GPS On The Motorcycle: Tool or Toy? Peter Jones - DGPS Guy July 14, 1999 BMW MOA National Rally Rhinebeck, New York
Peter Jones - DGPS Guy • U.S. Coast Guard for 17 years. • Former enlisted helicopter flight mech / SAR crew and avionics technician. • First commissioned billet: U.S. Coast Guard Navigation Center, Alexandria, VA • Command & Control of DGPS & LORAN • DGPS Management and some operations.
GPS On The Motorcycle • GPS 101 • User equipment comparisons • Waypoint & route management • Software tools and Internet resources • Neat adjuncts • Discussion
GPS 101 • GPS = Global Positioning System • Provides continuous, all-weather, real-time position, velocity, and time information, anywhere in the world. • Provides two levels of service: • Standard Positioning Service: 100m (95%) • Anyone with a receiver - signal is free of charge • Precise Positioning Service: ~22m • Authorized users only (DOD) - Protected by crypto
GPS 101: User Base • Traditional navigators (marine & aviation) • Surveyors & chart makers • Agriculture • Utilities (timing) • New technologies and applications • “Intelligent Transportation Systems” • Self-piloting cars • You name it...
GPS 101: Satellites • 24 satellites in 6 orbital planes. • Currently have 27 satellites in orbit. • Three spares are online and transmitting. • Semi-synchronous orbit at 11,000 miles. • Controlled by USAF Space Command. • USAF has committed to providing a continuous GPS service without interruption to the civil user.
GPS 101: Tech Stuff • Each satellite transmits navigation signals on 2 L-band frequencies, L-1 (1575.42 MHz) and L-2 (1227.6 MHz). • Position is calculated from distance and time measurements to satellites. • 3 measurements needed to determine exact two-dimensional position. User must provide altitude. • 4 measurements needed to determine exact three-dimensional position. • The probability that 4 or more GPS satellites are in view anywhere on or near the earth (over a 24 hour period) is at least 99.9% (w/ complete constellation).
Selective Availability (S/A) • DOD’s intentional degradation of the signal to deny the bad guy highly accurate positioning for weapons delivery. • S/A is what keeps SPS accuracy at <100 meters (95%). • S/A can be changed slowly; limits are classified. • USAF has committed to limiting S/A to 100m, 95% • Typically around 50m for last couple years. • PPS has S/A filtered out by crypto equipment.
S/A (cont.) • On March 29, 1996 the President announced policy on GPS, with intentions to discontinue the use of S/A within a decade. Beginning in the year 2000, the President will make an annual determination on continued use of SA. • Post-S/A GPS should provide accuracies similar to PPS. Users will probably see better than 20m routinely (can’t wait!).
Velocity Accuracy • Generally very accurate except for S/A. • S/A limited to 4m/sec by signal spec. • Typically much less • Most modern receivers measure speed using doppler shift measurements not position • In general a very accurate speedometer
Enhancements / Augmentations • Differential GPS (DGPS): • Maritime (Coast Guard) • Aviation (FAA) • Commercial Provider • Private / Local • Hobbyist (Amateur Radio) • Enables highly accurate positioning by providing error corrections via data-link. • Coast Guard system typically provides accuracies better than 2 meters.
GPS Outages • Simply Put: It Doesn’t Happen. • Internet-based warnings are worth what you paid for them. • The Reality: • Very limited area ECM testing could affect users. Unlikely to have serious affect because government agencies (FAA, USCG, etc.) are watching out for users (hey, we’re here to help!).
End-of-Week (EOW) Rollover • GPS Epoch based on weeks from 0000 to 1023 (standard 10-bit digital counter). • GPS week counter will roll over at23:59:47 UTC on August 21, 1999. • Not a GPS design flaw! • GPS receivers not built to published standards may crash or fail to track satellites at the time of rollover. • Most modern receivers are not affected by the EOW rollover. • Receivers that are affected will probably work again after being reset. • Users should contact the factory for more information.
Consumer Hardware • Garmin • Seem to have the best software support • Popular among hobbyists • Diverse product line • Lowrance / Eagle • Competitively priced • Some neat features • Perhaps not as much software • Both have excellent customer service rep.
Garmin GPS-III+ Small & light Street level uploadable maps from CD can hold about 1 mid-sized metro area in 1.4 MB but no POI’s. Good battery life (18+ hours) Garmin StreetPilot Large form factor Street level uploadable maps from CD or ROM can hold up to 16MB of data incl. POI’s. Poor battery life esp. for ColorMap (2 hrs). Receiver Comparisons
Receiver Comparisons (cont.) • Eagle MapGuide Pro • More RAM than Garmin GPS-III • More flexibility in selecting portions to upload • Lower cost • Some say UI not as intuitive...
Consumer Software • Commercial: • Street Atlas by DeLorme • Precision Mapping by Chicago Map • Microsoft Expedia / Streets • Shareware • Waypoint+ • G7TO • GPSy (Mac)
Waypoint Naming Techniques • Many receivers limited to 6 or 8 characters. • Come up with a system that makes sense to you! • Abbreviated names for location waypoints. • Three characters for each half of a road change. • I95231 = a turn from I95 onto Hwy 231. • MOHOLD = a turn from Mohican St onto Old Bridge Rd. • Use comments field!
Building Routes • Create a waypoint for each road change. • Adding waypoints for significant direction changes (very curvy roads) helps make your map easier to follow and computed times more accurate. • Can use receiver keyboard (slow) or software: • Waypoint+ • G7TO -or- G7TOWin • Street Atlas
Street Atlas Routing • Create waypoints at each road change using stops. Don’t use vias. • Each waypoint *must* have unique name. • Rename using mouse and right-click. • Not critical with StreetPilot. • Before computing route, upload it! • “Upload Directions to GPS” • Must select GPS Initialize first or menu choice does not appear (groan).
Street Atlas Routing (cont.) • Can still use auto-routing to help select route. • Minor change to route removes superfluous waypoints. • Quickly builds good routes. • 30 waypoint limit per route (receiver limitation). • Thanks to unknown IBMWR President for this technique. • Flaky with StreetPilot • Can still use this technique to build waypoint list and then load manually or with shareware.
Track Logs • Most units record bread-crumb trail. • Storage varies with unit. Largest may be in Garmin GPS-III/III+. • Garmin units have adjustable resolution. • Download using shareware (Waypoint+ or G7TO), then import into Street Atlas. • Downloading into Street Atlas less flexible. • Limits number of records received • Doesn’t separate track lines or points
Internet Resources • http://joe.mehaffey.com • Everything under the sun on GPS. • http://www.waypoint.org/ • Promising waypoint repository. • http://www.crash.de/wpb/ • Motorcycle oriented waypoint database. • http://www.bridge.de/~tom/garmin.htm • Motorcycle oriented GPS pages. • http://www.murkworks.net/~erkaneva • Complete U.S. BMW dealer waypoint file!
Neat Adjuncts: APRS • Automatic Position Reporting System • Automatically transmits position, speed, and direction • Receives from fellow travelers • Position available via shareware and WWW • Requires Amateur “Ham” Radio License