The Keys to the Datum GatesA Users Guide to the Trimble TerraSync Workflow
PurposeUsers must pass through many datum gates to successfully collect and process GPS data. The increasing availability of sub-meter accurate GPS, imagery and other spatial datasets is keeping users even more honest every step as once ‘minor datum shifts’ can no longer be overlooked. Although a challenging topic for users of all levels, ignoring datums will introduce significant errors in the data you have worked so hard to collect.
When moving GPS data to a GIS, at each step, ask yourself: 1) to which datum is the GPS data currently referenced, 2) how might this step change that, and 3) to which datum is the resulting data file referenced. For steps where datums demand your consideration, this series of articles provides -
May these guides offer you the keys to successfully pass through each Datum Gate.
Where to StartThis series of papers was inspired by an excel sheet created by Joel Cusick, NPS to guide users through the various datum choices when collecting GPS data and and processing it for use in a GIS. The 'cases' referred to on this site are as follows. View the excel sheet to overview the various choices and then open the tutorial for the case that most closely matches your own workflow.
ESRI ArcPad data collection software Case 3: Trimble GPS Analyst desktop software with WAAS real-time correction or lacking any real-time correction Case 4: Trimble GPS Analyst with NDGPS or OmniStar real-time correction Trimble TerraSync data collection software Case 7 : WAAS real-time correction or lacking any real-time correction Case 8 : NDGPS or OmniStar real-time correction
NoteDatums are tough concept. In writing these articles, it seemed like just when we had a grasp of it all, one question had us starting from a new. It is expected it will take you as many reads to grasp these concepts as it did for us to write these articles. Please feel free to post comments or contact us as needed. |
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