Process Help SUROBS - reduce angle and distance survey observations

 

Process Name	Menu Path	Link to Command Table
SUROBS	Command line only	Click here

 

• Introduction

• Files, Fields and Parameters

• Notes

• Example

• Errors

Introduction

SUROBS is a process which reduces survey angle and distance measurements.

How to use

Angle and distance measurements are processed to output average values and associated mean standard errors. This represents an advanced alternative to process SURTAC, in which no reduction is performed and no standard errors are computed. SUROBS also allows tolerances to flag unacceptable input measurements. Base-line bearing computations, reference plan distance and difference in elevation may also be computed.

File Handling

There are three compulsory and one optional input files required by SUROBS. These may be summarized as:

• &HEADER: a file containing survey job and location information (compulsory).

• &OBSERV: a file containing the survey measurements to be reduced (compulsory).

• &CONTROL: a file containing the coordinates and identification of established survey stations that will be used in the survey (compulsory).

• &TOL: a file containing measurements tolerances for flagging errors in the input measurement file (optional).

 

There is one compulsory and one optional output file in SUROBS. These are:

• &OUT: output file containing reduced survey observations (compulsory).

• &ERROR: output file containing measurements that do not meet specifications defined in &TOL input file (optional).

Field Handling

All fields of the input files are compulsory. Therefore if any of these files are output from another process such as SURLOG or SURTAC the remaining compulsory fields should be added using for example process ADDDDD. The summary of compulsory fields required in the input files is:

 

&HEADER	&OBSERV	&CONTROL	&TOL	&OUT	&ERROR
*JOBNUM *SURVEYOR *LEVEL *SECTION *INSTTYPE	*JOBNUM *INSTSTN *INSTHT *RO *TARGET *HZTARG *VATARG *SDTARG *TARGHT *HZRO *VARO *SDRO *ROHT	*STATION *X *Y *Z *RO *WCB *QB *HDIST *VDIFF *PLANE *FACTOR *REFRACT *HDERR *WCBERR *VAERR *ERRFLAG *LOXORIG *LOYORIG *LOZORIG	*INSTTYPE *STNTYPE *HDTOL *HZTOL *VATOL *VDTOL	*INSTSTN *INSTHT *RO *TARGET *HZA *WCB *QB *WCBERR *VA *HDIST *HDERR *RDIST *VDIFF *VDERR *PLANE *FACTOR *REFRACT *ERRFLAG	*INSTSTN *INSTHT *RO *TARGET *HZA *WCB *QB *WCBERR *VA *HDIST *HDERR *RDIST *VDIFF *VDERR *PLANE *FACTOR *REFRACT *ERRFLAG

 

Stations are identified by field *STATION in input file &CONTROL and fields *INSTSTN, *TARGET and *RO in input file &OBSERV. These must be alphanumeric and eight characters in length. A particular survey instrument or method used may be specified in a four-character alphanumeric field *INSTTYPE of files &HEADER and &TOL. Alphanumeric fields *SURVEYOR, *LEVEL and *SECTION of file &HEADER refer to descriptive information of the surveyor and region of the survey and must be eight characters in length. Field *STNTYPE in file &TOL refers to the station type (RO or TARGET) for tolerances specification and must be four characters in length. Field QB refers to the quadrant bearing and must be twelve characters in length. All the remaining fields are numeric.

Mathematical Algorithms

   

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Files, Fields and Parameters

