Lecture 1: Intor, Calcs, Observations, Errors, Codes Flashcards
(33 cards)
Surv201 values:
1. Manaakitaka =
2. Kotahitaka =
3. Whanautaka =
4. Rangatiratka =
- Be kind and generous, respect each other, the group and the work
- Teamwork in an environment of collective effort
- Working together to hear diverse voices and points of view
- Everybody contributes and everybody is heard
A polar is when you know ____ and you want to calculate ____
When you know the coords of A (the mark you’re at), and the bearing and distance from A to B, and you want to calculate the coords of B
A polar is sometimes incorrectly called a
Traverse (several points)
A join is when you know ____ and you want to calculate ____
When you know the coords of A and B. and you want to calculate the coords of A to B
Missing lines are
Consecutive polars ending with a join
Missing lines are widely used in survey calculations, especially for
Boundaries
Two main methods for calculating a missing line
- Enter bearings and distances and add dNs and dEs in memory followed by rectangular to polar conversion (preffered method)
- Do consecutive polars (data traverse) followed by a join from end point to the start point
A result should not be given to a precision that
Makes your measuring equipment appear more accurate than it is. (E.g do not give directions to 0.01 seconds when using a 1’ T/Station)
Unless otherwise specified, the number of decimal places of the inputs you are given should determine
The precision of the outputs (e.g if input coords are to 2 decimal places, do not give outputs to 3 decimal places)
For scale factors, you need to consider that six decimal places are needed to give correct millimetres at a distance of
One kilometre
Least count is
The smallest value an instrument can accurately measure
Equipment manufacturerd provide the least count in their instruments. True or False?
True
In angular measurement, define direction
Unorientated (e.g the raw reading off a total station)
In angular measurement, define bearing
Oriented with respect to a meridian (Grid Bearing, True Bearing etc)
In angular measurement, define orientation
Obtaining bearings from directions
In angular measurement, define angle
The angular difference between two directions or two bearings
In angular measurement, define Azimuth
A special case of bearing which is measured clockwise from true north
An O.C (orientation correction) may total to
A few seconds or many degrees
For calculations in any coordinate system, we need to use bearings from
The specific system.
A levelled instrument should be centred over
Survey mark
Total station observing routine
- Set the approximate bearing of the R.O (reference object: furthest, distinct target)
- Observe LF, RF
- Completion is one round of all observations, set is LF/Rf for one observation.
For longer distances, calculate the linear effect by
Taking the tangent (angular misclose) and multplying by the distance (LE = D tan (angle))
After a bearing observation with long lines and for accurate work, surveyors can add
A final column and close back on the first reference object (RO)
The options for distributing angular miscloses
- Hold previously observed bearings fixed (even if marks move, for more modern equipment or for tectonic movement)
- Check that departures from previous bearings are acceptable then upgrade data
- Put more error into short lines, less into long lines
- Give lower weight to indistinct or unplumbed targets
- Either do adjustments in the fieldbook or else in calcs (latter preferable for large jobs and multiple loops)
