GIS Files 2: Geographical data

2.2: Surveying and remote sensing (4)

Pen computers

Whatever the method used for measuring the shape and location objects, modern surveyors rarely record information by hand drawing detail on a master survey document (see surveyor on left of picture with large board). Instead, they use hand-held pen computers equipped with flat, touch-sensitive screens (see surveyor on right of picture). These computers allow the surveyor to draw and click directly onto the screen to update map information while out in the field. Importantly, this means that new map features can be inputted directly as digital data.

Ordnance Survey surveyors use such a system known as PRISM – standing for Portable Revision and Integrated Survey Module. It enables the coordinates of new objects to be added in reference to the existing features. Features that have been demolished can be deleted while text names can be added using a freehand character recognition facility. So even if the geographical objects have been measured with the most rudimentary and time-honoured techniques – a tape measure for instance – the information will still be recorded in electronic form out in the field.

Now we have looked at obtaining geospatial data, we need to look at how we relate it to the world or to other datasets in section 2.3 – Position matters.

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