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Coordinate Systems
With an Unknown system, non-georeferenced coordinates
can now be imported, however this system will now need
to be localized to be useful for CoGo and Staking in J-Field.
See Localizations for more information (
p. 126
).
Coordinate System Selection
Influences in CoGo
Inverse
The selected coordinate system of
a Page has important implications
for CoGo in J-Field. The Javad
design team, composed of
knowledgeable geodesists and
gifted engineers, has included
many tools for surveyors to
address so-called “Grid vs. Ground”
issues. In CoGo Inverse, for instance, a surveyor can view the
results of the inverse between points in several different
ways.
Direction
Directions can be viewed as one of four types by simply
toggling the direction button.
Š
Geo
Š
Grid
Š
Mag Geo
Š
Mag Grid
Geo
Geo direction type refers to Geodetic bearings, this computes
the direction from the beginning point (P1) turned from
polar North to the ending point (P2), independent of gravity
(normal to the ellipsoid). The geodetic bearing actually
changes along this line (unless the line is longitudinal)
because of the convergence of meridians (recall that all
longitudinal lines converge at the poles). Because of this
convergence, other than points on the same longitude,
the forward bearing (P1>P2) will differ from the reverse
bearing (P2>P1) by 180° and the convergence angle. The
magnitude of the convergence angle will increase as points
are further apart East and West and the rate of this change
in magnitude will increase as the latitude increases. Note
that the Geo direction type can always be viewed regardless
of the current coordinate system.
Grid
If the current Page Coordinate System is a projection, such
as State Plane, the direction can be viewed in Grid, which is
figured from North at the central meridian of the projection
by treating all meridians as parallel. With Grid, the direction
between two points is the same along the entire line
between those points, so that the forward Grid bearing
(P1>P2) is precisely 180° from the reverse Grid bearing
(P2>P1). If a geodetic system (latitude and longitude) or
geocentric Cartesian system (ECEF/XYZ) is current, the Grid
direction type will report the same direction as the Geo