Input Files

Name	Description	I/O Status	Required	Type
HEADER	Input header information, containing survey job and location information. This file may have been created by the SURLOG process (input of field recorder data) or the screen editor process AED. This file must contain the following fields ((N) denotes Numeric, (A,8) denotes Alphanumeric field type and length):- JOBNUM (N) Survey job number. SURVEYOR (A,8) Surveyor's name. LEVEL (A,8) Region of survey. SECTION (A,8) Area of survey. INSTTYPE (A,4) Survey instrument or methods used.	Input	Yes	Undefined
OBSERV	Input file of survey measurements. This file must contain the following fields ((N) denotes Numeric, (A,8) denotes Alphanumeric field type and length):- JOBNUM (N) Survey job number. INSTSTN (A,8) Survey station identifier for the instrument location. INSTHT (N) Instrument height. (Negative for instruments set below the survey station). RO (A,8) Survey station identifier for the reference object survey station. TARGET (A,8) Identifier of the survey station located. HZTARG (N) Horizontal direction measured to the target. VATARG (N) Vertical direction measured to the target. SDTARG (N) Slope distance measured to the target. TARGHT (N) Target height. (Negative for target set below the target point). HZRO (N) Horizontal direction measured to the reference object. VARO (N) Vertical direction measured to the reference object. SDRO (N) Slope distance measured to the referenec object. ROHT (N) Target height at the reference object. (Negative for target set below the target point). This file file may have been created as output from the SURLOG process.	Input	Yes	Undefined
CONTROL	Input file of survey control stations. This file must contain the following fields ((N) denotes Numeric, (A,8) denotes Alphanumeric field type and length):- STATION (A,8) Survey station identifier. X (N) X coordinate value. Y (N) Y coordinate value. Z (N) Z coordinate value. RO (A,8) Identity of station used to locate STATION. WCB (N) Whole Circle Bearing from STATION to RO. Referred to as azimuth elsewhere in your application. QB (A,12)Quadrant Bearing STATION to RO. (e.g. N 45.0000 E). HDIST (N) Horizontal distance from STATION to RO. RDIST (N) Reduced distance from STATION to RO, as computed at PLANE elevation. VDIFF (N) Vertical difference in height from STATION to RO. PLANE (N) Elevation to which HDIST has reduced to compute RDIST. If absent (-), no further reduction has been computed. FACTOR (N) Scale factor used to compute RDIST. REFRACT (N) Coefficient of refraction used to compute VDIFF where only a single forward vertical angle is used. HDERR (N) Mean standard error or range of horizontal distances from RO to STATION. WCBERR (N) Mean standard error or range of horizontal angles used in computing the bearing from RO to STATION. VAERR (N) Mean standard error or range of vertical angles used in computing VDIFF from RO to STATION. VDERR (N) Mean standard error or range of computed VDIFF from RO to STATION. ERRFLAG (N) Flag to identify when a measurement tolerance is exceeded. ADJUST (N) Flag to identify if the station coordinates are adjusted. LOXORIG (N) Implicit local X origin field. LOYORIG (N) Implicit local Y origin field. LOZORIG (N) Implicit local Z origin field.	Input	Yes	Undefined
TOL	Optional file of measurement tolerances for the flagging of errors in measurements processed from the input OBSERV file, and written to the output ERROR file, if supplied. This file must contain the following fields:- INSTTYPE (A,4) Survey instrument or methods used. STNTYPE (A,4) Must contain a value RO or TARGET, to allow different tolerances to be specified for checks onto existing base-lines (RO) and the establishment of new base- lines (TARGET). HDTOL (N) Maximum mean standard error of observed horizontal distance measurements. HZTOL (N) Maximum mean standard error of observed horizontal angle measurements. VATOL (N) Maximum mean standard error of observed vertical angle measurements. VDTOL (N) Maximum mean standard error of computed differences in elevation.	Input	No	Undefined

