Project Settings

The project settings are set by selecting Settings > Project from the menu, or pressing the SE icon on the tool bar. The project settings dialog box has six tabbed windows, Coordinate System, Input Files, Preprocessing, Adjustment, Standard Errors, and Output Options. Following is an explanation of the different project settings tabbed windows.

Notice that there are two buttons at the lower left of the dialog box. The 'Save Project' button can be used to store the current settings to the active project. If there is no active project then the user will be prompted for a new project file name. Projects can also be saved using the 'File/Save Project' menu option from the main menu. The 'Save as Default' button can be used to save the current project settings as the default settings whenever a new project is created. Default project settings  can also be defined using the 'File/Save Project as default' menu option from the main menu.

Coordinate System

The Coordinate System tab contains settings that relate to the project coordinate system, output units, the adjustment model and other geodetic settings.

You can select either the 3D model or the 2D/1D mathematical model. If you choose 2D/1D mathematical model you can choose to only perform a horizontal adjustment, a vertical adjustment or both. In the 3D model both horizontal and vertical are adjusted simultaneously. The 3D model requires that you choose a geodetic coordinate system. Local, assumed coordinate systems cannot be used with the 3D model. GPS vectors can only be used when using the 3D model.

If using the 2D/1D mathematical model you can select Local (assumed coordinate system), or a geodetic coordinate system such State Plane NAD83, State Plane NAD27, UTM, or a user-defined coordinate system as the coordinate system. When using the 3D model you cannot use a local system.

Select the 'Horizontal Units for' output of coordinate values (Meters, US Feet, or International Feet). In the 3D model both horizontal and vertical units are assumed to be the same. In the 2D/1D model horizontal and vertical units can differ. The 'Horizontal unit' setting in this screen refers to the output units. It is permissible to have input units in feet and output units in meters. Input units are set in the 'Input Files' tabbed screen.

If you choose SPC 1983, SPC 1927, or UTM,  the appropriate zone will need to be chosen. The grid scale factor is computed for each measured line using the method described in section 4.2 of NPAA Manual NOS NGS 5, "State Plane Coordinate System of 1983", by James E. Stem.

If using the 2D/1D model and you select a geodetic coordinate system, you have a choice as to how the elevation factor is computed. You can choose to either enter a project elevation or you can choose to have elevations factors computed for each distance based on computed elevations. In order to use the 'Compute Elevation from Raw Data'  all HI's and foresight rod heights must be collected for all points.

If you choose a geodetic coordinate system and are using the 2D/1D model you will want to select "Project Elevation" if any of your raw data measurements are missing any rod heights or instrument heights. There must be enough information to compute elevations for all points in order to compute elevation factors. For most survey projects it is sufficient to use an approximate elevation, such as can be obtained from a Quad Sheet for the project elevation.

Geoid Modeling

If you are using either the 3D  or the 2D/1D adjustment model using SPC 1983 or UTM  reduction you must choose a geoid modeling method. A project geoid separation can be entered or the GEOID99 or GEOID03 grid models can be used. The project must fall within the geographic range of the geoid grid files in order to use GEOID99 or GEOID03 models.

Geoid modeling is used as follows. Entering a 0.0 value for the separation is the method to use if you wish to ignore the geoid separation. In the 2D, 1D model it is assumed that elevations entered as control are entered as orthometric heights. Since grid reduction requires the data be reduced to the ellipsoid, the geoid separation is used to compute ellipsoid elevations. The difference between using geoid modeling and not using geoid modeling or using a project geoid separation is insignificant for most surveys of limited extents. In the 3D model it is also assumed that elevations entered as control are orthometric heights. Since the adjustment is performed on the ellipsoid, the geoid separation is used to compute ellipsoid elevations prior to adjustment. After the adjustment is completed the adjusted orthometric elevations will be computed from the adjusted ellipsoid elevations and the computed geoid separation for each point.

Geoid modeling is especially important for projects covering large extents. If you incorporate GPS vector data from an OPUS solution into your project it will be necessary to use geoid modeling, otherwise your results will be poor.

If you choose the GEOID99 or GEOID03 modeling option, geoid separations are computed by interpolation with data points retrieved from geoid separation files. The geoid separation files should be found in the primary  the installation directory. Grid files have an extension of .grd. These files should have been installed during the installation of SurvNet. These files can be downloaded from the Carlson/C&G website, carlsonsw.com, if needed. The geoid files used by SurvNet are not in the same format as the geoid files available from NGS. The geoid files used by SurvNet must come from Carlson/C&G, either installed during installation or downloaded from the Carlson website.

