User manual TRIMBLE TERRASYNC 5.00 GETTING STARTED GUIDE REV A

[. . . ] GETTING STARTED GUIDE TerraSyncTM software GETTING STARTED GUIDE TerraSyncTM software Version 5. 00 Revision A October 2010 F Trimble Navigation Limited 10355 Westmoor Drive Suite #100 Westminster, CO 80021 USA www. trimble. com Legal Notices Copyright and Trademarks ©2000--2010, Trimble Navigation Limited. Portions of the software are copyright © 1995-2008 LizardTech, Inc. For STL support, the software uses the Moscow Center for SPARC Technology adaptation of the SGI Standard Template Library. Copyright © 1994 Hewlett-Packard Company, Copyright © 1996 1997 Silicon Graphics Computer Systems, Inc. , Copyright © 1997 Moscow Center for SPARC Technology. [. . . ] If you are collecting a series of features and you have a clear view of the sky and so are unlikely to lose carrier lock, you can move to the next feature before the required accuracy is reached. CAUTION ­ Do not move to another feature before the required accuracy is reached unless you are unlikely to lose lock on the required number of satellites. If you lose lock while collecting a series of features, you will need to re-collect all of the features to obtain features with the required accuracy. Provided that the predicted accuracy value passes the threshold of accuracy you require for the features, all of the features collected while carrier lock was maintained will achieve the same accuracy after H-Star processing. TerraSync Software Getting Started Guide 97 5 High-Accuracy Data Collection Carrier phase postprocessing workflow and required infrastructure This section explains in more detail how to obtain the accuracies specified for carrier phase data collection and postprocessing. During GNSS data collection where the TerraSync software logs carrier phase data, measurements are collected from each individual satellite. Carrier phase processing corrects the collected GNSS positions using the data from individual satellites, so the positions generated during postprocessing are more accurate than positions logged in the field. By logging carrier phase data, you can achieve accuracies of better than 30 cm after carrier phase processing. The following table is a general guide to accuracies that can be obtained with carrier phase data collection. Table 5. 1 Typical accuracies achieved after carrier phase data collection Accuracy 20 cm +5ppm 10 cm +5ppm 1 cm +5ppm Time since acquiring lock 10 minutes 20 minutes 45 minutes Required infrastructure for carrier phase data For carrier phase postprocessing, a carefully surveyed base station is essential. This must be within 80 km at all times (and within 10 km if you are aiming for accuracy at the 1-2 cm level). The base station must log dual frequency (L1/L2) GNSS data at a frequency no lower than 1/30 Hz (once every 30 seconds). Collecting sufficient high-accuracy data When you open a new data file, the TerraSync software starts to log carrier data in the background. This allows the carrier block to start as soon as you open the file, not just when you begin to log a feature. As soon as four or more satellites are available, a counter starts. When enough time has elapsed for the GNSS positions to obtain the accuracy you require (see Table 5. 1, page 98), all of the carrier phase data recorded during that period can be used during postprocessing. Note ­ When you open an existing file with carrier features, the TerraSync software does not automatically log background carrier data. Carrier logging only begins when you start logging positions to the file. These may be not-in-feature positions, position records for a new feature, or updated positions for an existing feature. 98 TerraSync Software Getting Started Guide High-Accuracy Data Collection 5 When you start a new feature that is set to carrier accuracy, the logging icon appears in the Status bar. When the TerraSync software has logged carrier phase data continuously for the minimum time (10 minutes), the success beep sounds. If you try to close a file before the minimum time is up, the TerraSync software asks you to confirm that you want to close the file. If you do close the file, you may lose carrier accuracy for some features. Once the counter is running, you can choose to end the current feature and stay where you are until the minimum time is up. When the success beep sounds, move to the next feature. Using this method, you can be sure that you have sufficient data to generate precise positions. Alternatively, if you think you are unlikely to lose lock, you can move to the next feature before sufficient carrier phase data has been collected. This is possible because all features recorded during a block achieve the precision associated with that block. [. . . ] A bearing that is relative to true north uses the north celestial pole as its north reference. UTC is a time standard based closely on local solar meantime at the Greenwich meridian (GMT). GNSS time is directly related to UTC. UTM Universal Transverse Mercator Map Projection. A special case of the Transverse Mercator projection. [. . . ]