The Tools page allows you to perform a variety of tasks, including traversing, loop closures, geoid height modeling and coordinate transformations.
This is perhaps the most powerful tool on the Tools page. From this tab, you can calculate loop closures, open-ended traverses or simple side shots for 1D, 2D and 3D vertical, local plane, grid (State Plane) and geodetic surveys.
To provide this power and flexibility, Columbus 4 uses the same adjustment engine found on the Adjust and Adjust File pages. You select the route of the traverse, the applicable observations that are available (between stations in the route), the traverse type (vertical, grid, geodetic, etc.) and the vertical component to use (orthometric or ellipsoidal height), and Columbus 4 will compute the traverse. For each station in the traverse, a closure is computed by differencing the traverse generated coordinate against its known coordinate (the coordinate values currently set for this station).
Redundant observations are handled by the least squares adjustment engine and are weighted using their standard deviations or variances. Coordinate observations can be used, as well as field observations.
While setting up the station route, Columbus 4 automatically knows which observations are applicable, based on the traverse type. Observations can be deselected by un-checking their check box. For 2D traverses, you can specify a mean project height or you can tell Columbus 4 to use the known approximate height for each station (orthometric or ellipsoidal, based on the height field options selected).
Underneath the hood, Columbus 4 is computing the approximate coordinates for each forward station (just like in a network adjustment). Then, the iterative adjustment engine takes over to determine the best solution based on the observations selected. If there are no redundant observations between stations (for example, between each station pair we have exactly one horizontal angle, one zenith angle and one slope distance), the answer is the same as would be computed using an advanced COGO tool. When redundant observations are introduced, the redundancy is taken into account, just as it is in a Least Squares Adjustment: the weights (generated from the observation SD or Variance) for each observation dictate the result.
Only the first and possibly second station (if Fix First Two Stations is checked) in the traverse are held fixed. The second station is only fixed when the first station is acting as a starting back sight. In this case, the known coordinates for the starting back sight must be provided for the back sight station.
Like network adjustment, many of the Preference page settings will influence the traverse results. For example, you may have set up a default standard deviation for each chord distance, or you may have provided a default deflection of the vertical value for the entire traverse.
When performing a grid traverse, be sure to set up the correct grid zone in the Preferences page. For grid and geodetic traverses, you will also need to ensure you have the correct Datum set up in the Preferences page.
After defining your route (station order), observations and traverse type, etc., click Start to compute the traverse. Examine the Coords and Closures tab to view the results. From this tab, you can Keep new coordinates into the project, create a report, and/or generate an Excel CSV (comma-delimited) file from the results.
Use this tab to compute up to 10 different inverse types between two stations. 1D and 3D inverses can use either orthometric or ellipsoidal height. 2D inverses can be based on current station heights (orthometric or ellipsoid) or by entering an average height.
1D Height Difference: Computes the difference in height
2D Geodetic: Computes the 2D geodesic distance and azimuth on the spheroid (1 and 3 below apply)
2D Grid: Computes the 2D grid distance, mapping angle, etc. based on the average station height pair or an entered mean height (1 and 2 below apply; and 3 or 4 below applies)
2D Mean Bearing: Computes the 2D mean bearing and horizontal distance based on the average station height pair or an entered mean height (1 and 3 below apply)
2D Local Plane: Computes the 2D azimuth and horizontal distance based on the average station height pair or an entered mean height (5 below applies)
3D Astro-Geodetic: Computes the azimuth, zenith angle and slope distance based on each station height (1, 3, and 6 below apply)
3D Grid: Computes the 3D grid distance, mapping angle, etc. based on each station height (1 and 2 below apply; and 3 or 4 below applies)
3D GPS dXYZ: Computes the 3D GPS dX, dY, dZ vector based on each station height (1 and 3 below apply)
3D NEU: Computes the 3D Local Tangent Plane dNorth, dEast, dUp vector based on each station height (1 and 3 below apply)
3D Local Plane: Computes the 3D azimuth and slope distance based on each station height (5 below applies)
3. Uses geodetic coordinates (lat, lon and/or hgt)
4. Uses grid coordinates (north, east and/or hgt)
5. Uses local coordinates (north, east and/or hgt)
6. Uses deflections of the vertical (at each station) if available. If available, the inverse is what would be measured in the field (mark-to-mark). If not available, the inverse is based on the ellipsoidal model alone (no correction for plumbing the instrument based on gravity).
