Understanding Points and Coordinates

Use these definitions to understand the differences between the various types of points and point properties in your project.



Point	A point is a named object that represents a location with either local or global latitude and longitude coordinates, and possibly a height or elevation. Points are usually measured in the field and then brought into a project by importing them in a GPS, GNSS, or points file (.dat, .T01, .pts or .csv), but they can also be created in this software. When you create a point in this software, it contains a single coordinate that is identified as "Office entered". A point can contain multiple coordinate objects, each with a different location and quality. See Coordinate below. You cannot edit a point directly, you must edit one or more of its coordinate objects. If it does not have a coordinate object, you must add one. CAD points can, however, be edited directly. The term “point” may also be used generically to mean a coordinate (essentially a location in 3D space). When you are asked to specify a “point” in this software, it often means that you can specify a coordinate or a named point as described above.
CAD point / Lightweight point	A CAD (or lightweight) point is a simple, unnamed object that represents a location with grid (X,Y) coordinates and possibly height or elevation (Z) value. Because CAD points do not include global and local latitude and longitude coordinates like regular points, they are non-transformable; if you change your coordinate system, grid points do not move. Unlike points, CAD points can be edited directly in the Properties pane. CAD points are brought into a project by importing them in a CAD file (.dxf, .dwg, .dgn, or .svl); they cannot be created in this program.
Point ID	A point ID is the identifier of a named, field-observed or office-entered point object (see Point above).
Coordinate	A coordinate is a pair of X and Y or northing and easting values (in 2D), or a set of X, Y, and Z or northing, easting, and elevation values (in 3D) that defines a location in 3D space. If only two coordinates are given, the Z value or elevation may be 0 (relative to the current coordinate system) or may be undefined. When a coordinate is required in this software, you may be prompted to specify a “location” or a “point”. Read-only point coordinates are displayed in the Points Properties pane as shown here... 1. Grid Coordinate - A grid coordinate is a standard projected coordinate consisting of an easting, northing, and elevation in the zone and geoid model specified for the project's coordinate system. Grid coordinates may be adjusted, when required, using the Local Site Settings or Site Calibration command. The zone name and geoid model name are displayed in the Grid Coordinate section header. 2. Local Coordinate - A local coordinate consists of a latitude, longitude, and ellipsoidal height in the geodetic datum associated with the project's coordinate system zone. The parameters used to transform between global and local coordinates are displayed on the Datum transformation tab in Project Settings > Coordinate System. The parameters may be null when the global and local datum are the same. The local datum name is displayed in the Local Coordinate section header. 3. Global Coordinate - A global coordinate consists of a latitude, longitude, and ellipsoidal height in the global reference datum specified for the project's coordinate system. The global reference datum is used to express reference positions in the specified country. This ensures that VRS coordinates can be imported as global coordinates, while RTX coordinates are automatically converted from ITRF2014 at the measurement epoch to the global reference datum. The global reference datum name and global reference epoch are displayed in the Global Coordinate section header. Notes: To make changes to the project's coordinate system, select Project Settings in the Quick Access Toolbar and select Coordinate System in the left pane. See Coordinate System Settings for additional instructions. When a site calibration has been performed or you are using ground coordinates in the project, the Grid Coordinate section label is replaced by Calibrated Coordinate or Ground Coordinate. A geoid model is optional in TBC. When no geoid is specified, the elevation of a grid coordinate is the same as the local ellipsoidal height. In this case, the grid coordinate will be defined using only the coordinate system zone. When “WGS 1984” is specified as the global reference datum in the project, time-dependent transformations are deactivated in TBC because the global reference datum is unknown. In this case, the label “WGS 1984” is still used for consistency with other software, but no reference epoch is provided.