Survey Network Adjustment
This function allows you to adjust survey networks using a least squares adjustment method. You have the choice of doing the adjustment in 3D (that is, adjusting the x, y and z coords of the unfixed stations), or 2D (that is, only adjusting the x and y coords of the unfixed stations).
To run this function: Choose Survey > Stations > Survey network adjustment, or...
For a 3D adjustment the function uses any combination of direction (ie bearing), distance (ie slope distance), horizontal angle, or vertical angle observations. For a 2D adjustment the function uses any combination of direction (ie bearing), distance (ie horizontal distance), or horizontal angle observations.
You can define stations to be unfixed or fixed in the adjustment. Unfixed stations will have their coords adjusted by the least squares system. Fixed stations are used as reference stations in the adjustment and do not have their coords changed.
This function can accept angles either entered in degrees (ie DDD.MMSS format) or in grads, depending on "Angle units" value in your default settings.
When you perform an adjustment you are given the option of whether or not to save the adjusted unfixed stations to the database. You are advised to first perform the adjustment without saving the station coords, then when you are happy with the new values, do the adjustment again this time saving the coords.
The function is particularly useful as a tool to calculate a homogeneous set of co-ordinates for a mapping, engineering or mining project. As the Control Network on a project is extended it is normal to encounter different techniques of measurement or different instruments. This function easily copes with such differences as it allows you to enter different error parameters for each observation, thereby allowing you to model the use of different instruments in the same network.
If you have a station errors table (see here for more information on this table) in your survey database, this function will use the rules in that table relating to 3D or 2D survey network adjustments to do QA checks on the newly adjusted unfixed stations.
Pre-requisites for an Adjustment:
- You must have the coords of all fixed stations in the network already stored in the survey database.
- You must have the coords of all the unfixed stations in the network already stored in the survey database. It is important that these initial estimates are as close as possible to the final values. Otherwise, the nature of the least squares equations used in the adjustment might prevent the adjustment from converging.
- For a 3D adjustment the total number of observations must be more than three times the number of unfixed stations in the network. Also each unfixed station must appear as either a backsight, setup, or foresight in at least three different observations. These are basic requirements for the system to have a solution, since for a 3D system each unfixed station adds three variables to the system (namely the x, y, z coords of the station) and each observation adds one equation to the system.
- For a 2D adjustment the total number of observations must be more than twice the number of unfixed stations in the network. Also each unfixed station must appear as either a backsight, setup, or foresight in at least two different observations. These are basic requirements for the system to have a solution, since for a 2D system each unfixed station adds two variables to the system (namely the x, y coords of the station) and each observation adds one equation to the system.
- The rules for the minimum number of observations for 3D and 2D adjustments defined above are required because it is a basic algebraic requirement that a system has at least as many equations as variables for a solution to exist. Any observations in excess of this minimum number, are termed "redundant observations" and are very important. More redundant observations, will result in a stronger network and a greater precision of the final coords.
NOTE: For estimates of errors for measured angles, distances (including PPM values) and centring over station marks, check the manufacturers handbook for the instrument being used. Remember that if you are too optimistic about the precision of your observations, you will put a strain on the network, which may result in failure to produce a satisfactory result.
Choose Survey - Stations - Survey network adjustment to display the Use existing observations file? form:
Use existing observations file?
Tick the box to use an existing observations (.sna) file. Untick the box to enter a new set of observations.
Observations file
Enter the name of the existing observations file that you want to use.
Choose Apply on the Use existing observations file? form to display the Survey Network Observations form.
Survey Network Observations form
The various fields on this form are explained below. Firstly the fields in the Survey details and Options boxes:
Surveyor
Enter the name of the person who completed the survey. This will be inserted into the database with the new unfixed station coords and will appear in the reports produced by this function.
Survey date
Enter the date of the survey. The date must be entered in the form YYYY-MM-DD HH:MM:SS, although the HH:MM:SS part is optional, eg 2003-10-23 10:20:33 and 2003-10-23 are both acceptable values. This will be inserted into the database with the new unfixed station coords and will appear in the reports produced by this function.
