In our previous article, we introduced the standard marker used by Geodetic Engineers (GE) in marking the corners of one’s property, which is the Mohon. Ideally, these markings are the ones we will place at every corner of your lot for proper identification of your property lines after we surveyed the lot.
However, in some instances such as when the corner lies on an immovable rock or on a living tree, it is improbable that we can place the mohon on that corner. Section 88 of DENR Memorandum Circular No. 2010-13, Adoption of the Manual on Land Survey Procedures, provides for other acceptable lot corner markers such as the following:
In acceptable living trees – a cross chiselled upon the blaze of an acceptable living tree and at the point of intersection of the cross is a galvanized iron spike;
In wooden post of durable hardwood of not less than 15cm in diameter forming part of a house, a fence, or other permanent structures – galvanized iron spike set at the center of a cross to be marked thereon;
In concrete posts, masonry, concrete walls, immovable rock, or boulders – galvanized iron spike driven into the structure or a cross mark chiselled upon such structure, when marking using galvanized iron spike is not feasible;
In metal pipes having an outside diameter greater than 2 cm – such pipes shall be filled with concrete and shall be defined either by a galvanized iron spike or by a conical hole not exceeding 2 cm in diameter and not less than 1 cm in depth, or by a cross mark chiselled on the concrete top.
Image 1. To mark a corner located in concrete walls, it is acceptable to use galvanized iron spike in delineating the appropriate corner.
In these instances, these markers are accepted as substitutes for the standard mohon. So, if your GE did not place mohon at some corners of your lot for some specific, don’t blame him or ask instantly for a refund. 🙂 Look first for these other markings which s/he could have placed at that specific corner. 😉
An approved survey plan is a survey plan approved either by the Department of Environment and Natural Resources (DENR) or by the Land Registration Authority (LRA). Such plans are considered public documents and can be requested from the approving agencies mentioned.
These plans normally consist of the plotting of the parcel or parcels of land, the survey plan number, the name of the Geodetic Engineer (GE) who executed the survey, the date of the survey conducted as well as the date of the plan’s approval, the technical descriptions of the property, and other pertinent details to identify the subject property’s location.
Use of Survey Plans
Aside from the technical descriptions in the land title, GEs also use the technical descriptions in the approved survey plans as reference in executing their surveys.
If you are a landowner or a would-be landowner, you may also want to request the survey plan of the subject property to know the shape of the parcel of land.
Depending on the region or office where the plan can be requested, the processing of the request for survey plan ranges from one day to two weeks, in some regions, it might take about a month. Its cost also ranges from PHP 20.00 – PHP 400.00 per plan.
To identify the plan number of the property, one can find it in the first paragraph of its land title:
Image set 1. Boxed in red are the survey plan numbers which can be requested in LRA and DENR-NCR respectively.
How to determine if the plan is approved?
One can check if the survey plan is approved if such contains the specific survey plan number at the bottom right side of the document, along with the date of approval, and the signatures of the authorized personnel.
Image 2. Sample of the Subdivision Survey Plan (PSD) approved by the LRA. Highlighted at the bottom right side of the plan is the corresponding survey plan number which can be requested in LRA for duplicate copies.
Image 3. Sample of the Relocation Survey Plan (REL) approved by the DENR. Highlighted at the bottom right side of the plan is the corresponding survey plan number which can be requested in DNER for duplicate copies.
Know some of the survey symbols which DENR uses
The DENR is the authorized agency that can approve all types of surveys, both for titled and untitled lands. Here are some of the survey symbols they use in the approval of the plans:
Image 4. Survey symbols used by the DENR in their approval of the surveys executed by Geodetic Engineers.
Source: DENR Memorandum Circular No. 2010-13.
If you will engage a contractor in the survey of your property, make sure that s/he is a licensed Geodetic Engineer especially if the survey requires approval either by the LRA or by the DENR for subsequent titling and other purposes.
On Part 1 of this series, we introduced one of the equipment used by Surveyors in doing land surveys, the Total Station. Now, let’s take a look at another equipment used in land surveys – the GNSS and see its edge over the other equipment commonly used by surveyors and Geodetic Engineers.
The Global Navigation Satellite System (GNSS)
GNSS is a general term that encompasses all types of satellite-based positioning systems. It is a constellation of satellites that orbits the Earth and continuously transmit signals that enable the user to determine positioning, navigation, and timing services on a global or regional basis.
