Uploading/Downloading using a TOPCON GTS700(FC6) data recorder
When you are uploading data to the instrument, you can set an option in Surpac to control whether or not an end of file character is written at the end of an upload file. This is done by selecting the Edit data recorder configuration option button on the Topcon Fc6 Data Recorder form.
All required data can be accessed directly from special records in the data recorder. Recording of observed point co-ordinates in the data recorder is not supported. The Topcon has alphanumeric capabilities so the point number field may contain either numbers or descriptions. Within the observed point record a special optional field exists for the recording of a string number. If the string number is never recorded for the points in a survey then all points will be in string 1.
TOPCON FC6 DATA
GTS-700 v3.0 JOB D:\ANZAC,SITE PLAN NAME G.MACPHAIL INST GX1225 UNITS M,D SCALE 1.000000,1.000000,0.000000 DATE 02/06/97,11:07:26 ATMOS 25, 994 STN 9000,1.582,STN XYZ 100.000,100.000,10.000 BKB 9500,0.0000,0.0000 BS 9500 HV 0.0000, 92.1542 SS 100,0.100,WALL,01 SD 311.03460,97.40140,5.5630 SS 101,0.100,WALL,01 SD 359.39560,92.09070,3.5360 SS 102,0.100,WALL,01 SS 9001,0.100,STN SD 125.12070,103.29480,8.4760 |
The "BKB" record defines the backsight station name, in this example "9500". The "BKB" record may be followed by a "BS" record which indicates that an observation to the backsight station has been taken to orientate the horizontal circle. This in turn must be followed by a "HV", "HD" or "SD" record to define the horizontal angle to the backsight station. The example above shows a "HV" record being used for this purpose. Note: It is also allowable to leave the "BKB" record out, and just define the backsight station name by using a "BS" record, followed by a "HV", "HD" or "SD" record to define the horizontal angle to the backsight station.
NOTE: In the above coding example the string number is defined as the fourth item in an "SS" observation record. Some Topcon instruments can only write three items to an "SS" observation record when outputting in FC6 format. You can set an option in Surpac to read the string number from the third item in an "SS" observation record. This is done by selecting the Edit data recorder configuration option button on the Topcon Fc6 Data Recorder form. See here for more details. Note, that if you do set this option, then the coding schemes for single face pointings to new stations, and resection, remain exactly as described below. That is, the STN and RES codes must still be placed as the third item in an "SS" observation record.
Single Face Pointings To New Stations
Surveyed points may be stored as new stations in the survey database. To identify a surveyed point as a new station the "SS" record must have the code "STN" in the point code field. The point identifier is then used as the name for the new station. The last "SS" record in the example above demonstrates this.
If you are surveying a new station underground and want to store the height from the floor to the target, you must enter the height in millimetres separated by a comma immediately after the "STN" codes in the point code field. For example,
`STNABC,-2357'
In this example, the height from the floor to the target at station `ABC' is 2.357.
You are given some options regarding the creation of the new station. This is done via the Options for New Station form, see here for more details.
Use of station errors table: If a station errors table exists in the survey database, information regarding the order of the new station may be displayed. See here for more details.
RESECTION
Resection is a method for determining the unknown 3D position of an occupied station by measuring angles and distances to stations whose 3D coordinates are known. Surpac allows you to enter observations to multiple known stations, and uses a least squares solver to find the best coords for the unknown station based on all the data. The least squares solver uses several parameters related to the instrument accuracy of the particular data recorder (measured angle standard deviations etc). These parameters are set using the Data Recorders Configuration function described previously.
The Topcon GTS700(FC6) data recorder supports resection in Surpac.
Note on the use of Resection: Resection is a form of triangulation. Therefore for optimum results, points for observation (i.e. the resected point and the known stations to be used for the resection observations) should be selected to give strong geometric figures. That is, for the resection observations you should avoid features such as very acute turned angles between known stations, and having the new resection point and two or more of the known stations being used for the resection being in (approximately) a straight line. Another well documented limitation of the Resection method is that if you are performing a resection without recording any slope distances (i.e. you only record horizontal and vertical angles), then the resection point itself and the first three known stations used in the resection observations must not all lie on the same circle.