Checked by
Enter the name of the person who checked the survey. This will be inserted into the database with the new unfixed station coords and will appear in the reports produced by this function.
Field book
Enter the name of the field book where the survey observations are recorded. This will be inserted into the database with the new unfixed station coords and will appear in the reports produced by this function.
Pages
Enter the pages in the field book where the survey observations are recorded. This will be inserted into the database with the new unfixed station coords and will appear in the reports produced by this function.
Comment
Enter an optional comment. This will only appear in the reports produced by this function, and will not appear in the database.
3D Adjustment or 2D Adjustment
Do you wish to perform a 3D adjustment (that is, adjust the x, y and z coords of the unfixed stations), or a 2D adjustment (that is, only adjust the x and y coords of the unfixed stations).
Maximum number of iterations
Enter the maximum number of times the least squares iteration process is to be repeated to calculate the new unfixed station coords. An example value is 8.
Convergence tolerance
Enter the convergence tolerance for the least squares iterations. This value should be entered in the same units as the station x, y and z coords. The least squares system will be deemed to be converged when all the unfixed station coords vary by less than the convergence tolerance between successive iterations. An example value is 0.001.
Adjustment report file
Enter the name for the adjustment report file.
Station orders report file
This field will only be selectable if a station errors table exists in the survey database. Enter the name for the station orders report file.
Report file format
Choose the file format for the output report file(s).
Save stations to database?
Do you want to save the new station coords to the survey database? You are advised to first perform the adjustment without saving the station coords, then when you are happy with the new values, do the adjustment again this time saving the coords.
Save observations?
This option allows you to save the entered observations to a .sna text file. This is so that if you want to run the same adjustment again you can reuse this .sna file and not have to reenter all the observations manually.
Observations file
Enter the name for the observations file.
Next the fields on the Survey Network Observations form Stations tab, are explained:
Stations tab
Fixed stations
Enter the names of the stations whose coords are fixed and will not be changed. These stations must exist in the survey database.
Unfixed stations
Enter the stations that are to be adjusted. Provisional coords for these stations must exist in the survey database.
Next the fields on the Survey Network Observations form Directions tab, are explained:
Directions tab
Setup
Enter the name of the setup station.
Foresight
Enter the name of the foresight station.
Direction
Enter the direction. The direction is just the bearing of the foresight station relative to the setup station. If the "Angle units" value in your default settings is "degrees" then enter the angle in DDD.MMSS, if the "Angle units" value is "grads" then enter the angle in grads. An example value is 309.191600.
Inst Centr Err
Enter an estimate (as a distance) of the centring error of placing the instrument over (or under) the station mark. An example value is 0.0030.
Targ Centr Err
Enter an estimate (as a distance) of the centring error of placing the foresight target over (or under) the station mark. An example value is 0.0030.
Std Dev.
Enter an estimate of the standard deviation of the measured angle. If the "Angle units" value in your default settings is "degrees" then enter a value in seconds (eg 3.0, 30.0 120.0, 300.0 etc), if the "Angle units" value is "grads" then enter a value in grads. An example value is 3.
Next the fields on the Survey Network Observations form Distances tab, are explained:
Distances tab
Setup
Enter the name of the setup station.
Foresight
Enter the name of the foresight station.
Inst Ht
This field will only appear if you have chosen to do a 3D adjustment.
Enter the height of the instrument axis above the station. The convention used is that distances measured up to the axis are positive while distances measured from the station down to the axis are negative. Therefore if the station is in the back of the drive, the instrument height will be negative.
An example value is 0.000.
Targ Ht
This field will only appear if you have chosen to do a 3D adjustment. Enter the height of the target above the station. The convention used is that distances measured up to the target are positive while distances measured from the station down to the target are negative. Therefore if the station is in the back of the drive, the target height will be negative. An example value is 0.000.
Distance
Enter the distance observed from the setup to the foresight target. If the adjustment is 3D this will be a slope distance, if the adjustment is 2D this will be a horizontal distance. An example value is 5.6780.
