G lobal P ositioning S ystem.

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Gotten to be alright with the GPS information accumulation procedure intended for the SWAP program ... The Global Positioning System (GPS) is an exact overall radio-route ...
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G lobal P ositioning S ystem GeoXT Training January 20, 2003

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Training Provided by Information Center for the Environment University of California, Davis Instructor: Sky Harrison

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SWAP Training Objectives Provide adequate composed, hands-on, and field preparing to satisfy the GPS part of the Drinking Water Source Assessment Program Obtain general learning of essential GPS ideas Become acquainted with the nuts and bolts of operations of the Trimble GeoXT Become OK with the GPS information gathering process intended for the SWAP program

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DHS Objectives Collect precise areas for all open drinking water sources in California Integrate information accumulation into typical every day work routine Standardize information accumulation Make it simple!

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What is GPS? The Global Positioning System (GPS) is an exact overall radio-route framework, and comprises of a group of stars of satellites and their ground stations, worked and kept up by the US Department of Defense (DoD).

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User How Does it Work? The GPS Segments Space Colorado Springs Control

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Space Segment 24 satellites in 6 slanted circles 4 satellites for each circle - 12 hour transformations 12,600 miles (20,000 km) height

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U S Air Force Control Segment Managed by the U.S. Aviation based armed forces 4 checking and 3 transfer stations Daily ephemeris (area) upgrades Transmits clock and circle remedies Disable utilization of satellites Degrade exactness of the signals

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User Segment U.S. Military Civilian delivery Scientific high precision applications Resource supervisors (GIS information catch) Survey and mapping control

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What is GPS Used For? Applications Point Features Line and Area Features Navigation GIS Data Capture

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Nest trees Survey landmarks Fence corners Trail markers Instream structures Search and protect Monitoring gadgets Reference focuses Cultural destinations Wells Helispots Photo focuses Hazard locales Vehicles Point Features

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Roads Trails Fire edges Cultural destinations Campgrounds Fences Timber deal units Stream channels Vegetation sort Riparian territory Line and Area Features

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Navigation Relocate purposes of enthusiasm with known directions Locate mapped highlights utilizing anticipated or evaluated organizes

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Spatial Data Recording Method utilized relies on upon highlight sort Point Feature Calculates the normal of all positions Line Feature Each position joined to the following in time arrangement Calculates the length Area (polygon) Feature Joins every position to the following in time succession Joins the last position to the main Calculates the range

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GIS Data Capture Tag GPS positions with highlight and quality information Define components of enthusiasm before field work Collect information in a GIS-good configuration Generate all documents expected to drive GIS information stacking Allow particular yield to GIS taking into account highlight name or property estimations

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Data Dictionaries Data lexicons are a key during the time spent depicting the article or questions be mapped, alluded to as "elements." Descriptions of these elements can increase the value of the positional information gathered. Quality PS-Code Source Number Date Value 32S/13E-17K01 M 001 12/13/99 Feature PWS - 4010001

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Trilateration from satellites to decide position Satellite positions in space are known

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Measuring the separation to a satellite Determination of the "pseudo" reach is finished by measuring travel time of GPS radio signs going at the pace of light.

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separation = Elapsed time x 186,000 miles for each second Pseudo Range Trilateration

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x miles The separation (x) from one satellite lets us know we\'re found some place on the surface of a nonexistent circle focused on that satellite with a span of x.

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Distance estimations from two satellites confines our area to the crossing point of two circles, which is a circle.

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A third estimation contracts our area to only two focuses.

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A fourth estimation figures out which point is our actual area

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Satellite Clock Errors Ephemeris Errors Atmospheric Effects Receiver Errors Operator information and mindfulness Number of obvious satellites Satellite Geometry Occupation time Multipath GPS Position Accuracy Many elements can influence the exactness of GPS information. Exactness can run from 1 centimeter to more than 40 meters Significant Parameters:

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Satellite Geometry HDOP (Horizontal Dilution Of Precision) Using satellites from the 4 compass quadrants will give a decent Horizontal arrangement (Low HDOP) . Utilizing satellites from just 1 or 2 quadrants will give a poor Horizontal arrangement (HIGH HDOP).

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Satellite Geometry VDOP (Vertical Dilution Of Precision) Using satellites well spread out in the sky will give a decent Vertical Solution (Low VDOP). Utilizing just satellites which are found low coming soon will bring about a poor Vertical Solution (HIGH VDOP).

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Satellite Geometry PDOP (Position Dilution Of Precision) PDOP is the blend of both the Horizontal and Vertical segments of position mistake brought about by satellite geometry. PDOP Values 2-4 = Excellent 4-6 = Good 6-8 = Fair 8-10 = Poor 10-12 = Marginal above 12 PDOP is too High Do Not Use

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Selective Availability (S/A) DISCOUNTINUED MAY 1, 2000 Intentionally corrupted exactness controlled by the Department of Defense It was the most exceedingly bad wellspring of mistake Artificial clock and ephemeris (locational) blunders were acquainted with throw framework off Prevented unfriendly strengths from getting to the most precise GPS capacity

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GPS Position Accuracy General Statement of Accuracy: Taking the greater part of the blunder sources into record, GPS precision will be roughly 10 meters for most GPS units. Be that as it may, any given position may bring about precision as low as 5 meters or up to 40 meters. ** Selective Availability OFF No Post-handled or Real-time Differential Correction

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Increasing GPS Accuracy through Differential Correction Rover or Remote (obscure) Base Station (known)

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Community Base Stations Semi-Permanent base station for differential revision Automated information accumulation Multiple meanderers inside 300 mile span can utilize information Internet access to base documents 12-channel beneficiary

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Uncorrected File 18 meter precision from known position Any one point could be off base by 40 Meters. Accuracy: half of focuses inside 25 meter sweep circle normal GPS position Known position approx. 180 seconds 1 point for each second

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File After Differential Correction 1-5 meter exactness from known position utilizing GeoExplorer III Precision: half of focuses inside 5 meter range circle normal GPS position Known position approx. 180 seconds 1 point for each second

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Limiting Factors Dense overhang Steep geography Large and various structures Microwave radio wire obstruction

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Thank You Sky Harrison Information Center for the Environment University of California, Davis http://ice.ucdavis.edu Phone: (530) 752-0532 Email: sky@ice.ucdavis.edu

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