The Global Positioning Sytem II 10/13/ /13/2015 GEO327G/386G, UT Austin /13/2015 GEO327G/386G, UT Austin 5-4

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1 The Global Positioning System II Field Experiments Mexico DGPS Field Campaign Cenotes in Tamaulipas, MX, near Aldama 10/13/2015 GEO327G/386G, UT Austin /13/2015 GEO327G/386G, UT Austin 5-2 Are Cenote Water Levels Related? DGPS Static Survey of Cenote Water Levels 10/13/2015 GEO327G/386G, UT Austin /13/2015 GEO327G/386G, UT Austin 5-4 M. Helper, GEO 327G/386G, UT Austin 1

2 Determining Orthometric Heights Determining Orthometric Heights Ortho. Height = H.A.E. Geoid Height Earth Surface Geoid Ellipsoid Geoid Height Height above MSL (Orthometric height) H.A.E. Geoid height = H.A.E. 10/13/2015 GEO327G/386G, UT Austin 5-5 Ortho. Height = (H.A.E. Geoid Height) Need: 1) Ellipsoid model GRS80 NAVD88 reference stations: HARN (+ 2 cm), CORS (+ ~2 cm) 2) Geoid model GEOID99 ( + 5 cm for US) Procedure: Base receiver at reference station, rover at point of interest a) measure HAE, apply DGS corrections b) subtract local Geoid Height 10/13/2015 GEO327G/386G, UT Austin 5-6 Sources of Error Geoid error model less well constrained in areas of few gravity measurement NAVD88 error benchmark stability, measurement errors GPS errors need precise ephemeri, tropospheric delay model, equipment (antennae should be same for base and rover) Static Carrier-phase solutions obtained by: Commercial post-processing software e.g. Trimble Pathfinder office Web-based services Automated Gipsy JPL/NASA - global SCOUT Scripps, UCSB - global OPUS NGS (US and territories) All services require files in RINEX format 10/13/2015 GEO327G/386G, UT Austin /13/2015 GEO327G/386G, UT Austin 5-8 M. Helper, GEO 327G/386G, UT Austin 2

3 UTM NAD83 13N Spence 7.5 ' Quad Meters MN True N is ~1 degrees East of grid N. Results GPS Applications Today Horizontal accuracies of <1 cm Vertical accuracies of 2-5 cm for 4 hrs of data Surveying Tectonics, Cadastre, Geodesy Map Making georeferencing, field studies Navigation vehicles, missiles, robots, etc. Tracking people, vehicles, pets Geotagging apply coordinates to digital data (photos, etc.) Clock Synchronization (+ 10 ns) 10/13/2015 GEO327G/386G, UT Austin /13/2015 GEO327G/386G, UT Austin 5-10 GPS and Geologic Mapping Two techniques: GPS receiver and separate, gridded paper maps Mapping-grade receiver with mapping software and interactive touch screen Low-Tech Mapping Gridded maps/photos, pencil, GPS receiver :12,002 Contour Interval = 20 feet Õ16 degrees 10/13/2015 GEO327G/386G, UT Austin M. Helper, GEO 327G/386G, UT Austin 3

4 High-Tech Mapping Tools Field Hardware Windows CE or PocketPC devices Outdoor tablet computers Win XP Field GIS/GPS Software ESRI Software ArcPad ArcMap GPS-equipped Windows Mobile Devices Small, low res., color screens Limited CPU Resistive stylus pen Up to 12 hrs. battery life Light, portable Variably rugged Small, low res., color screens Outdoor Tablet Computers Large, outdoor-viewable, high res. color screens Inductive stylus pen 3-4 hr. battery life Heavy, rugged M. Helper, GEO 327G/386G, UT Austin 4

5 ArcPad Uses standard data formats shapefile, tif, SID, etc. Good GPS support Supports custom forms Well-integrated with ArcGIS products Easy to use GIS-GPS Software 17 Qal Tablet Running ArcPad GPS Location pccm pcdm 18 ArcGIS - ArcMap Software Tablet Running ArcMap Desktop software in the field Powerful Drawing tools best feature Edit Geodatabases in the field Minimal GPS capture tools M. Helper, GEO 327G/386G, UT Austin 5

6 High-Tech Mapping Tools Field Hardware Mobile Phones Ipad or other tablet Field GIS/GPS Apps. Apple OS, Android OS Surveying Apps. ios Apps High-Tech Mapping Tools PDF Maps igis 10/13/2015 GEO327G/386G, UT Austin 21 10/13/2015 GEO327G/386G, UT Austin 22 High-Tech Mapping Tools App Distinctions Will maps work offline? Will GPS work offline? Does it drop pins, geotag photos, notes etc.? E.g. PDFMaps and many others free Apps Does it allow capture of lines and polygons too? E.g. igis, FieldMove, a few others; free to $$ ArcGIS Collector App Assisted GPS (A-GPS) Mobile Devices with GPS and WiFi or Cellular Service, e.g. LBS (location-based services)-capable phone 1. GPS Almanac provided from Server; TTFF faster position found by phone (Mobile Station Assisted: MSA GPS ) 2. GPS data sent to server, position sent back (Mobile Station Based: MSB GPS ) 10/13/2015 GEO327G/386G, UT Austin 23 10/13/2015 GEO327G/386G, UT Austin 5-24 M. Helper, GEO 327G/386G, UT Austin 6

7 Receiver attributes Receiver attributes # of Channels One channel required for each frequency (L1, +/- L2) 8 minimum (4 SVs); 12 or more desirable Antenna Remote, fixed Power source Internal, external Data Storage Way-points vs. data logging Positions vs. raw data Data upload & download Data dictionary upload for storing positions by attributes (pt., line, area) DGPS capable Beacon antenna for realtime DGPS Download and postprocess WAAS capable Ionosphere Correction or model Dual channel vs. single channel receiver Troposphere model? 10/13/2015 GEO327G/386G, UT Austin /13/2015 GEO327G/386G, UT Austin 5-26 GPS Equipment Hand-helds $100-$450 navigation instruments Garmin Magellan GPS for PDAs +/- ~15 meters For survey apps.: Way Points collection Manual entry into GIS, no attribute info. stored Differential ready but no post-processing GPS Equipment Sub Meter (x, y) Accuracy, Hand-helds: $1000-$5000 Trimble Ashtech Topcon Sokkia others Datalogging with data dictionary to upload/store attribute info. GPS signal data collection for later post-processing Custom RTK and beacon antennae feasible 10/13/2015 GEO327G/386G, UT Austin /13/2015 GEO327G/386G, UT Austin 5-28 M. Helper, GEO 327G/386G, UT Austin 7

8 GPS Equipment Geodetic-quality Instruments Trimble Ashtech Sokkia Others Cm mm in x and y; 2 cm in z Stationary Antenna Large memory for continuous data collection Recent Developments Hand-held equipment Field GIS WAAS, LAAS European Union Galileo System (2014) Russia - Glonass (presently 9 SVs; 24 by 2007) Chinese Beidou System (COMPASS, 2020) IRNSS India (2012) Japan - QZSS 10/13/2015 GEO327G/386G, UT Austin /13/2015 GEO327G/386G, UT Austin 5-30 M. Helper, GEO 327G/386G, UT Austin 8