Iowa DOT SPR RB22-011 Aug 2012ResultsThe following is a summary <strong>of</strong> <strong>to</strong>pics discussed at the completion <strong>of</strong> the project.Data S<strong>to</strong>rage and Computer IssuesComputing and s<strong>to</strong>rage requirements need <strong>to</strong> be separated in<strong>to</strong> two distinct categories;Data processing and extraction, versus end-user usage, and tend <strong>to</strong> be s<strong>of</strong>tware dependent.Delivered LAS and image files for this project <strong>to</strong>taled almost 31GB.Data ProcessingAcceptable performance can be achieved with modest hardware such as a dual-coreprocessor (hyper-threading a plus), 32-bit operating system, 4GB RAM, mid-levelgraphics board, 500GB internal hard drive and the ability <strong>to</strong> attach external drives viaeSATA or USB 3.0 interfaces when needed. However, higher-end hardware does achievemeasurable performance gains and reduced time expenditure. The size <strong>of</strong> the project datafiles is subject <strong>to</strong> many variables such as scan density, vehicle travel speed, etc. The RieglVMX-250 produces approximately 500 <strong>to</strong> 700MB <strong>of</strong> raw scan data per mile <strong>of</strong> scanningwhen set for a scan density <strong>of</strong> 600,000 points per second and travelling at 40 mph. Theraw scan data is s<strong>to</strong>red in a compacted format. There is nearly a 6-fold increase in the size<strong>of</strong> the scan data after post-processing. Camera data, when enabled, producesapproximately 900MB <strong>of</strong> imagery data per mile using a 2-camera, 5 megapixel system.Data ExtractionData extraction is performed using the final, adjusted LAS files. The Riegl VMX-250system, configured as described, produces approximately 1.0 <strong>to</strong> 1.4GB <strong>of</strong> LAS data permile <strong>of</strong> scan. Extraction <strong>to</strong>ols are capable <strong>of</strong> segmenting the LAS data in<strong>to</strong> moremanageable working-file sizes. Experience will determine the maximum manageabledata-set size for a particular hardware platform. Systems are capable <strong>of</strong> loading one mile<strong>of</strong> LAS data at a time while maintaining acceptable performance during extraction.Clipping <strong>of</strong> the LAS data outside <strong>of</strong> the area <strong>of</strong> interest allows for longer, wider ormultiple segments <strong>to</strong> be loaded. The primary limitation in our environment is the fact thatMicro<strong>Station</strong>, at this time, is still 32-bit platform. Certain Micros<strong>of</strong>t Windows systemsettings will allow Micro<strong>Station</strong> <strong>to</strong> access more than 2GB RAM, but Micro<strong>Station</strong>’saccess <strong>to</strong> this additional memory is via way <strong>of</strong> memory paging. When Micro<strong>Station</strong> <strong>of</strong>fersa 64-bit platform; manageable data set sizes as well as overall performance shouldincrease.End-User UsageThe typical finished products from a scan mission are the CAD design files and the LASpoint cloud files. The CAD files typically produced are indistinguishable fromconventionally derived products. Hardware platforms currently providing satisfac<strong>to</strong>ryperformance will suffer no adverse impacts from the incorporation <strong>of</strong> scan-derivedproducts. Several free and commercial utilities are available for the viewing <strong>of</strong> the LASfiles. One example is the free-ware s<strong>of</strong>tware viewer Quick Terrain Reader, developed byJohns Hopkins University's Applied Physics Lab. Suitable performance is achieved usingthe lower-end systems described above, although larger models will see substantiallyincreased performance when viewed on higher end, 64-bit platforms with greater than4GB RAM and pr<strong>of</strong>essional grade graphics boards.Page 14 <strong>of</strong> 19
Iowa DOT SPR RB22-011 Aug 2012AccuracyThe data acquiredthrough the MTLS anddata processing meetsthe Iowa DOTspecifications forengineering survey.The adjacent tablesummarizes theaccuracy <strong>of</strong> the 76control points thatwere covered by thescanning.The following table is an example <strong>of</strong> the accuracy for 16 <strong>of</strong> the 76 control points.Page 15 <strong>of</strong> 19
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