68
SporTrak Color GPS M apping R eceiver
Appendix
Compass
The SporTrak Color includes all t
he f eatur es f ound in all of t he SporT rak mapping ser
ies
of GPS r eceiv er s along wit h a 3-axis electr
onic com pass, a bar ome ter and t em per atur e
sensor .
The follo wing t e xt pr ovides y ou wit h some inf ormation about some of t
he na vig ational
terms t hat ar e used wit h the electr onic com pass.
Heading vs. Bearing vs. Course Over Ground
The SporTrak Color adds Cour se Ov er Gr ound (C OG) to t he lis t of dat a par ame ter s t hat
you can select f
or t he cus tomizable f ields t hat ar e displa yed on t he na vig ation scr eens. The
SporTrak Color also uses C
OG on the com pass scr een t o pr ovide y ou wit h additional
information t hat will assis t you in na vig ating t o y our desir ed des tination.
Heading, in t he SporT rak Color , is no t com puted fr om t he GPS inf ormation as it is in t
he
other SporT rak Color pr oducts, but r ather it uses t he electr onic com pass t o de termine
whic h w ay you ar e f acing.
The follo wing is a br ief descr iption of ho w t he SporT rak Color int er pre ts heading,
bear ing, and C OG. If you alr eady under stand t hese t erms y ou can skip o ver t he f ollo wing
section.
Heading
Heading in t he SporT rak Color is t he dir ection t hat t he ant enna (locat ed at t he t op of t he
SporTrak Color) is pointing. T o g e t the bes t repr esent ation of y our heading, y ou need t o
hold t he SporT rak Color wit h the ant enna pointing in t
he dir ection y ou ar e tr avelling.
Holding it at an angle, lef
t or r ight, will accur atel y displa y the heading of t
he r eceiv er , but
it w on ’t be a true r epr esent ation of y our dir ection of tr avel. (As y ou will see ne
xt, COG
provides a true indication of y
our dir ection of tr avel, r eg ardless of whic h w ay the SporT rak
Color is pointing.) Heading is displa
yed all t he time.
Course Over Ground (COG)
COG is t he dir ection y ou ar e tr avelling. W ith the SporT rak Color held dir ectl y in fr ont of
you, y ou w ould t hink t hat heading and C
OG would be t he same, but t
hat is no t alw ays
the case. Boat
er s ar e q uite f amiliar wit h heading and C OG being dif fer ent due t o tides
and curr ent.
An e xam ple of t hat w ould be a boat tr
avelling along wit
h a
heading of 0
°
. At the same time, t
her e ar e curr ents in t he w ater
pushing t he boat t o one side. This w
ould cause t he boat t o dr ift
of f cour se in t he dir ection of t he curr ent. Ho w muc h it mo ves
depends on t he speed of t
he boat and t he f orce of t he curr ent.
In this e xam ple, t he r esulting C OG or dir ection of tr avel is 1 5
°
.
COG
15
°
Heading
0
°
Cu
rre
nt
