Define a Labeling Scale Factor

Use the Labeling Scale Factor command to define a combined scale factor (referred to in this topic more simply as a scale factor) to be used to convert grid distances to ground distances displayed in line segment labels. Two options allow you to display ground distances that are independent of the earth's curvature either by (1) entering, or using points to calculate, a single fixed scale factor or (2) by selecting, or using points to calculate, a single fixed position to determine the scale factor. The third option is to use an individual scale factor at each label location that is dependent on the earth's curvature, as is used in the Inverse command.

Historically in TBC, all ground distances have used slightly different combined scale factors due to the fact that the program always computes on the ellipsoid and uses projections to account for the earth's curvature. This is true for all TBC projects, including scale-only projects and those where local site settings have been used to make grid and ground the same. Although this is technically correct, it leads to problems if you do not want geodetics to be involved. For example, you cannot accurately reproduce the linework using only the labeled bearings and ground distances. The Labeling Scale Factor command provides the option to use a single scale factor to convert from grid to ground based on the assumption the world is planar (no geodetics involved).

Important note! The calculation of coordinates, total station reduction calculations, inversed distance, and so on are all unchanged with this command. Only ground-distance labels are affected.

Prerequisites:

Licensed module. See the Subscription Plans page. For a license matrix by command, see the License page in the TBC Community. Also see View and manage licensed features.

To define a labeling scale factor:

Select Labeling Scale Factor in Drafting > Labels.
In the Labeling Scale Factor dialog, select the appropriate option. As you make changes, the updated scale factor is displayed at the top of the command pane.
- Use a fixed scale factor - This option is a good choice if you want to define a single, specific scale factor to apply to all ground-distance labels in the project—perhaps a scale factor provided by the customer or dictated by local regulations. You can also use this option to calculate a single scale factor based on a point selection. Note that the scale factor will not automatically update at a later time, even if the coordinate system is changed. In addition, if the scale factor is based on a point selection, there is no record kept of the coordinate used to calculate the scale factor. Either way, changes to your project that should require a change of scale factor do not cause the scale factor to automatically update.
  Do one of the following
  - To define a single, specific labeling scale factor, type it directly in the field provided. (Do not click the Calculate from Selection button.)
  - To define a single labeling scale factor based on the average position of one or more points, select the point(s) in the Project Explorer or Plan View and click the Calculate from Selection button. The selected point(s) should be in the vicinity of where you want to create ground-distance labels. At least one of the points must include an elevation, or an elevation must be defined for the project.
- Use a fixed position - This option is a good choice if you want to specify a coordinate to be used to create a single labeling scale factor to apply to all ground-distance labels in the project. You can also use this option to calculate a coordinate and scale factor based on a point selection. Note that the scale factor will automatically update as necessary if the coordinate system is changed. Also note that the selected coordinate will continue to display as a record in the Labeling Scale Factor dialog even after it is closed and re-opened.
  Do one of the following:
  - To enter a specific coordinate to use to calculate a single labeling scale factor, type it directly in the three fields provided. Or, select the location in the Plan View and enter an Elevation. (Do not click the Calculate from Selection button.)
  - To specify a coordinate to be used to calculate a single scale factor based on the average position of one or more points, select the point(s) in the Project Explorer or Plan View and click the Calculate from Selection button. The selected point(s) should be in the vicinity of where you want to create labels. At least one of the points must include an elevation, or an elevation must be defined for the project.
- Use geodetics - This option is a good choice if, instead of using a single scale factor for all ground-distance labels, you want individually computed scale factors to be applied to each label based on a geodetic scale that considers the associated object's location. Ground distances are computed in the traditional manner employed by the Inverse command, This option is particularly applicable if linework you are labeling is not closed, such as in the case of a corridor.
Click Apply.