TDS Field File (.RW5)

The Raw Data file is made up of a sequence of ASCII text records. Each record contains data for a
complete field operation, such as a traverse or a side shot. These fields are separated by commas.

Each record is started with a two letter code and a comma to identify the type of record.
Each field is preceded by a two letter code as the field header. the value or data in a
field follows directly after the field header.

Record Types
JB - Job Record
MO - Mode Setup Record
SP - Store Point
OC - Occupy Station Record
LS - Line of Sight Record
TR - Traverse Record
SS - Side shot Record (BD, BR, FD, FR)
BK - Backsight Record
--GS - GPS Record

Job Record - JB
Record Type: JB
   NM - Job Name
   DT - Date
   TM - Time

Mode Setup Record - MO
Record Type: MO
   AD - Azimuth Direction (0=North, 1=South)
   UN - Units (0=feet, 1=Metres, 2=US Feet)
   SF - Scale factor (for Distances)
   EC - Earth Curvature (0=Off, 1=On)
   EO - EDM Offset (?)
   AU - ?

GPS Record - '--GS'
Record Type: --GS
   PN - Point Number
   N - Northing (the header is N space)
   E - Easting (the header is E space)
   EL - Elevation
   -- = Note
e.g.--GS,PN10000,N 5000.0000,E 5000.0000,EL100.0000,--BLD CNR

Store Point Record - SP
Record Type: SP
   PN - Point Number
   N - Northing (the header is N space)
   E - Easting (the header is E space)
   EL - Elevation
   -- = Note
e.g.SP,PN10000,N 5000.0000,E 5000.0000,EL100.0000,--BLD CNR

Occupy Station Record - OC
Record Type: OC
   OP - Occupied Point (station setup number)
   N - Northing (ignored)
   E - Easting (ignored)
   EL - Elevation (ignored)
   -- = Note (ignored)
e.g.OC,OP10000,N 5000.0000,E 5000.0000,EL100.000,--BLD CNR

For a station setup, the station definition is ignored as the station co-ords are always defined
previously by an SP record.
It does create a Station setup for the (OP) point and the following LS record will supply the height of Instrument.
Also, the following BK record will be used to set the Station Setup Azimuth Swing.

Line of Sight - LS
Record Type: LS
   HI - Height of Instrument. This value is applied to the current station setup
   HR - height of Rod (Height of Target). This value is used for all subsequent observations until changed.

Traverse Record - TR
Sideshot Record - SS
Record Type: TR or SS
   OP - Occupy Point number
   FP - Foresight Point (observed point)
(one of the following)
   AZ - Azimuth
   BR - Bearing
   AR - Angle right(angle from backsight clockwise)
   AR - Angle Left(angle from backsight anti-clockwise)
   DR - Deflection Right(angle from backsight+180 clockwise)
   DL - Deflection Left(angle from backsight+180 anticlockwise)
(one of the following)
   ZE - Zenithangle from vertical up
   VA - Vertical Angleangle from horizontal
   CE - Change Elevation (vertical height difference)
(one of the following)
   SD - Slope Distance
   HD - Horizontal Distance

BD, BR, FD, FR records are treated like SS records.

Backsight Record
Record Type: BK
   OP - Occupy Point Number
   BP - Back Point (observed point)
   BC - Back Circle (circle reading when observing backsight point)

Back to Read Field Session File.

Discussion - Explanation of Terms
e.g. BK,OP9710,BP9709,BS355.0542,BC9.2637
The BS is the computed bearing between the two setup locations, 9710 to 9709.
Since it is not necessary to make the circle reading of the theodolite match the computed bearing, an
orientation correction must be defined for the circle reading. From the above line you can determine that all
circle readings at 9710 will need to have an angular offset (orientation correction) applied of:
(355 05' 42" - 369 26' 37") = -14 20' 55" in order to get the oriented bearings for the side-shots.

In the US it is common for surveyors to "zero" the backsight pointing. This means they set the horizontal
angle reading to zero each time they are taking a backsight shot, regardless of what the bearing may be.

Surveyors often think of the circle readings as approximations of bearings. In the US they treat all circle
readings as a measured angle turned from the back-sight, usually in a clockwise direction.

Hence, AR is the clockwise angle turned from the backsight line. (which explains why the circle is zero'd for
the backsight) AL, is the anti-clockwise circle turned from the backsight line. AR is more common,
I've never come across anybody who sets their theodolite to measure angles in the counter-clockwise direction.

Deflection angle is based on a slightly different approach. Imagine the circle reading is set to 180 degrees
for the backsight, and then the theodolite is turned 180 degrees to point along the 0 circle-reading line,
or in other words to point along the same direction as the previous foresight of the traverse.
Deflection left is the angle measured to the left of this line forward pointing line, and deflection right is the
angle measured to its right.