Inst Centr Err
Enter an estimate (as a distance) of the centring error of placing the instrument over (or under) the station mark. An example value is 0.0030.
Targ Centr Err
Enter an estimate (as a distance) of the centring error of placing the foresight target over (or under) the station mark. An example value is 0.0030.
Inst Ht SD
This field will only appear if you have chosen to do a 3D adjustment.
Enter an estimate (as a distance) of the error involved in measuring the instrument height.
An example value is 0.0030.
Targ Ht SD
This field will only appear if you have chosen to do a 3D adjustment.
Enter an estimate (as a distance) of the error involved in measuring the target height.
An example value is 0.0030.
Std Dev.
Enter (as a distance) the standard deviation of the slope distance measurement. An example value is 0.0050.
PPM
Enter the Parts Per Million error of the slope distance measurement. An example value is 2.
Next the fields on the Survey Network Observations form Horizontal Angles tab, are explained:
Horizontal Angles tab
Backsight
Enter the name of the backsight station.
Setup
Enter the name of the setup station.
Foresight
Enter the name of the foresight station.
Angle
Enter the observed angle. If the "Angle units" value in your default settings is "degrees" then enter the angle in DDD.MMSS, if the "Angle units" value is "grads" then enter the angle in grads. An example value is 42.142500.
Back Centr Err
Enter an estimate (as a distance) of the centring error of placing the backsight target over (or under) the station mark. An example value is 0.0030.
Inst Centr Err
Enter an estimate (as a distance) of the centring error of placing the instrument over (or under) the station mark. An example value is 0.0030.
Targ Centr Err
Enter an estimate (as a distance) of the centring error of placing the foresight target over (or under) the station mark. An example value is 0.0030.
Std Dev.
Enter an estimate of the standard deviation of the measured angle. If the "Angle units" value in your default settings is "degrees" then enter a value in seconds (eg 3.0, 30.0 120.0, 300.0 etc), if the "Angle units" value is "grads" then enter a value in grads. An example value is 3.
Next the fields on the Survey Network Observations form Vertical Angles tab, are explained.
Vertical Angles
Note: the fields on this tab will only be selectable if you have chosen a 3D adjustment:
Setup
Enter the name of the setup station.
Foresight
Enter the name of the foresight station.
Inst Ht
Enter the height of the instrument axis above the station. The convention used is that distances measured up to the axis are positive while distances measured from the station down to the axis are negative. Therefore if the station is in the back of the drive, the instrument height will be negative. An example value is 0.0000.
Targ Ht
Enter the height of the target above the station. The convention used is that distances measured up to the target are positive while distances measured from the station down to the target are negative. Therefore if the station is in the back of the drive, the target height will be negative. An example value is 0.0000.
Angle
Enter the observed angle. If the "Angle units" value in your default settings is "degrees" then enter the angle in DDD.MMSS, if the "Angle units" value is "grads" then enter the angle in grads. An example value is 87.470800.
Inst Centr Err
Enter an estimate (as a distance) of the centring error of placing the instrument over (or under) the station mark. An example value is 0.0030.
Targ Centr Err
Enter an estimate (as a distance) of the centring error of placing the foresight target over (or under) the station mark. An example value is 0.0030.
Inst Ht SD
Enter an estimate (as a distance) of the error involved in measuring the instrument height. An example value is 0.0030.
Targ Ht SD
Enter an estimate (as a distance) of the error involved in measuring the target height. An example value is 0.0030.
Std Dev.
Enter an estimate of the standard deviation of the measured angle. If the "Angle units" value in your default settings is "degrees" then enter a value in seconds (eg 3.0, 30.0 120.0, 300.0 etc), if the "Angle units" value is "grads" then enter a value in grads. An example value is 3.
Complete the Survey Network Observations form and choose Apply to proceed.
Results
If the Save observations box was ticked on the Survey Network Observations form, the observation data is saved to the defined .sna text file.
The calculations on the network are performed and the results are written to the Adjustment Report File defined on the Survey Network Observations form. This file should be printed and perused carefully to examine the results and to ensure the validity of the entered observations.
