THE POSITION AND ORIENTATION SYSTEM (POS) FOR 
    
SURVEY APPLICATIONS 
Erik Lithopoulos, Dr. Blake Reid, Dr. Bruno Scherzinger 
Applied Analytics Corporation 
550 Alden Road, Unit 113 
Markham, Ontario, Canada, L3R 6A8 
WG II/1 - Integrated Sensor Orientation 
KEY WORDS: Sensor Integration, Sensor Orientation, Attitude, Inertial, GPS 
ABSTRACT 
The Position and Orientation System (POS) is an integrated inertial/GPS system that generates accurate position (latitude, 
longitude, altitude) and orientation (roll, pitch, heading) for airborne survey/mapping applications as well as various other 
land and marine applications. POS is a GPS-aided strapdown inertial navigator that uses a Kalman filter and a closed-loop error 
controller to provide an optimally blended position and orientation solution from inertial data from an IMU and aiding data 
from a GPS receiver. This paper gives a brief description of POS and compares it to other available technologies. It then 
describes the various application areas of POS for airborne vehicles (POS/AV). Some applications from other POS variants, 
POS/LV for Land Vehicles, POS/MV for Marine Vessels, are also described. 
1. INTRODUCTION 
The Position and Orientation System (POS) developed by 
Applied Analytics Corporation is a Kalman filter-based 
integrated navigation system designed for airborne surveys 
and mapping. POS performs an automatic leveling and 
heading in air-alignment and computes a real-time position 
(latitude, longitude, altitude) and orientation (roll, pitch, 
heading) solution using Kalman filter based aided inertial 
navigation algorithms. The primary aiding sensor for most 
applications is GPS or differential GPS. POS technology is 
an example of conversion of military integrated navigation 
technology to meet commercial applications. 
POS consists of two components the Inertial Measurement 
Unit (IMU), and the POS Computer System (PCS). The IMU 
is self contained and consists of three gyros and three 
accelerometers in orthogonal triads. It is small, lightweight 
and can be mounted directly onto most sensors. The PCS is a 
19" rack mountable chassis that contains the data acquisition 
electronics, data recording equipment, GPS receiver and 
various ports for easy interfacing to other sensors. POS/AV 
is used in conjunction with various airborne sensors to 
provide accurate attitude measurements (roll, pitch, true 
heading and crab angle) as well as uninterrupted position. 
These measurements can be provided in real-time or in post- 
processing for enhanced accuracy by using the recorded raw 
data and the post-processing software ‘POSPROC’. The type 
of sensors that POS/AV is typically used with include 
multispectral scanners, scanning lasers, cameras (both film 
and digital) and Synthetic Aperture Radar (SAR). Although 
the use of POS/AV varies somewhat between applications, 
its main purpose is to provide accurate pitch/roll/heading 
measurements for motion compensation and geocoding 
without or with only minimal use of ground control points. 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B3. Vienna 1996 
2. PHYSICAL DESCRIPTION 
The major components of POS are the POS computer system 
(PCS) and the IMU. Unlike an inertial navigation system 
(INS) or attitude and heading reference system (AHRS), POS 
uses an IMU that is self-contained and separate from the PCS, 
connected to the PCS by a data interface and power cable. 
The IMU is selected from among several different candidates 
to be small, light and commensurate in cost and performance 
with the targeted application. POS "navigates" the IMU, i.e. 
computes the IMU position and orientation. The IMU is 
separated from the PCS to allow it to be mounted directly to 
or close beside the survey instrument or reference point 
  
Figure 1. Core POS Showing the IMU and PCS. 
whose position and orientation are sought. IMUs that are 
currently used with POS are the Litton LR-86 dry tuned gyro 
IMU, the LN-200 IFOG-based IMU also from Litton, and the 
BAT IMU from Allied Signal. All these IMUs are small and 
lightweight, and therefore can be mounted directly to 
instruments or platforms on which larger and heavier inertial 
reference systems could not fit. The LR-86 has dimensions of 
3.3x5x5.6 inches and weighs 4.2 lbs. The LN-200 is even 
smaller at 3.5x3.35 inches (diameter x height) and 1.5 lbs. 
Figure 1 shows the core POS configuration comprising the 
LR-86 IMU and the PCS.