Academic literature on the topic 'Coordinates precise'

Atomic coordinates in the Worldwide Protein Data Bank (wwPDB) are generally reported to greater precision than the experimental structure determinations have actually achieved. By using information theory and data compression to study the compressibility of protein atomic coordinates, it is possible to quantify the amount of randomness in the coordinate data and thereby to determine the realistic precision of the reported coordinates. On average, the value of each Cαcoordinate in a set of selected protein structures solved at a variety of resolutions is good to about 0.1 Å.

According to problems in manufacturing and measuring process of cycloidal gear used in RV reducer, the profile coordinates of cycloidal gear captured by three coordinates measuring instrument Surveying and mapping do not coincide with the designed tooth profile coordinates in theory, it is difficult to precisely capture the addendum and dedendum of each cycloidal gear teeth, furthermore, the captured addendum and dedendum do not coincide with the actual tooth items. For these problems, this paper introduced a method can accurately calculating the manufacturing error of cycloidal gear.Based on the captured coordinate points of cycloidal gear tooth profile, firstly, find out 39 approximate addendums by calculating and comparing the radial radius of all points, divide the whole scanning points into 39 profile points groups by the 39 approximate addendums, with each group include a whole single tooth profile. Then, in each profile points group, interpolate the spline and precisely calculate the addendums and dedendums by fitting and recalculating radial radius.Set up the coordinate system of surveying and mapping profile by the 39 addendums. calibrate the coordinate system of surveying and mapping profile with the new coordinate system through coordinate transformation, calculate the radial runout error at top and root of tooth profile, pitch error, adjacent pitch error and accumulated pitch error as well as other manufacturing errors of the cycloidial gear at last.Through experiment, this process solve the problem in measuring process of cycloidal gear that the captured point by three coordinates measuring instrument could not be directly used for calculating the errors items.

Positioning by navigation satellites is carried out in three-dimensional geocentric cartesian coordinates, X, Y, Z. This applies to both the Transit System, which has now been in operation for over 20 years, and the Global Positioning System which is being tested and is due to become operational in 1988. Traditionally, the cartographer, the seafaring navigator and the geodetic surveyor have always expressed their coordinates in geographical terms, i.e. latitude and longtitude, whereas the land-based civil engineer, surveyor and the foot (or mechanized) soldier preferred theirs in terms of projection grid coordinates, i.e. northings and eastings. Transformations between these various coordinate systems involve not only complex algebraical formulae, but also some very specific numerical parameters, which are appropriate for different countries and continents and which can only be determined empirically. Moreover, the treatment and interpretation of the different systems of coordinates may frequently involve some very basic conceptual misunderstandings. These include confusing astronomical latitudes and longitudes with their geodetic counterparts, treating projection northings and eastings as if they were ordinary plane coordinates and, in the case of positions derived from observations to Transit satellites, applying the wrong set of transformation parameters or using inappropriate geoidal contour maps. These are typical examples of the sort of common misconceptions leading to gross errors and affecting even the most precisely determined absolute positions. Relative positioning, with respect to another point or a framework of points with known coordinates, eliminates some of the worst effects of these systematic sources of error, and is commonly used in geodetic surveying. However, instantaneous navigation (especially by using satellites) is most likely to be based on continuously determined, successive absolute positions and will therefore inevitably be affected by reference system errors. This is particularly important in the case of land navigation where much higher accuracies will be expected. This is a review paper with definitions and descriptions of the various types of coordinate systems and their mutual relationships. Geographical and geodetic coordinates are discussed in section 2, and projection grid coordinates in section 3. This is followed, in section 5, by a description of three-dimensional cartesian coordinates used in conjunction with navigation satellites. A brief discussion on current and proposed navigation satellite systems is given in section 6 and the paper is concluded in section 7.

I analyse the role of simultaneity in relativistic rotation by building incrementally on its role in simpler scenarios. Historically, rotation has been analysed in 1 + 1 dimensions; but my stance is that a 2 + 1 -dimensional treatment is necessary. This treatment requires a discussion of what constitutes a frame, how coordinate choices differ from frame choices, and how poor coordinates can be misleading. I determine how precisely we are able to define a meaningful time coordinate on a gravity-free rotating Earth, and discuss complications due to gravity on our real Earth. I end with a critique of several statements made in relativistic precision-timing literature, that I maintain contradict the tenets of relativity. Those statements tend to be made in the context of satellite-based navigation; but they are independent of that technology, and hence are not validated by its success. I suggest that if relativistic precision-timing adheres to such analyses, our civilian timing is likely to suffer in the near future as clocks become ever more precise.

