Create New Line Features with Distance/ Bearing /Coordinate Geometry (COGO) Create New Line Features with Distance/ Bearing /Coordinate Geometry (COGO)After selecting the Create Dist/Bearing/COGO Line tool, select the starting location of the new line feature by left clicking at the desired start location. Note that while selecting the start point for the line, the Snapping feature can be used to help align the line with existing features.
After selecting the starting location, the
Distance/Bearing/COGO Input dialog
(pictured below) will display, allowing the user to enter distance/bearing
information for additional points either as separate distance/bearing
values, as a COGO (Coordinate Geometry) coordinates (see below for explanation),
or as a quadrant/bearing/distance value. Once all of the points have been
entered, press Done to complete the process and create the new line feature.
After selecting the Specify Using COGO
(Coordinate Geometry), the user can enter a COGO string that represents
an arc. The string format is as follows:
C <chord
length> R <radius> C <chord bearing> <direction>
chord length is the length of the chord from the segment start point to the end point in the specified units.
radius is the radius of the arc in the specified units.
chord bearing uses the same form as the bearing in the COGO line.
direction is L (left turn, counter-clockwise) or R (right turn, clockwise)
The COGO Arc definition will be stored in the list in this same format.
The Easting and Northing will be the end point of the arc segment. When
the line feature is created, the COGO arc info will be used to generate
a polyline representation of the arc.
This format will also be used to store the
arc definitions in the text file.
C 102.71 R 75 C S78-52-10EL
C - Chord length is 102.71
R - Radius is 75
C - Chord bearing is S78-52-10E
L - indicates Left turn
If the option to Close Path Using Compass Rulewhen Completing Feature is enabled, all of the points will be adjusted using the compass rule to ensure that the shape is closed. The compass rule evenly distributes the shift required to close the shape to all vertices and is commonly used by surveyors.
To achieve very fast entry of large collections
of distance/bearing of quadrant/distance/bearing values use the number
pad and press Enter after each value. This will take the cursor to the
next field and finally add the point when Enter is pressed on the last
field. This will also take the cursor back to the first field to allow
continuously adding points with only one hand.
When entering data using the Specify
Separate Distance and Bearing Values option, the bearing values
are degrees clockwise from true north, 0 degrees is north, 90 degrees
is east, etc. For the Specify Using
Quadrant/Bearing/Distance option, it is best to specify a quadrant
value of 1 to 4, with 1 being the NE quadrant, 2 being the SE quadrant,
3 being the SW quadrant, and 4 being the NW quadrant. The bearing values
are then east of the NS line for quadrants 1 and 2 and west of the NS
line for quadrants 3 and 4.
It is also important to remember that any bearing are specified relative
to true north, unless either of the options to Use
Grid Bearings Rather Than Bearing Relative to True North or Bearing is angle from previous line segment
are checked. A positive value for the Bearing will compute an angle clockwise
relative to the previous segment. A negative value will compute
an angle counter-clockwise relative to the previous segment.
The 'Bearing is angle from previous line segment' option is used, the angle
of the first segment must still be relative to True North. The check
box will be disabled until after the first segment or point has been added. Example: For the first segment,
use Distance of 1000 m and Bearing of 0 degrees, and click the Add Point
button. Now put a check in the box next to 'Bearing is angle from
previous line segment', enter 45 in the Bearing field and click Add Point.
You will see a new line at a 45 degree angle from the first line,
and the list of Distance/Bearing values will include "1000 meters
at 45". Leave the fields the same and click Add Point again.
Now Global Mapper will add a line at 45 degrees from the previous
segment, or 90 degrees from true north, and "1000 meters at 90"
will be added to the value list.
If the projection isn't oriented so that 'up' is also true north (most
projected systems, like UTM, are not unless right at the projection center)
a line of bearing 0 won't be straight up, but will be slightly skewed
so that it points at the North Pole. A line of bearing 0 will be straight
up in projections like Geographic or Mercator where true north is always
straight up.
If checked, the DMS (degree/minute/second)
Values Specified in Decimal Degrees
option, the user can enter DM (degree/minute) or DMS (degree/minute/second)
values as decimal degrees. For example with this option checked, a value
of 40.3020 is interpreted as 40 degrees, 30 minutes, and 20 seconds. The
basic format of degree fields when this option is checked is DD.MMSS.
Create Numbered Points Starting with - If this box is checked, then in addition to the line, a point is created at each vertex starting at the specified number and increasing by 1 for each point. The last number is remembered, if another line is created it will start at the next number by default.
N 23:14:12 W 340
S 04:18:56 E 230
The first character of a COGO input string must be either the character 'N' or 'S' to indicate whether the bearing is relative to the north or south directions. After another space, the angle begins. The angle can be in any angle specification that Global Mapper supports, including degrees, degrees/minutes, or degrees/minutes/seconds. A space follows the angle, and is then followed by either the 'E' or 'W' characters. A space separates the bearing from the distance (which should be in appropriate linear units).
For those unfamiliar with the notation for bearings: Picture yourself in the center of a circle. The first hemisphere notation tells you whether you should face north or south. Then you read the angle and either turn that many degrees to the east or west, depending on the second hemisphere notation. Finally, you move distance units in that direction to get to the next station.