The Adjustment Report File with either show that the adjustment has successfully converged, or that it has failed to converge. If it has failed to converge you should check the input observations for typing errors etc. If convergence has occurred and you requested that the new unfixed stations are saved to the database, then you are notified that the stations have been saved.
An example of an Adjustment Report File is shown below:
| Aug 11, 2004 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Survey Network Adjustment Report | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Surveyor : Robert Sisson | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Survey Date : 2001-01-01 12:00:01 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Checked By : Fred Jones | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Field Book : Book1 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Pages : 11-17 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Comment : Final survey network adjustment | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| A 3D adjustment has been performed | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Fixed Stations | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Station | Y | X | Z |
| RES_STN1 | 1024.715 | 969.832 | 101.508 |
| RES_STN2 | 1016.053 | 997.615 | 100.395 |
| RES_STN3 | 1005.656 | 1000.498 | 100.027 |
| RES_STN4 | 999.560 | 1009.640 | 99.958 |
Unfixed Stations
| Station | Y | X | Z |
| TEST1STATION | 1000.100 | 999.900 | 100.100 |
Directions
| Setup | Foresight | Direction (ddd.mmss) | Inst Centr Err | Targ Centr Err | Std Dev. (seconds) |
| TEST1STATION | RES_STN1 | 309.191600 | 0.0030 | 0.0030 | 3.000000 |
| TEST1STATION | RES_STN2 | 351.322700 | 0.0030 | 0.0030 | 3.000000 |
Slope Distances
| Setup | Foresight | Inst Ht | Targ Ht | Distance | Inst Centr Err | Targ Centr Err | Inst Ht Sd | Targ Ht Sd | Std Dev. | Ppm |
| TEST1STATION | RES_STN1 | 0.0000 | 0.0000 | 39.0280 | 0.0030 | 0.0030 | 0.0030 | 0.0030 | 0.0050 | 2.0000 |
| TEST1STATION | RES_STN2 | 0.0000 | 0.0000 | 16.2340 | 0.0030 | 0.0030 | 0.0030 | 0.0030 | 0.0050 | 2.0000 |
| TEST1STATION | RES_STN3 | 0.0000 | 0.0000 | 5.6780 | 0.0030 | 0.0030 | 0.0030 | 0.0030 | 0.0050 | 2.0000 |
| TEST1STATION | RES_STN4 | 0.0000 | 0.0000 | 9.6500 | 0.0030 | 0.0030 | 0.0030 | 0.0030 | 0.0050 | 2.0000 |
Horizontal Angles
| Backsight | Setup | Foresight | Angle (ddd.mmss) | Back Centr Err | Inst Centr Err | Targ Centr Err | Std Dev. (seconds) |
| RES_STN1 | TEST1STATION | RES_STN2 | 42.142500 | 0.0030 | 0.0030 | 0.0030 | 3.000000 |
| RES_STN1 | TEST1STATION | RES_STN3 | 55.430500 | 0.0030 | 0.0030 | 0.0030 | 3.000000 |
| RES_STN1 | TEST1STATION | RES_STN4 | 143.181000 | 0.0030 | 0.0030 | 0.0030 | 3.000000 |
Vertical Angles
| Setup | Foresight | Inst Ht | Targ Ht | Angle (ddd.mmss) | Inst Centr Err | Targ Centr Err | Inst Ht Sd | Targ Ht Sd | Std Dev. (seconds) |
| TEST1STATION | RES_STN1 | 0.0000 | 0.0000 | 87.470800 | 0.0030 | 0.0030 | 0.0030 | 0.0030 | 3.000000 |
| TEST1STATION | RES_STN2 | 0.0000 | 0.0000 | 88.361500 | 0.0030 | 0.0030 | 0.0030 | 0.0030 | 3.000000 |