Image 1. Kinds of GNSS
GPS is a type of GNSS. It is a constellation of satellites developed by the United States Department of Defense. There are 4 kinds of GNSS in the world: GPS, GLONASS, Galileo, and BeiDou. GNSS-compatible equipment can use satellites from other networks beyond the GPS system, and more satellites mean increased receiver accuracy and reliability. All GNSS receivers are compatible with GPS, but GPS receivers are not necessarily compatible with GNSS.
GPS and GNSS consist of three segments: the space segment (satellites), the control segment (ground control stations), and the user segment (GNSS or GPS receivers). Some function of the space segment is to receive and store information sent by the ground (control) station and send location information to users in real-time. The control segment is what instructs/performs necessary commands for the space segment and processes all the products for the end-users use. The user segment refers to the GNSS or GPS receiver.
Real-time kinematic positioning (RTK)
RTK is a technology used to improve the accuracy of GNSS positioning. RTK uses one stationary reference receiver called the base station, and one moving receiver called the rover.
Base stations are stationary and their location is known. It is comprised of an antenna, a radio modulator, and an amplifier. The modulator converts the correction data into a radio signal. The amplifier increases the signal’s power, which determines how far the information can travel. The base station calculates its position by utilizing the signals received from the satellites and it is compared to its known location and identifies any errors and generates a correction signal.
The rover is the GNSS Receiver whose location needs to be determined. It utilizes the correction signal from the base station to improve its own calculated position. Rovers can be moved from point to point, stopping momentarily at each new point.
Image 2. Real-time Kinematic GNSS
Advantages of Using RTK
The primary advantage of using RTK is that a large number of positions can be established in a short amount of time. It provides centimeter-level positioning accuracy and eliminates human errors caused in traditional surveying. RTK relies on satellite, radio positioning and communication, this makes conducting survey faster. It provides GPS position in real-time and has better waypoint navigation which is required for challenging environments.
Image 3. LPH LSS Personnel with the RTK survey equipment.
If you have projects that would require RTK surveying do not hesitate to contact our team in LPH Land Surveying Services
______________________________ Allen Instruments and Supplies. (n.d.) Digital and Auto Level Equipment. Retrieved from: https://www.alleninstruments.com/geospatial-solutions/survey-engineering/digital-and-auto-levels/Iqbal, S. (8 July 2021). Digital Level Surveying – Advantages – Component – Types. Retrieved from: https://definecivil.com/digital-level-surveying/
TERRISGPS. (n.d.) GNSS/GPS Differences Explained. Retrieved from: http://www.terrisgps.com/gnss-gps-differences-explained/
Editorial Team – everythingrf. (27 July 2020) What is Real Time Kinematics. Retrieved from: https://www.everythingrf.com/community/what-is-real-time-kinematics
One of the most common requirements in applying for a building permit is a Lot Plan. If you are wondering where you can get one, just leave us a message here, and we will get back to you within the day containing the details we need from you in order for us to prepare one. 🙂
So what is a Lot Plan? It is a two-dimensional map containing the plot of your land based on the technical descriptions appearing on your land title, or on the technical descriptions appearing on previously approved surveys conducted over the subject land, or on the actual survey conducted by the Geodetic Engineer. It will provide not only the dimensions of each property line but also the shape of the subject land.
Image 1. Lot Plan containing the technical descriptions and shape of the subject land, along with other information necessary for the identification of the subject land.
Lot Plans are needed to be signed, certified, and sealed by a duly licensed Geodetic Engineer (GE) for such to be considered valid and with authority. So, before engaging one in plotting the dimensions of your land, make sure that he or she is a licensed GE, as your LGU might require you a photocopy of his/her Professional Tax Receipt and PRC ID, which only licensed GEs will have. Plus, you can be more certain that he or she will produce the output in a professional manner.
Did you ever see a Geodetic Engineer and wondered what are the instruments they are using? In this article, you will know more about the tools they use to provide quality service.
The most common equipment used by Geodetic Engineers in acquiring spatial data is currently the Total Station along with its accessories – Prism Pole, Prism, and Survey Tripod.
Image 1. Total Station. Shot taken in one of LPH LSS’ Survey Projects in Pililla, Rizal.
Total Stations are always mistaken for a piece of equipment in photography. Passerby during a survey sometimes strike a pose hoping that the surveyor captures a photo of them but are always disappointed when pointed out that it doesn’t have the capability to take photos.
