1992 Vol. 17, No. 4
This paper gives the method of Helmert-Weight Factor of Variance Component Estimation, and then, the formula, the condition that can be estimated are given too. In the view of mathematical analysis, it is possible that the negative variance exists and why it exists. In the same time, comparing the method of Helmert-WF with that of Helmert, the defect of Helmert method is pointed by a special mode. Given examples show the conclusions are correct.
A low-cost and quick mappping technique on near-synchronous, small-scale and macrocosm is developed using digital NOAA/AVHRR data. The satellite photomap of China is made from imagery and symbol base maps according to cartographic techniques strictly. This is the first small-scale, integrated and standard false-color satellite photomap of China, especially if contains the whole South China Sea that is rather difficult to use other remotely sensed data such as Landsat or SPOT. The false color composite of AVHRR thermal infrared, near infrared and visible red channels is used to provide rich information and colourful tones. The data processing includes map projection transformation, image enhancement both on contrast stretch and image sharpening, color balance adjustment, cloud removing, separated processing of land and sea, modification of image seasonal aspect with vegetation index image and mosaic. Geographic elements, map symbols and letterings were selected and desinged carefully considering the finial load of the photomap content and vision effect. This false-color satellite photomap of China has been selected by the 17th ISPRS Congress as a poster achievement.
Viewing from a new angle, the authors of this paper put forward a CAC-based general multi-focal projection with much flexibility and universality. In addition to an introduction to the basic principle, the paper offers a few projection formulas which satisfy the complex demands of users, and some corresponding examples shown by sketches as well. The authors hold that most existing variable-scale projections and multi-focal projections can be generalized or generated by employing the proposed method, and that wider applications can also be made.
Based on criteria of Sensitivity and reliability a optimization design of the monitoring network to monitor horizontal displacements of the dam of Baogang Waterleading reservoir is in this paper carried out. Some problems in planning of this network is from the point of view of netquality investigated. From 25 observation epochs 13 epochs are selected and proceeded with the calculation of horizontal displacements and geometrical analysis. It is to point out that the importance selecting datum of monitoring network correctly and the method how to make the deformation forecast with more epoch observations. Finally the physical interpretation for Dam Deformation is also brief discussed. All of those have practical significance for the same monitoring project.
The fast computation of terrain correction in a large area is significant for modern geodetic practice, especially in rough mountain areas. In this paper one FFT method of terrain correction computation is seleted for this kind of areas through theoretic analysing and a mathmatic model for practical application is proposed. The computation experiment shows that the results caculated by this model are as accurate as those caculated by bicubie spline prism method in extremely rough mountain areas.
According to the theory of expert system and the principle of complex classification of grass land, a prototype of grass resource investigation expert system by remote sensing is developped. The system——GRIES (Grass Resource Investigation Expert System) has the same structure as a usual expert system. The authors design an model of uncertain inference to solve the uncertainty and uncomplety of the knowledge and the data. With the experiments of some examples, a combination of the technique of expert system and remote sensing can make full use of various auxiliary-information to overcome the disadvantages existing in maximum-likelyhood classification. At the meanwhile, GRIES can take the advantage of the knowledge and experiences of the experts to improve the accuracy of classification. After some changes of the knowledge-base and the data-base, GRIES can also be used in the areas such as vegetation field analysis, landuse investigation, predication of growth of crops and other kinds of resources investigation by remote sensing.
In an experiment a metric camera was used for taking pictures of profilling generated by a reconstructed laser theodolite. Points of profilling of a dam's tunnel on the river Yangzi were obtained with accuracy of ±3mm after subseguent photogrammetric process.
The area symbol's automatic plotting plays an important role in the thematic mapping systems. Hatching method is often used in plotting area symbols. However, because of its simple graphic construction, when it is used to plot a complicated map, the effects of classification and contrast are not very optimal. So, the authors put forward a new method——the pattern-hatching method in this paper. This new method is based on the hatching method, using different kinds of hatching lines, break hatching lines to form many new patterns and realize the automatic output of the area symbols. The design of this pattern-hatching method is very simple and practical. Not only could it be in interactive output, but also could automatically form different kinds of patterns. On the one hand, it has the advantages of the hatching method, on the other hand, it also has the advantages of itselfautomatically forming the various area symbols. With the pattern-hatching method, the authors plotted successffully the thematic maps of the LPMCGIS-the Lesso Plateau Microcomputer Geographical Information System, and gain a very optimal effect.
From the view of memory allocation, the paper describes the designning theory and relization of WC-SunSir (Chinese System Card of Microcomputer Netware). Based on the minimum memory of system software and word libray, the card solves memory lacking of application software on netware, what's more, it also can be served as a word processing system. The card can distinguish the video type automatically and run displaying programs. Using compressing technology and smothly enlarging technology in word processing system, it provides the users with different word input ways. It accomplishes the task of netware connecting better in 3+Com and NOVELL and gains the experts, appreciation.
This paper describes the design of telephone timer and taximeter based on the single-chip microcomputer, it points out the idea of recognizing dial pulse and dual-tone multiple frequency division dialing. Meanuhile, it fully uses the sources of single-chip microcomputer and notes to bring software into full play. Obviously, it features as follows: proper structural, easy using and high cost perfermance.
The paper analyses the curved deformation of precision guide as it bears the added load in remaking a simulate aerophotogrammetric instrument to an analytic one, and gives the method using unloading technology to overcome guide curved deformation, and presents the principle, structure and design method of unloading device.
Rayleigh-Sommerfeld theory of planar screen diffraction is extended to spherical cases, related diffraction formula and its far field approximant within the spherical coordinate system are produced. On this basis, the statistic characters of far field speckle intensity are studied, the far field speckle intensity is theoreticaly verified to be spatial stable stachastic process. Lateral and longitudinal correlation radii are deduced, which are different from planar cases.
In this paper, the feature of the propagation and transformation of Gaussian beam through an optical system is analysed detailedly on the bassis of the ABCD law of Gaussian beam in terms of Gaussian Brackets. Then, a variety of typically optical systems or some special eases are discussed deeply. Finally, some important conclusions, which are practically applied, are obtained.