Draft operational guidelines of digital india land records modernization programme (dilrmp) introduction

9.3.1 Terrain conditions: Where the land area is within a gradient of 15%, aerial photography or high-resolution satellite imagery is expected to give adequately accurate output. However, in undulating terrain and hilly slopes, pure ground method using TS+GPS may be used for cadastral survey.
9.3.2 Vegetative cover: Dense vegetation obstructs the line of sight in the vertical direction, thus preventing the aerial and satellite images from capturing the field boundaries. Pure ground based methods using TS+GPS are suitable in these conditions. In open areas, devoid of vegetation, aerial photography or satellite imagery is likely to give adequately accurate output. However, sparse vegetative cover prevents pinpointing the field corners and in these conditions, aerial photography or satellite imagery should be supplemented by ground truthing.
9.3.3 Built-up areas: In urban areas, high-rise buildings prevent aerial/satellite images from capturing building corners and boundaries. A lot of shadow areas appear in the remote sensing data, depending upon the height of the buildings. In these conditions, pure ground based methods using TS+GPS are preferable for cadastral survey. Where there are lower built-up areas, aerial images or high-resolution satellite images are likely to give better results.
9.3.4 Size of survey area: In a small survey area, ground-based survey will give faster output, but in a larger area, such as a district, aerial photography or high-resolution satellite imagery is likely to suffice.
9.3.5 Accuracy: In cadastral survey, the scale of the map and precision of the instruments greatly influences its accuracy. The accuracy of the survey is the highest with TS followed by, plain table and chain survey, respectively.
9.3.6 Timeliness: Pure ground truthing methods of cadastral survey such as chain, plain table and total station, which require 100% measurement to be made on the ground, are time-consuming. Ortho-products from aerial photos and satellite images supplemented by ground validation greatly reduce the time factor in preparation of cadastral maps.
9.3.7 Cost: The cost is the driving force in adopting a particular technology for cadastral survey. High-resolution satellite images from CARTOSAT series are cost effective, compared to digital aerial images and pure ground methods.
9.4 For reaching the stage of integrated land information management system which ultimately lead to conclusive titling as envisaged in erstwhile scheme of NLRMP, the States/UTs shall undertake survey/re-survey using modern technology of surveying & mapping, i.e., aerial photography or high resolution satellite imagery combined with ground truthing using TS+GPS so as to ensure true ground depiction on cadastral maps and land records, adopting the methodology most appropriate for the terrain, location, etc. and update the survey & settlement records subject to provisions contained in Policy Circular dated 08^th December 2016 mentioned hereinafter in Para 9.9.
9.5 For fresh survey, in areas where cadastral maps are not available, the following options are suggested:

1. 
   Total System (TS) + Differential Global Positioning System (DGPS)
   
2. 
   Aerial Photographs + TS + DGPS
   

In open areas, the process will be greatly facilitated by the use of aerial photography, combined with TS+DGPS for ground truthing. In densely vegetated areas, use of TS+DGPS is suitable. In hilly areas, use of terrain-corrected aerial photographs (digitally-rectified ortho-photographs) with TS+DGPS for ground truthing may be appropriate. All efforts should be made to arrange for aerial photography; however, where it is not possible to arrange for aerial photography, TS+DGPS must be adopted for completing the work with the desired level of accuracy.