Guidelines on RTK-GNSS Use in Lot Surveys

Legal basis and purpose

The Circular is issued pursuant to DAO No. 2007-29, the Revised Regulations on Land Surveys.
The Circular is intended to keep abreast of advancements in modern surveying and mapping technology.
The Circular is intended to improve delivery of public service.
The Circular prescribes guidelines for using RTK-GNSS in conducting lot surveys with tertiary accuracy.

Coverage and scope of use

Geodetic Engineers must use registered RTK-GNSS Receivers before using RTK-GNSS in land surveys (Section 1).
The RTK-GNSS may be used in conducting all kinds of lot surveys with tertiary accuracy (Section 2.1).
Real-time kinematic surveying requires a base receiver and at least one rover receiver (Section 2.2).
Required procedures under DMC 2010-13 must be followed in conducting land survey using RTK-GNSS (Section 2.5).

Receiver registration requirement

Before Geodetic Engineers can use RTK-GNSS, RTK-GNSS Receivers must first be registered under Section 22 of DAO 2007-29 (Section 1).

Technical requirements and survey conditions

The RTK-GNSS instrument must be Dual Frequency Receivers with specifications stated in Section 202(g) of DMC 2010-13, also referred to as the Manual on Land Survey Procedures (Section 2.1).
RTK surveying must use one GNSS receiver as base station and at least one other GNSS receiver as rover (Section 2.2).
The GNSS Receiver (base) must be placed on a point with:
- unobstructed view of the sky, and
- horizon clearance of at least 15° in all directions, and
- known WGS-84 coordinates (Section 2.3).
The RTK receiver (rover) must be:
- mounted on a range pole, and
- supported by a bipod during observation to avoid unnecessary movement (not hand held) (Section 2.4).

Required operational procedures

Land survey procedures must follow Sections 20–27 of DMC 2010-13 (Section 2.5).
The following conditions must also be present for use of RTK in land survey (Section 2.6):
- The lot to be surveyed must be in an open field or areas where all corners have horizon clearance of at least 15° in all directions (Section 2.6(a)).
- The Electronic Total Station (ETS) must augment RTK in these ground situations (Section 2.6(b)):
  - Lot corners surrounded by buildings and other structures where the 15° horizon clearance requirement is not met.
  - Lot corners surrounded by deciduous trees with thick canopy because of marginal sky visibility.
  - Lot corners coinciding with the corner of an existing concrete fence.
  - Lot corners coinciding with a building wall.
  - Lot corners located beneath a 20 meter radius high voltage power transmission line and other communication facilities (Section 2.6(b)(1)–(5)).
- When lot corners coincide with an existing concrete fence, RTK may also be used by placing the receiver directly on top of the corner (Section 2.6(c)).
- The Root Mean Square (RMS) value must be monitored:
  - If RMS exceeds 70, transfer to another station/location.
  - For a more precise RTK survey, RMS should be 35 or below (Section 2.6(d)).
- The RTK observation time/session length for each lot corner must be not less than two (2) minutes.
- Each station/location must track at least five (5) satellites with good geometry (Section 2.6(e)).
- RTK must be initialized prior to start of data collection, maintain lock to satellites and the base station radio signal while transferring from one station/location to another (Section 2.6(f)).
- A baseline must be established using RTK with:
  - intervisible ends, and
  - length of at least 200 meters but not more than one (1) kilometer,
  - established within the vicinity preferably not more than one (1) kilometer from the lot (Section 2.6(g)).
- The RTK observation distance must be compared with the ETS distance, and the difference must not exceed:
  - one (1) centimeter for every fifty (50) meters, or
  - twenty (20) centimeter for every one (1) kilometer (Section 2.6(g)).
- The baseline check is equivalent to Tertiary Accuracy of 1:5,000, required for lot survey accuracy under Section 29 of DAO 2007-29 (Section 2.6(g)).

Observation field notes requirements

GNSS-RTK Observation Field Notes must include the following items (Section 3):
- Section 3.1 Instrument
  - Antenna:
    - Type
    - Serial Number
    - Set-up (Tripod, Plumbing Pole, etc.)
  - Receiver:
    - Type
    - Brand and Model
    - Serial Number
    - Frequency
- Section 3.2 Survey Style (RTK, Fast Static, etc.).
- Section 3.3 Date.
- Section 3.4 Weather.
- Section 3.5 Location: Barangay, City/Municipality, Province, Island.
- Section 3.6 Project Name/Description.
- Section 3.7 Base:
  - Station:
    - Name
    - File Name
    - Type of monument/mark
    - Dimension
    - Inscription
  - Antenna Height:
    - Slope
    - True Vertical
  - Time:
    - Start
    - Stop
    - Remarks
- Section 3.8 Rover (can be more than one unit):
  - Station:
    - Name
    - File Name
    - Type of monument/mark
    - Dimension
    - Inscription
  - Antenna Height:
    - Slope
    - True Vertical
  - Time:
    - Start
    - Stop
    - Remarks

Acceptance, processing, and verification

DENR Regional Offices must accept, process, and verify survey returns submitted using RTK-GNSS.
Verification and processing must be done in accordance with the Manual on Land Survey Procedures (Section 4).

Effectivity and publication conditions

The Circular takes effect after fifteen (15) days from the date of publication in a newspaper of general circulation (Section 5).
The Circular also takes effect upon acknowledgement of the Office of the National Administrative Register (ONAR) (Section 5).