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" <mikemaysenderogroup.com>
>To: "GPS-talkusers-freelists.org"
<GPS-talkusersfreelists.org>
>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
>>
>>MikeMaySenderoGroup.com
>>http://www.SenderoGroup.c
om
>>
>>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
>>
>>
>>
>>
>
>