共查询到20条相似文献，搜索用时 528 毫秒
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The impact of fires on environment can have adverse effects. To fully understand the synoptic behaviour of fire events, information on the spatial distributions and their pattern are highly important. In this study, we used 9-year (1997–2005) integrated fire count datasets derived from Along Track Scanning Radiometer (ATSR) satellite to geographically map the distribution of fire events in the Madhya Pradesh state, central India. We then used robust spatial metrics to test the spatial pattern of fire events against the hypothesis of complete spatial randomness (CSR). Specifically, we used the index of dispersion, Green's index, in addition to nearest neighbour statistic for testing CSR. Also, quantification of clustering is carried out using Ripley's K-function. To spatially map the fire events, we used Kernel density estimation that relies on bi-variate probability density functions. Results from using different spatial pattern metrics and nearest neighbour statistics suggested relatively high clustering of fire events in the study area. In addition, results from Ripley's K-function suggested the fire events to be clustered at a lag-distance of ～60 mile radius. By converting original fire ignition locations that are based on historical records to continuous density surfaces, the probability of fire events could be mapped effectively using kernel density estimation. As each fire event is the result of certain spatial process including biophysical and anthropogenic attributes, results from this study can provide useful information on fire management at a local district level. Also, the analysis presented in this study illustrates how spatial patterns in the point datasets can be quantified using different dispersion indices, clustering and density estimation techniques. 相似文献
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《地球空间信息科学学报》2006,9(2):102-102
Contributions are welcomed on one of the following subjects or in related areas:GIS;geodynamic;physical geo-surveying;GPS;geo-surveying;engineering surveying;RS;photogrammmetry;mappingapparatus;cartology;graphics. Paper submitted in the electronic text on… 相似文献
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《地球空间信息科学学报》2003,(4)
Contributions are welcomed on one of the following subjects or in related areas: GIS Geodynamic Physical geo-surveying GPS Geo-surveying Engineering surveying RS Photogrammmetry Mapping apparatus Cartology GraphicsPaper submitted in the electronic text on a diskette should be sent along with two printed copies. The main text should be preceded by the abstract of no more than 300 words,followed by key words. Full references should be listed in the order of the citations in the text under the 相似文献
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《地球空间信息科学学报》2007,10(2):90-90
Contributions are welcomed on one of the following subjects or in related areas:·GIS ·Geodynamic ·Physical 相似文献
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《地球空间信息科学学报》2007,10(1):3-3
Contributions are welcomed on one of the following subjects or in related areas: ·GIS ·Geodynamic ·Physical geo-surveying ·GPS ·Geo-surveying ·Engineering surveying ·RS ·Photogrammmetry ·Mapping apparatus ·Cartology ·Graphics Paper submitted sh 相似文献
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《地球空间信息科学学报》2006,9(4):243-243
Contributions are welcomed on one of thefollowing subjects or in related areas :·GIS·Geodynamic·Physical geo-surveying·GPS·Geo-surveying·Engineering surveying·RS·Photogrammmetry·Mapping apparatus·Cartology·GraphicsPaper submitted should be sent 相似文献
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PLL bandwidth and noise in 100 Hz GPS measurements 总被引：1，自引：0，他引：1
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Realtime kinematic precise point positioning (PPP) requires 1 Hz GPS satellite clock corrections. An efficient clock estimation
approach is presented. It applies a combined dual-thread algorithm consisting of an undifferenced (UD) and epoch-differenced
(ED) engine. The UD engine produces absolute clock values every 5 s, and the ED engine produces relative clock values between
neighboring epochs at 1-s interval. A final 1-Hz satellite clock can be generated by combining the UD absolute clock and ED
relative clock efficiently and accurately. Forty stations from a global tracking network are used to estimate the realtime
1-Hz clock with the proposed method. Both the efficiency and accuracy of the resultant clock corrections are validated. Efficiency
test shows that the UD processing thread requires an average time of 1.88 s on a 1-GHz CPU PC for one epoch of data, while
ED processing requires only 0.25 s. Accuracy validation test shows that the estimated 1-Hz clock agrees with IGS final clock
