The Three Imperatives
The three components in this integrated approach are –
A CREDIBLE SURVEY TECHNIQUE
LAND RECORD DATA ENTRY
SERVICE DELIVERY SYSTEM
The Survey Technology
The Survey technologies presently in use are
- traditional
- Total Stations and other laser-based systems
- Aerial photo-reconnaissance
- Global Positioning Satellite based systems
- Satellite imagery
All these systems suffer from some major infirmities
- Total Stations are accurate but extremely time consuming. They are also labour- intensive thus providing only a partial improvement in terms of accuracy but most of the other parameters remain the same.
- Aerial Photo-reconnaissance is both accurate and relatively quicker. It is possible to render 1:20000 photographs into 1:4000 scale maps by using photogrammetry techniques with accuracy of upto 5 cms on ground. However, there are some extremely delicate issues involved , specially for a border state like Rajasthan.
- Overflying large tracts is restricted. In the border districts, it may be impossible to obtain permissions for doing aerial reconnaissance.
- Ferrying distance for the aircrafts can be very long because of the shortage of air strips in Rajasthan.
- The cost of a complete integrated system is more than Rs. 150 per hectare.
- The time taken for even small areas is fairly long - upto a year in most cases .
- GPS is both accurate and quick by using kinematic systems with a station on the ground and feeding the coordinates to a 3 or 4 satellite system. With georeferencing available from the coordinates fixed by the Survey of India, an accurate survey can be done within a few days for an average village. However, the cost is prohibitive. It can be anything between Rs. 225-250 for a completely integrated sytems design.
- Satellite Imagery is the quickest but accuracy is a major issue. It is also the cheapest with a completely integrated systems design possible for around Rs. 50 per hectare. However, the besst that is available today is a 1 metre resolution image which is just not good enough. In fact, the max. tolerance cannot exceed 10 cms.
With all these factors weighing on our minds, we have devised a system which would combine the best elements of these systems in a way that we get a solution which is quick, cheap and accurate. It is of course necessary to run this on the ground to prove the system . What it involves using the recently available 1 metre resolution images from the Satellites. These images are vectorised in relation to roughly 20 to 100 GPS positions obtained on the ground using a ground earth station. The vectorised satellite image is georeferenced and overlaid in relation to these points. There is this difficulty of matching the Satellite images against the points obtained by the GPS. This is done using standard imaging softwares and the techniques of edge-matching and union. The result is 99% accurate which is good enough for the purpose of Land Surveys for fixing field boundaries. A tolerance of around 20 cm. is good enough for this exercise as the field boundaries themselves can vary greatly in their width depending upon the terrain and the type of soil.
The cost of devising a system based on these parameters is around Rs. 100 per hectares. It also has the advantage that we are able to complete the survey task as soon as the 20 points on the ground are fixed and the information is relayed to the data-host. The rest of the work is then done in the laboratory.