Compass survey 
When the place to be surveyed is large, chain and compass surveying is preferable. A compass is used to degree the magnetic bearing of a line. There are 
forms of compass which is probably typically used. 1. The prismatic compass and 2. The surveyors` compass. 
1. The prismatic compass: It is round in form and its diameter varies from eighty five mm to 110 mm. A pivot is supplied on the centre of the field. It includes a magnetic needle. The needle is set up to an aluminum ring that`s graduated to 1/2. A mild spring break is set up to the interior of the bottom to damp the oscillations of the needle and convey it to relaxation earlier than taking a reading. 
A reflecting prism lets in reading of the angles and is covered from moisture and dirt and so on via a prism cap. The prism base and vertical statistics are made convex which magnifies the readings. the item vane is located diametrically contrary to the prism. It is hinged to the difficulty of the field and includes a horse hair. A come to be aware about reflecting replicate is supplied on the difficulty of the item vane to allow bearing of very excessive or low gadgets to be taken. A metallic cowl is supplied to surround the compass and the item vane. 
2. Surveyor`s compass: Surveyor`s compass resembles the prismatic compass however with a mild difference. The graduated card is set up to the field and North ninety at south and at East and West interchanged 
1 Methods of the usage of prismatic compass 
The compass is commonly set up on a mild tripod which includes a vertical spindle in a ball and socket joint which the field is screwed. By manner of this arrangement, the tool may be speedy leveled and furthermore grew to emerge as round in a horizontal aircraft and clamped in any position. Centering: The compass want to be focused over the station wherein the bearing is to be taken. This is finished via losing a small piece of stone from the centre of the compass without a doubt so it falls at the pinnacle of the peg marking the station (or via the usage of plumb bob) and via adjusting the legs of the tripod. 
Leveling : The compass want to then be leveled via eye, via manner of technique of the usage of a ball and socket joint without a doubt so the graduated ring also can swing pretty freely. It want to be clamped on the equal time as leveled. Observing Bearing: A ranging rod is saved at the subsequent station. 
The compass is grew to come to be till the ranging rod on the station is bisected via the hair on the equal time as regarded via the slit above the prism. 
When the needle includes relaxation, via urgent the knob if necessary, the reading is stated at which the hair line seems to out the picturegraph of the graduated ring. The sighting og the ranging rod and the reading is finished simultaneously. The reading offers the bearing of the road. 
2 bearing of line: 
The bearing of a line is the horizontal way of thinking made via the road with a particular reference line referred to as the meridian. There are 
forms of bearings. 
i) Magnetic Bearing: The route indicated via a freely supported magnetic needle unaffected via network appealing forces, is referred to as the magnetic meridian. The way of thinking among any line and magnetic meridian is referred to as magnetic bearing or actually bearing. 
ii)The Bearing: The line joining6the geographical north and south poles is referred to as the proper meridian or geographical meridian. The way of thinking among any line and the proper meridian is referred to as proper bearing of azimuth.