RailFanning is a gift you give yourself. - Varun

2) Reconnaissance survey
This survey consists of a rapid and rough investigation of the area with a view to determine the technical feasibility of the proposal as well as the rough cost of one or more alternatives to the new line. The reconnaissance survey (RECCE) is normally based on contoured survey maps and other data already available without carrying out detailed investigations in the field. With the help of the maps, different alternative alignments of the new line are studied.
The general topography of the country is studied by the survey team and...
more...

then field data are collected.
2.1) Survey Instruments
The reconnaissance survey is mostly conducted using survey instruments that rapidly measure approximate distances and heights. Prismatic compass, Aneroid barometer, Abney level or hand level or clinometer, Binocular, Pedometer are the survey instruments used.
2.2) Modern Surveying Instruments and Techniques
Modern surveying instruments make extensive use of infrared beams, laser beams, as well as computers. Using these instruments, it is possible to carry out fairly accurate surveying efficiently at all times, eliminating human error.
2.3) Field Data
The following field data are collected during the reconnaissance survey.
(a) General topography of the country
(b) Approximate heights of the different points falling on the alignment
(c) Positions of rivers, streams, and some hydrological details of the same
(d) Positions of roads and highways
(e) Nature of soil at different places
(f) Rough location of various station sites
(g) Controlling points on the alignment, through which the railway line must pass
(h) Facilities for construction
2.4) Project Report for Reconnaissance Survey
Based on the above data, a report should be prepared by the engineer in charge of the project bringing out clearly from the financial point of view whether or not the prospects of the line surveyed are such as to make it worthwhile to undertake further investigations to construct the line. The project report should be accompanied by an abstract estimate of the cost of the line.
The report and estimate should be accompanied by a map of the area on a scale of 20 km to 1 cm and an index map of 2.5 km to 1 cm.
Source: click here