If you choose to enter a project geoid separation the best way to determine a project geoid separation is by using the GEOID03 option of the NGS on-line Geodetic Toolkit. Enter a latitude and longitude of the project midpoint and the program will output a project separation.

Working With User-defined Coordinate Systems

SurvNet allows the creation of user-defined geodetic coordinate systems (UDP). The ability to create user-defined coordinate system allows the user to create geodetic coordinate systems based on projections that are not explicitly supported by SurvNet. A SurvNet user-defined coordinate system consists of an ellipsoid, and a map projection,. The ellipsoid can be one of the explicitly supported ellipsoids or a user-defined ellipsoid. The supported map projections are Transverse Mercator, Lambert Conformal Conic with 1 standard parallel, Lambert Conformal Conic with 2 standard parallels, Oblique Mercator (NGS), and Double Stereographic projection. User-defined coordinate systems are created, edited, and attached to a project from the Project Settings 'Coordinate System' dialog box. To attach an existing UDP file, *.udp, to a project use the 'Select' button. To edit an existing UDP file or create a new UDP file use the 'Edit' button.

The User-defined Oblique Mercator projection used by SurvNet uses the Oblique Mercator projection formulas published in the NGS document "State Plane Coordinate System of 1983' by James Stem. This implementation of the Oblique Mercator projection  uses the convention of the False North and East being the natural origin, as opposed to the origin being the center of the projection.

The following dialog box is used to create the user-defined coordinate system. The ellipsoid needs to be defined and the appropriate map projection and projection parameters need to be entered. The appropriate parameter fields will be displayed depending on the projection type chosen.

Input Files

Raw Data Files: Use the 'Add' button to insert raw total station files into the list. Use the 'Remove' button to remove raw files from the list. All the files in this list are included in the least squares adjustments. Having the ability to choose multiple files allows one to keep control in one file and measurements in another file. Or different files collected at different times can be processed all at one time. If you have multiple crews working on the same project using different equipment, you can have "crew-specific" raw data files with standard error settings for their particular equipment. Having separate data files is also a convenient method of working with large projects. It is often easier to  debug and process  individual raw files. Once the individual files are processing correctly all the files can be included for a final adjustment.

You can select C&G (.CGR) raw files, Carlson (.RW5) files or SDMS (.PRJ) files for processing. You cannot select different file types. For example, you cannot select both .CGR and .RW5 files in the same project to be processed at the same time. Notice that you have the ability to highlight multiple files when removing or adding files

Carlson RW5 files can contain GPS vector records. If you wish to use the vectors from the RW5 file, check the "Include any GPS Vectors" box. You can also select RW5 files containing vectors in the GPS vector Files area.

Level Raw Files: Differential and Trig level files can be entered and processed. There are two type of level file supported by SurvNET:

       .TLV files - this is the new Carlson level file. It can contain Trig-Level and/or Differential-Level data. This is the file created by SurvCE version 2.0 or higher.
       .LEV files - this is Carlson's old level file format. It can contain single-wire or three-wire differential-level data.

You can view/edit these files by pressing the "Edit" button next to the level file input field.

Under the tools menu pull down, you have the option to convert level files from other formats to either a TLV or LEV format.

GPS Vector Files: GPS vector files can be entered and processed. Both GPS vector files and total station raw files can be combined and processed together. You must have chosen the 3D mathematical model in the Coordinate System tab in order to include GPS vectors in the adjustment.

Currently, the following GPS vector file formats are supported.

ASCII (StarNET)
Ashtech / Thales: Thales files typically have .obn extensions and are binary files.
Carlson RW5 files containing GPS vector records
GeoLab (.IOB)
LandXML, (*.xml)
Leica: Leica files are ASCII files.
NGS G-File
NGS G-File from an OPUS report
StarNet ASCII GPS: See below for more information on StarNet format. These files typically have .GPS extensions.
Topcon (.tvf): Topcon .tvf files are ASCII files.
Topcon (.xml): Topcon also can output their GPS vectors in XML format which is in ASCII format.
Trimble Data Exchange Format (.asc): These files are in ASCII format
Trimble data collection (.dc): These files are ASCII.
Trimble LandXML (.jxl)

The following is a typical vector record in the StarNet ASCII format. GPS vectors typically consist of the 'from' and 'to' point number, the delta X, delta Y, delta Z values from the 'from' and 'to' point, with the XYZ deltas being in the geocentric coordinate system. Additionally the variance/covariance values of the delta XYZ's are included in the vector file.

