The performance of a capacitance-wire wave recorder
A capacitanoe-wire wave recorder circuit was used in conjunction with a p.t»f,e. wire probe to establish what errors are associated with using such a system for the measurement of small waves. In the experiments the probe was moved relative to the water, rather than vico versa and both photographic and electrical methods were employed to investigate the errors introduced by the meniscus, the wetting of the wire and the effects of wire thickness on the wave shapes. The electrical methods involved accurate recording of the probe movement by means of a linear potentiometer and a comparison of this movement with the wave form produced from the circuit measuring the chasige in capacitance of the probe caused by its movement in the water. The effects of increasing the operation! frequency of the recording circuit was also investigated.
Determination of the profiles of water waves
Tlw tvqmitor tjpc depth gayqe, dest'rihc~rl in //lis pq)pr, record the longitudinal proliles ancl cross-zectinns or undular faci/itntes n('cu/'n/i7 rei~~rdings (I/ t/7~ profi/rs o/ //ITPP surgc w;ivcs produced in ii prismoidnl channel. Thcsc waves r/itliPnsiona/ li'(1ter li'fmJLs propn,qo/er/ in prisnroir/n/ o/)en are produced when il sudden sustiiincd quontity or water is i~/iantir/s. The circuitry, priticip/e ant/ cnlihrotion of' //if, discharged into the ch;inncl. which contains an initial level gni/~~:~ nre out/ined, ii*it/i pnrtic.u/nr rqfirenc-r 10 //re of still water. The wave cross-scction is obtained by comnt1i-an~age.r <! f ' usinK srnnriurd indusrricd equipnretrr. piling the records from it number of probes on and offset
An operational method for estimating signal to noise ratios from data acquired with imaging spectrometers
A method, using the concept of local means and local standard deviations of small imaging blocks and using a box counting procedure, has been developed for unsupervised estimation of the average signal to noise ratios of images in which the noise is additive. The method has been applied to simulated images with Gaussian noise, to images acquired with the Airborne Visible Infrared Imaging Spectrometer and with the Geophysical and Environmental Research Imaging Spectrometer. The method is compared with other techniques for estimating signal to noise ratios from imaging data. It is believed that the method is generally applicable to images having many small homogeneous blocks. Because the method does not take into account interband effects, it is not appropriate to use the method to estimate signal to noise ratios from images having nonnegligible interband radiometric calibration errors at spatial scales less than or equal to the size of the small imaging blocks used in the noise estimation.