A graphometer is a surveying instrument which consists of a semi-circle which has been divided into degrees and minutes, and has a pair of sight veins at either end as well as a movable alidade with a pair of sights at either end. It was used to calculate distances by means of triangulation and to determine positions of specific points on land or at sea .Many graphometers, although not all of them, have a built in magnetic compass.
It is a fairly simple instrument to use, however the results achieved using this instrument are not as accurate as results obtained using modern equipment. These instruments do not have the same high levels of durability that modern equipment can display; this is due to the type of material these instruments are usually made from, namely brass or wood. Although the graphometer itself is light weight and compact, the tripod stand which it sits on is heavier and more difficult to transport. Today these instruments are no longer in use or production, they are considered to be historical artifacts which are purchased for large amounts of money by collectors depending on their age, condition and rarity.
(Science Museum, 2003)
(Science and society picture library, 2008)
New equipment: Field computer: Field computers are handheld devices, which are light weight and compact. One of the disadvantages of using a device like this is that it is battery operated which means that the battery will need to be charged regularly and a spare battery will need to be carried around .Although these devices are fairly easy to use, a person who is not comfortable using a computer may find that using a device like this can be complicated. The accuracy of these devices varies depending on the specific make and model of field computer that is being used .Hand held devices designed for land surveying purposes can produce results which are accurate to within cm.