The Spot (10 metre resolution) data were mapped from the following scenes: - SPOT Scene 246 - 491 (March 13 1988) - SPOT Scene 246 - 491 (March 15 1988) All mapping work was captured using a Zeiss P2 analytical stereo plotter and Microstation version 5 on a Universal Transverse Mercator grid. The horizontal mapping accuracy was +/- 50 metres. The vertical mapping accuracy ... was +/- 20 metres. The polygon data were edited, cleaned and polygonised using Arc/Info. Maximum fuzzy tolerance for cleaning was 0.01 metres.
In May 2003, the contour data were further smoothed in ArcInfo. The process of smoothing and editing the contours involved the following steps: - The Contour data were built for both lines and polygons. - Contours with a DQI value of 167 and 168 (SPOT derived) were extracted from the main contour file. (Contours on the Filson Nunatak were based on more accurate data and so these were also cut out and excluded). Contours with a height value less than 160 metres and a length less than 3000 metres were also excluded. - The ArcEdit generalise command was used to smooth the remaining contours with a tolerance of 120m. These contours were then cleaned with a fuzzy tolerance of 1m and a dangle tolerance of 10m. The contours were then splined with a grain tolerance of 5m and then generalised with a tolerance of 10m. - The contours were then manually edited in ArcEdit to resolve obvious problems such as arc intersections. - The contours were again generalised with a tolerance of 20m then splined with a grain tolerance of 1m and then generalised with a tolerance of 2m. - The smoothed contours were then inserted back into the original coverage to replace the original unsmoothed versions. - The coverage was then rebuilt for polygons and polygon errors were resolved. - Plots of the Framnes contour data were then produced and a visual check of the contour data were performed. This highlighted a number of individual contours which required additional smoothing. - Two alternative approaches were used in ArcEdit to smooth the individual arcs: - - Vertices were either added, moved or deleted as required to smooth the individual arc before the arc was splined. - - Individual arcs were split and then unsplit to remove a problematic Pseudo Node. Once removed Vertices could be added, moved or deleted as required to smooth the individual arc before the arc was splined. - The coverage was then rebuilt for polygons to ensure there were no polygon errors. - Q_Info 167 was replaced with 478 and Q_Info 168 was replaced with 479.
Contact the Australian Antarctic Data Centre for access to these data.