The Global Positioning System II Field Experiments. 10/10/2013 GEO327G/386G, UT Austin 5-1

Transcription

1 The Global Positioning System II Field Experiments 10/10/2013 GEO327G/386G, UT Austin 5-1

2 Mexico DGPS Field Campaign Cenotes in Tamaulipas, MX, near Aldama 10/10/2013 GEO327G/386G, UT Austin 5-2

3 Are Cenote Water Levels Related? 10/10/2013 GEO327G/386G, UT Austin 5-3

4 DGPS Static Survey of Cenote Water Levels 10/10/2013 GEO327G/386G, UT Austin 5-4

5 Determining Orthometric Heights Ortho. Height = H.A.E. Geoid Height Height above MSL (Orthometric height) H.A.E. Earth Surface Geoid height = H.A.E. Geoid Ellipsoid Geoid Height 10/10/2013 GEO327G/386G, UT Austin 5-5

6 Determining Orthometric Heights 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 10/10/2013 GEO327G/386G, UT Austin 5-6

7 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) 10/10/2013 GEO327G/386G, UT Austin 5-7

8 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 10/10/2013 GEO327G/386G, UT Austin 5-8

9 Results Horizontal accuracies of <1 cm Vertical accuracies of 2-5 cm for 4 hrs of data 10/10/2013 GEO327G/386G, UT Austin 5-9

10 GPS Applications Today 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) 10/10/2013 GEO327G/386G, UT Austin 5-10

11 GPS and Geologic Mapping Two techniques: GPS receiver and separate, gridded paper maps Mapping-grade receiver with mapping software and interactive touch screen 10/10/2013 GEO327G/386G, UT Austin 5-11

12 Low-Tech Mapping Gridded maps/photos, pencil, GPS receiver UTM NAD83 13N Spence 7.5 ' Quad Meters 1:12,002 Contour Interval = 20 feet MN Õ16 degrees True N is ~1 degrees East of grid N. 10/10/2013 GEO327G/386G, UT Austin 12

13 High-Tech Mapping Tools Field Hardware Windows CE or PocketPC devices Outdoor tablet computers Win XP Field GIS/GPS Software ESRI Software ArcPad ArcMap 10/10/2013 GEO327G/386G, UT Austin 13

14 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 10/10/2013 GEO327G/386G, UT Austin 14

15 Small, low res., color screens 10/10/2013 GEO327G/386G, UT Austin 15

16 Outdoor Tablet Computers Large, outdoor-viewable, high res. color screens Inductive stylus pen 3-4 hr. battery life Heavy, rugged 10/10/2013 GEO327G/386G, UT Austin 16

17 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 10/10/2013 GEO327G/386G, UT Austin 17

18 Tablet Running ArcPad Qal pcdm pccm 10/10/2013 GPS Location GEO327G/386G, UT Austin 18

19 ArcGIS - ArcMap Software Desktop software in the field Powerful Drawing tools best feature Edit Geodatabases in the field Minimal GPS capture tools 10/10/2013 GEO327G/386G, UT Austin 19

20 Tablet Running ArcMap 10/10/2013 GEO327G/386G, UT Austin 20

21 High-Tech Mapping Tools Field Hardware Mobile Phones Ipad or other tablet Field GIS/GPS Apps. Apple OS, Android OS Surveying Apps. 10/10/2013 GEO327G/386G, UT Austin 21

22 Assisted GPS (A-GPS) Mobile Devices with GPS and WiFi or Cellular Service, e.g. LBS-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 ) 10/10/2013 GEO327G/386G, UT Austin 5-22

23 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) 10/10/2013 GEO327G/386G, UT Austin 5-23

24 Receiver attributes DGPS capable Beacon antenna for realtime DGPS Download and postprocess Ionosphere Correction or model Dual channel vs. single channel receiver Troposphere model? WAAS capable 10/10/2013 GEO327G/386G, UT Austin 5-24

25 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 10/10/2013 GEO327G/386G, UT Austin 5-25

26 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 10/10/2013 GEO327G/386G, UT Austin 5-26

27 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 10/10/2013 GEO327G/386G, UT Austin 5-27

28 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 10/10/2013 GEO327G/386G, UT Austin 5-28