Output Files

Name	I/O Status	Required	Type	Description
OUT	Output	Yes	Undefined	Output file of reduced survey observations. This file may be used as input to the SURCAL process, in order to compute survey station coordinates. This file will contain the following fields:- INSTSTN (A,8) Survey station identifier for the instrument location. INSTHT (N) Instrument height. (Negative for instruments set below the survey station). RO (A,8) Survey station identifier for the reference object survey station. TARGET (A,8) Identifier of the survey station located. HZA (N) Mean horizontal angle measurement made to the target station. WCB (N) Whole Circle Bearing from INSTSTN to TARGET. QB (A,12)Quadrant Bearing INSTSTN to TARGET. WCBERR (N) Mean standard error or range of measurements taken to establish the Whole Circle Bearing INSTSTN - TARGET. VA (N) Mean vertical angle measurement made to the target station. HDIST (N) Mean horizontal distance from INSTSTN to TARGET. HDERR (N) Mean standard error or range of horizontal distances from slope distances and vertical angles. RDIST (N) Reference plane distance from INSTSTN to TARGET as computed from the horizontal distance HDIST. VDIFF (N) Mean difference in elevation from INSTSTN to TARGET. VDERR (N) Mean standard error or range of computed height differences from INSTSTN to TARGET. PLANE (N) Reference plane used to compute RDIST from HDIST. If absent, RDIST = HDIST. FACTOR (N) Scale factor used to compute RDIST after reduction to PLANE. The default must be 1. REFRACT (N) Coefficient of refraction used to adjust vertical angles where single measurements are made. ERRFLAG (N) Error flag field. Four digits may be set as follows:- ABCD e.g. 1001 A Horizontal angle tolerance was/was not exceeded. 1/0 B Vertical angle or vertical difference tolerances were /were not exceeded. 1/0 C Horizontal distance tolerance was/was not exceeded. 1/0 D The previous base-line (INSTSTN to RO) carried/ did not carry errors. >1/0
ERROR	Output	No	Undefined	Optional output file of measurements that do not meet the tolerances specified in the input tolerance file ( TOL). If this file is not defined, all measurements will be sent to the output file . This file will contain the same fields as the output file of reduced survey measurements ( OUT).

Parameters

Name	Description	Required	Default	Range	Values
ANGLE	Units of angle measurements : 1 = Degrees, minutes and seconds. [0-360] in the form DDD.MMSS 2 = Gradians. [0-400] The default angle unit is degrees, minutes and seconds (1).	No	1	1,2	1,2
VADMEAN	Compute the mean of both forward and reverse angle and measurements if available. This will obviate the need to adjust for curvature and refract, defined in parameter REFRACT. The default is (1), to use forward and reverse measurements.	No	1	Undefined	Undefined
ERRTYPE	Sets the error fields to report the mean standard error [1] or the range [2] of measurements. The default is to report mean standard errors (1).	No	1	1,2	1,2
PLANE	Optional reference plane elevation to which horizontal distances will be computed. The default is not to reduce horizontal distances to reference plane (-).	No	-	Undefined	Undefined
FACTOR	Optional scale factor that may be applied to the reduced distance RDIST. The default setting is (1).	No	1	Undefined	Undefined
REFRACT	Optional coeficient of refraction used for adjustment of vertical angles. The default is not to apply correction to vertical angle (-).	No	-	Undefined	Undefined
PRINT	Set to one to display a summary of results to the screen. The default is not to print summary results (0).	No	0	0,1	0,1

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Notes

1. When only one record is available for a particular measurement then the output error fields referring to range or standard error are set to absent value.

2. A maximum of twenty redundant observations for each pair INSTSTN-TARGET are allowed. If this limit is exceeded the process is exited with an error message.

3. Checks are made for inconsistent angle measurements (for example, vertical angles readings of more than 90 , WCB and horizontal angle readings of more than 360 or less than 0 ). For these cases the records are ignored. In case of absent data for the horizontal angle to the reference station (field *HZRO), then a value of 0 is assumed.

4. An important note refers to the precision of the coordinates handled in SUROBS. Although all variables are stored and handled by Double-Precision type variables and arrays, input and output measurements and coordinates are held in single precision type variables. In order to avoid output problems with values over 7 digits long, the use of parameters @LOXORIG, @LOYORIG and @LOZORIG is strongly recommended.

