Main Window
The main window consists of the following
elements, from top to bottom:
-
a
Datum pull-down list, which displays the code
and name of the currently selected datum, and which you can use to select a
different datum,
-
an
Ellipsoid field, which displays the code and
name of the reference ellipsoid associated with the currently selected datum,
-
a
pull-down list that displays the name of the currently selected coordinate
reference frame, and which you can use to select a different coordinate
reference frame,
-
a
set of zero or more parameter fields and/or controls for the currently selected
coordinate reference frame,
-
a
set of coordinate fields and/or controls for the currently selected coordinate
reference frame, which you can use to specify coordinate values that are to be
converted,
– the standard error fields, in which input coordinate accuracy values can be entered, and which display output coordinate accuracy values for the most recent conversion. There are three fields. The 90% circular error (CE), in meters, estimates the horizontal accuracy of the output coordinates. The 90% linear error (LE), in meters, estimates the vertical accuracy of geodetic heights. The 90% spherical error (SE), in meters, estimates the three-dimensional accuracy of geocentric and local Cartesian coordinates.
– the Source pull-down menu, which displays the names of possible sources for input coordinates. These include GPS coordinates, various types of hardcopy maps, and various types of digital geospatial data. Selecting one of these entries causes all three of the standard error fields to be set to values appropriate for the selected source.
-
Red
indicates that one of the selected coordinate reference frames is incompatible
with the corresponding datum selection, and therefore any attempted conversion
operation will result in an error. Typically,
this occurs when one of the currently selected coordinate reference frames
(e.g., British National Grid) is only compatible with datums that use a
specific ellipsoid (e.g., Airy).
-
Yellow
indicates that the valid regions for the two selected datums are disjoint from
one another, and therefore any attempted conversion operation will result in a
warning. Typically, this occurs when two
local datums for different parts of the world (e.g., Europe and
-
Green
indicates that the current coordinate reference frame and datum selections are
compatible with one another.