The GO record is a comment. The G1 record includes the 'from' and 'to' point and the delta X, delta Y, and delta Z in the geocentric coordinate system. The G2 record is the variance of X,Y, and Z. The G3 record contains the covariance of XY, the covariance ZX, and the covariance ZY. Most all GPS vector files contain the same data fields in varying formats.

Use the 'Add' button to insert GPS vector files into the list. Use the 'Delete' button to remove GPS vector files from the list. All the files in this list will be used in the least squares adjustments. All the GPS files in the list must be in the same format. If the GPS file format is ASCII you have the option to edit the GPS vector files. The Edit option allows the editing of any of the ASCII GPS files using Notepad. Typically, only point numbers would be the fields in a GPS vector file that a user would have need to edit. The variance/covariance values are used to determine the weights that the GPS vectors will receive during the adjustment and are not typically edited.

For a variety of reasons it is common for GPS vector data collected with  GPS equipment to have point names that do not match the point names used in the total station data. Generally the easiest way to handle this situation is to first convert the GPS data into the StarNet ASCII .format using the 'Tools/Convert GPS file to ASCII' menu option. Once the file has been converted to ASCII it is straightforward to change the G1 records using any text editor to reflect the correct point numbers.

Supplemental Control File: The supplemental control file option allows the user to designate an additional coordinate file to be used as control. The supplemental control files can be from a variety of different file types.

    Carlson SQLite (*.crdb)
    C&G numeric (*.crd)
    C&G alphanumeric (*.cgc)
    Carlson numeric(*.crd)
    Carlson alphanumeric(*.crd)
    Autodesk Land Desktop (*.mdb)
    Simplicity (*.zak)
    ASCII P,N,E,Z,D,C (*.nez)
    ASCII P,Lat,Long,Ortho,D,C (*.txt)
    CSV ASCII NEZ with std. errors
    SDMS (.ctl) control file

Note: You should never use the same file for supplemental control points and for final output. Least squares considers all points to be measurements. If the output file is also used as a supplemental control file then after the  project has been processed  all the points in the project would now be in the control file and all the points in the file would now be considered control points if the project was processed again. The simplest and most straight-forward method to define control for a project is to include the control coordinates in a raw data file.

Preprocessing

The Preprocessing tab contains settings that are used in the preprocessing of the raw data.

Compute Traverse Closures: Traditional traverse closures can be computed for both GPS loops and total station traverses. This option has no effect on the computation of final least squares adjusted coordinates. This option is useful for surveyors who due to statutory requirements are still required to compute traditional traverse closures and for those surveyors who still like to view traverse closures prior to the least squares adjustment. This option is used to specify a previously created closure file.

To use this option the user has to first create a traverse closure file. The file contains a .cls extension. The traverse closure file is a file containing an ordered list of the point numbers comprising the traverse. Since the raw data for SurvNet is not expected to be in any particular order it is required that the user most specify the points and the correct order of the points in the traverse loop. Both GPS loops and angle/distance traverses can be defined in a single traverse closure file. More details on creating the traverse closure files follow in a later section of this manual.

Pt. Number Substitution String: This option is used to automatically renumber point names based on this string. Some data collectors do not allow the user to use the same point number twice during data collection. In least squares it is common to collect measurements to the same point from different locations. If the data collector does not allow the collection of data from different points using the same point number this option can be used to automatically renumber these points during processing. For example you could enter the string '=' in the Pt. Number Substitution String. Then if you shot point 1 but had to call it something else such as 101 you could enter '=1' in the description field and during preprocessing point 101 would be renumbered as point '1'. With small projects it may be just as easy to edit the raw data.

Adjustment

Convergence Threshold: During each iteration corrections are computed. When the corrections are less than the threshold value the solution has converged. This value should be somewhat less than the accuracy of the measurements. For example, if you can only measure distances to the nearest .01' then a reasonable convergence threshold value would be .005'.

Confidence Interval: This setting is used when calculating the size of error ellipses, and in the chi-square testing. For example, a 95% confidence interval means that there is a 95% chance that the error is within the tolerances shown.

Enable sideshots for relative error ellipses: Check this box if you want to see the error ellipses and relative error ellipses of sideshots. This checkbox must be set if you want to use the "relative error ellipse inverse" function with sideshots. When turned off this toggle filters out sideshots during the least squares processing. Since the sideshots are excluded from the least squares processing error ellipses cannot be computed for these points. When this toggle is off, the sideshots are computed after the network has been adjusted. The final coordinate values of the sideshots will be the same regardless of this setting.

Large numbers of sideshots slow down least squares processing. It is best to uncheck this box while debugging your project to avoid having to wait for the computer to finish processing. After the project processes correctly you may turn on the option for the final processing.

