- Traversing Basics
- Overview
- Purpose
- record field measures accurately & neatly (LEGAL NOTES)
- in order to produce a MAP
- What is recorded
measurements- direction (Brg)
- slope distance (SD)
- slope angle
- calculated values
- convert slope distance to horiz. dist. (SD --> HD)
- diff. in elevation (DE)
- sketch of map features
- wildlife trees, look-out tower, cabin (points)
- creeks, trails, roads (lines)
- forest stand, gravel pit, wetland (polygons)
- Plotting the map
- you plot a series of line segments ...
- need direction & HD between each point
- need to reduce ground distance by map scale
- Plot profile
- it's a graph where ...
- X-axis = HD
- Y-axis = Elev.
-
- A page
- Columns of data
- Stn (= accum. distance)
- Brg
- SD
- slope %
- HD
- DE
- Elev.
-
- bottom up
- matches direction of travel
- mapping page corresponds to notes page
- you map what's in front of you
- zig-zag fashion
- measures BETWEEN stations are clear
- room to write note for a station (e.g. stn A = crk)
- miscellaneous
- Stn ID
- use letters (i.e. Stn A, Stn B ...)
- use cumm. distance (i.e. Stn 0+045, Stn 1+004 ...)
- use Crew ID (i.e. Stn DC1, Stn DC2 ...)
- if stn is permanent, mark in field with ID
- POC = point of commencement
- POT = point of termination (or EOT = end of traverse)
- repeat Stn on next page
- B page
- mapping page
- sketch important features
- features sketched in relation to your line of traverse
- record brg & dist for features nearby
- take bearings for lines/boundaries that you cross
- record width (streams & roads)
- Direction
-
- "top of the world"
- end of earth's rotational axisxis
- Santa's Workshop
-
- where the needle points
- difference is declination
- declination varies with
- location
- time
- for us ... magnetic N is to the east of True N
- check that compass is set to proper declination
- record the "forward direction"
- record azimuth (0 - 360)
- record 3 digits ...
- E is 90, record as ... 090
- N can be 0 or 360, record as ... 360
- Distance / Angle
- review of slopes
- ratio (percent)
- ratios are fractions ... a / b
- if you do the division ...
- ... result is a proportion
- ... top as a "%" of the bottom
- e.g. total students = 20, 12 are female ...
- ... 12 / 20 = 0.60 (or 60%)
- 60% of the total students are female
- = opposite / adjacent = tangent ... i.e. tan is the ratio
- = elev. change / HD
... elev. change as a "%" of HD- e.g. rise / run = 5m / 10m = 0.5 (50%)
- (0.5 * HD = elev diff.)
- but ... we don't know HD ...
- degrees
- 360 in a circle
- horizontal (flat) = 0
- "straight up" = 90
- halfway between = 45
- converting
- tan - converts degrees to ratio ... try tan of 45 degrees
- arctan - converts ratio to degrees ... try arctan of 1.0
- degrees -> TAN -> ratio ("%")
- ratio ("%") -> ARCTAN -> degrees
-
- field notes in SD ... map is in HD ... need to calculate HD ...
- we need trig
- SOH CAH TOA
- these are ratios
- bottons (sin, cos, tan) on calculator convert degrees --> ratio
- Cosine (COS)
- converts degrees to a ratio ...
- = adjacent / hypotenuse
- = HD / SD
- is HD as a "%" of SD ... = "conversion ratio"
- what is the COS of 25 degrees?
- 0.906
- or ... for every 100m SD, we moved 90.6m HD
- "how it works"
- remember ... COS(slope) = HD / SD
- rearrange formula ...
- HD = SD * COS(slope degrees)
- example
- read 17 degrees on clino
- travelled 50m slope distance
- HD = 50m * COS(17)
- = 50m * 0.956
- = 47.8m
- by convention we record slope in %
- % more precise ...
- reminder ... a slope of 45 degrees = 100%
- 1 degree error
- 100m @ 45deg = 70.7m
- 100m @ 46deg = 69.5m
- diff. = 1.2m over 70.7m HD
- 1.2/ 70.7 = 1.7% error
- 1 percent error
- 100m @ 100% = 70.7m
- 100m @ 101% = 70.4m
- diff. = 0.3m over 70.7m HD
- 0.3/ 70.7 = 0.4% error
- need to convert % --> degrees
- then apply COS to convert SD --> HD
- remember we record SD & % in field ...