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Example

!SUROBS  &HEADER(HEADER),&OBSERV(OBSERV),&CONTROL(CONTRALL),
         &OUT(OUT),@ANGLE=1.0,@VADMEAN=1.0,@ERRTYPE=1.0,
         @FACTOR=1.0,@PRINT=1.0

A sample output to the screen and to the printer/output print file is:

PROCESS SUROBS

Survey stations are identified by field STATION 
Summary of parameters to be used:-

Angle units will be degrees 
Forward/Reverse measurements     [ ON]
Standard error report            [ ON]

Results for :-

Survey job number     :           1.0
Surveyor"s name       :      SURVEYOR 
Region of survey      :      REGION A 
Area of survey        :        AREA B 
Survey instrument     :         SET3B 

Reduced results for reference station STA1 :

INSTRUMENT STATION      =         STN1 
HORIZONTAL DISTANCE     =      39.9373
ELEVATION DIFFERENCE    =     150.8012
REDUCED DISTANCE        =      39.9373
HORIZONTAL DIST. ERROR  =      39.8373
ELEVATION DIFF. ERROR   =     150.7012

Reduced results for target STN2 :

INSTRUMENT STATION      =         STN1 
RO STATION              =         STA1 
TARGET STATION          =         STN2 
INSTRUMENT HEIGHT       =       5.3000
W.C.BEARING             =      33.3126
QUADRANT BEARING        =  N 33.3126 E
HORIZONTAL ANGLE        =       3.3126
ELEVATION DIFFERENCE    =     148.8419
HORIZONTAL DISTANCE     =      39.2084
REDUCED DISTANCE        =      39.2084
ERROR FLAG              =        00000
VERTICAL ANGLE ERROR    =       0.5000
HORIZONTAL ANGLE ERROR  =       6.0000
W.C.BEARING ERROR       =       6.0000
ELEVATION DIFF. ERROR   =       0.0000
HORIZONTAL DIST. ERROR  =       0.0000

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Error and Warning Messages

Message	Description	Solution
*** Error - File &HEADER is missing essential field FFFFFFFF.	A compulsory field FFFFFFFF is missing from the input &HEADER file and must be added to the file (for example using process ADDD). Fatal; the process is exited.
*** Error - File &OBSERV is missing essential field FFFFFFFF.	A compulsory field FFFFFFFF is missing from the input &OBSERV file and must be added to the file (for example using process ADDD). Fatal; the process is exited.
*** Error - File &CONTROL is missing essential field FFFFFFFF.	A compulsory field FFFFFFFF is missing from the input &CONTROL file and must be added to the file (for example using process ADDD). Fatal; the process is exited.
*** Error - File &TOL is missing essential field FFFFFFFF.	A compulsory field FFFFFFFF is missing from the &TOL optional input file and must be added to the file (for example using process ADDD). Fatal; the process is exited.
*** Error - Both files &TOL and &ERROR have to be specified.	The optional input file &TOL and the optional output file &ERROR must be both specified when tolerances are to be used. Fatal; the process is exited.
*** Error - Field FFFFFFFF of &HEADER file has to be nn characters long.	The alphanumeric field FFFFFFFF is defined in the input &HEADER file with an incorrect length. Fatal; the process is exited.
*** Error - Field FFFFFFFF of &OBSERV file has to be nn characters long.	The alphanumeric field FFFFFFFF is defined in the input &OBSERV file with an incorrect length. Fatal; the process is exited.
*** Error - Field FFFFFFFF of &CONTROL file has to be nn characters long.	The alphanumeric field FFFFFFFF is defined in the input &CONTROL file with an incorrect length. Fatal; the process is exited.
*** Error - Field FFFFFFFF of &TOL file has to be nn characters long.	The alphanumeric field FFFFFFFF is defined in the input &TOL file with an incorrect length. Fatal; the process is exited.
*** Error - Field FFFFFFFF has to be nn characters long in both inpu t file s &OBS ERV and &TOL .	A mismatch of field lengths or types was found for field FFFFFFFF in input files &OBSERV and &TOL. Fatal; the process is exited.
*** Error - Field FFFFFFFF has to be nn characters long in both inpu t file s &HEA DER and &TOL .	A mismatch of field lengths or types was found for field FFFFFFFF in input files &HEADER and &TOL. Fatal; the process is exited.