The implementation of resection for the Topcon GTS700(FC6) data recorder is best illustrated by an example from a raw data file:
GTS-700 v3.0 JOB D:\ANZAC,SITE PLAN NAME G.MACPHAIL INST GX1225 UNITS M,D SCALE 1.000000,1.000000,0.000000 DATE 02/06/97,11:07:26 STN 50,0.000,STN BKB 33,0.0000,0.0000 BS 33 HV 309.1831, 92.1542 SS 33,0.000,RES SD 309.18310,87.47080,39.0280 SS 34,0.000,RES SD 351.32560,88.36150,16.2340 SS 35,0.000,RES SD 5.01360,89.42300,5.6780 SS 36,0.000,RES SD 92.36410,90.15080,9.6500 SS 100,0.000,WALL,01 SD 238.17380,92.51030,38.9670 SS 101,0.000,WALL,01 SD 195.15320,87.56430,10.6770 |
In the example above we have set up our instrument at an unknown station called 50 (which currently does not exist in the database). The nominated known backsight station is 33. We then take observations (horizontal angle, vertical angle and slope distance) to 4 known stations 33, 34, 35 and 36 (these four stations must currently be in the database). These MUST be in clockwise order and the first station MUST be the nominated backsight station. The observations are identified as resection observations using the point code field. To identify an observation as a resection observation the "SS" record must have the code "RES" in the point code field. The point identifier is then used as the known station to which the resection observation is made. Once an observation has been identified as a resection observation all following observations will be taken as resection observations until an observation is encountered that does not have "RES" in the point code field.
When the resection observations cease all the resection observations are put into a least squares solver and the coordinates of the unknown station are calculated. At this point you are given the option of putting the new resected station into the database as a permanent record, or just using the calculated coordinates temporarily. Now you can continue taking readings as though the resected station is a KNOWN instrument station, and the backsight station used is the one that you nominated for the resection observations. So in the example above, by the time we get to the first normal observation (i.e. the observation with a point identifier of "100"), the station 50 is now a known station and it is used as the instrument station for this observation, and 33 is used as the backsight station. The normal observation is now surveyed as usual and its point coordinates are calculated and put in the string file.
Surpac also supports double face resection (for face left and face right observation pairs). Here the face left observation must come first (and the face left observation must have a vertical angle between 0 and 180 degrees), and the face right observation to the same station second. The readings pairs are meaned before being used in the least squares solver. Note: You cannot mix single face and double face observations in the same resection calculation. Below is an example of a double face resection:
GTS-700 v3.0 JOB D:\ANZAC,SITE PLAN NAME G.MACPHAIL INST GX1225 UNITS M,D SCALE 1.000000,1.000000,0.000000 DATE 02/06/97,11:07:26 STN 50,0.000,STN BKB 33,0.0000,0.0000 BS 33 HV 309.1831, 92.1542 SS 33,0.000,RES SD 309.18310,87.47080,39.0280 SS 33,0.000,RES SD 129.18310,272.12520,39.0280 SS 34,0.000,RES SD 351.32560,88.36150,16.2340 SS 34,0.000,RES SD 171.32560,271.23450,16.2340 SS 35,0.000,RES SD 5.01360,89.42300,5.6780 SS 35,0.000,RES SD 185.01360,270.17300,5.6780 SS 36,0.000,RES SD 92.36410,90.15080,9.6500 SS 36,0.000,RES SD 272.36410,269.44520,9.6500 SS 100,0.000,WALL,01 SD 238.17380,92.51030,38.9670 SS 101,0.000,WALL,01 SD 195.15320,87.56430,10.6770 |
You are given some options regarding the creation of the resected station. This is done via the Options for Resected Station form, see here for more details.
Use of station errors table: If a station errors table exists in the survey database, information regarding the order of the new resected station may be displayed. See here for more details.
