On the Detection of Drifting Sea Mines using Above- and Underwater Sensors

Small drifting objects can be a big threat to surface ships, especially when the objects are explosion hazards like sea mines that have become detached from their moorings. Timely detection of such objects is crucial in order to be able to perform adequate evasive manoeuvres. However, the vertical position of drifting mines is a serious challenge for detection with both above- and underwater sensors, as the surface objects are usually only partly above and under water, and surface effects such as wave occlusion and scattering apply to both sides. On the other hand, above- and underwater sensors may complement each other as poor detection from above may imply good detection from below, and vice versa. This paper reports on sea trial results for the detection of drifting sea mines using a prototype surface-scanning infrared lidar from above and operational mine-hunting sonar systems from below. For the sonar experiments, both a forwardlooking hull-mounted sonar and an upward-looking self-propelled variable-depth sonar have been applied. Spherical exercise mines were used as mine-like objects, painted in a realistic warshot colour for the optical test

Task-specific sensor settings for electro-optical systems in a marine environment

Present-day naval operations take place in coastal environments as well as narrow straits all over the world. Coastal environments around the world are exhibiting a number of threats to naval forces. In particular, a large number of asymmetric threats can be present in environments with cluttered backgrounds as well as rapidly varying atmospheric conditions. The automatic detection of small targets by electro-optical systems may be hampered by small surface structure variations at the surface and near the horizon. In current electro-optical sensor systems processing of imagery is seldom task-specific. Using task-specific settings of sensors, processing and fusion, can improve the performance of electro-optical systems dramatically. This paper discusses the effect of dynamic sensor settings as function of specific tasks and environmental parameters and how these can play a role in the management of sensors in a naval application. In addition, a series of experiments with different targets are presented to demonstrate the benefit of sensor management. Some sensor management approaches for application in infrared systems are discussed. © 2010 Copyright SPIE - The International Society for Optical Engineering

Worldwide distribution of soil dielectric and thermal properties

Ground penetrating radar and thermal sensors hold much promise for the detection of non-metallic land mines. In previous work we have shown that the performance of ground penetrating radar strongly depends on field soil conditions such as texture, water content, and soil-water salinity since these soil parameters determine the dielectric soil properties. From soil physics and field measurements we know that the performance of thermal sensors also strongly depends on soil texture and water content. There is it critical that field soil conditions are taken into account when radar and thermal sensors are employed. The objectives of this contribution are (i) to make an inventory of readily available soil data bases world wide and (ii) to investigate how the information contained in these data bases can be used for derivation of soil dielectric and thermal properties relevant for operation of land mine sensors

Prediction of soil effects on GPR signatures

In previous work we have shown that GPR signatures are affected by soil texture and soil water content. In this contribution we will use a three dimensional electromagnetic model and a hydrological soil model to explore in more detail the relationships between GPR signatures, soil physical conditions and GPR detection performance. First, we will use the HYDRUS2D hydrological model to calculate a soil water content distribution around a land-mine. This model has been verified against measured soil water distributions in previous work. Next, we will use existing pedotransfer functions (e.g. Topp, Peplinski, Dobson, Ulaby) to convert the predicted soil water contents around the land-mines as well as known soil textures and bulk densities into soil parameters relevant to the electromagnetic behaviour of the soil medium. This will enable a mapping between the hydrological model and the electromagnetic GPR model. Using existing and new laboratory and field measurements from the land-mine test facilities at TNO-FEL we will make a first attempt to verify our modelling approach for the prediction of GPR signatures in field soils. Finally a detection algorithm is used to evaluate the GPR detection performance with respect to changing environmental soil conditions

Effect of soil moisture on landmine detection using ground penetrating radar

Soil surface temperatures not only exhibit daily and annual cycles but also are very variable in space and time. Without knowledge of the spatial and temporal variability of soil surface temperatures, it will be difficult to determine what times of day are most suitable for mine detection using Thermal Infra Red (TIR) technology. In this study we monitor the spatial and temporal variability of soil surface temperatures under a range of soil texture and soil moisture conditions on undisturbed plots and plots with a buried anti-tank mine in arid New Mexico. We also analyzed soil surface temperature measurements taken at the test facility for land mine detection systems at the TNO Physics and Electronics Laboratory under the temperate climatic conditions of The Netherlands. The measurements in both areas show a cyclic behavior of the thermal signatures of the mines during the day and night that can be predicted by physics of the mine-soil-sensor system. However, unexpected behavior of the thermal signatures in a silt loam demonstrated that prediction of thermal signatures of buried mines is not straightforward

Impact of soil water content on landmine detection using radar and thermal infared sensors

Land mines are a major problem in many areas of the world. In spite of the fact that many different types of land mines sensors have been developed, the detection of non-metallic land mines remains very difficult. Most landmine detection sensors are affected by soil properties such as water content, temperature, electrical conductivity and dielectric constant. The most important of these is water content since it directly influences the three other properties. In this study, the ground penetrating radar and thermal IR sensors were used to identify non-metallic landmines in different soil and water content condition