- converting SD --> HD ...
- steps
- Arctan(slope ratio) ... to convert to degrees
- COS(slope degrees) ... to get "conversion ratio"
- "conversion ratio" * SD ... to get HD
- equation
- HD = SD * COS (Arctan[slope ratio])
- example
- slope = 65%
- SD = 30m
- HD = ?
Arctan(0.65) ... = 33 degrees
COS(33) ... = 0.838 (conversion ratio)
SD * 0.838 = 30m * 0.838 = 25.2m
- how to get "DE"
- look at "survey triangle"
- slope is in degrees OR % ...
- the percent is really rise / run ... (DE / HD)
- by the way ... the % on the clino is really TAN
- consider a slope of 25% ...
- ... top number as a % of bottom number
- ... so DE is 25% of HD
- so if we have HD and slope% we can get elev. change
- DE = slope % * HD
- example
- read -30% on clinometer
- travelled 20m
- elev. change = - 0.3 * 20m = -6m
- you went downhill and "lost" 6m elevation
- Elevation
- starting elevation
- may be known
- may be "made-up" (often start with 100m)
- thus each station = spot ht.
- elev. of last Stn +/- elev diff = elev. of new Stn
- e.g. last stn was 123m ...
- ... gained 10m ...
- ... elev. @ new stn = 123m + 10m = 133m
- Traversing Pointers
- direction/ bearing
- hold compass LEVEL at eye level
- sight through notch to target
- look in mirror and ...
- ... "put red in the shed" (align needle w/ housing) ...
- ... ALIGN black line over post
- front shot & back shot ... within 2 degrees
- record FRONT shot
- distance
- hold chain/tape straight - no zig-zags
- parallel to slope, no sag
- communication
- coming up!
- chain!!
- mark!
- slope
- find "zero" on your partner
- open both eyes
- left eye looks at "zero"
- right eye looks at clino
- read the % (right side) and degrees (left side)
- record + or minus ... of FORWARD shot
- Plotting the map
- Douglas protractor for direction
- place centre hole over station
- ensure N "is up"
- mark bearing on edge of protractor
- point at centre and mark at edge denote direction of travel
- trace a light line (can mark exact distance at next step)
- plot HD
- needs to be "reduced" to scale of map
- HD of 80m on a 1:5,000 map ??
- 2 Step Process
- 1) we map in cm so first convert M --> CM
- 2) then reduce to scale of map
- example
- 80m on the ground, 1: 5,000 map
- 1) 80m * 100 = 8,000 cm on the ground
- 2) reduce by 5000 ... 8,000cm / 5,000 = 1.6cm
- OR ... in 1 step
- 1:5,000 same as ...
- 1cm on the map = 50m on the ground
- map --> ground ... "expand by 50" ... *50
- 3 cm on map ... 3 * 50m = 150m on ground
- ground --> map ... "shrink by 50" ... /50
- 80m / 50 = 1.6cm
- record elevation (spot ht) for each station
- use B page and sketch on "features of interest"
- Summary
- Field Notes
- Stn, Brg (ave 2), SD, slope%
- .... calc HD, DE & Elev.
- sketch map on B page
- Pointers
- communicate! (coming up!, chain!, mark!)
- straight chain (no sag or zig-zag)
- brg within 2 degrees
- FORWARD shots for brg - use 3 digits
- FORWARD shot for slope, remember + or -
- Calculations
- HD = COS [ArcTAN(slope%)] * SD
- D.E. = slope % * HD
- map dist (cm) = HD (m) * 100 / map scale
- Plotting the profile
- graphing exercise
- X-axis is the route taken
- route can be straight or "meandering"
- road profile is an example of "meandering"
- Y-axis is elevation
- X & Y axes can be different scales
- plot X,Y coordinates and then connect the dots
- plot (graph) =
- "profile" (hill or road)
- "X-section" (stream)
