Geomatics Engineering: Locating Soundings Methods

Study Notes

Students will gain knowledge on methods used for locating soundings.
Focus areas include observations from the shore, from a sounding boat, and using both.

Three primary observation methods: from the shore, the sounding boat, and a combination of both.

By Transit and Stadia:
- Establish a range line and set up a transit.
- Hold a leveling staff vertically and row the boat along the range line.
- Take stadia readings and compute distances with tacheometric formulae.
Range and One Angle from the Shore:
- Set multiple range lines and place the transit perpendicular to a chosen range.
- Row the boat along the range line, with signal coordination for angle recording.
By Two Angles from the Shore:
- Requires two transits at visible points for angle measurement.
- Observers note angles simultaneously when a signal is given from the boat.
- Calculations involve using the sine rule for triangulation.

Range and One Angle from the Boat:
- Set up range lines and fix a signal at the end of one line.
- Measure angles at the moment of soundings and record the time.
Two Angles from the Boat:
- Measure angles simultaneously from known points on shore using a sextant.
- Calculate coordinates based on previously noted angles.

Range and Time Interval:
- Set up range lines and note the time of soundings taken at uniform velocity.
- Distances can be calculated using the boat's speed and timing between soundings.
Intersecting Ranges:
- Permanent marking of range lines aids in tracking changes in the water body’s bottom.
- Repeated soundings are taken at intersection points of range lines.
Distances along a Stretched Wire Across a River:
- A wire between two banks is marked for measuring distances to reference points on shore.
- Soundings taken under each tagged point; this method is highly accurate but costly.

Method suitability varies with water depth and conditions; some are only applicable to shallow, smooth waters.
Precision of observations is dependent on the setup of instruments and conditions during measurement.
Timing and proper coordination are critical in ensuring accuracy in soundings.