Localisation is the redefining of an arbitrary position to the a real world position using a GPS receiver to measure the reference between the two points.
When working with survey designs it is NOT always possible to have a reference point relative to the project in Geographical Coordinates. This is common in Total Station surveys where an arbitrary point (1000,1000 or 10,000, 10,000) is used. When transferring the design from a desktop design to a GPS field software to stake out or reference the design in the field we have two options.
Locate the field reference (arbitrary) point in the field and perform a Static Survey (see HOWTO Static Survey). A bench mark or PM is usually installed for future use in related projects. Once this position has been established as described, add a Point within the desktop design with the accurate coordinates from the corrected Static Survey.
Next, Select all the points and geometry in the desktop design (less the the new Base point) and move all the data to the Static Survey coordinated point.
Before transferring the project to the survey controller (SurvCE), it is important to update the CDR File (coordinates) by selecting Points, Points Utilities, Update CDR File from Drawing. This changes the coordinates of each point to the points referenced to the Static Survey Point in the CDR file.
If time is limited, then a data localization can be performed in the field. If there is a “known” reference point or PM available, set the Base receiver over this point. If no reference point available an averaged GPS Base position will suffice near the arbitrary point.
Using Carlson SurvCE, choose the Equipment tab, on the right side at the top is Localization.
There are two different ways to perform a digital localization. Using 1 Point or 4 Points. Using 1 Point assumes the scale and orientation are correct and performs a block shift of the coordinated positions referenced to the “required/accurate” reference position. If there is some doubt as to scaling or rotation of the survey then a 4 Point localization is required to correct any issues.
The process is the same for both methods. Remembering, additional points can be added later to change the localization from 1 Point to 4 Points; should this be necessary by adding more reference points.
Steps to perform a simple Localization:
- Using Carlson SurvCE, choose the Equipment tab, on the right side at the top is Localization.
- Set the Projection System required
- Set the Geoid File to be used to utilize the gravity model.
- Add Points to be referenced to the Localization
- The Point can be selected from data added to the CRD file or Grid coordinates can be entered into Northing, Easting, Elevation boxes.
- To reference the GPS coordinates, occupy the known point, making sure that the GPS receiver is set level and held steady (Bipod or Tripod recommended), Read from the GPS.
- Depending on the Localization Method (1 or 4) to be used the Localization for Option Two is complete.
- If the 4 point option is required, repeat the process for the other 3 points using known reference points in the field matching the arbitrary reference points in the project.
- If using the localization for other Jobs where the same arbitrary position was referenced, this Localization file can be re-used.
This completes the Localization process.
For more detailed information explaining the individual settings and processes in Localization, reference the Carlson SurvCE v5 Manual. The Carlson SurvCE v5 Manual is available from www.carlsonsw.com/support/manuals webpage.