---------------------------------------------------------- Avionics-List Digest Archive --- Total Messages Posted Fri 05/05/06: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 09:38 AM - Use of GPS......... () ________________________________ Message 1 _____________________________________ Time: 09:38:43 AM PST US From: Subject: Avionics-List: Use of GPS......... --> Avionics-List message posted by: 5/5/2006 Responding to a previous posting by Bo, copied below. Hello Listers, I want to express my appreciation for all who posted on this subject. It has been an exemplary exchange of reasonable and useful opinions and facts. I'd like to throw in some tidbits that may have some value: 1) From NACO one may purchase a CD-ROM that contains a digital navaid file. http://naco.faa.gov/ecomp/ProductDetails.aspx?ProductID=DAICD This CD-ROM provides the lat long location of navaids, including localizers. Be careful when using this data though because the format may be slightly different than that contained in your GPS box. 2) An examination of localizer installations shows that the DME antenna and the localizer antenna are not precisely co located. The DME antenna is usually mounted on the electronic shelter that is a short distance away from the localizer antenna array. 3) When flying an approach, regardless of which kind of approach, keep clearly in mind what distance you are reading on your GPS display. A) Is it to the next fix on the approach sequence as is typical in a published RNAV (GPS) approach? (The runway end itself is usually the final fix in this sequence). B) Is it the "DME" distance to the geographical location of the localizer / DME antennas on a published ILS or localizer approach? In which case the runway end "distance to" reading should appear printed on the approach plate. C) Is it the distance to some navaid such as an ADF, VOR, VORTAC, or compass locater? D) Is it the distance to some named five letter fix located on the field? F) Is it the distance to some named five letter missed approach point? G) Is it the distance to a five letter named fix at the end of the runway? H) Is it the distance to the lat long printed for the field on the approach plate that you have entered into your GPS? You get the idea -- pay close attention to what the distance to number represents. 4) My tendency when flying ILS approaches is to fly the approach using my SL-30 as the primary navigation device feeding my external CDI and use my Garmin GNS 430 as a "big picture" aid and set up the GPS "navigating to" point as desired. This GPS navigating to point is usually either the localizer or the runway end depending upon the approach information available. I feel that this gives me the best combination of precision and big picture. OC Time: 08:17:13 PM PST US From: Kelly McMullen Subject: Re: AeroElectric-List: Use of GPS in lieu of ADF and DME, was: Converting IFR GPS to Terminal --> AeroElectric-List message posted by: Kelly McMullen Bob, I think the only thing that is added is that you have to verify that the DME location is in the database, especially where it is a loc/dme approach where it presumably is at the far end of the runway, at the Loc antenna. I don't know that all of those are in a non-approach GPS data base. Otherwise I agree with everything else you are presenting. Bo