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2024 Trials Prep > Land Nav > Flashcards

Land Nav Flashcards

1
Q

What are the types of maps?

A

Planimetric
Topographic
Large scale USGS (United States Geological Survey)
Small scale Forest Service

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2
Q

What does a Planimetric map show?

A

Flat, no terrain shape information.

Typically show arrangement of features such as roads, buildings, water, fences, vegetation, bridges, railroads.

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3
Q

What does a Topographic map show?

A

Shows the Shape of the land.

Shows both natural and manmade features including mountains, valleys, plains, lakes, rivers, and vegetation, roads, boundaries, transmission lines, and major buildings and shows elevation with contour lines.

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4
Q

What does a large scale USGS map show?

A

Similar to a topo map with terrain detail but larger scales cover a smaller area in more detail.

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5
Q

What does a small scale Forest Service map show?

A

Smaller scale means it covers a larger area are the cost of less details.

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6
Q

What map scale is the Forest Service?

A

1:126,720

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7
Q

What map scale is Nat. Geo Map?

A

1:70,000

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8
Q

What scale is a 7.5 minute Topo map?

A

1:24,000

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9
Q

Why does distortion occur on a map?

A

Maps represent a curved surface on a flat piece of paper. Navigation usually takes place in a small area, on large scale maps where distortion is minimal and controllable

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10
Q

Projection is..

A

A method to put earth’s surface on flat map

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11
Q

Mercator Projection is used for

A

Used for topo maps

Major distortions

Preserves angles

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12
Q

What is datum?

A

A mathematical model used to calculate the size and shape of the earth

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13
Q

Which datum is based off of a single point?

A

NAD 27 (North American Datum of 1927). This is still used by forest services

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14
Q

NAD83 is based off of

A

250,000 points and 600 satellite Doppler stations

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15
Q

Which datum is used by the Global Positioning System?

A

World Geodetic System of 1984 (WGS 84)

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16
Q

Which datums are basically the same,and the most common on maps and used by Sheriff, D.P.S., CAP Rescue Aircraft etc?

A

NAD83 and WGS84

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17
Q

What is scale?

A

Ratio of map distance to ground distance in similar units

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18
Q

1:24,000 means..

A

1 inch on map = 24,000 inches on the ground.

1:250,000 covers a very large area

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19
Q

Graphic Mileage Scale- Map distance and ground distance are in different..

A

Different units. 7.5 min TOPO Map: 1 inch = 2,000 ft

20
Q

Contour lines are commonly spaced..

A

20ft or 40ft (20 is more detailed)

Intermediate Contour- Thin lines, elevation not shown

Index Contour- Thick lines with elevation shown

21
Q

What does a benchmark show?

A

elevation associated with ground marker i.e brass cap on ground

22
Q

What is spot elevation on a map?

A

Elevation shown randomly, not associated with a marker

23
Q

Forest Service map tidbits

A

½” = 1 mile

Range Lines- Run N and S

Township Lines- Run E and W

NO UTM coordinates

NO contour lines

24
Q

USGS 7.5min Topo Map Tidbits

A

Large Scale, detailed view

Has much more information

Adjacent map names

Has UTM, Lat Long, and Range Township

UTM numbers around edge every 1000m**

Lat and Long marked on edge every 2.5 minutes**

NOT UPDATED OFTEN- features may not exist

Purple tint will indicate revisions from aerial photographs

25
Q

Issues with map accuracy can include

A

Forest fires can create cleared areas which eventually become meadows

Meadows can fill in with trees

Roads are changed, closed, moved

Urban areas change frequently

Occasional publication/printing errors

Declination changes with time

26
Q

Anatomy of a compass

A

Baseplate

Direction of travel arrow (does’t move, on baseplate)

Orienting arrow- align with needle during fieldwork

Magnetic needle- Aligns with earth’s magnetic field

Orienting lines- Align with North South on map

Index line- marks the bearing you set by rotating the compass housing

27
Q

Cardinal Points on a compass

A

0 or 360*- N

90*- E

180*- S

270*- W

28
Q

True north is

A

The axis around which the earth rotates

29
Q

Magnetic north is

A

The direction your compass needle points

30
Q

Declination is

A

Difference between true North and magnetic North

West USA (AZ)- has an EAST declination. I.E. magnetic North is GREATER than true North

East USA- has WEST declination so magnetic North is LESS than true North

31
Q

Symbols and abbreviations regarding north

A

Star- True North

MN- Magnetic North

GN- Grid North

32
Q

How do you use declination?