accurately. The RMS values of all the available GPS satellite clock bias are less than 0.2 ns (6 cm), and most of them are
less than 0.1 ns (3 cm). All the RMS values of Signal in Space Range Error (SISRE) are at centimeter level. Applying the accurate
and realtime clock to realtime PPP, an accuracy of 10 cm in the horizontal and 20 cm in the vertical is achieved after a short
period of initialization. 相似文献
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Commuters’ non-linear response to time distances 总被引：2，自引：0，他引：2
Established analyses of labour market commuting are based on random choice models and gravity type models. In these models generalised transport costs are formulated as exponential or log-linear distance dependent functions. This paper presents empirical observations, which imply that time distances influence the commuting behaviour in a non-linear way, such that the time sensitivity is much lower for very short and long distances, whereas intermediate distances display a high time sensitivity. This is explained in a model that is parameterised and estimated. The results are important for understanding and predicting commuter behaviour. It also helps to delineate space, as in classical traditions, into local, intra-regional and extra-regional space. 相似文献
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From Physical Space to Visual Image Space 总被引：1，自引：0，他引：1
YE Zetian LIN Hui LIU Xianlin YE Zetian Ph.D Chinese Academy of Surveying Mapping Beitaiping Road Haidian District Beijing China. 《地球空间信息科学学报》2003,6(2):42-47
1 IntroductionVirtualreality (VR)isaformofhuman computerinterface(HCI) [1 ] .Andnowitisamajorbranchofcomputing ,cover ingabroadspectrumofhumaninteractionwithcomputers .Itrangesfromtheinteractionwithrealenvironmentstothatwithsyntheticallygeneratedworlds[2 ] .Usually ,intheinterac tiveprocess ,oneofthemainoutputsofcomputerisgraphicsonthescreen .Thegraphicsarethemaininformationsourcereceivedbyhumanfromthecomputers .Tohuman ,visionisthemostimportantorgantogaininformationfromthenaturalworld .S… 相似文献
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J. M. Juan A. Aragon-Angel J. Sanz G. González-Casado A. Rovira-Garcia 《Journal of Geodesy》2017,91(11):1383-1397
Ionospheric scintillation produces strong disruptive effects on global navigation satellite system (GNSS) signals, ranging from degrading performances to rendering these signals useless for accurate navigation. The current paper presents a novel approach to detect scintillation on the GNSS signals based on its effect on the ionospheric-free combination of carrier phases, i.e. the standard combination of measurements used in precise point positioning (PPP). The method is implemented using actual data, thereby having both its feasibility and its usefulness assessed at the same time. The results identify the main effects of scintillation, which consist of an increased level of noise in the ionospheric-free combination of measurements and the introduction of cycle-slips into the signals. Also discussed is how mis-detected cycle-slips contaminate the rate of change of the total electron content index (ROTI) values, which is especially important for low-latitude receivers. By considering the effect of single jumps in the individual frequencies, the proposed method is able to isolate, over the combined signal, the frequency experiencing the cycle-slip. Moreover, because of the use of the ionospheric-free combination, the method captures the diffractive nature of the scintillation phenomena that, in the end, is the relevant effect on PPP. Finally, a new scintillation index is introduced that is associated with the degradation of the performance in navigation. 相似文献
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Isard’s contributions to spatial interaction modeling 总被引：2，自引：0，他引：2
This short review, surveys Isards role in promoting what has become known as spatial interaction modeling. Some contextual information on the milieu from which his work emerged is given, together with a selected number of works that are judged to have been influenced (directly and indirectly) by his work. It is suggested that this burgeoning field owes a lot to the foundations laid in the gravity model chapter of Methods. The review is supplemented by a rather extensive bibliography of additional works that are indicative of the breadth of the impact of this field. 相似文献
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ZHANG Shiyu ZHONG Min 《地球空间信息科学学报》2007,10(4):260-264
Using the model data for surface mass changes of the atmosphere, ocean, soil moisture and snow depth, the vertical crustal displacements of 25 ficual stations in China were calculated according to the ... 相似文献