Summary of important points for resection:
- The first resection observation must be to the nominated backsight station;
- The resection observations must be to stations taken in clockwise order;
- You are allowed a maximum of 20 resection observations to calculate the coords of a resection station, or 20 pairs of readings for double face observations;
- You must have horizontal angle and vertical angle readings for resection observations, but you have the option of whether to use slope distances in the calculations. For a particular resection observation line, if the slope distance is set to 0.0 in the raw data file then only the angles for that observation will be used in the least squares solver for the resection station coordinates. To achieve this for the Topcon GTS700(FC6) you would have to manually edit the raw data file, to change the recorded slope distance value to 0.0. You can have some resection observations with and some without slope distances in the same resection calculation. For double face resection you can also have face left with a slope distance and face right without a slope distance (or vice versa). Note that slope distances are still required for all conventional point surveys.
- If angles and slope distances are present then resection observations to a minimum of two known stations are required. If only angles are present then resection observations to a minimum of three known stations are required;
- If an underground database is used and the new resected station is stored in the database, then the nominated backsight station is stored as the 'station from' and the reverse bearing from the new station to the nominated backsight station is stored as the 'reverse bearing'.
Below is an example of the report created when resections are encountered.
RESECTION REPORT
Purpose : Testing purpose
|
Setup information : |
|
|
Resected Station |
50 |
|
Instrument height |
0.000 |
|
Backsight station |
33 |
|
Backsight reference angle |
309.1831 |
|
Stations Used |
Y |
X |
Z |
Target Height |
|
33 |
1024.715 |
969.832 |
101.508 |
0.000 |
|
34 |
1016.053 |
997.615 |
100.395 |
0.000 |
|
35 |
1005.656 |
1000.498 |
100.027 |
0.000 |
|
36 |
999.560 |
1009.640 |
99.958 |
0.000 |
UNADJUSTED OBSERVATIONS
|
Station |
H. Angle |
V. Angle |
Slope Dist. |
|
33 |
309.1831 |
87.4708 |
39.028 |
|
34 |
351.3256 |
88.3615 |
16.234 |
|
35 |
5.0136 |
89.4230 |
5.678 |
|
36 |
92.3641 |
90.1508 |
9.650 |
INSTRUMENT ACCURACIES
|
Angle Standard Deviation (seconds) |
: |
3.000000 |
|
|
Distance standard deviation |
: |
0.002000 |
|
|
Distance ppm |
: |
2.000000 |
|
|
Instrument height standard deviation |
: |
0.003000 |
|
|
Instrument centring standard deviation |
: |
0.003000 |
|
|
Target height standard deviation |
: |
0.003000 |
|
|
Target centring standard deviation |
: |
0.003000 |
Results
|
Resected Station |
Y |
X |
Z |
|
50 |
1000.002 |
1000.002 |
999.999 |
|
Standard Deviation |
0.0016 |
0.0017 |
0.0000 |
Station 50 has been inserted into the database.
OBSERVATION ADJUSTMENTS
|
Station |
H. Angle |
V. Angle |
Slope Dist. |
|
33 |
-0.0027 |
-0.0005 |
0.000 |
|
34 |
-0.0055 |
-0.0008 |
-0.003 |
|
35 |
0.0103 |
0.0032 |
-0.003 |
|
36 |
0.0020 |
-0.0031 |
-0.002 |
Note: The Observation Adjustments are tabulated above to help highlight any erroneous observations.
Note on "Standard deviations" in the RESULTS section of the RESECTION REPORT file: In general the more stations that you take readings to for the resection, the better these values become as a measure of the accuracy of the coordinates of the unknown station. This is because the more readings that exist the more "redundant" information there is. Redundant information is important in a least squares adjustment as it helps to show the consistency of the observations used to calculate the coordinates. However, even if you only take resection observations to the minimum of two fixed stations there is still some redundant information, that is one slope distance and one vertical angle, so the standard deviations are still meaningful even in this most simple case.