| TEST1STATION | RES_STN3 | 0.0000 | 0.0000 | 89.423000 | 0.0030 | 0.0030 | 0.0030 | 0.0030 | 3.000000 |
| TEST1STATION | RES_STN4 | 0.0000 | 0.0000 | 90.150800 | 0.0030 | 0.0030 | 0.0030 | 0.0030 | 3.000000 |
** The least squares solution successfully converged **
Number of iterations : 2
Max iterations allowed : 8
Convergence tolerance : 0.001
Results for Iteration: 1
Unfixed Station Coordinates
| Station | Y | X | Z |
| TEST1STATION | 1000.100 | 999.900 | 100.100 |
Direction Residuals
| Setup | Foresight | Direction (ddd.mmss) | Residual (ddd.mmss) |
| TEST1STATION | RES_STN1 | 309.191600 | 0.005700 |
| TEST1STATION | RES_STN2 | 351.322700 | -0.182900 |
Slope Distance Residuals
| Setup | Foresight | Distance | Residual |
| TEST1STATION | RES_STN1 | 39.0280 | 0.1440 |
| TEST1STATION | RES_STN2 | 16.2340 | 0.1155 |
| TEST1STATION | RES_STN3 | 5.6780 | 0.0894 |
| TEST1STATION | RES_STN4 | 9.6500 | -0.1060 |
Horizontal Angle Residuals
| Backsight | Setup | Foresight | Angle (ddd.mmss) | Residual (ddd.mmss) |
| RES_STN1 | TEST1STATION | RES_STN2 | 42.142500 | -0.181200 |
| RES_STN1 | TEST1STATION | RES_STN3 | 55.430500 | 1.071100 |
| RES_STN1 | TEST1STATION | RES_STN4 | 143.181000 | 0.335500 |
Vertical Angle Residuals
| Setup | Foresight | Angle (ddd.mmss) | Residual (ddd.mmss) |
| TEST1STATION | RES_STN1 | 87.470800 | -0.082100 |
| TEST1STATION | RES_STN2 | 88.361500 | -0.205000 |
| TEST1STATION | RES_STN3 | 89.423000 | -1.022400 |
| TEST1STATION | RES_STN4 | 90.150800 | -0.345400 |
Final Results:
Unfixed Station Coordinates
| Station | Y | X | Z |
| TEST1STATION | 1000.002 | 999.999 | 100.000 |
Differences between final and initial unfixed station coordinates
| Station | Delta Y | Delta X | Delta Z |
| TEST1STATION | -0.098 | 0.099 | -0.100 |
Result Standard Deviations
| Station | Y | X | Z |
| TEST1STATION | 0.0010 | 0.0009 | 0.0009 |
Direction Residuals
| Setup | Foresight | Direction (ddd.mmss) | Residual (ddd.mmss) |
| TEST1STATION | RES_STN1 | 309.191600 | -0.001400 |
| TEST1STATION | RES_STN2 | 351.322700 | -0.004500 |
Slope Distance Residuals
| Setup | Foresight | Distance | Residual |
| TEST1STATION | RES_STN1 | 39.0280 | 0.0020 |
| TEST1STATION | RES_STN2 | 16.2340 | 0.0021 |
| TEST1STATION | RES_STN3 | 5.6780 | 0.0019 |
| TEST1STATION | RES_STN4 | 9.6500 | -0.0016 |
Horizontal Angle Residuals
| Backsight | Setup | Foresight | Angle (ddd.mmss) | Residual (ddd.mmss) |
| RES_STN1 | TEST1STATION | RES_STN2 | 42.142500 | 0.004300 |
| RES_STN1 | TEST1STATION | RES_STN3 | 55.430500 | 0.001700 |
| RES_STN1 | TEST1STATION | RES_STN4 | 143.181000 | -0.001200 |
Vertical Angle Residuals
| Setup | Foresight | Angle (ddd.mmss) | Residual (ddd.mmss) |
| TEST1STATION | RES_STN1 | 87.470800 | 0.000100 |
| TEST1STATION | RES_STN2 | 88.361500 | -0.000400 |
| TEST1STATION | RES_STN3 | 89.423000 | -0.010600 |
| TEST1STATION | RES_STN4 | 90.150800 | 0.001200 |
QA checks done by the station errors table
If you have a station errors table (see here for more information on this table) in your survey database, this function will use the rules in that table relating to 3D or 2D survey network adjustments to do QA checks on the newly adjusted unfixed stations.