FUNCTIONS AND FEATURES
A Total Station is a lightweight optical instrument that performs the following functions:
Total Station surpasses the conventional theodolite by means of having the same function as the theodolite combined with the function of an auto-level and electronic distance meter. The main features that make it a horsepower are:
All functions are controlled by a keyboard
The values of distance, angle, height, and coordinates of the observed point are displayed on the digital panel
The coordinates of the reflector/prism and its angle/bearing can be stored and recalled for the next setup of the instrument.
If you know the coordinates of a particular point, the instrument displays the angle through which the instrument is to be turned and the distance of the reflector/prism should be moved.
ACCESSORIES
Image 3. Prism/Reflector (Photo taken from: https://surveyinstrumentsales.com/survey-instrument-sales-single-tilt-prism-assembly-with-orange-target.html)
Reflector/Survey Prism redirects a measuring beam back to an Electronic Distance Meter(EDM)/ Total Station which determines the distance of an object to a specific survey point. They are often attached to a prism pole in order for it to focus on a specific position. It needs to be properly aligned with the instrument to ensure accurate results.
Image 4. Prism Pole (Image taken from: https://geographicinstrument.en.made-in-china.com/product/xNdEigYHJfWD/China-3m-Survey-Prism-Pole-for-Total-Station-P3-4-.html)
Prism Poles are used together with the reflector/survey prism to focus it in a specific location and ensure solid and stable readings.
Image 5. Instrument Man alongside the Total Station mounted on the tripod
Survey Tripods are three-legged stands that are designed to provide a stable foundation for the total station and a variety of surveying equipment.
There are other types of survey equipment Geodetic Engineers use in collecting spatial data which depends on the extent or the scope of the project and its duration. If you want to know more about it or would like to avail the services of a Geodetic Engineer, you can reach Lira Perin Habana, founder of LPH Land Surveying Services. She has been a licensed GE since 2014. She is a registered member of the Geodetic Engineers of the Philippines – NCR Chapter (GEP-NCR) and has been consistently providing reliable service to their clients since 2016.
______________________________ Engineer Supply. (n.d.). Prisms. Retrieved from: https://www.engineersupply.com/prisms.aspx
Engineer Supply. (n.d.). Prism Poles. Retrieved from: https://www.engineersupply.com/prism-poles.aspx
The Constructor. (n.d.). Modern Surveying Instruments and their Use. Retrieved from:https://theconstructor.org/surveying/modern-surveying-instruments-uses/16
Are you planning to put a fence around your property but you are not certain where the start and end of your property is? If that is the case, better let your Geodetic Engineer install mohons over your property first.
A mohon, in layman’s terms, is a cylindrical concrete marker that is used as the standard marker to delineate a property boundary. These markers are also used as reference points for subsequent surveying projects. Other markers known as Geodetic Monuments have established coordinates or positions where surveyors can refer the exact locations of another property’s boundaries. Surveyors then mark the positions of the boundaries using a mohon/survey monument.
What does a mohon look like?
Based on Executive Order No. 192 dated June 10, 1987, and DENR Administrative Order No. 2007-29 (DAO 07-29) dated July 31, 2007, the following shall be the dimension for Geodetic Monuments:
Table 1.Dimensions of Geodetic Monuments as per DAO 07-29.
For Geodetic Monuments, they should be fabricated with a reinforced steel bar (10 mm in diameter for vertical bars and 8 mm in diameter for ties) and satisfying the requirements of class A concrete specifications in the ratio of 1:2:4 such as 1 cubic meter of cement, 2 cubic meters of sand, and 4 cubic meters of gravel.
Image1. Graphic representation on the properties of a Geodetic Monument.
It shall be marked on top with engraved letters which consist of 5 parts namely Provincial Code, Control Point Number, Year Established, Order of Accuracy, and the office or entity that established the Reference Monument.
Image 2. An example of a Geodetic Monument which can be found in Digos City, Davao Del Sur (Source: Photo retrieved from: https://landsurveyorsunited.com/photo/bbm-boundary-benchamrk)
For Standard Lot Corner which you can see in your surveyed properties:
Image 3. Graphic representation on the properties of a mohon used in private surveys
Image 4. A mohon placed in a surveyed lot.
