Searching for mines is a time consuming and relatively hazardous operation that is heavily weighted in the favour of the miner if the defending force has not prepared the battlespace beforehand. In simple terms, if the environment in which the enemy is likely to launch a mine attack is known, and the defending forces are familiar with the bottom conditions then the enemy mines are more easily localised and subsequently eliminated. The method of achieving this familiarity with the environment is known by a number of terms but most commonly used is Q-Route Survey or just Route Survey. From the introduction of minehunting sonars in the 60's Navies have been interested in developing databases of the minelike bottom objects with theareas that they may operate the battlespace. These efforts have been plagued by a number of fundemental equipment and philosophical problems. Apart from the difficulties faced with precisely positioning the mine-like objects on the bottom the general navigation and plotting accuracies of the vessels was very poor. This contributed to so great a lack of confidence by succeeding vessel commanders about the validity of the database of bottom objects that the databases invariably failed. The failure of a MCM database is catastrophic for the defenders, after an attack, as it means that all bottom objects would need to be reinvestigated to prove they were not mines.
Even in moderately cluttered bottom conditions such as in harbours or approaches where there may be 300-400 objects per kilometer of 600m wide channel the investigation and discrimination of all these objects would involve a speed of advance for the dedicated minehunting vessel of less than one knot!
There had to be a more efficient way. In the early 80's the sidescan sonar systems were being supplemented by the fabulously powerful 286 computers. This allowed the sonar signal to be digitised, displayed on a screen and recorded to magnetic medium then stored.
This opened the way for the sidescan sonar to be used to define the battlespace. The first generation systems have done a quite good job of achieving the aims when employed by efficient, well trained crews. However, this has been the exception rather than the rule, and the quality of the data so far collected probably less than optimum. In addition the storage of this early data was invariably based on the basis of positioning all the "minelike contacts" geographically and a consequent lack of care with storage of the original sonar data.
The sidescan sonar tools used by navies for the task of route survey are typically about 10 years old and comprise a hybrid Analogue sonar with digital recording and display of the data. A few Navies have developed first generation MCM GIS systems and sidescan sonar digital mosaic production facilities.
Over the past few years the Analogue sonars have become obsolescent with the introduction of fully digital sonars offering the advantage of better performance over long cable lengths and better control over data quality. Also, during the same period there has been a plethora of GIS packages come into the marketplace at very small investment costs for the underlying software.
These changes offer the opportunity to maximise the effectiveness of battlespace preparations at a very low investment cost. The key to success in this type of operation is the use of effective and proven techniques for the data collection and management with good quality control. The storage and review, including processing and reporting, of the collected data centrally using a Geographic Information System (GIS) linked to an Image Processing System (IPS) is the final step in the process.
Route survey is normally divided into a number of discrete phases. These are:
Route or area selection, where the battlespace is defined by selecting areas most favourable to searching. Hard bottom, smallest number of minelike objects, poor burial...