5.8 GPS, Plotters and Radar

Question 1

When using GPS, a good margin of safety is on longitude and latitude is …

Answer 1

100 meters, notwithstanding most units being far more accurate than that

Question 2

GPS units don’t need to run continuously (to save battery.) Instead… (four steps)

Answer 2

1. Turn on 2. Get coordinates 3. Plot fix on chart 4. Double check 5. Turn back off.

Question 3

On ocean crossing, do GPS fix every __ __ __ hours. On coastal cruising, do so every ___ ___ ___.

Answer 3

three or four; hour or more

Question 4

GPS units, in addition to giving you your current position can also provide

Answer 4

speed, direction and COG/SOG

Question 5

You can usually save ____ ____ _____ to your GPS unit for future use

Answer 5

frequently used waypoints

Question 6

“Route navigation”

Answer 6

The process of using intermeidate waypoints to avoid certain areas or follow certain paths

Question 7

What is a GPS-assisted grounding?

Answer 7

GPS operating along does not know where underwater danger points are, or know the skippers margin of safety, or the leeward side of a danger point

Question 8

If paths are equally available on either side of an obstruction, pass it on the

Answer 8

leeward side

Question 9

The benefit of the MOB function on a GPS is that it …….. ; however, it must be _____ very soon after the person goes overboard, and does not take into account any ________ moving the MOB.

Answer 9

continuously provides a course heading back to the MOB location; activated very soon; current or wind

Question 10

The waypoint alarm may not sound on a GPS if you pass…

Answer 10

…. too far from the waypoint

Question 11

Some GPS units have a waypoint _____ alarm to sound regardless of how far away

Answer 11

abeam

Question 12

You should always double check that a GPS-generate course or route doesn’t….

Answer 12

…. take you close to any dangers (it just doesn’t know)

Question 13

Careful of using a buoy’s specific coordinates as a waypoint because (2 reasons):

Answer 13

1. Others may be doing the exact same thing
2. You might hit it

Question 14

A waypoint does not have to be a specific object, instead can merely be a

Answer 14

… point of specific lat and long. Double check!

Question 15

1’ of latitude change is equal to ____ feet

Answer 15

6076

Question 16

GPS plotters frequently show positions as XXX* XX.XX1’ E/W and that .001 equates to

Answer 16

six feet

Question 17

SOG and COG – compare to knotmeter and compass reading

Answer 17

Latter take into consideration current and leeway affects

Question 18

A waypoint log is….

Answer 18

a written down set of waypoints creating a route. A regularly used route can be named and saved in most GPS units

Question 19

A GPS will always show you the direction and distance to your waypoint, REGARDLESS OF…. The ____-_____ Error function can show you

Answer 19

… how are off you are of a planned route. Could be taking you over a hazard.

Cross Track Error (CTE or XTE)

Question 20

The purpose of the CTE or XTE function is to show you…

Answer 20

…. how far left or right of your INTENDED route you are.

Question 21

Sailing on heading 050. COG is 057. Steering to 043 will keep you closer to…., but will have you travelling ….., not _____ back to it.

Instead, you must ___ ____, and steer to something like ____ to reaquire planned route. Then steer ___ to stay on that intended ____ course route.

Answer 21

intended route, parallel to the intended route, tracking

over-compensate, 033; 043; 050

Question 22

If the boat is stopped, but GPS is indicating SOG and COG, that is a good indication of

Answer 22

drift and set of curret

Question 23

The importance of setting a departure point in addition to first waypoint is…

Answer 23

… deviation of intended course or CTE can only be measured with a point of origin

Question 24

GPS can help avoid danger areas by setting an ______ Cirle around it.

If entered, (what will happen?)

Answer 24

Avoidance Circle around it

an alarm will sound

Question 25

What is the risk in setting an avoidance circle?

Answer 25

Must be SURE that the object at the center is not considered a waypoint destination, but instead something to AVOID. Double/triple check Avoidance Circle settings

Question 26

In addition to avoidance circles, another way to avoid a danger is to set a warning…

Always build in a…

Answer 26

latitude (or longitude).

… safety margin

Question 27

On large scale charts (so… small area shown, small number after 1:X)… one can draw additional ______ and ______ lines to provide more precision

Answer 27

latitude and longitude

Question 28

To avoid rapid fluctations and confusion, most GPS will allow you to calculate the _____ of COG and SOG over a set period of time

Answer 28

average

Question 29

When you read lat and lon on a GPS, be wary of ____-_____ error.

Focus on the numbers from ___ to ___, and don’t overly worry about ____ of a hundredths or thousands of a _____

Answer 29

over-precision error.

left to right, minute.

Question 30

1 Minute equals ___ NM or ___ feet

Answer 30

one NM or 6076 feet

Question 31

0.1 Minutes equals __ NM or __ feet

Answer 31

1/10 of NM, or 607.6 feet

Question 32

0.01 Minutes equal __ NM or __ feet

Answer 32

1/100th of NM or 60.76 feet

Question 33

0.001 Minutes equal __ NM or __ feet

Answer 33

1/1000th NM, or 6.076 feet

Question 34

140 minutes = ___ degrees, ____ NM, and ___ feet

Answer 34

140/60 or 2 degrees 20 minutes, or 2.33 degrees, 140 NMs, and (140x6076) feet

Question 35

It is important that the GPS ____ agrees with the same on the paper/electronic chart being used.

Answer 35

datum or horizontal datum

Question 36

The most common horizontal datum is

Answer 36

WGS 84

Question 37

“WGS 84” stands for and is…

Answer 37

World Geodesic System of 1984, most common lon lat datum

Question 38

WGS 84, WGS 72, NAD 27, AUSTR 84, GBR 36

Answer 38

All examples of varying horizontal datum around the globe. Be sure GPS is set to the proper one.

Question 39

Some GPS units can calculate ___ and _____, substituing for Tables __, __, __ in TCTs.

Answer 39

tide and current, 1, 2, 3

Question 40

Radar is an abbreviation for

Answer 40

Radio Detection and Direction

Question 41

To measure distance, most radar units have two approaches

Answer 41

1. concentric rings of common distance
2. mouse/cursor to draw a line

Question 42

It is useful to compare the shape of coastal ____ on the GPS to the ____

Changing the range of the concentric rings can sometimes..

Answer 42

shape; chart

…bring the shapes shown into alignment

Question 43

Radar units sometimes display _____ headings, which must be converted into ____ headings for use on a chart

Answer 43

relative; magnetic

Question 44

The risk of longer ranges (say, 12 miles) on a radar is that _____ objects can be ____.

To avoid issue….

Answer 44

closer; missed

switch between ranges

Question 45

Which is usually more accurate, a radar’s range detection or direction detection, and why?

Answer 45

range more accurate than direction, since the beam of radio signals sent out are not precise but have width to them.

Question 46

Verify all fixes with…

Answer 46

soundings

Question 47

A relative degree marking should include…

Answer 47

the letter R

Question 48

When taking multiple bearings on another crossing ship, it is important to keep…

Answer 48

… the heading of the boat the same, otherwise successive bearings make no sense

Question 50

Radar is good but not great. Why?

What can be done to improve on radar bearings, assuming visibility available?

Answer 50

Issued in a wide beam, so not as accurate.

Confirm with visual, handheld bearings