GEODETIC APPLICATIONS

Landscale office following the developments of sciense and technology offers to our customers the following geodetic application services:

  • Land survey-cadastral survey
  • Triangulation
  • Layout design Buildings-Engineering Structures
  • Settlement demarcations
  • Foreshore demarcations
  • Stream and construction lines demarcations
  • Implementation Act
  • Seperately Implementation Act - Reformative Implementation Act
  • Private urban planning
  • Cadastral corrections
  • Survey with DRONE

Measurements by Geodetic methods

Practical measurements with geodetic methods are implemented in 2 phases:

  • Outdoor measurements
  • Office calculations
Outdoor measurements

The level is used for determining height differences and height reference systems, commonly referred to mean sea level.

The traditional spirit level produces these practically most useful heights above sea level directly; the more economical use of GPS instruments for height determination requires precise knowledge of the figure of the geoid, as GPS only gives heights above the GRS80 reference ellipsoid.

As geoid knowledge accumulates, one may expect the use of GPS heighting to spread.

The theodolite is used to measure horizontal and vertical angles to target points. These angles are referred to the local vertical. The tacheometer additionally determines, electronically or electro-optically, the distance to target, and is highly automated to even robotic in its operations.

The method of free station position is widely used. For local detail surveys, tacheometers are commonly employed although the old-fashioned rectangular technique using angle prism and steel tape is still an inexpensive alternative.

Real-time kinematic (RTK) GPS techniques are used as well. Data collected are tagged and recorded digitally for entry into a Geographic Information System (GIS) database.

Geodetic GPS receivers produce directly three-dimensional coordinates in a geocentric coordinate frame. Such a frame is, e.g., WGS84, or the frames that are regularly produced and published by the International Earth Rotation and Reference Systems Service (IERS).

GPS receivers have almost completely replaced terrestrial instruments for large-scale base network surveys.

For planet-wide geodetic surveys, previously impossible, we can still mention satellite laser ranging (SLR) and lunar laser ranging (LLR) and very-long-baseline interferometry (VLBI) techniques.

All these techniques also serve to monitor irregularities in Earth's rotation as well as plate tectonic motions.

Office calculations

In surveying and mapping, important fields of application of geodesy, two general types of coordinate systems are used in the plane:

- Plano-polar, in which points in a plane are defined by a distance s from a specified point along a ray having a specified direction α with respect to a base line or axis;

- Rectangular, points are defined by distances from two perpendicular axes called x and y. It is geodetic practice—contrary to the mathematical convention—to let the x-axis point to the north and the y-axis to the east.

Rectangular coordinates in the plane can be used intuitively with respect to one's current location, in which case the x-axis will point to the local north.

More formally, such coordinates can be obtained from three-dimensional coordinates using the artifice of a map projection. It is not possible to map the curved surface of Earth onto a flat map surface without deformation.

The compromise most often chosen—called a conformal projection—preserves angles and length ratios, so that small circles are mapped as small circles and small squares as squares.

Because geodetic point coordinates (and heights) are always obtained in a system that has been constructed itself using real observations, geodesists introduce the concept of a "geodetic datum": a physical realization of a coordinate system used for describing point locations.

The realization is the result of choosing conventional coordinate values for one or more datum points.

In the case of height data, it suffices to choose one datum point: the reference benchmark, typically a tide gauge at the shore.

In the abstract, a coordinate system as used in mathematics and geodesy is called a "coordinate system" in ISO terminology, whereas the International Earth Rotation and Reference Systems Service (IERS) uses the term "reference system".

When these coordinates are realized by choosing datum points and fixing a geodetic datum, ISO says "coordinate reference system", while IERS says "reference frame".

The ISO term for a datum transformation again is a "coordinate transformation"