Download (46Kb)


    The formalization of property rights within land administration projects and programs typically involves the spatial definition and description (survey and mapping) of individual parcel boundaries. In many cases informal property rights have arisen because of overly expensive, slow and complex surveying methods. As countries such as Albania move towards a private property system, boundary definition of millions of parcels is required. In countries like Belize, surveying has fallen behind the demand for registering freehold rights and state land leases, with the result that the formal record lacks an adequate spatial definition of parcels. In both cases, there is a crucial need for a surveying methodology that is quick, inexpensive and within the reach of the existing surveying professionals. Over the past ten years GPS has emerged as a major tool for undertaking precise surveys. More recently, it has made inroads in those applications requiring lower precision surveys and is fast becoming a primary technology for acquiring data for input into geographical and land information systems (GIS/LIS). So-called "sub-meter" GPS receivers can provide coordinates which are sufficiently accurate for cadastral purposes in rural areas. More importantly, these receivers offer an opportunity to significantly lower the cost and time typically required for cadastral surveys. Cadastral surveying is the branch of Surveying dealing with the definition, measurement, relocation and mapping of land parcels to which registerable land rights are attached. It involves the application of legal boundary principles, as well as measurement theory and techniques. Boundary principles are used to assess boundary evidence in the form of measurements, historical records, verbal testimony from landowners, physical monuments and accessories. In this sense (and also because it affects people's legal rights to land), it is far more complex than merely mapping ground features or land-use boundaries. In designing and testing a GPS methodology for cadastral surveying we have prioritized the following criteria: • speed (must significantly outperform current approaches) • cost (must significantly reduce current unit survey costs) • appropriate (must be within the reach of local surveyors) • realistic accuracy (match real needs ) • simple field operation (data collection must be simple to allow for variable field conditions) 2 In the past cadastral standards in developing countries, and elsewhere, have tended to be designed to achieve the highest accuracy that the technology can deliver with little consideration for time and cost. We have attempted at all times to avoid this "supply" driven approach and to apply a "demand" driven approach based solidly on the cadastral needs of developing countries. This paper will describe the performance of the GPS technology under the controlled conditions of the UF test site. It will also summarize the cadastral conditions and results of the field tests undertaken in Albania and Belize. This experience was used as a basis for developing standards, specifications and procedures for a new GPS-based approach to cadastral surveying, which is described in the latter part of this paper. 2. Performance of GPS Technology under Controlled Conditions 2.1 Control Tests at UF Test Site With any new technology it is essential to understand how it performs under the different types of conditions in which it will be applied. The performance claims of the manufacturers should be regarded as optimistic and in many cases their tests may not take into account conditions which apply to a specific application area, such as cadastral surveying. For this reason, a number of control tests were undertaken at a cadastral test site on the UF campus. The test site consists of 49 monumented points which are set out so as to form 28 small parcels or polygons. Coordinates for all these points were determined to a very high degree of accuracy using geodetic GPS receivers and total stations. For the purposes of our tests, they can be regarded as "true" coordinates. In order to test the GPS technology for the demands of cadastral surveying in developing countries, the following tests were carried out: • Investigation of positional accuracy vs baseline distance (2-200 kms) • Investigation of positional accuracy vs occupation time (15-60 seconds) • Performance of Geodetic vs 12-channel sub-meter receiver as base station • Utilization of second base station for improving accuracy and data authentication • Performance of different processing software (MCORR300 vs MCORR400) In addition to the tests site points, other geodetic control points at varying distances from the control site were used for these tests. The coordinates of these control points are known to a very high degree of accuracy as they are part of the Florida High Accuracy Reference Network (HARN). The geodetic control points are situated at the following distances from the test site: 2km, 32km, 68 km, 87km, 107km, 148km, 178km, 235km. For all tests these points were occupied by the base station receiver (Trimble 4000SE or 12 channel Pathfinder ProXL) and the test sites by the rover receiver (Trimble Pathfinder ProXL). The base stations were used to determine the differential corrections that were applied to the rover positions.

    Item Type: Technical Reports (Technical Report)
    Related URLs:
      Publisher: University of Florida
      Subjects: (Z) Other or Unspecified
      Publication Sources: (3) Other Source > (3C) Other Universities
      Date Deposited: 13 Aug 2015 11:28
      Last Modified: 13 Aug 2015 11:28

      Actions (login required)

      View Item