There are a number of marks that can be seen on top of a mohon. The most common is PS. “PS” stands for Private Survey/Surveyor; it is common in properties surveyed by Geodetic Engineers owned/claimed by its clients. To name more of the marks, we also have PSP which are private surveys done to properties owned/claimed by a Province, BL or Bureau of Lands are Government executed surveys, and PLS or Public Land Subdivision are Government executed subdivision surveys.
Other Possible Markings
There are instances that the boundary can not be established with the standard monuments due to concrete walls, buildings, trees etc. According to the manual, the following are allowed as a substitute boundary mark:
Concrete posts which are part of the fence that are not less than 10cm in diameter or metal pipes with no less than 2cm in outside diameter.
Edible fruit trees or trees belonging to the first group as per forestry classification with no less than 15cm in diameter.
Concrete walls.
Fixed or immovable hard rocks with an exposed surface of more than one meter in diameter.
Peg, being of a composition that will resist destruction by fire, natural corrosion, or decay with a nominal dimension of 50 millimeters square in cross-section for at least 100 millimeters from the top and not less than 400 millimeters in length.
Image 5. Steel Rod, an acceptable corner mark (photo retrieved from: https://www.indiamart.com/proddetail/steel-rods-5993843891.html)
Interference or Disturbance of Mohon
Interference or disturbance of mohon is considered a crime and is punishable by law. Under Article 313 of the Revised Penal Code on altering boundaries or landmarks, “Any person who shall alter the boundary marks or monuments of towns, provinces, or estates, or any other marks intended to designate the boundaries of the same, shall be punished by arresto menor or a fine not exceeding Twenty thousand pesos (P20,000), or both.”
If you are planning to verify or if you are in doubt that your property’s boundaries or mohon were altered or disturbed, you can reach Lira Perin Habana, founder of LPH Land Surveying Services. She has been a licensed GE since 2014. She is a registered member of the Geodetic Engineers of the Philippines – NCR Chapter (GEP-NCR) and has been consistently providing reliable service to their clients since 2016.
For some Geodetic Engineers, requesting a certified true copy of title through the assistance of the landowner is a primary step in order to push through with the land survey of the property. This is a necessary condition in order to validate the authenticity of the land title itself. If such land title has no available certified true copy in the Register of Deeds (RD), suspicions over the client’s title may arise as it may mean that the subject land title can be fake. But, there are instances that such copy was just lost in the records especially if the copy was not yet in the electronic database of LRA. If such instances occur, feel free to contact us here so we can connect you with proper agencies that can assist you with these types of concerns.
If you are not familiar with where and how you can request a certified true copy of title, one can file a request for such copy in their local Register (sometimes referred to as Registry) of Deeds or in the Land Registration Authority (LRA) Central Office located in East Avenue corner NIA Road, Quezon City. Normally, the price per copy runs about P270 for the first three pages as of the date of this writing. Additional fees will incur if there are more than three pages or if the place where one filed his request is in a different branch where the property is situated. For example: if one requested a certified copy of title in Makati but the title originated in the Register of Deeds – Puerto Princesa Branch, there will be additional fees tagged in the Invoice as IT Service – Network Transmittal Fee, which costs about P450.00. The processing period normally takes about 3-5 working days from the date of payment, depending on the branch of RD.
So, here are the steps in requesting a certified copy of the title:
Fill out the upper part of the Request Form (LTCP Form 0012 Version 2.0):
LTCP Form 0012 Version 2.0. “Information Request Form”
3. Present the filled-out request form together with other requirements prescribed in the RD (such requirements are usually photocopies of the subject title and photocopy of the requestor’s ID) to receive the assessment form and payment order (“billing”).
4. Pay to the cashier the amount reflected in the billing.
5. After payment, the cashier will give you the official receipt (in pink form). Depending on the processing days of the RD, you may have to wait a few days to get the certified title.
6. Return to RD on your scheduled date of claiming and present the pink slip. Don’t forget to check the copy of the title before leaving the premises!
The Geodetic Engineering (GE) profession, through its national organization, the Geodetic Engineers of the Philippines, Inc. (GEP), prescribed tariffs per region as a guide for GE in pricing survey rates.
For Relocation Survey, here is the tariff prescribed by GEP-NCR and is currently adopted for properties within NCR by duly recognized GE:
Image 1. 27th Annual Regional Convention. Summary of GEP-NCR Geodetic Engineering Services Rates CY 2015-2016, at 37.
