Data in a polygon.

[45romeo]

I have a bunch of x,y point data that I have reduced to a regular polygon that is bounded by straight lines on the north, south ,east and west. What I want to do is farther sort the data by weather it is inside or out sided of a four sided polygon that is not oriented to the cardinal directions. the four corners of the polygon starting in the nw and working clockwise are :
987664.3312
16274156.0668

989619.8648
16273133.5327

989036.7498
16271869.6288

987203.9753
16273209.5904

Any help on how to define this polygon or to tell if a point was left or right of a line between two points would be appreciated!

Thanks in Advance
45romeo

 

[Gerald Higgins]

Are the lines joining each corner, straight ?

If so, I think it would be possible, by evaluating the slope of each line, to determine which side of each line any point is on.