The oceans cover 71% of the earth's surface and cold regions occupy all latitudes north and south above about 65; if we add to the oceans and cold regions the mountainous parts of the world then, together, these environments account for a major part of the globe's surface and yet it is difficult to make measurements in any of them. Deserts and forest, which are either sparsely populated or inhospitable or both, further reduce those parts of the planet that have been measured adequately. This chapter investigates what the problems are and what can be done about them.

The oceans

Sensor compatibility

All the sensors covered under the topic of fresh water measurement (Chapter 10) can also be used in the sea. These include water level staff gauges, float and pressure water level sensors for tidal records (Fig. 13.1), all the water quality sensors (Warner 1972) and current meters. The same sensors that measure atmospheric variables over the land are equally suitable for their measurement over the sea, although there may be problems with how to expose them. Also applicable to use at sea without any modification are data loggers and telemetry systems. So rather than there being a completely different range of instruments for the ocean, it is more a matter of how the instruments are deployed that differs between land and sea applications. There are two main ocean platforms on which instruments are operated – ships and buoys (to which might be added small islands).