NaviPac A7. Template tracking 17 April, 2012 Page 1 of 8
Table of content INTRODUCTION 3 DEFINITION 3 SAMPLE WORKFLOW 3 SETTING UP PRIMARY OBJECTS 3 SETTING UP COMBINED OBJECT 4 CALCULATIONS 6 CONTROL 7 DISPLAY 8 17 April, 2012 Page 2 of 8
Introduction This document describes how to perform a template tracking job in NaviPac version 3. The purpose of template tracking is to improve positioning of external vessels, templates or UW objects by the use of multiple navigation inputs. If it s based on good quality data, the routine can also be used to calculate heading of the template. Definition Each of the navigational inputs (e.g. transponder from USBL, position from tracking systems or position from remote GPS) must be assigned to an ordinary object. Two or three objects are hereafter assigned to a secondary (or combined object), as the operator must specify offsets from template reference point to each primary object on the template. Sample workflow We have a situation, where a tug boat (with NaviPac onboard) must move a huge template. There are no people onboard the template, at no electrical devices. The Template must therefore be positioned using two high accurate laser meters (Leica autotrack). Setting up primary objects The two laser meters are defined as dynamic positioning systems: 17 April, 2012 Page 3 of 8
and each instrument are assigned to an object name (in the example TUG 1 and TUG 2): Both primary objects can now be used as any other ordinary object in NaviPac, i.e. they can be displayed on Helmsmans Display or Objectpos, they can be logged or they can be send to external devices. The above describes a scenario based on remote objects but exact same could be performed using USBL based template tracking. Setting up combined object When you have defined the two (or three) primary objects, you now have to define a secondary object. A secondary object is a special case of User Defined Objects in NaviPac, and must be defined in Instruments Interfaces, User defined Offsets: 17 April, 2012 Page 4 of 8
Enter a suitable name and select the Type to Secondary. Offsets and Relative To can be ignored in this case. Pressing right mouse and selected Edit Special Settings 17 April, 2012 Page 5 of 8
In this dialogue, you must select which primary objects to use (TUG 1 and TUG 2), and define the offset from the My Final TUG reference point to each of the primary objects. Calculations NaviPac will now at each cycle perform the following steps (based on the simple two primary setup). 1. Calculate position of each of the primary objects 2. If one of the two primary objects are missing, no combined position is calculated. 3. Compare distance between the two primary objects and the entered local offsets. If that distance differs too much, an alarm is generated and no combined position is calculated. 4. Calculate the heading of the combined object by comparing direction between the two absolute positions and the defined local offset direction. 5. Based on the calculated heading, each of the two primary objects is now moved to the reference point. Hereby we get two candidates for the reference point. 6. The final reference position is now calculated as the average between the two candidates. If we operate with three primary objects, it s just performed as an averaging process. 17 April, 2012 Page 6 of 8
Control The operator can on-the-fly change which objects to use for the calculation and the relative offsets. This is possible through the online menu Edit, User Defined Offsets: By double-clicking on the combined object, the following dialogue pops-up: It s just like the one in set-up, and the operator can changes relative offsets or select/de-select primary objects. 17 April, 2012 Page 7 of 8
Display The combined object can be handled as any other object, i.e. it can be displayed, logged and send to external devices. Furthermore it s possible to monitor the position calculation. This is done in the Object Positions window by selecting View, View combined offset, 17 April, 2012 Page 8 of 8