Special Science Report

February 28, 2008

Guy de Carufel


Project:
GPS precision study


Personnel:
Guy de Carufel, Cassandra Marion, Aravind Seeni


Operations Data Collected:
In EVA-15, Cassandra Morion acted as the navigator in the GPS precision study, where she performed the same exercise as Philip Cunio had done previously in EVA-14. She navigated to several waypoints (6 in total) using provided biased positioning at a certain frequency of availability (every 1 or 2 minutes depending on leg). The difference in this EVA was that panoramic pictures of each waypoint were now available for her to better locate the waypoints from visual cues. This was also an attempt to demonstrate the effectiveness in locating a point using a simplified version of thee Field Documentations Methodology (FDM) developed by Stacy Sklar. Panoramic photographs were only available for the first two waypoints, taken during EVA-14. As a secondary objective, the FDM was used at the remaining waypoints so that it can be used in EVA-17.

In EVA-17, Aravind Seeni went to all 6 waypoints using the same frequency of availability as before:

WP 1,3,5: 1 minute avail.
WP 2,4,6: 2 minutes avail.

The same method of navigation was used as before using the graphing calculator to store every position, headings and bearings. The difference done in this EVA was that no bias was added to the position, such that these navigation efforts can be used as a reference to compare the other tracks against. Panoramic pictures were available for every waypoint. Situating using FDM was also observed.


Technical/Equipment Issues:
Equipment used was GPS device, programmed graphing calculator, camera and stopwatch. No difficulties.


Discussion:
Preliminary observations demonstrate that the time required to reach the area about the waypoint
(40-metre range) was very similar for all 3 EVA's. The differences where observed in finding the actual marker (a large stone "W"). The panoramic photographs of the areas around the waypoints where very useful in locating the marker in most cases. Also, it was observed that for different imposed positioning errors there is an optimal minimum distance to be traveled between positioning acquisition for the heading information to be relevant.

Next step will be to analyse the data collected from the GPS tracks, all data collected on the Graphic calculators, and voice recordings. The objective will be to make a comparative study between the navigation exercises and demonstrate trends and positioning requirements for effective navigation. Efficient methods for navigation in limited positioning constraints will be presented based on observations made in EVA's.

Improvements for this study will be presented for a future longer duration study to produce more quantitative results, which can be repeated.


Questions for CSO:
None.

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