GF-14 satellite is a new generation of sub-meter stereo surveying and mapping satellite in China,carrying dual-line array stereo mapping cameras to achieve 1∶10000 scale topographic mapping without Ground Control Poi...GF-14 satellite is a new generation of sub-meter stereo surveying and mapping satellite in China,carrying dual-line array stereo mapping cameras to achieve 1∶10000 scale topographic mapping without Ground Control Points(GCPs).In fact,space-based high-precision mapping without GCPs is a challenging task that depends on the close cooperation of several payloads and links,of which on-orbit geometric calibration is one of the most critical links.In this paper,the on-orbit geometric calibration of the dual-line array cameras of GF-14 satellite was performed using the control points collected in the high-precision digital calibration field,and the calibration parameters of the dual-line array cameras were solved as a whole by alternate iterations of forward and backward intersection.On this basis,the location accuracy of the stereo images using the calibration parameters was preliminarily evaluated by using several test fields around the world.The evaluation result shows that the direct forward intersection accuracy of GF-14 satellite images without GCPs after on-orbit geometric calibration reaches 2.34 meters(RMS)in plane and 1.97 meters(RMS)in elevation.展开更多
It′s generally believed that the appropriate stimuli for sound field tests are warble tones and narrow band noise, while pure tone can only be a signal used in the free field and earphone listening conditions. In thi...It′s generally believed that the appropriate stimuli for sound field tests are warble tones and narrow band noise, while pure tone can only be a signal used in the free field and earphone listening conditions. In this study, we take a measurement of sound pressure distribution, sound field variability, and effects of frequency shifting on sound pressure levels (SPLs) at reference points of pure tone in an audiometric test room. It was found that the pure tone SPLs were also distributed uniformly at some sound field areas although it was not so well as warble tones. This indicated that the test results were relatively stable to head movement and/or frequency shifting in those regions, which was confirmed by the clinical measurements on 20 subjects with severe sensorineural hearing loss. Our study concluded that pure tones could also be suitable for sound field audiometry if subjects were seated at a proper location on the basis of the sound field calibrations.展开更多
In crosswell observation of electromagnetic tomography, now there is no feasible way to calibrate the in situ radiation constant, while the effect of induced wave field always exists in observational data. Therefor...In crosswell observation of electromagnetic tomography, now there is no feasible way to calibrate the in situ radiation constant, while the effect of induced wave field always exists in observational data. Therefore the absorption coefficient obtained by a common used image reconstruction method is only a relative value. The consistency of tomograms in linked profiles inevitably is affected seriously. An improved equation involving the effect of induced wave field and an alternative tracing method to calculate the in situ radiation constant is proposed in the present paper. Based on the results from a series of parameter calibration performed in water and the experiments with rock samples, the standard meter readings of borehole electromagnetic systems, types EW—1 and JWQ—3, are accurately defined here. Additionally, frequency reduction and boundary smoothing of linked profiles are discussed. In research on groundwater prospecting in Tanggongta, Inner Mongolia, we used the above mentioned method and obtained the tomograms of linked profiles with good consistency. The absorption coefficient in the tomogram are not only reasonable and reliable, but also coincided with the result from rock parameter measurement. The depth, extension direction and water bearing structure of two aquifers were well detected. This result correctly guides hydrologic drilling there.展开更多
基金Independent Project of State Key Laboratory of Geo-information Engineering(SKLGIE2022-ZZ-01)The Youth Science Innovation Fund(No.2023-01)。
文摘GF-14 satellite is a new generation of sub-meter stereo surveying and mapping satellite in China,carrying dual-line array stereo mapping cameras to achieve 1∶10000 scale topographic mapping without Ground Control Points(GCPs).In fact,space-based high-precision mapping without GCPs is a challenging task that depends on the close cooperation of several payloads and links,of which on-orbit geometric calibration is one of the most critical links.In this paper,the on-orbit geometric calibration of the dual-line array cameras of GF-14 satellite was performed using the control points collected in the high-precision digital calibration field,and the calibration parameters of the dual-line array cameras were solved as a whole by alternate iterations of forward and backward intersection.On this basis,the location accuracy of the stereo images using the calibration parameters was preliminarily evaluated by using several test fields around the world.The evaluation result shows that the direct forward intersection accuracy of GF-14 satellite images without GCPs after on-orbit geometric calibration reaches 2.34 meters(RMS)in plane and 1.97 meters(RMS)in elevation.
文摘It′s generally believed that the appropriate stimuli for sound field tests are warble tones and narrow band noise, while pure tone can only be a signal used in the free field and earphone listening conditions. In this study, we take a measurement of sound pressure distribution, sound field variability, and effects of frequency shifting on sound pressure levels (SPLs) at reference points of pure tone in an audiometric test room. It was found that the pure tone SPLs were also distributed uniformly at some sound field areas although it was not so well as warble tones. This indicated that the test results were relatively stable to head movement and/or frequency shifting in those regions, which was confirmed by the clinical measurements on 20 subjects with severe sensorineural hearing loss. Our study concluded that pure tones could also be suitable for sound field audiometry if subjects were seated at a proper location on the basis of the sound field calibrations.
文摘In crosswell observation of electromagnetic tomography, now there is no feasible way to calibrate the in situ radiation constant, while the effect of induced wave field always exists in observational data. Therefore the absorption coefficient obtained by a common used image reconstruction method is only a relative value. The consistency of tomograms in linked profiles inevitably is affected seriously. An improved equation involving the effect of induced wave field and an alternative tracing method to calculate the in situ radiation constant is proposed in the present paper. Based on the results from a series of parameter calibration performed in water and the experiments with rock samples, the standard meter readings of borehole electromagnetic systems, types EW—1 and JWQ—3, are accurately defined here. Additionally, frequency reduction and boundary smoothing of linked profiles are discussed. In research on groundwater prospecting in Tanggongta, Inner Mongolia, we used the above mentioned method and obtained the tomograms of linked profiles with good consistency. The absorption coefficient in the tomogram are not only reasonable and reliable, but also coincided with the result from rock parameter measurement. The depth, extension direction and water bearing structure of two aquifers were well detected. This result correctly guides hydrologic drilling there.
