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The main technical indicators of positioning measurement
First, the main technical requirements of the satellite positioning engineering control network
The formula for calculating the baseline accuracy of each level of control network is as follows.
where: is the error in the baseline length (mm); a is a fixed error (mm); b is the proportional error coefficient (mm km); d is the average side length (km).
Second, the requirements for the layout of the control network of the satellite positioning project
1.The comprehensive design should be carried out according to the actual situation of the survey area, the accuracy requirements, the condition of the satellite, the type and number of receivers, and the existing measurement data in the survey area.
2.When the first-level network is deployed, it is advisable to jointly measure more than 2 high-level national control points or high-level control points of the local coordinate system; For the long side in the control network, it is advisable to form a geodetic quadrilateral or midpoint polygon.
3.The control network should be composed of independent observation edges to form one or more closed loops or attached routes; The number of sides forming a closed loop or an attached route in each level of control network should not be more than 6.
4.The total number of observations of independent baselines in each level of control network should not be less than 15 times.
5.The encryption network should be based on the needs of the project, and on the premise of meeting the accuracy requirements of this specification, a relatively flexible network layout method can be adopted.
6.For survey areas using GPS-RTK mapping, the distribution and location of reference stations should be taken into account in the layout of the control network.
3. Technical requirements for on-site selection
1.The point should be selected in a place where the soil is solid, stable and reliable, and at the same time it should be conducive to encryption and expansion, and each control point should have at least one viewing direction.
2.The point should be selected in a wide field of view, the height angle should be more than 15°, and there should be no obstacles; There should be no interference sources that strongly interfere with the reception of satellite signals or objects that strongly reflect satellite signals near the point.
3.Take advantage of legacy control points that meet requirements.
Note] With regard to the "height angle", the reference to the relevant specification is as follows:
Global Positioning System (GPS) Measurement Code GB T 18314-2009 Provisions on site selection (72.1): "The height angle of the obstacle in the field of view should not exceed 15°. "Provisions for observations (101.2): "Satellite cut-off altitude angle °....
Technical Specification for Reference Station Networks for Continuous Operation of Global Navigation Satellite Systems GB T 28588-2012 Provisions on Site Selection (72.1): "There should be satellite visibility conditions with an altitude angle of more than 10° horizon".
Code for Engineering Surveying GB 50026-2007 on Satellite Positioning Measurement (32.5): "The point should be selected in a wide field of view, the height angle should be more than 15 °, and there should be no obstacles. ”
Technical Specification for Satellite Positioning Urban Surveying CJJ T 73-2010 Regulations on the location of CORS stations (43.2): "The height angle in the field of view should not be greater than 10°. "On the construction of the urban GPS control network (53.11): "Satellite altitude angle 15°." ”
In summary, the "altitude angle" includes the height angle of obstacles in the field of view that affects satellite observation and the satellite cut-off altitude angle that affects the quality of observation (in satellite positioning measurements, the occlusion height angle set to shield the influence of occlusions [such as buildings, trees, etc.) and multipath effects, satellites below this angle of view airspace are not tracked).