Electronic Engineering and Physics

Rotating mirror systems based on the Miller Principle are a mainstay modality for ultra-high speed imaging within the range 1-25 million frames per second. Importantly, the true temporal accuracy of observations recorded in such cameras is sensitive to the framing rate that the system directly associates with each individual data acquisition. The purpose for the present investigation was to examine the validity of such system-reported frame rates in a widely used commercial system (a Cordin 550-62 model) by independently measuring the framing rate at the instant of triggering. Here, we found a small but significant difference between such measurements: the average discrepancy (over the entire spectrum of frame rates used) was found to be 0.66 ± 0.48%, with a maximum difference of 2.33%. The principal reason for this discrepancy was traced to nonoptimized sampling of the mirror rotation rate within the system protocol. This paper thus serves three purposes: (i) we highlight a straightforward diagnostic approach to facilitate scrutiny of rotating-mirror system integrity; (ii) we raise awareness of the intrinsic errors associated with data previously acquired with this particular system and model; and (iii), we recommend that future control routines address the sampling issue by implementing realtime measurement at the instant of triggering.

We investigated the occurrence of small but significant inaccuracies in the temporal integrity of a commercial high-speed [rotating mirror] imaging system (a Cordin 550-62 camera). Utilizing a relatively straightforward hardware addition, independent measurements of the actual frame rate at the point of camera triggering were conducted, and then compared to the Cordin system's self-reported frame rate values for each recording. The present data thus represents a follow-up to our earlier preliminary report on this instrument's performance, where we initially discovered that disparities between the true and reported values could arise 1 . Interestingly, the data trends observed in the present report suggest a disparity, the nature of which is consistent with the Cordin camera reporting a frame rate that arises a short time before the trigger event, i.e. that the system's sampling algorithm senses the frame rate with a finite pre-trigger implemented, which runs counter to the procedure suggested by the manufacturer. As well as presenting the context, and supporting evidence for our own conclusions, we also developed an approach to reduce the error in the reported values by a factor of 7, from an average of 0.78% +/-0.04% to 0.11% +/-0.08% over the present data set.

The UAE Space Reconnaissance Center (SRC) is accounted as a major national and regional source of up-to-date geospatial data, with direct reception of IKONOS, IRS and KOMPSAT satellite imagery as well as access to some other satellite and aerial imagery resources; an activity which covers the whole Middle East region. The main concern in monitoring the environment of UAE and surrounding countries is the desertification process, the monitoring of which requires careful watching of the sand movement and some other relevant features. This paper through lights on the roll of various types of satellite images in monitoring desertification, by utilization of IKONOS, IRS Pan and Landsat TM images covering part of Liwa and Alain areas, representing the two main dune regimes; Liwa and Manadir, which constitutes the northeastern edge of the Empty Quarter sand sea. The availability of high resolution images makes it possible to detect the yearly or even seasonal sand movements, being controlled by the prevailing wind conditions and distance from the main sand source. The results clarify that movements of up to 25m was encountered at some small sand dunes and about 10m for larger sand dunes, towards the SSE and SSW in Liwa area. In Rimah area a movement of up to 30m was noticed at a small sand dune towards the ENE and about 12m shift in the hinge of a larger sand dune towards the NW. Temporary or permanent? movement of thin sand sheets can reach 100's of meters, was easily detected on Landsat images; ~ 25km NE of Alain city. The 5m panchromatic images, on the other hand, helped in tracing sand movements measured in few 10's of meters, and interpretability of such images was enhanced by merging them with Landsat imagery. In addition to providing accurate images and image maps to the concern units in the UAE Armed Forces, the SRC is enhancing mutual cooperation with the civilian sector, where satellite images can benefit in applications such as monitoring of environment and agriculture activity, exploration of natural resources, urban planning and mapping.

Success in imagery understanding and interpretation is greatly dependant on our knowledge of the earth surface geography and geomorphology as well as all kinds of man-made features and activities, which has changed the nature either positively or negatively in considerable areas on Earth. It is quite important to know about the components of the earth surface and physico-chemical factors, which has controlled the development of the surface and configurations of image elements including soil/rocks, vegetation and urban activity. To achieve a reasonable understanding of an image or map, one should start with knowing or revising relevant scientific phenomena's of chemistry, physics, geology/ geomorphology / geography, basic mathematics and statistics, maps and how to use computers. This introduction to basic scientific concepts will be followed by an introduction to map reading & projections, remote sensing, image processing, principles of imagery interpretation and an overview of imagery applications with emphasis on the specific field of application of each user. Practically oriented education of imagery users is very essential for better utilization of images and enable profitable investments in remote sensing technology applications.