I.Construction Layout 1.Definition Construction layout refers to the construction of the building on the design drawing. According to a certain method, in the field measurement work, the actual process involves accurately locating the proposed design onto the actual construction site. During the layout process, construction projects often have complex and diverse characteristics, requiring the integration of multiple methods to determine the positions of points and lines corresponding to the buildings. The selection of layout methods depends on the type of construction, construction methods, construction locations, construction conditions, control point distribution, and accuracy requirements for layout. Therefore, layout personnel need extensive experience to choose the appropriate surveying methods and different combinations of station points. In this process, factors such as...

 l. Introduce of PPP（Precise Point Positioning）   Currently, Real-Time Kinematic (RTK) and Precise Point Positioning (PPP) technologies are the most widely and deeply researched technologies for high-precision positioning based on GNSS. RTK technology offers high accuracy, fast convergence, and good dynamic performance. However, it is limited by factors such as baseline length and network availability, and it can be relatively expensive. On the other hand, PPP technology, although slower in convergence compared to RTK, only requires a single receiver for positioning, is not limited by the operational range, and has lower costs. Furthermore, with continuous technological advancements, the accuracy level of PPP has reached a comparable level to RTK. Therefore, PPP has become the preferred choice for high-precision positioning in non...

 l. BackgroundAt present, the most widely used positioning method in the surveying and mapping industry is GNSS positioning. The conventional civil GNSS positioning accuracy is about 5-10 meters, which cannot meet the application of high-precision. So how is the centimeter-level positioning used in the surveying and mapping industry? Today we will take you through the GNSS positioning principle and introduce how to realize centimeter-level height positioning.    ll. The GNSS Localization Principle1. The Basic Concept of GNSSThe Global Navigation Satellite System (GNSS) is a global navigation system based on satellites that provides time/space references and all real-time dynamic information related to positional information. GNSS consists of different satellite systems in many countries, including the U.S. GPS system, the E...

In geodetic survey, the common used coordinate systems are Geodetic Coordinate System, Spatial Rectangular Coordinate System, Gauss-Krueger Plane Rectangular Coordinate System and so on. Based on the same reference ellipsoid, the above three coordinate systems are equivalent, corresponding with each other, only in different coordinate forms.     Geodetic Coordinate System Geodetic coordinate system is the basic coordinate system for geodetic survey, the base for calculation in geodetic survey, study on the size for earth shape and map compilation.   Geodetic coordinate system takes the reference ellipsoid as the datum plane. The position of ground point P is represented by geodetic longitude L, latitude B and height H. Geodetic coordinates are used in geodesy, surveying and mapping, etc.     Principle of Geodetic Coordinate System: When a point is on t...

 

   

  The error of RTK measurement and positioning mainly comes from the following stages: GPS satellite broadcast signal, satellite signal propagation and the ground receiving the identification satellite signal.   1.Conversion Parameter Influence During RTK surveying, it is required to calculate conversion parameters first, that is, WGS-84 coordinate system shall be converted into the local coordinate system. The accuracy of parameters directly affects the accuracy of surveying. The factors affecting the conversion parameters include: the accuracy and the distribution of conversion control point, different results caused by varied ways in RTK surveying like when using conversion parameters, the base RTK receiver shall not be moved, only after which that it is allowed to measure control points. Otherwise, systematic error will be generated, causing that t...

Recently, float solution has appeared frequently while using a same CORS account for the same RTK in the same area, especially in the afternoon, which was rare to happen before. The main of reason can be regarded as that the ionosphere is active.    After learning from a lot of relative information, following 6 problems maybe are the most concerned: 1. What is ionosphere? 2. How does ionosphere affect the "Fixed Solutions"? 3. Which factors will make ionosphere active? 4. Why did float solutionsrarely happen in the past, but did frequently recently? 5. Are there any methods to solve the float solution while using CORS accountsfor RTK? 6. Is the effect of active ionosphere short-time or long-term?   1. What is ionosphere? 1.1 Ionosphere Ionosphere is the upper atmosphere ionized by high-energy radiation from the sun and cosmic rays. Above 60 kil...

There is a misunderstanding shall be clarified first that precision of resection is the highest because there is no alignment error of survey station and instrument height, some people like to take CPIII measurement in high-speed railway as an example.   For CPIII measurement in high-speed railway, it is conducted in a very small surveying range. Besides, the know points for resection are far more than two points.  The purpose for CPIII measurement in high-speed railway is to make precision measurement. What matters for it is precision. It is the precision at 1mm or even lower. In this case, resection is the best method.   However, in common daily survey operation, there is no need to pursuit for that precision. For example, resection can directly get the station height (i.e. the sight line of the instrument), to eliminate the survey error of instru...