• 22 Jul 2021
      • News,

Topographic Survey with GNSS

Topographic surveying, which involves operations to graphically represent a portion of the Earth’s surface, can be applied to various fields such as architecture and archaeology, and can be carried out using different instruments. We have already explored the evolution of topographic instruments and the advantages of using a total station, which has gained widespread use among industry professionals due to its reliability, precision, and accessibility.

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In this article, we want to illustrate the characteristics, functionalities, and benefits of using GPS in topographic surveying.
First and foremost, it is important to clarify the difference between GPS and GNSS.

What is the difference between GPS and GNSS?

GPS, or Global Positioning System, is an American global satellite positioning system that is still widely used for geolocation services. GPS consists of a constellation of 24 satellites divided into 6 orbital planes, with 4 satellites in each plane. The satellites transmit information on three frequencies (L1, L2, L5).
IlHowever, GPS is not the only satellite positioning system in existence. There are many other satellites in orbit owned by major world powers. For example, Russia has GLONASS, China has BEIDOU or COMPASS, India has IRNSS, Japan has QZSS, and Europe has Galileo and SBAS. Because GPS is not the only satellite positioning system available, it is more appropriate to refer to GNSS, which stands for Global Navigation Satellite System.

Global satellite navigation systems, through appropriate receiving instruments, can provide useful information regarding position and velocity. This explains why they have been effective in topographic surveying for determining the position of points on the Earth’s surface.
By calculating the time between the transmission of a signal from a satellite in space and its reception by an antenna on the ground, the antenna’s position can be determined. The underlying physical principle of this type of measurement is the formula V = S / T.

Topographic Surveying with GNSS

GNSS systems were initially applied in the military domain to precisely determine the position of targets. However, their applications span various fields, including automatic guidance of agricultural vehicles, search and rescue operations, wildlife tracking, territory monitoring, geophysics, and topography.

Topographic surveying with GNSS utilizes the reception of signals sent by satellites in orbit, the coordinates of which are known. Starting from these points, additional points with known coordinates are established and used as a reference network for measurement.

GNSS Positioning Methods in Topographic Surveying

GNSS positioning methods can vary:

  • Absolute positioning: This is performed with a single receiver, using signals received from GNSS satellites.
  • Relative positioning: This is conducted with two or more receivers and determines the relative position, i.e., the difference between the coordinates of the antenna positions.
  • Differential positioning: This is executed with a mobile receiver, utilizing signals received from GNSS satellites, along with a correction message from a reference station, which enhances the positioning accuracy.
  • Static positioning: Static GNSS networks consist of points materialized on the ground, and the technique employed is known as base-rover RTK. It involves two receivers independently recording observations, with position calculation done in post-processing.
  • Kinematic positioning: Dynamic GNSS networks consist of permanent GNSS stations operating 24/7. The technique used is network or NRTK RTK. The operator sends their position to the permanent GNSS station and receives a correction message. Kinematic positioning is more precise than static positioning and requires a dual-frequency receiver and a mobile modem.

Topographic Surveying with iRTK5 GNSS RTK System

The iRTK5 GNSS RTK System is equipped with next-generation GNSS technology, unlimited communication capabilities, and an innovative design, providing a high-quality GNSS RTK solution.

It is the industry’s best surveying solution.

Are you interested in learning more about the technical features and functionalities of the instrument? Are you interested in rental options or flexible payment plans? Request a free consultation right away!

In this article, we aimed to delve into topographic surveying with GPS and GNSS and introduced the useful iRTK5 instrument from Novatest for your field operations.

If you’re interested in discovering all the products and services that Novatest offers to professionals in the field of surveying and geodesy, please fill out the form, and you will be contacted.

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