[gps-talkusers] Re: irectionality of the POI
- From: "Carl Simmons" <carlsimmons@xxxxxxxxxxx>
- To: <gps-talkusers@xxxxxxxxxxxxx>
- Date: Thu, 11 May 2006 21:25:44 -0700
Kevin,
One of the most important areas of providing guidance with any GPS system
is that a correct heading must be established. Just as when giving
directions to a person the first piece of information would be what
direction is the person facing. The GPS system has to determine the heading
by plotting your travels over a period of time. This is one of the most
complex areas of any GPS system.
To help understand the complexity I will try to explain the basics. The GPS
system will know your current position by having your location by latitude
and longitude. The accuracy on this point is dependent on the current GPS
signal strength. Then after a period of time the system will again determine
your position. With these two points a direction of travel can be
established. Now enters the complexity. Take a case that you did not move
over this period of time, but the GPS signal accuracy varies. This will
change your position and now a direction of travel is determined with out
your moving. This is just one of the variables one must consider when
establishing a heading direction.
As you can understand the GPS system can not provide accurate guidance until
a correct heading has been established. This is the main rule of trusting
the guidance is to assure that the heading is correct. For example if you
know you are traveling North and the GPS heading indicates east any guidance
information could be incorrect. One method I use is to check my heading
with a compass and compare with the GPS heading. One other method is to
inquire the heading direction and travel a distance and check again then
again. When the heading remains the same you can figure this heading is
correct.
I know this is a lengthy lesson but a very important item in understanding
the methods used to provide guidance. I hope this helps.
Carl Simmons
Sendero Group Training and Technical Support
1-888-757-6810 Ext. 106
carl@xxxxxxxxxxxxxxxx
-----Original Message-----
From: gps-talkusers-bounce@xxxxxxxxxxxxx
[mailto:gps-talkusers-bounce@xxxxxxxxxxxxx] On Behalf Of Kevin Chao
Sent: Thursday, May 11, 2006 7:30 PM
To: Gps List
Subject: [gps-talkusers] irectionality of the POI
Dear List,
I have a question regarding the directionality of the POI's. I
have noticed with both commercial POI's and person POI's, for
some reason I am getting a off-readings, for example, it will say
"Mc Donald's 9 o'clock," when it is really 3 o'clock; I have
experienced this with both the commercial POI's and the one's I
marked myself, so I am not sure where the issue lies.
I am currently using version 3.3, so I don't know if this is a
fix that was introduced in version 3.5, if it is I am looking
forward to it.
Thank you for the information you are able to provide regarding
my query.
Kevin
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