Choosing a Survey Grid

A survey can have one grid that relates its coordinates to geodetic positions.

Selecting a Grid for a New Survey

• From the Survey Information dialog, choose Grid.
• Select a Grid from the pull down list.
  
• If you selected one of the State Plane grids, you will also need to select a Zone.
  
• Enter a Grid Factor. This factor relates your measured data to grid coordinates. It is used in all computations involving horizontal distance.
  
• Choose Ellipse to edit or check the ellipse data used in the computations.
  
• If your survey is in Feet, specify whether you want to convert to meters using the International Foot (0.3048 M/FT) or the US Survey Foot (0.3048006096 M/FT).
  
• Choose OK.

The grid selection you just made is primarily used to convert Latitude and Longitude to grid coordinates. The Grid Factor is used throughout the program to convert measured distance to grid coordinates. This information is stored with the survey in the TRV file.

Changing the Grid of an Existing Survey

To change the grid of an existing survey without doing a transformation, choose Tools | Survey Information, Grid. Select the options you want and choose OK.

This action simply updates the grid information stored with the survey. It does not transform any coordinates. If you want to transform the survey from one grid to another, you need to choose Tools | Transform Survey from the Traverses Manager.

Converting a Survey From One Grid to Another

In order to compare a survey based on one grid with a survey based on another grid, you must first convert one survey to the same grid as another. You might also import data based on one grid and want to convert it to the survey grid.

• Make a backup copy of the survey. You might save it under a different filename.
  
• From the Traverses Manager, choose Tools | Transform Survey. TPC displays the current survey grid settings in the From box.
  
• Choose the Grid, Zone, Grid Factor and Ellipse you want to convert to.
  
• From the Transform What list, choose All.
  
• Choose OK.

Converting Imported Traverses to the Survey Grid

At times, you might also import data based on one grid and want to convert it to the survey grid. TPC lets you specify the grid settings for those traverses and convert them to the same grid as the survey.

• Make a backup copy of the survey. You might save it under a different filename.
  
• In the Traverses Manager, select the imported traverses you want to convert to the Survey Grid.
  
• From the Traverses Manager, choose Tools | Transform Survey. TPC displays the current survey grid settings in the From box.
  
• Update the grid settings in the To box so they match the settings in the From box.
  
• Set the grid settings in the From box to match the settings of the imported traverses. TPC has no way of knowing what grid these traverses were based on - you need to supply this information.
  
• From the Transform What box, choose Selected.
  
• Choose OK.

Editing Zone Constants

The constants for the State Plane coordinate projections are stored in the ZONE.DAT file. Each line contains values for one zone. This file is self documenting, with definitions at the top of the file. To edit the zone values, open this file in any text editor and make the changes.

Editions

Premium, Professional

Related Topics

Coordinate Transformations