NCFS Ranger Training Chapter 3

how many feet in a chain

66

how many links in a chain

100

how many inches in a link

7.92

how many chains in a mile

80

how many feet in a mile

5,280

how many rods/poles in a chain

4

how many feet in a rod/pole

16.5

common sources of error when using GPS to determine acreage

• user error

• multipath error: when GPS signals bounce off large trees, rocks, or buildings

• poor PDOP: caused by failing to do adequate mission planning prior to measuring

common sources of error when using GIS to determine acreage

• using a photo where the subject area cannot be differentiated from surrounding areas

• not properly accounting for shadows along the southern edge of a clearcut

• failing to subtract SMZs, decks, or roads that will not be treated

• insufficient photo resolution

• not properly georeferencing a photo

• trying to measure an area you have never seen on ground

• after a harvest, determining the margin of a field from the actual clearcut (skidder traffic will wear both areas making them look the same on an aerial photo)

what is magnetic declination

the angular difference between true north and magnetic north

fractional scale example

1:2400

working scale example

1 in = 660 ft

NCFS lat and long format

degrees, and decimal minutes (XX° XX.X’)

how many sq feet in an acre

43,560

how many sq chains in an acre

10

how many acres in a sq mile

640

RMS meaning

root mean square

RMS number

< 10

what scale for digitizing

1:2400 or less

what is PDOP

position dilution of precision

PDOP number

< 6

what should elevation mask be set to

15°

what is a multipath error

when GPS signal bounces off things in the environment and creates a messy signal

what satellites does NCFS use

GLONASS and GNSS

official NCFS datum

NAD 83

NCFS minimum SNR setting

39 dBHz

how many satellites for 3D fix