Computations are based on Preference Settings, including Active Datum and Grid Zone. For the 3D Astro-Geodetic inverse, deflections of the vertical for each station will be used, unless they are overridden in Preferences. When using orthometric heights (for 1D and 3D inverses), you can apply an Approx Geoid Height correction to approximate ellipsoidal height. (This correction is also set up in Preferences.)
- Select the station route (station to station) to indicate which AT and TO station pairs will be inversed. Inverses are computed as each station is selected.
- If a Result Tab is empty (in other words, there are no results), it means that inverse type is not supported for the selected Coordinate Type (see below).
- Change the inverse types computed by selecting the Coordinate Type selector (1D Height Leveling, 2D Lat Lon, 3D Grid N E Hgt, etc.).
- There is only one set of North and East coordinates per station record. When using grid coordinates, enter grid coordinates for each station. When using a Local Plane coordinate system, enter local coordinates for each station.
- From each Result Tab, you can create a report file or a CSV file. The report file contains more detail about which coordinate components were used for the inverse computation. The CSV file can be imported into most spreadsheet programs.
- Select the geoid model you wish to use. The EGM 96 global geoid model will always be used for each station.
- Determine which height field you want to update (orthometric or ellipsoidal) for each station. If you choose orthometric height, a new orthometric height for each station will be computed by subtracting the generated geoidal height from the stations known ellipsoidal height.
Likewise, if ellipsoidal height is chosen, the ellipsoidal height for each station will be computed by adding the new geoidal height to the station’s known orthometric height. Geoidal heights are not saved for each station.
- Select the stations to compute by selecting the corresponding check box.
- Click Compute Geoidal Height.
- Keep the updated coordinates into the project, create a report, and/or generate an Excel CSV (comma-delimited) file from the results.
Deflection Modeling tab
Use this tab to generate deflection of the vertical corrections using the NGS Deflec12A – 2012 model. Supported regions include Conus, Alaska, Hawaii, Guam, Puerto Rico and Samoa.
- Select the stations to compute by selecting the corresponding station check box.
- Click Compute Deflec 12A.
- Keep the updated deflection values into the project, create a report, and/or generate an Excel CSV (comma-delimited) file from the results.
Geodetic to/from Grid Coordinate Transformations tab
Use this tab to transform geodetic coordinates to/from grid coordinates.
- Set the desired Datum and Grid Zone within the Preferences page.
- Select whether to use Orthometric Height (from each station) or Ellipsoidal Height to compute height scale factors.
If you choose Orthometric Height, you may want to enter an approximate Geoid Height (for the project area) within the Preferences – Advanced tab. This approximate Geoid Height will be added to each Orthometric Height when computing the Height scale.
Some grids are based on Orthometric Height (for example, grids in the United States based on the NAD 27 datum). If this is the case, be sure to set the Approximate Geoid Height to zero.
- Select the stations to compute by selecting the corresponding check box.
- Click Geo to Grid or Grid to Geo to transform from geodetic to grid or grid to geodetic, respectively.
- Keep new coordinates into the project, create a report, and/or generate an Excel CSV (comma-delimited) file from the results.
Data Export tab
This tab allows you to export coordinate data in the current project to Excel-compatible CSV (comma-delimited) and Google KML files. Be sure to Keep coordinates (into the project) from any computation (for example, adjusted network coordinates) before exporting.
Project Export tab
This tab allows you to export your current project to a Columbus 4 project file. This file can be modified as needed for use in the Adjust File page, or it can be uploaded to the cloud from within the Project page. For users who don’t want to store projects into the cloud, this option can be used to store each project locally.
You can also export your current project to a Columbus 3.X format for use in the Windows version of Columbus (release 3.8.1.X). When loading the resulting file into Columbus 3.8.1.X, Options settings must be updated, since they are not exported from Columbus 4.