Here, if your property’s land area is, say 1,000 sq.m., the cost for doing a Relocation Survey will be: PHP20,000.00
Meanwhile, for a property whose land area is 23 ha, the cost will be PHP 190,000.00
Separate rates are provided for the other types of survey such as Subdivision and Topographic Survey:
For Subdivision:
Image 2. 27th Annual Regional Convention. Summary of GEP-NCR Geodetic Engineering Services Rates CY 2015-2016, at 44.
For Topographic Survey:
Image 3. 27th Annual Regional Convention. Summary of GEP-NCR Geodetic Engineering Services Rates CY 2015-2016, at 46.
CONCLUSION:
The tariffs listed are the rates suggested by the GEP-NCR for the conduct of land surveys. These can still increase or decrease depending on your regional tariff as well as with the other factors your Geodetic Engineer will consider before handling your project. 😉
Just a word of caution before engaging any contractor to deal with the survey of your precious landholdings – deal with legitimate persons who are authorized to conduct land surveys and sign and seal maps and plans of the survey they made.
By going for cheaper rates from non-legitimate persons, one may be risking the quality of service your landholdings should have deserved. Such persons are not bound by the laws governing the GE profession. Check his or her license number on the PRC website to verify you are dealing with a professional you can rely on and fully trust.
Have you come across individuals wearing bright-colored vests and hard hats that operate camera-like instruments along the side of the roads or on a construction site? I guess you wondered what they were doing and even posed for a picture when you thought they focused the instrument on you and hoped that they would get nothing but your best angle. Unfortunately, they are not photographers or anything of the like. They are Geodetic Engineers (GE) and the instrument that they use is not for photography, rather, it is called a Total Station, a piece of equipment that can measure distances and angles to lay out the boundaries of a parcel of land.
In the Philippines, Geodetic Engineers (GE) are licensed professionals accredited by the Philippine Regulation Commission (PRC) to do geodetic surveying works. Sometimes called by the unfamiliar ones as surveyors, lisensyadong maninilip, or agrimensores, Geodetic Engineers are the ones authorized to establish property boundaries. Unlike surveyors, these folks acquired their hard-earned PRC licenses after passing the Geodetic Engineering Board Exam administered by the PRC and taking the Oath of Profession of Geodetic Engineers before the Board of Geodetic Engineering. Their practices are governed by the statutes prescribed in the Philippine Geodetic Engineering Act of 1998 (R.A. 8560) and its internal rules and regulations.
What does a GE do?
Geodetic Engineers provide information to guide the work of other engineers, architects, urban and regional planners, geologists, and developers. They typically measure distances and angles between points on, above, and below the Earth’s surface. They go to survey sites and locate reference points or “mojon” and utilize them to determine the position of specific features. They examine land records, survey records, and land titles and validate them if they are up to date and accurate on the ground. They record data from field surveys and verify its accuracy, from which they prepare plots, maps, and reports that will be presented to clients and government agencies. They also provide spatial data to assess the surrounding terrain and landscape, as well as the shape and contour of the Earth’s surface for the purpose of development in engineering, mapmaking, and construction projects. And last but not least is that Geodetic Engineers establish official land and water boundaries for deeds, leases, and other legal documents and testify in court regarding survey work.[1]
Tools and Equipment
Geodetic Engineers use different methods and technologies to acquire spatial data which includes GPS, GIS, Total Stations, 3D scanners, Digital Levels, graduated rods, drones, and other instruments that are used to determine the metes and bounds of lands, the position of points on the surface of the Earth, ground elevation, water depth, and other features related to geodesy.[2] Total Station is currently the most common instrument used by a GE. It is useful for measuring vertical angles, horizontal angles, distances, and coordinates.
GEs also utilize the Global Positioning System (GPS), a system of satellites that locates reference points with a high degree of precision, to collect relevant information about the terrain they are surveying and interpret and verify the results on a computer. They are also highly trained to use Geographic Information Systems (GIS), a platform to organize, interpret, analyze, and present spatial data through various methods and visualizations.
There are other services a Geodetic Engineer can provide depending on the client’s needs. Lira Perin Habana, the owner of LPH Land Surveying Services, has been a licensed GE since 2014. She is a registered member of the Geodetic Engineers of the Philippines – NCR Chapter (GEP-NCR) and has been consistently providing reliable service to their clients since 2016.
