Spaced Out :: 09 2010

Smith, M.J. and Knight, J.(in press)
Quaternary Science Reviews

A database comprising some ~5200 individual striation measurements on bedrock surfaces across the island of Ireland was used to produce maps of flowsets corresponding to individual ice flow events during the last (late Devensian) glacial cycle. These flowsets were identified on the basis of regional-scale correspondence between striae orientations which, when linked together spatially, are able to identify consistent ice flow vectors. Four main chronological stages are identified on the basis of this evidence: (i) incursion of Scottish ice into Ireland; (ii) glacial maximum conditions; (iii) ice retreat and dissolution; and (iv) development of localised ice domes. Striae-based reconstructions of the glaciology of the last Irish ice sheet are qualitatively different from those based on bedform (mainly drumlin and ribbed moraine) evidence. Significant differences are apparent in upland areas which have fewer preserved bedforms and a higher concentration of striae. Combining bedform and striae datasets will enable a better understanding of the temporal evolution of the ice sheet. It is likely that both datasets record a snapshot of ice flow direction and subglacial conditions and environments immediately prior to preservation of this directional evidence.

I’ve blogged a couple of times about the utility of CSVs as a file format for the distribution of data. They are horribly inefficient, but incredibly simple and widely supported. For that reason they are good for distributing data and forever crop up on Wikileaks and Free Our Data. Excel usually grabs CSV as an extension, but its quite often easier to have something that’s designed for the job and CSVed does this admirably. You get a spreadsheet like view that allows in-cell editing, but its the many other touches that are nice. Drag-and-drop rows and columns, append files, change delimiters, split columns, prefix/suffix, filtering, sorting. The list is quite long and targeted at these dealing with large scale manipulation of CSVs.

CSVed comes highly recommended, but, like Excel there is the odd glitch. Its only with Excel 2010 that some of the file constraints are easing, but upto this point you are pretty much limited to 256 columns and 64,000 rows. I often end up with more than 256 columns when dealing with spectral data from a spectroradiometer (usually well over a thousand). Unfortunately CSVed hangs when trying to load these and Excel won’t load them, which usually leaves me using R to load the data and then transposing the file for further manipulation.

SSTL have just announced the development of three new satellites in a £100M investment. What’s interesting with this announcement is that it’s a partnership between SSTL and its data processing subsidiary DMCii and will be operated commercially, leasing time on the satellites to nations that would otherwise not be able to afford their own satellite.

We have taken delivery of a new GeoWall system at Kingston which Ken has been painstakingly putting together. It does just look like a very large Meccano set. Anyway, we have been thinking about some 3D datasets to show, initially through ArcScene. Given we have a Leica ScanStation 2 (although I might take issue with it being “affordable” and “entry-level”!), we thought it would be good to show-off some of our laser scan data and, initially, one of the campus buildings.

This data is scanned and stored in Cyclone. Cyclone’s earlier iterations were more closely aligned with CAD, as users were initially producing 3D models of existing infrastructure. The data itself is simple; x,y,z triples of position, but millions of them. Whilst the LAS format is common for the transfer of airborne LiDAR data, the shapefile is a convenient storage format and understood by just about anything. In ArcScene its then simply a case of changing the base heights to the elevation field and its done. Simple. Except Cyclone only exports as a textfile file; no problem, ArcMap can probably handle it. And I’m sure it probably can, except I gave up trying to work out exactly which ToolBox tool is required and, if its not comma or tab separated, how it should imported and whether a schema ini file is needed. I fired up Global Mapper instead which just has a text import filter and a shapefile export filter. Nothing fancy, no drama; it did it. OK, so the 170Mb file took a few minutes to process (on my slow machine!), but it didn’t hang, crash, give an unintelligible error message or anything else. It loaded in to ArcScene fine. Sometimes its nice just to have something that’s straightforward (and it would help if Leica could take the shapefile exporter from LPS and stick it in Cyclone. Different heritage and development teams so I don’t expect it to happen!).

M.B. Gousie and M.J. SmithProceedings of Spatial Accuracy Assessment in Natural Resources and Environmental Sciences, Leicester
It is well known that a digital elevation model (DEM) may contain systematic or other errors. In many 3-D visualization systems, problems in the data may be highlighted, but it is often difficult for the viewer to discern the exact nature of the problem. We present DEMView, a viewing and error assessment system specifically for use with DEMs. The system displays a DEM in 3-D with the usual translation, rotation, and zooming tools. However, the system incorporates a suite of visual (qualitative) and statistical (quantitative) assessment tools that help a researcher determine and analyze errors and uncertainty in a given DEM. A case study shows the efficacy of the system.