1. SVY 207: Lecture 15 Instruments and Applications
Aim of this lecture:
To learn GPS specifications appropriate to different applications
Short lecture (15 min)
Receivers
Antennas
Applications
Specifications
Practical example to think about! (35 min)
Work in pairs
Report back to class
Quiz (5 min)

2. Receivers Receiver types
In order of historical development for civilian surveying:
TYPE SINGLE-FREQ DUAL-FREQ Example
Squaring: 12 22 Series-X
P code: 1(P), P1(P) 2(P), P2(P) Rogue, Z-12
Single frequency: 1(C), P1(C) Hand helds
C/A with squaring: 1(C), P1(C) 22 Old Ashtechs
Cross correlating: 1(C), P1(C) X), P2(X) Rogue
Z-tracking: 1(C), P1(C) Z), P2(Z) Z-12
Cross correlation actually measures: PX  (P1  P2) because P code is same X  (1  2)
Receiver then constructs following observations: P2(X)  P1(C)  PX 2(X)  1(C)  X
Z-tracking uses some non-secret knowledge about encryption
Note: receivers can switch to P code if A/S is off

3. Receivers Size and Portability Software Rack mounted Portable
Hand held
Software
Measurement software (code correlation, etc.)
Data management (RAM, flashcards, PCMCIA etc.)
Radio link (differential or RTK) OR GSM mobile phone
Interface (keypad, display, PC, modem, controller)
Navigation solution (where am I, which way am I going?)
GIS (where am I on a map? )
Kalman filter, and integration with other data types

4. Antennas Antenna types single or dual frequency
Helical (bulky) or microstrip (flat)
Backplanes
antenna often bolted down on top of a backplane
to reduce multipathing
can be a large metallic disc
can be a “choke ring”
Size/Portability
Backplanes are obviously heavier and larger
Antennas can be
mounted on ground (reduce multipath)
placed on tripod (improve horizon)
fixed to a “bipod” for large scale surveying
can be physically integrated with receiver
Leica AT502
Ashtech Choke ring

5. Applications navigation geophysics photo-control
civil-engineering control
seismic surveying
agriculture
in-car navigation (+ GIS)
connecting reference systems (e.g., channel tunnel)
large scale mapping
Antenna Calibration

6. Specifications Considerations:
quality: precision, accuracy, reliability
type of data: L1, P1, L2, P2 (all or some?)
type of receiver, antenna, software
point, differential, or relative positioning
redundancy (e.g., guard against blunders, fatal errors)
latency: real-time or post-processing
radio link OR GSM link - future 3G
broadcast or IGS orbits
frequency: solution rate
kinematic or static
data logging rate
portability versus permanence
weight, ruggedness, number of operators
type of receiver, antenna, antenna mount (tripod,..)

7. A practical example to think about!
As the senior surveyor working for a large engineering company you have been asked to plan the field work and data analysis for a GPS campaign. The campaign requires a high precision (1 cm) GPS survey of a number of offshore oil platforms over distances of up to 70km. The GPS points to be established on each platform are to be occupied with continuously recording GPS receivers.
List the factors you should consider when planning the campaign. You should consider; hardware, software, data communications.

8. Quiz
For each of the following applications, state the specifications on the GPS equipment and method:
(1) Establish a global control network with highest accuracy
(2) Position an oil tanker as it comes into port

9. Quiz
(3) Land an aircraft automatically
(4) Position a hiker

10. Quiz (5) Provide positions to a car driver
(6) Provide machine guidance to a bulldozer for bulk earthworks

11. (7) Survey 40 points on a volcano over distances of up to 5 km
(8) Set out a road centreline over distances up to 5km with cm accuracy in plan