Compose a 3250 words assignment on engineering and construction.
Compose a 3250 words assignment on engineering and construction. Needs to be plagiarism free! An alternative to this differential method is Precise Point Positioning (PPP). PPP achieves centimeter accuracies using only a single receiver by using precise orbital and clock data instead of the standard broadcast navigation message in post-processing. A popular way of carrying out post-processing is by using online PPP post-processing services. In recent years, several post processing services have been developed by government agencies, universities, and survey companies.
To date, no such study using PPP measurements has been undertaken in Ireland. As GNSS orbit and clock products are by their nature global, PPP is rapidly becoming a technique that has the potential to replace existing range-limited GNSS relative positioning methods (Marreiros, 2012). .
PPP is a relatively new positioning technique developed in the 1990s, it has an advantage over traditional differential methods in that it removes the need for the user to establish their own local reference station or to have access to reference stations operated by others (Rizos et al., 2012). PPP is a very good alternative positioning technique that can be used all over the world as the GNSS orbit and clock products used in the PPP solution are by their nature global (ESA, 2011). Additionally, PPP can provide more consistency over large areas because its position solutions are referred to as a global reference frame whereas DGNSS position solutions are relative to local base stations (Gao, 2006). PPP offers a valuable solution where a control network or Continuously Operating Reference Stations (CORS) is simply unavailable (Van Sickle, 2009). As there is only one receiver being used and no corrections being sent by a base station, pseudo-range observations and phase information are combined to fix the integer ambiguities on undifferenced phase measurements. This is what distinguishes PPP from DGNSS.
Currently many autonomous and relative GNSS measurement and positioning techniques can be used to achieve varying levels of accuracies. Table 1 outlines the main techniques and the achievable accuracies currently in use.