Firstly the station_order values of all the fixed stations used in the adjustment are checked. All the fixed stations must have a station_order value that has been defined in the station errors table.
When the adjustment has successfully converged several values indicating the quality of the estimation of each of the unfixed stations are determined. These relate to the station coordinate standard deviations and the number of observations used to obtain the estimate for each station. Low coordinate standard deviation values and a large number of observations used to estimate a particular station, indicate that the station estimation is likely to be more accurate.
For a 3D adjustment the following values are used for each unfixed station:
- The x, y and z standard deviations of the station coords.
- The number of observations that involved that station as a backsight, setup or foresight.
- The x and y standard deviations of the station coords.
- The number of observations that involved that station as a backsight, setup or foresight.
An example of a Station Orders Report File for a 3D adjustment is shown below:
| Aug 12, 2004 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Survey Network Adjustment Station Orders Report | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Surveyor : Robert Sisson | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Survey Date : 2001-01-01 12:00:01 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Checked By : Fred Jones | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Field Book : Book1 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Pages : 11-17 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Comment : Final survey network adjustment | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Orders of Fixed Stations | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Station | Order |
| RES_STN1 | 2nd |
| RES_STN2 | 1st |
| RES_STN3 | 1st |
| RES_STN4 | 1st |
| Lowest Fixed Station Order: 2nd | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Station Order for Unfixed Station: TEST1STATION | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Orders from station errors table | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Parameter | Num Meas | Value | Order |
| 3D SURVEY NETWORK ADJUSTMENT X STANDARD DEVIATION | 13 | 0.0009 | 1st |
| 3D SURVEY NETWORK ADJUSTMENT Y STANDARD DEVIATION | 13 | 0.0010 | 1st |
| 3D SURVEY NETWORK ADJUSTMENT Z STANDARD DEVIATION | 13 | 0.0009 | 1st |
| Preliminary new station order from station errors table: 1st | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Final new station order: 2nd | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Corresponding action from station errors table: WARNING | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Interpretation of the Station Orders Report File
The Station Orders Report File assigns a new order value to each unfixed station in the adjustment. The various parts of the report are explained below:
- Orders of Fixed Stations. This table displays the station_order values of each of the fixed stations used in the adjustment.
- Lowest Fixed Station Order. This is the lowest ranking order of all the orders of the fixed stations. Any adjusted station network can only be as strong as the least accurate fixed station in the network. Therefore none of the new unfixed stations can be assigned a station_order value that is more accurate than this value.
- Orders from station errors table. For the particular unfixed station being considered this table shows the x, y and z coord standard deviation values (or just x and y coord standard deviation values for a 2D adjustment), the number of observations that involved that station as a backsight, setup or foresight, and the corresponding order for those values from the station errors table.
- Preliminary new station order from station errors table. This value represents the lowest ranking of the three orders (or 2 orders for a 2D adjustment) displayed in the Orders from station errors table.
- Final new station order. This value is the lower ranking of the Preliminary new station order from station errors table and the Lowest Fixed Station Order. This final comparison is done because none of the new unfixed stations can be assigned a station_order value that is more accurate than this value the Lowest Fixed Station Order.
- Corresponding action from the station errors table. This is the action from the station errors table that correspond to the Final new station order value.
- If any of the orders have a corresponding action from the station errors table of ERROR, then none of the new stations are inserted into the database.
- If none of the orders have corresponding actions of ERROR or WARNING then all of the new stations are inserted into the database.
- If none of the orders have corresponding actions of ERROR but some of the orders have corresponding actions of WARNING, then the Save Stations With Warning Action? form is displayed:
Follow the information given on the Save Stations With Warning Action? form and either select Apply on the form to save the selected stations together with stations that had orders with corresponding actions of CONTINUE or INFORMATIONAL, or select Cancel to not save any of the stations.