QuestionsQuestions (DENR MEMORANDUM CIRCULAR NO. 2010-06)
It is issued pursuant to Section 22 of DENR Administrative Order (DAO) No. 2005-13, titled “Revised Guidelines for the Implementation of the Philippine Reference System of 1992.”
To provide standards in converting and transforming cadastral data/maps into PRS92, ensure spatial consistency during integration and plotting, and adopt basic database management practices to ensure quality, integrity, and accessibility of datasets.
It covers the transformation and integration of all cadastral data to PRS92 and provides database management mechanisms covering the transformed datasets.
Integration is transforming and consolidating data/surveys/maps into PRS92; transformation is converting spatial datasets from one coordinate system to another; PRS92 is the national common coordinate reference system for all surveys and maps under EO 45 (1993), as amended by EO 321 (2000) and EO 280 (2004).
The process starts with conversion of lot corners, survey project controls, and other reference points. The Manual states that transformation and integration of approved cadastral data must follow the process flow shown in Annex A.
Sources include lot data computation sheets, lot description sheets, field notes, monument description books, monument recovery reports, municipal/boundary index maps, project control maps, traverse computation sheets, political boundary computation sheets, and other relevant records. Priority order: (1) lot data computation sheets; (2) lot description sheets; (3) reconstruct using original field notes; (4) if all unavailable, resurvey under the new reference system.
The coordinates to be used must be in Philippine Plane Coordinate System—Transverse Mercator / Luzon 1911 (PPCS-TM/Luzon 1911). If based on LPCS, they must be converted to PPCS-TM/Luzon 1911 using LMB procedures.
The Manual requires converting using lot description sheets containing the bearings and distances of boundary survey lines and parcels (Section 4.3). If those are also unavailable, reconstruct computation/description sheets from original field notes (Section 4.4); if still unavailable, resurvey (Section 4.5).
Only after all efforts to research and retrieve records from other sources (e.g., Register of Deeds/LRA, LGUs/Assessor’s Office, court, and other agencies/individuals) have been exerted, and the affected lot is not titled/decreed.
The new survey shall already be PRS92-compliant and shall no longer be transformed using local transformation parameters.
For cadastral survey projects under graphical cadastre, lot data computation must be generated after resurvey of affected lots conducted under PRS92, referenced to existing PRS92 control points, and then converted for incorporation into the digital cadastral database.
Errors must be properly noted. For discrepancies in untitled/undecreed parcels, corrections are made by Lands Management Services (LMS) of the regional office. If titled/decreed, corrections must be made through court proceedings per LMB guidelines.
Local transformation parameters are determined by LMS for each city/municipality using recovered old PTM and PRS92 grid coordinates of control points and four-parameter conformal (linear conformal) transformation with shift, solved via least squares. Rotation, scaling, and translation preserve shape.
Weights: Reference Monuments = 4; Project Control Points = 2; Lot Corners = 0.5.
Points with residual errors exceeding 1.0 m should not be used in deriving the transformation parameters, and the process is repeated until residuals and standard deviation are within allowable limits.
NAMRIA assesses accuracy in collaboration with LMB, including preliminary checking of control-point distribution/number, ground validation using check points transformed into PRS92, and verification along adjoining municipality/project boundaries using a minimum of ten transformed undisturbed lot corners; discrepancies may require review and possible resurvey.
The Regional Technical Director for Lands recommends approval to LMB. NAMRIA and LMB implement appropriate mechanisms for approval of parameters (e.g., through control/reference-point database build-up or other acceptable strategies).
Copying/transfer without proper authority is dealt with under applicable laws, rules, and regulations, and will be meted with appropriate penalties.