What about land survey directions?

[Jack]

A very similar question was asked over a year ago, but all the
responses were confused and there was no actual answer given, so I
thought I'd ask myself.

I have a survey map for a piece of land, and the perimeter of the
property is defined by the line segments between a set of 34 points.
I do not have lat/long values for these points -- instead, I have 34
"survey directions" which are effectively bearing and range values.
This format is explained in the Wikipedia page on 'plat'. Here is the
relevant section:

The property boundaries are indicated by bearing and distance. The
bearing is in the format of degrees, minutes, seconds with compass
point letters before and afterward to indicate the compass quadrant.
For example N 38 00 00 E is 38 degrees into the northeast quadrant or
38 degrees east of north. Similarly S 22 00 00 W is 22 degrees west of
south. Note that north here is true north, so magnetic orientation
must be corrected for magnetic declination.

As an example, point L1 has a direction "N 43deg21min45sec W" and a
distance "100.76 feet". This means point L2 can be found 100.76 feet
from point L1 at a bearing roughly 43.3 degrees north of west.

I recognize that I have not identified a lat/long value for any
individual point to act as an anchor, but eleven points lie along a
curved section of road so I figure I could slide the file around until
it fits the curve and then it'd be in the right place. I may be able
to get an approximate value for one of the points but it'd be just
approximate.

Given all that, how do I make a KML file to draw the polygon defined
by these points?

[Roman N]

Hi Jack,

So you'd have to somehow map these coordinates into lat/lng; the
question is of course, how to do this mapping.

Your best bet (if no utilities already exist for this) is to write a
program or small script that converts such points to lat/lng and then
generates the necessary KML.

I'd recommend using JavaScript, so that you could then interactively
do the approximation/fitting and visualize the results with the Earth
API (http://code.google.com/apis/earth).

Your main goal is probably to write code to solve this problem:
- calculate the point that is D meters away, in bearing/direction H,
from origin point O.

Some links that will help:
http://williams.best.vwh.net/avform.htm#Intermediate (thanks fraser!)
http://earth-api-samples.googlecode.com/svn/trunk/lib/math3d.js
http://earth-api-samples.googlecode.com/svn/trunk/lib/geplugin-helpers.js

I realize this is less satisfactory of an answer than a full on code
sample, but it should be a good starting point; I don't know of any
existing tools that have accomplished this task.

Roman

[csnoke]

To answer your question... I think the best way to do what you're
asking would be to use Google Sketch-up to draw out the shape of your
parcel. Start by opening Sketch up and Tools>Get current view, the
using the Protractor tool lay out the first angle and Pencil tool to
draw the first line, continue along the rest of the calls. Using this
method you could rough out the entire shape of the parcel. Then use
the Tools>Google Earth>Place Model to get the file overlayed on google
earth.

One thing I think you might find... the plat map or description you
have likely states something like "Basis of bearings being the such
and such line of the such and such parcel..." meaning that the
bearings you have are not necessarily based off of magnetic north. It
other words.. your sketchup drawing will need a rotation and a shift
in order to fit... this could present a problem since there's not a
lot of flexibility once you place the model in google earth. You may
have to try place it once then going back into sketch up and rotating
the model and trying to place it again to get it to fit.

One other thing.. don't be too surprised if you parcel doesn't close
within a few feet (or more).

Good luck!