Rita, I carry a compass some of the time. I mostly use it inside complicted buildings but it it can be handy in cities. One of these days, I hope we have a Bluetooth receiver with a compass built in. Mike At 07:36 PM 6/29/2006, you wrote: >Mike do you think it is a good idea to have a compass as well as the gps to >make sure of accurate direction? >Rita >----- Original Message ----- From: "Michael May" <mikemay@xxxxxxxxxxxxxxxx> >To: <gps-talkusers@xxxxxxxxxxxxx> >Sent: Tuesday, June 27, 2006 10:46 PM >Subject: [gps-talkusers] Re: how to deal with multi path in cities > > >>Dave, >> >>The location does not vary in terms of its absolute position. You might here >>that it is to your left, then to your right. However, it would always be at a >>consistent compass direction and the distance to the location would be >>reliable. >> >>Mike >>At 06:07 PM 6/27/2006, you wrote: >>>Mike, if the heading varies during signal degradation, would the location of >>>what ever you are looking for vary as well? >>> >>>Dave >>> >>>taxation WITH representation isn't so hot, either! >>> >>>----- Original Message ----- From: "Michael May" <mikemay@xxxxxxxxxxxxxxxx> >>>To: "GPS-talkusers-freelists.org" <GPS-talkusers@xxxxxxxxxxxxx> >>>Sent: Tuesday, June 27, 2006 7:19 AM >>>Subject: [gps-talkusers] how to deal with multi path in cities >>> >>> >>>>There is one minor down side to the latest super sensative GPS receivers. >>>>When you are among tall buildings, it is amazing how well these receivers, >>>>like the Holux, report several satellites. The problem is that the quality >>>>of those signals is degraded because they are bouncing between the >>>>buildings. this is called multi path. The good news is that your position >>>>can be tracked but the bad news is that your accuracy and particularly your >>>>heading is degraded by this multi path. >>>> >>>>You'll know this is happening when you find your direction of travel >>>>swinging all over the place. Walk in a constant direction and keep hitting >>>>the H key for heading and see if there is any consistency or not. If you >>>>see 90 degree shifts in your heading, you are experiencing multi path. >>>> >>>>So I ask myself, "Self, what can I do about heading swings?" First, note >>>>that the compass direction for your destination will not shift as the >>>>compass reading is by definition constent. If your destination is reported >>>>as Northwest, that will not change no matter what your relative heading >>>>says. You must then rely on this compass direction by either using an >>>>actual tactile or audio compass to verify your real heading, or determine >>>>your compass direction from the GPS when you are not among tall buildings >>>>and keep track of that heading once you are among the buildings. In other >>>>words, if the GPS heading is going to be flakey, it is up to you to know >>>>the compass direction. >>>> >>>>If you know the compass direction, you can then utilize the other >>>>information the system is giving you to navigate a route or to use the >>>>getting warmer method to get to your destination. >>>> >>>>Besides the compass direction, you will want to rely heavily on the >>>>distance to your destination or waypoint decreasing. Even if your heading >>>>is reported to be South and your Destination is north, if the distance to >>>>the destination decreases, don't turn around. A decreasing distance to your >>>>destination is something you can depend upon. >>>> >>>>This multi path is not something that will vary among receivers or systems. >>>>We have tested the $900 Garmin Nuvi receiver against the Holux in this kind >>>>of situation and there was no difference. >>>> >>>>Until you get out of the tall buildings, pay close attention to that >>>>compass direction and to the distance to destination. >>>>Mike >>>> >>>> >>>> >>>>Michael G. May >>>> >>>>CEO Sendero Group >>>> >>>>Developers and distributors of BrailleNote GPS >>>>Distributing BrailleNote, VoiceNote, Talks, Miniguide, The Tissot Silen-T >>>>tactile watch, and the ID Mate bar code reader >>>> >>>>MikeMay@xxxxxxxxxxxxxxxx >>>>http://www.SenderoGroup.com >>>> >>>>1-888-757-6810, Fax (530) 757-6830, Mobile (530) 304-0007 >>>>Sendero Group, LLC >>>>1118 Maple Lane, Davis, CA 95616-1723, USA >>>> >>>>Latitude, 38 33 9.239 North >>>>Longitude, 121 45 40.145 West >>>> >>>> >>>> >>> >> > >