineering, mapping, property

Recent Advances

• Many recent advances in measuring location

• Most advances developed initially by military

• Important characteristic of recent positioning systems

Inertial Surveying Systems

• Background

• Basic approach

• Applications

Doppler Satellite Surveying

• Background

• Basic approach

• Applications

Global Positioning System (GPS)

• Increasing prominence in

• Background

• General idea

Readings

• Chapter 19 – sections 19.7 – 19.11