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Local Vs. Grid Coordinates

Given a complete set of plans for a 20km roadway project. The job is to make it sure that design components are correctly positioned on ground. If you're given this task, what coordinate system you'll be employing on ground, local or grid?

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  • Hi Paul,

    It's kinda chaotic situation here. :( On the other side of the coin, surveying jobs surface due to boundary disputes. :)

    Regards.

  • Hello Arnel,

     

    It sounds like a situation that has both good and bad possible outcomes. On the one hand without strict regulation how can a legal body find the surveyor at fault on the other it brings more liability to you because you are the responsible author of the calculations. Tough one...but it sounds like it makes you a better surveyor having to contend.

     

    I try to be as cautious with my suggestions as possible and hope that they were not offending in any way. In any event I hope your survey goes well, I looked up your coordinate system on the web. I like being able to talk with surveyors like you. This site is great.

     

    Respectfully,

    Paul

  • Hi Paul,

    I do my own coordinate transformation and have them verified in the field. Local to Grid, Grid to Local, and other Affine/Linear transformation processes.

    The biggest irony in Philippine practice is the regulating body's incompetence to effectively manage the very meat of land surveying and mapping - Geodesy. What is more painful is wasting rougly a $50M taxpayer's money. Yes, it is very sad and unfortunate that people manning the regulating body don't have the ability cope up with the mandate. Proof? We don't have any website or any mechanism that regulates Philippine practice with regards to coordinate transformation. :(

    Arnel


    Paul Quagge said:

    Hello Arnel,

     

    Working on highway projects here in the us the state DOT usually provides a set of plans that are already at ground...the plan is conceptually an island tied to known reference monuments. If you have a set of plans in grid and you are required to calculate distances in ground and knowing your zones as you described earlier...does your national entity that created the reference system have a website similar to this:

     

    http://geodesy.noaa.gov/

     

    The ngs toolkit provides alot of information to transform data.

     

    I would also recommend this book:

     

    http://books.google.com/books/about/Basic_GIS_Coordinates_Second_Ed...

     

    In any event if you follow the steps to calculate the distances you need, it can be done...

     

    Is there a regulatory group that standardizes what needs to be provided to the surveyor?

     

    Just thinking....

  • Hello Arnel,

     

    Working on highway projects here in the us the state DOT usually provides a set of plans that are already at ground...the plan is conceptually an island tied to known reference monuments. If you have a set of plans in grid and you are required to calculate distances in ground and knowing your zones as you described earlier...does your national entity that created the reference system have a website similar to this:

     

    http://geodesy.noaa.gov/

     

    The ngs toolkit provides alot of information to transform data.

     

    I would also recommend this book:

     

    http://books.google.com/books/about/Basic_GIS_Coordinates_Second_Ed...

     

    In any event if you follow the steps to calculate the distances you need, it can be done...

     

    Is there a regulatory group that standardizes what needs to be provided to the surveyor?

     

    Just thinking....

  • Also in the guidelines, we are allowed 1 deg zone overlap.

    Arnel M. Domag said:

    My previous projects are generally cross section and topo surveys. I also do as-builts.

    We do have our own Philippine Reference System of 1992 - a TM and a Clarke 1866. Our system is divided into five 2 degree zones. A lot narrower than your 6deg wide US State Plane system. With our 2 degree low distortion zone width, project zones are preclassified in our guidelines with less concerns on distortion issues.

    Being a small office with lesser opportunity, I wasn't able to get into huge projects that traverse three or more zones.

    Regards,

    Arnel

  • My previous projects are generally cross section and topo surveys. I also do as-builts.

    We do have our own Philippine Reference System of 1992 - a TM and a Clarke 1866. Our system is divided into five 2 degree zones. A lot narrower than your 6deg wide US State Plane system. With our 2 degree low distortion zone width, project zones are preclassified in our guidelines with less concerns on distortion issues.

    Being a small office with lesser opportunity, I wasn't able to get into huge projects that traverse three or more zones.

    Regards,

    Arnel

  • Hello Arnel,

     

    I like the photos you have displayed on this website. I have a couple of questions about your road survey.

     

    Are you staking centerline, edge of pavement, shoulder, ditch, cut/fill, slope stakes, drainage structures, etc for the contractor building the road? What kind of plans do they have?

     

    Do you know where you are located within your distortion zone? US State Plane Coordinate zones are 158 mile wide. In most cases outside of the dividing lines you are greater than 1...1.0000789 to go from ground to grid....along the dividing lines you are at 1:1, no distortion....inside the lines you are less than 1...0.99999879 to go from ground to grid....if you are surveying where there is low distortion between the grid and the gound there may not be a big difference but if your ground has incline and elevation there may be significant differences.

     

    What coordinate system are you on?

     

    Paul

  • The most important thing to do is to publish "Surveyor's Note"s to provide details of the basis of your survey. You can show the grid if you have them in a list that is marked as such even if you find it more convenient to use local.
    Show the equation or a table of your control points if you have time in both formats. As long as you have good notes and a statement like "The Surveyor's Notes are an essential part of the survey and are to be a part of this project. Contact [your contact information including email address] for the project surveyor's notes."

    If you go back to the beginning of surveying, you will see that the notes and maps of a survey are essential for future surveyors to "retrace the steps" of the previous surveyor. That is basic to the profession to apply to every project, small or large. www.gbreisch.com Gary W. Breisch, Registered Land Surveyor. Surveying since 1965.
    Gary W. Breisch | Solar, Gardening, BeeKeeping & Bee Products, Electric Vehicles, and related equip…
    Solar, Gardening, BeeKeeping & Bee Products, Electric Vehicles, and related equipment.
    • If I understand you right, I am quite confused on showing tabulated equations for the project control points. There are infinite number of convergence and scale factor values in a given project irrespective of size. There are inconsistencies in the field in reference to design grid coordinates. Taking backsigts is an admission of guilt to ignore convergence and scale factor values.
      Design values emanate from non-surveyors who do not have working knowledge in Geodesy. I guess, it is the job of surveyor to correctly stake out design components on ground.
  • If the plans are based on grid coordinates I would stake it using grid coordinates. If the plans have ground coordinates I would stake it using ground coordinates. Modern survey tools are designed to work both ways. If they are not designed to work both ways they need to be.
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