Enter Survey Coordinates into Parcel Fabric Traverse Grid

Question

I have a survey that only gives me the coordinate points for a parcel I need to draw into the parcel fabric. I am used to seeing bearings and distances - how do I take these coordinate points and turn them into bearings and distances without teaching myself a bunch of trig? Alternately, is there a tool in the parcel fabric wherein I can enter the points instead of the bearing and distance to create the parcel?

points.JPG

ThomasHoman · Answer

Hi Anne,

Hopefully I don't make too much of a hash of this - I have had many mentors over the years so hope to do them justice.

The lat/long coordinates are great for determining coordinates on our earth but poor for logical distance distance determination. For example the length from 0.0 to 0.1 degrees at the equator is different than the distance from 43.5 to 43.6 degrees in Souix Falls. Thus an artificial XY projected grid is created that covers and manages error within a specific area. For example where I cam in Arizona there are 3 projection zones running North/South while South Dakota appears to have two that run more East/West. The Arizona zones have a specific error budget (AZ zones have default error budgets of 1:10,000) to manage coordinate distortion when moving from a sphere to a plane.

The surveyor that created your plat also appears to have created (via the 0.999851261 scale factor) what amounts to a custom projection that places the error into a much smaller area. By adjusting the scale factor one effectively slides the projected plane to be more coincident with local elevation. This moves to the grid vs ground discussion where strong elevation changes in a zone can create significant variations in calculated horizontal distances.

One great resource is Michael Dennis' PHD, PE, RLS outstanding presentations on the subject. https://geodeticanalysis.com/ghost/

Regards,

Tom

AnneBransford1 · Answer

What an excellent and helpful reply! I have a few further questions - I don't actually know what the northing and easting are in terms of xy coordinates, or what the large numbers are in reference to. I don't have a ton of experience reading surveys. Everything else you mentioned makes a lot of sense, but I'm struggling with the basics a bit here.

ThomasHoman · Answer

Hi Anne,

Since you have the point coordinates along with their projection, what would you think of  adding the points as a CSV and then plotting the XY. Then it's just a matter of following/snapping the dots. Saves on the trig time

To create the CSV I cropped the jpg to the coordinates, brought the image into Acrobat Pro and used OCR functionality, exported to a text file, cleaned up and here you are. I'm sure there are many alternate ways to get from image to text but these resources were right at hand.

Looking a little deeper you will likely have to do a little scaling as the projection is incomplete. This can be attempted manually or via modifying the default coordinate system. You can right click on the projection assignment and choose to copy and modify then, if you select the Lambert Conformal projection the scale factor appears in the dialog and can be converted from the default 1.0 to the offered 0.999851261. Then the modified projection can be saved and applied. Hopefully that is the only deviation from the default projection parameters.

Regards,

Tom

Points.csv