A

Magnetic to grid- Add declination “major to general= promotion”

Grid to magnetic- subtract declination “gen to maj= demotion”

Magnetic north is moving about 24 miles NW a year

33
Q

Compass techniques: boxing the needle

A

Direction of travel arrow is placed where you want to go

Magnetic needle is placed in orienteering arrow

34
Q

Compass techniques: establishing a bearing

A

Use dominant eye

Point direction of travel arrow in front of you to object

Box needle

Take reading and account for declination when transferring to map

35
Q

Compass techniques: back bearing, or a reciprocal bearing

A

Direction of where you came

Same method as bearing but 180 degree difference

If original reading is less than 180, add 180

If original reading is greater than 180, subtract 180

“ I am 2 miles from High Mt. on a bearing of 250 degrees” When reporting, report the bearing FROM the reference feature

36
Q

Compass techniques: measuring a map bearing

A

Line up compass on line between two objects

Put direction of travel arrow in the direction of travel

Line up N.S. orienting lines on the compass to N.S. lines on map

Ignore magnetic needle

This does not account for declination so keep that in mind

37
Q

Compass techniques: intersection

A

The location of an unknown point by successively sighting it from at least two (preferably three) known positions

Your exact location must be known from each sighting

This is taking sightings of an object so that then you can go to a map and find out its exact location.

38
Q

Compass techniques: resection

A

Determining your location by sighting two known positions

You must know your rough location and be able to see points on the map

Modified Resection

Only sighting one location and one linear feature that you are on, like a road

39
Q

How to reduce error

A

A 1 degree error over 1 mile = approx. 100 ft. error. (greater distance sighted,the greater potential for error

Do short segments

Walking around an obstruction

Find an object on the bearing the other side and walk to it

Send someone around and have them line up to in bearing then walk to them

Count paces walking 90 degrees around it

40
Q

Map and compass common errors

A

Using your compass as the Only Source of navigation information. Double check against the terrain and other info frequently

Not stopping when navigation info from map and compass and other sources doesn’t match up or seems marginal, stop and find the problem

Being pulled off your bearing by terrain such as slopes or something that interests you

Leaving your bearing to explore without a marker to get back on bearing

Not believing your compass when you get confused and lose confidence. Check it against someone else’s or against mapped terrain features.

Not knowing your exact starting point

Assuming you have an innate sense of direction and traveling with no map or compass

Letting navigation errors compound without correction

When working on map- having direction of travel or N.S. arrows backwards

41
Q

Terrain features that can help orient you include

A

Safety Baseline

Major Feature

Obvious at night

Relatively close

Catch Feature

Feature on your route that you cross

Handrail

Feature along your route that you follow

Attack Point

Point to go to and then start micro navigation (bridge and road cross in the area)

Aiming off

Purposeful error to one side so you know which way to turn

Check point

Feature along route to check your location

Funneling

Features that funnel you to a point (ex. A stream and a ridgeline)

42
Q

How do you find you pace count?

A

Walk 100 meters and count your number of paces

One pace is a left and right step

Average is your 100 meter pace count to use for pace beads

Account for weight of pack and slope when estimating how many steps it will take

43
Q

Latitude and longitude formats.. what is used by DPS/dispatch?

A

Hemisphere degrees decimal minutes

This is also used by CAMRA, as well as UTM

44
Q

Lat/long tidbits

A

Prime Meridian

0 degrees longitude

Equator

0 degrees latitude

Latitude

Degree distance is constant

Longitude

Degree distance is not constant (closer together near poles)

45
Q

UTM (universal transverse mercator) tidbits

A

AZ in zones 11 and 12 (mostly 12)

Has Northing and Easting

7.5 min Topo, 1:24,000 scale

UTM Easting coordinates are measured relative to a central meridian (arbitrarily assigned at 500Km)

UTM Northing coordinates are measured relative to the equator

Incorporating GPS

CAMRA uses WGS84 datum

46
Q

what is the current declination

A

Ranges from 10.33 degrees (yuma) to 8.65 degrees (apline). Phoenix is at 9.7 degrees

47
Q

What 2 Datum’s are “essentially the same”

A

NAD83 and WGS84

2024 Trials Prep (16 decks)

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