Site Calibration

From ProStar Geocorp

Overview

A Site Calibration is the process of adjusting projected (grid) coordinates to fit the local control. A calibration calculates parameters for transforming WGS‑84 coordinates into local grid coordinates (NEE).

You should calculate and apply a calibration before:

  • Staking out points
  • Computing offset or intersection points

If you calibrate a project and then survey in real time, PointMan gives real-time solutions in terms of the local coordinate system and control points.

This section covers how to setup a Site Calibration in the PointMan mobile application and use it to collect calibrated northing/easting and elevation data. A Site Calibration can be setup a few different ways:

In PointMan for Transparent Earth (Current Version)

  • Fully "keyed-in" solution
  • Partially keyed-in and partially GPS-collected solution

In PointMan Plus (Cloud/Web Login - Coming Soon)

  • Fully "keyed-in" solution
  • Imported Trimble .dc file

Setup Procedure - PointMan for Transparent Earth (Mobile Device)

1. From the main PointMan map screen, tap the Menu button on the top left corner

2. Tap Settings

3. Next to Site, tap Edit

4. Tap New

5. Fill in the following fields:

  • Name
  • Units (metric or imperial. US Survey Foot coming soon)
  • Solution (2D or Manual) Note: Manual should be used whenever importing a .prj file. All values should be set to zero in the "proj string" except scale factor. Set this to 1

Adding Control Points

1. To key in control points, tap the New button and enter all the information. If you need to capture the Lat/Lon values, tap the GPS button in the top right corner

2. To import a CSV file of control points, tap Import

NOTE: At least 3 control points are required but ProStar recommends at least 4

Checking Residuals

2. Once at least 3 control points are added, PointMan will display a residual for each control point as well as a residual value for the entire solution.

IMPORTANT: If your residuals are high or out of tolerance, you can try the following fixes:

  • Use the Up/Down arrows to reorder your control points. The residual values will change automatically
  • Change the Base EPSG to match the datum that the control points were collected in. Sometimes .prj files can cause issues if they are not setup correctly
  • Remove any "bad" control points. PointMan will automatically recalculate the residuals

Collecting Calibrated Data

1. Tap OK to close the site calibration dialog

2. Select the Site in the Site dropdown in PointMan settings. You can use a VRS etc while collecting in the site

3. Once data is collected, PointMan will display the Lat/Lon ANDNorthing/Easting values for each point.

Exporting Calibrated Data

1. Tap on a feature and then tap Send

2. Select the features you wish to send. The Show More button pulls features from the extent of the map window, so you may want to zoom out to the extent of the project before tapping send

3. Tap OK

4. Select Shapefile or CSV and tap Options

5. In the PRJ box, select the EPSG you wish to export to. You can also select From File and use a .prj as your EPSG

6. In the Columns box, ensure that the Northing/Easting options are checked.

7. Tap OK and send the files