Note: If you wish to get statistics on certain selected sideshots, you can create an ALT file with the selected points. This will force them to be included in the calculation process - even if you have "Enable sideshots for relative error ellipses" unchecked.

Relative Err. Points File: The ALTA standards require that surveyors certify to the relative positional error between points. Relative error ellipses are an accepted method of determining the relative positional error required by the ALTA standards. The points that are to be included in the relative error checking are specified by the user. These points are defined in an ASCII file with an extension of .alt. To select an .alt file for relative error checking use the 'Select' button and then browse to the file's location.

There is a section later in the manual that describes how to create and edit the .alt file.

Include ALTA tolerance report: Turn this toggle on if you wish to include the ALTA tolerance section of the report.

Allowable Tolerance, PPM: These fields allow the user to set the allowable error for computations. Typically the user would enter the current ALTA error standards, i.e. 0.07' & 50 PPM.

See the later section in this manual for more detailed information on creating and interpreting the ALTA section of the report.

Standard Errors

Standard errors are the expected measurement errors based on the type equipment and field procedures being used. For example, if you are using a 5 second total station, you would expect the angles to be measured within +/- 5 seconds (Reading error).

The Distance Constant, PPM settings, and Angle Reading should be based on the equipment and field procedures being used. These values can be obtained from the published specifications for the total station. Or the distance PPM and constant can be computed for a specific EDM by performing an EDM calibration using an EDM calibration baseline.

Survey methods should also be taken into account when setting standard errors. For example, you might set the target centering standard error higher when you are sighting a held prism pole than you would if you were sighting a prism set on a tripod.

The settings from this dialog box will be used for the project default settings. These default standard errors can be overridden for specific measurements by placing SE records directly into the Raw Data File (see the above section on raw data files).

If the report generated when you process the data shows that generally you have consistently high standard residuals for a particular measurement value (angles, distances, etc.), then there is the chance that you have selected standard errors that are better than your instrument and methods can obtain. (See explanation of report file). Failing the chi-square test consistently is also an indication that the selected standard errors are not consistent with the field measurements.

You can set the standard errors for the following:

Distance and Angle Standard Errors

Distance Constant: Constant portion of the distance error. This value can be obtained from published EDM specifications, or from an EDM calibration.

Distance PPM: Parts per million component of the distance error. This value can be obtained from published EDM specification, or from an EDM calibration.

Horizontal Angle Pointing: The horizontal angle pointing error is influenced by atmospheric conditions, optics, experience and care taken by instrument operator.

Horizontal Angle Reading: Precision of horizontal angle measurements, obtain from theodolite specs.

Vertical Angle Pointing: The vertical angle pointing error is influenced by atmospheric conditions, optics, experience and care taken by instrument operator.

Vertical Angle Reading: Precision of vertical angle measurements, obtain from theodolite specs.

Instrument and Target Standard Errors

Target Centering: This value is the expected amount of error in setting the target or prism over the point.

Instrument Centering: The expected amount of error in setting the total station over the point.

Target Height: The expected amount of error in measuring the height of the target.

Control Standard Errors

GPS Standard Errors

Instrument Centering: This option is used to specify the error associated with centering a GPS receiver over a point.

Differential Leveling Standard Errors

These setting only effect level data and are not used when processing total station or GPS vector files.

Avg, Dist. To BS/FS: This option is used to define the average distance to the backsight and foresight during leveling.

Rod Reading Error per 100 ft./m: This option is used to define the expected level reading error.

Collimation Error: This is the expected differential leveling collimation error in seconds.

Standard Error Definition Files

Output Options

These settings apply to the output of data to the report and coordinate files.

Display Precision

 These settings determine the number of decimal places to display in the reports for the following types of data. The display precision has no effect on any computations, only the display of the reports.   

Coordinates (North, East, Elevation) - Chose 0-4 decimal places.
Distances - Chose 0-4 decimal places
Directions (Azimuths or Bearings) - nearest second, tenth of     second, or hundredth of second.

Format

These settings determine the format for the following types of data.     

Direction - Choose either bearings or azimuth for direction display. If the angle units are degrees, bearings are entered as QDD.MMSSss and azimuths are entered as DDD.MMSSss. If the angle units are grads, bearings are input as QGGG.ggggg and azimuths are input as GGG.ggggg.

Coordinate Display - Choose the order of coordinate display, either north-east or east-north.

Null Elevation - Choose the value for null elevations in the output ASCII coordinate NEZ file. The Null Elevation field defaults to SurvNet’s value for NO ELEVATION,of -999999999.0 .

