TPC Desktop Introduction 13
Introducing Survey Distance and Direction
Depending on the Edition you have, TPC can use different Distance and Direction types.
Survey Defaults
Each survey has a default
Distance
and
Direction
types. Once set, these defaults determine the initial
types used by COGO dialogs, drawings and
traverses. You can always override the defaults to
change the way TPC computes or displays the
data you are working with at the time.
The
Project Factors
dialog lets you set the default
distance and direction types, plus specify project
factors like elevation and mapping angle.
Grid
Grid distances and directions rely solely on cartesian coordinates and do not account for
elevation, grid factors or convergence. For small surveys, these are generally adequate and
simple to use.
Ground
TPC provides several types of ground distances that relate ground distance to grid distances
using elevation and grid factors. You always know when you’re using a grid distance and when
you’re using a ground distance.
Geodetic
TPC provides a number of geodetic types to choose from. These use geodetic positions and
equations to compute points (geodetic direct) and inverses (geodetic inverse). Geodetic tools are
available only in the Professional Edition.
PLSS
Computations on the PLSS (Public Lands
Survey System) is just a matter of choosing the
appropriate distance and direction types.
Example COGO Dialog
Notice the
Random Inverse
dialog shown here.
The title bar tells you it is displaying
True Bearing
,
Geo Dist
(geodetic
distance) and the units are in
feet
.
The fields themselves indicate
True
Bearing N90°00’00”W
.
The pulldowns in the
Options
box tell
which
Distance
and
Direction
are being used to compute the inverse.