In support of discussions regarding the use of coordinates in cadastral surveying, we provide an overview of federal government activities in geodesy and review issues related to geodetic coordinates and the compatibility of data, in particular spatial and temporal consistency. The Canadian Geodetic Survey is the Government of Canada’s lead agency in geodesy, and is the principal agency responsible for establishing the reference frames or datums used in determining geodetic coordinates in Canada. A summary of issues relating to epoch propagation addresses concerns specific to the use of precise geodetic coordinate systems today.

To realize the target of having a precise feature size measurement of multihole sheet metal part, this paper based on HALCON, first calibrates the camera with HALCON's calibration assistant. After acquiring the image of the multihole sheet metal part, the image coordinates of the center of fitting ellipse and the length of the long and short half shaft (pixel unit) can be gotten by proceeding a series of operations like thresholding, subpixel-precise contour extraction, fitting ellipses and so on. At last, the point coordinates in image are transformed into the plane Z=0 of the world coordinate system through translation and rotation, and the value of each feature size of the sheet metal part can be calculated.

In cableway tube of cable-stayed bridge construction, the precise location and loft cableway be installation accuracy an important part of construction. How fast, accurate the cableway tube precision positioning is the key to the construction of cable-stayed bridge tower column. In this paper, the actual project as an example, Creatively put forward based on the space linear equation and the method of measuring the elevation of Resemble-leveling method, Coordinates measured coordinates with the theoretical calculation coordinates difference. Through the cableway tube naturalization adjust, coordinate difference is zero, To determine the location of the installation of cableway tube. Thereby cableway tube positioning precision and speed of construction to improve.

The article notes that the replacement of the English name «Precise Point Positioning» (PPP) in Russian-language sources is possible using the term «accurate differential positioning» (TDP) technique. The author proposes to use both terms. This article contains information about the practical implementation of the PPP in the on-line service. The author has analyzed the research on the accuracy of PPP foreign and domestic experts and scholars. The author analyzed the data about the convergence time for PPP solutions. These data belong to another Russian scientist. The results of evaluating the accuracy of the PPP of different scientists led to the next. The author of this article gave the mean square errors topocentric coordinates of the geodetic points. The coordinates of the points must be obtained by dual-frequency GPS-measurements for a period of 24 hours with the help of PPP. The author proposed a formula for the calculation of the mean square error of the spatial position of geodetic point, if its position is obtained in the processing of dual-frequency GPS-observations of less than 24 hours. The article written conclusions about the features, defects and PPP development.

Three-dimensional joint models are important tools for investigating mechanisms related to normal and pathological joints. Often these models necessitate accurate three-dimensional joint surface geometric data so that reliable model results can be obtained; however, in models based on small joints, this is often problematic due to limitations of the present techniques. These limitations include insufficient measurement precision, the requirement of contact for the measurement process, and lack of entire joint description. This study presents a new non-contact method for precise determination of entire joint surfaces using multistation digital photogrammetry (MDPG) and is demonstrated by determining the cartilage and subchondral bone surfaces of the cat patellofemoral (PF) joint. The digital camera–lens setup was precisely calibrated using 16 photographs arranged to achieve highly convergent geometry to estimate interior and distortion parameters of the camera–lens setup. Subsequently, six photographs of each joint surface were then acquired for surface measurement. The digital images were directly imported to a computer and newly introduced semi-automatic computer algorithms were used to precisely determine the image coordinates. Finally, a rigorous mathematical procedure named the bundle adjustment was used to determine the three-dimensional coordinates of the joint surfaces and to estimate the precision of the coordinates. These estimations were validated by comparing the MDPG measurements of a cylinder and plane to an analytical model. The joint surfaces were successfully measured using the MDPG method with mean precision estimates in the least favorable coordinate direction being 10.3 μm for subchondral bone and 17.9 μm for cartilage. The difference in measurement precision for bone and cartilage primarily reflects differences in the translucent properties of the surfaces.