Angle Display - Choose the units you are working int, degrees or gradians.

ASCII NEZ Output

These settings determine the type and format of the output NEZ file. An ASCII .NEZ and .OUT files are always created after processing the raw data. The .OUT file will be a nicely formatted version of the .NEZ file suitable for printing. The .NEZ file will be an ASCII file suitable to be input into other programs. There are a variety of options for the format of the .NEZ file. Following are the different ASCII file output options.

P,N,E,Z,CD,DESC (fixed columns); - Point,north,east,elev.,code,desc in fixed columns separated by commas.

P,N,E,Z,CD,DESC; Point,north,east,elev.,code,desc separated by commas.

P N E Z CD DESC (fixed columns); Point,north,east,elev.,code,desc in fixed columns with no commas.

P N E Z CD DESC; Point,north,east,elev.,code,desc in fixed columns with no commas.

P,N,E,Z,DESC (fixed columns); Point,north,east,elev., desc in fixed columns separated by commas.

P,N,E,Z,DESC; Point,north,east,elev., desc separated by commas.

P N E Z DESC (fixed columns); Point,north,east,elev., desc in fixed columns with no commas.

P N E Z DESC; Point,north,east,elev.,code,desc separated by spaces.

P,E,N,Z,CD,DESC (fixed columns); - Point,east,north,elev.,code,desc in fixed columns separated by commas.

P,E,N,Z,CD,DESC; Point,east,north,elev.,code,desc separated by commas.

P E N Z CD DESC (fixed columns); Point,east,north,elev.,code,desc in fixed columns with no commas.

P E N Z CD DESC; Point,east,north,elev.,code,desc in fixed columns with no commas.

P,E,N,Z,DESC (fixed columns); Point,east,north,elev., desc in fixed columns separated by commas.

P,E,N,Z,DESC; Point,east,north,elev., desc separated by commas.

P E N Z DESC (fixed columns); Point,east,,northelev., desc in fixed columns with no commas.

P E N Z DESC; Point,east,north,elev.,code,desc separated by spaces.

CSV ASCII with std. errors (This format is useful as it can be used as a supplemental control input file type option, where the coordinate standard errors output for one project can be used as input for another project.)

* N/E Precision: number of places after the decimal to use for North and East values (0 -> 8) in the output NEZ ASCII file.

*  Elevation Precision: number of places after the decimal to use for Elevation values (0 -> 8) in the output NEZ ASCII file.

Coordinate File Output

If you want to write the calculated coordinates directly to a Carlson or C&G coordinate file, check the "Write to Coordinate File" box and select the file. You can choose the type of Carlson/C&G file to be created when you 'select' the file to be created. You may wish to leave this box unchecked until you are satisfied with the adjustment. Following are the different available coordinate output file options.

Overwrite: Overwrite the existing point. Notice that if you check the 'Do Not Ask Again' box all further duplicate points will be overwritten without prompting.

Do not Overwrite: The existing point will not be overwritten. Notice that if you check the 'Do Not Ask Again' box all further duplicate points will automatically not be overwritten - only new points will be written.

Scaled Coordinate File

This feature allows you to output to a second, "Scaled" coordinate file. The main purpose of this feature is to create a GROUND based coordinate file when working on a SPC system.

First check the "Create Scaled/Ground NEZ File" checkbox to turn the feature ON.

Select the TYPE coordinate file you wish to output to and select the file.

If your project is based on a SPC system, you will have the following scaling options:

To Ground. Use avg. computed combined SF
Manually enter SF

If you select the first option, the combined scale factor is calculated for each of the points and then the total is averaged. The inverse of this scale factor will be used to calculate the coordinates of the SCALED  coordinate file. This will give you GROUND coordinates for the project.

If you wish, you may also manually enter the desired scale factor.

If your project is based on a Local or Assumed coordinate system, you will only have the option to manually enter the scale factor as the scale factors cannot be calculated.

Next you will enter the point number you wish to SCALE around:

Pt. to Scale

Next you have the following TRANSLATION options:

Use current NE values
Enter new NE values
Enter translation values

The first option will use the current coordinates of the SCALE POINT, all other coordinate points will be scaled around this point.

The second option allows you to enter NEW coordinate values for the SCALE POINT. All the points will first be translated so that the SCALE POINT has the values entered here and then they will be scaled around the SCALE POINT.

The third option allows you to directly enter the delta-north and delta-east translation values. All the points will first be translated and then scaled.

If the Scaled Coordinate file exists when you process the project, you will see the following warning dialog box: If you pick OK the points in the Scaled File will be overwritten. If you Cancel no point will be written to the Scaled File.