______________________________ [1]Bureau of Labor Statistics, U.S. Department of Labor, Occupational Outlook Handbook, Surveyors, at https://www.bls.gov/ooh/architecture-and-engineering/surveyors.htm (visited July 18, 2021). [2]Professional Regulation Commission, Republic of the Philippines, General Practice of Geodetic Engineering at https://www.prc.gov.ph/geodetic-engineering (visited July 18, 2021).
#Topographic Survey #Topo Map #ContourLines #basics of surveying
Are you a landowner of a tract of land or a potential buyer of a property you found as viable for some economic purposes you have in mind, but then suddenly you feel uncertain whether that specific industry can cater to the current terrain of the land you are eyeing for?
Or an architect who was tasked to create an eco-friendly residential design based on the existing terrain conditions of the land your client has just bought in Baguio? But when you went to the site and you tried to capture the existing terrain conditions thru video clips and photos using your smartphone, it appears difficult to proceed with drafting an outstanding design fit for your client?
Or maybe you are a land developer planning to develop that vast area of land, and you have this idea of subdividing a large tract of land into multiple lots? And when the officer from Housing and Land Use Regulatory Board (HLURB) or the Mines and Geosciences Bureau (MGB) or your local zoning officer requested a copy of the Topographic Map, you replied with another question asking what it is for and is it that necessary?
The officer might have tried to explain something but still, at the end of his detailed explanation with matching hand gestures and probably a sample topo map on hand, all that is clear for you is that you have to look for a Geodetic Engineer asap.
Whether you are any of those mentioned or someone who is simply curious and wishes to know more about land surveying products and services, listen, you or someone close to you might benefit from this learning.
What is a Topographic “Topo” Map?
A topographic map is a representation of the earth’s surface in three dimensions. It shows the same features as a planimetric map and in addition indicates relief, usually through contours which are its distinguishing characteristics.1
Elevation contours are imaginary lines connecting points having the same elevation on the surface of the land above or below a reference surface, which usually mean sea level. Contours make it possible to show the height and shape of mountains, the depths of the ocean bottom, and the steepness of slopes. 2
Topo Maps are used to understand the landscape of a certain area mostly for planning and design considerations – be it for Civil Engineering or Architecture Designs, or Mining, or sometimes for recreational uses such as hiking and orienteering.
The preparation of general topographic maps is largely done by agencies of the government.3 In the Philippines, the National Mapping and Resource Information Authority (NAMRIA) is the leading agency responsible for such functions. NAMRIA’s website allows free access to these maps varies, which from a 1:50000 to 1:250,000 scale.
Image 3. A topographic map of Bulan, Sorsogon, in 1:250,000 scale, as downloaded from NAMRIA’s website (Source: https://www.namria.gov.ph/Downloads/topoMap250/bulan.jpg)
For projects which require more specific areas of interest (AOI) however, one can acquire a more detailed topographic map by conducting a more targeted topographic survey over the AOI.
Glimpse on what a Topographic Survey is
A topographic survey gathers data about the natural and man-made features of the land, as well as its terrain. Permanent features such as buildings, fences, trees, and streams accurately define the ground and its boundaries.4 [3]
Image 4. The team, while conducting Topographic Survey using an Electronic Total Station.
How is Topo Map Created?
A topo map can be created using computer software such as AutoCAD Civil3D, ArcGIS, or Surfer. Spatial data obtained from field surveys are imported into the software which can automatically generate contours. Depending on the needs of the project, one can set the contour interval (index) to 1m, 2m, or even up to 5m or greater.
Depending on the area or extent of the project and the required accuracy, our team can offer ways of how to maximize your budget based on your timeline.
To discuss your project with us and to find out more if it could benefit from a topographic survey, email us at lph.lphlandsurveyingservices@gmail.com.
______________________________ 1Juny Pilapil La Putt, Higher Surveying, 2008 Reprint Version, page 84. 2USGS, What is a topographic Map, available at https://www.usgs.gov/faqs/what-a-topographic-map?qt-news_science_products=0#qt-news_science_products (last accessed June 23, 2021). 3Juny Pilapil La Putt, Higher Surveying, 2008 Reprint Version, page 84. 4John MacIntyre, Everything You Need to Know About Topographic Surveys, available at https://www.technicsgroup.com/2019/05/everything-you-need-to-know-about-topographic-surveys/ (last accessed on June 21, 2021).
