In-situ update of geoparameter databases

Abstract

Low- and mid-frequency system performance is often controlled and degraded by bottom interaction, especially in littoral regions. However, performance prediction models generally give unreliable estimates of bottom interaction. The poor estimates are most often due to the databases that drive the models rather than the model physics. In this study a new approach is taken in rapid environmental assessment for overcoming this problem. The concept is to use in-situ propagation data to extract geoacoustic information about the bottom which is then used to update the bottom database. An analogous approach has long been employed for the water column, where in-situ bathythermograph (BT) data are used to update historical databases. While techniques for screening/merging BT data are now under development, there are no comparable techniques for treating bottom geoacoustic data. In this paper, a high-level methodology for updating bottom databases with in-situ measurements is outlined. The methodology includes a series of critical questions sequenced to lead to decisions about the robustness of the historical databases in a given region and the potential for database update. Results of the methodology, i.e., the in-situ measurements, modeling, and resulting bottom geoparameter database updates, from several littoral areas, will be shown.