NRCS Global Positioning Systems (GPS) & Geographic Information Systems (GIS) RESOURCE INVENTORY  Soil Survey  National Resources Inventory (NRI)  Wetlands Inventory  Snow Survey  Others  Easements REMOTE SENSING  Aerial Photography  Aerial Digital Imagery  Satellite Imagery  Airborne Video CUSTOMER SERVICE TOOLKIT  Conservation Planning  Resource Assessment  Interpreted Soils Information GLOBAL POSITIONING SYSTEM (GPS)  Where on Earth?!!? COMPUTER ASSISTED DESIGN MODELING AGNPS AnnAGNPS Others GPS is a data collection tool for GIS

Accuracy - Sources of GPS Error  Standard Positioning Service (SPS ) Selective Availability:0 to 100 meters Ionosphere:5.0 to 7.0 meters Troposphere:0.5 to 0.7 meters Satellite clocks:< 1 to 3.6 meters Orbital errors:< 1 meter Receiver noise:0.3 to 1.5 meters Multipath:undetermined User error:Up to a kilometer or more  Errors are cumulative!

Accuracy – SPS Performance  Required GPS SPS Accuracy Horizontal: 13 meters 95% Vertical: 16 meters 95%  Observed GPS SPS Accuracy Horizontal: 6 meters GPS data averaged over 24 hour periods for 244 days

 Must meet FGDC Geospatial data requirement: 10 1:24,000 scale  Must meet NRCS Navigation and positioning requirements for NRCS programs and activities: National Resource Inventory: meters Resource Planning: meters Soil Mapping: General Soil Mapping: Detailed meters Conservation Application: meters Conservation Certification: meters Survey & Engineering: Sub-meter Accuracy - NRCS Requirements Draft

Expected Accuracy varies by type of GPS unit Standard GPS - 15 m horizontal, 35m vertical NDGPS - 5 m horizontal WAAS - 7m total error, 3 m horizontal in tests Carrier Phase GPS - 10cm to 1meter Survey Grade - sub-centimeter

DGPS Unit 1 – Overview of GPS, DGPS, Equipment & Applications DGPS – Differential GPS  The ability to use differential corrections to improve GPS accuracy.  The use of differential corrections can be done in real time or “after the fact” or later time.

DGPS – Correcting Errors & Improving Accuracy  Differential corrections attempt to eliminate or minimize the Ionospheric and Tropospheric errors that effect GPS accuracy.  Differential corrections can be provided by: GPS Reference Stations GPS Augmentations

DGPS – Sources of Differential Corrections  GPS Reference Stations Local Area Reference Stations CORS – Continually Operating Reference Stations  GPS Augmentations FAA Augmentations Maritime & NDGPS High Accuracy NDGPS

DGPS Site GPS Receiver DGPS – DGPS – Post-processed Differential

NDGPS Site NDGPS Receiver GPS Receiver DGPS – DGPS – Real Time Differential

DGPS Augmentations  Space Based Augmentations FAA Wide Area Augmentation Service (WAAS) Commercial L Band Services  Ground Based Augmentations FAA Local Area Augmentation Service (LAAS) CORS - Continuous Operating Reference Stations Maritime Navigation System & NDGPS High Accuracy NDGPS

Ground Based Satellite Based DGPS – DGPS – FAA Augmentations

Maritime & NDGPS Nationwide Differential Global Positioning System  GPS Augmentation system For Surface Transportation that improves the accuracy and integrity of GPS for safety-of-life applications  Expanding Maritime DGPS Network Establishing Additional Radiobeacon Sites Standard interoperable nationwide service Transportation users include railroads, highways, public transportation, and waterways

NDGPS National Differential Global Positioning System September Active Sites

GPS Applications - Mobile Mapping Dual GPS / NDGPS External Antenna Notebook PC Running ArcView / ArcPad Mobile Communications GPS Map 76

The USDA “Tool Box” Has An Assortment of Tools. GPS Tools Configuration 1 & 2 Data Collection Tools Digital Camera / Mobile Devices Communication Tools Internet / Mobile phones Information Tools Desktop Computing / Servers