Shape files and Polygons

[Welshbird]

Ok - newbie here still.....

I have polygon files of areas, and what I need to do is take places (with an x,y) and calculate in which polygon they exist.

Is this even possible?

Fee

The question should be [red]Is it worth trying to do?[/red] not [blue] Can it be done?[/blue]

 

[sedj]

If you have a spatial database such as Oracle, its very easy (as long as you load the source data into it obviously).

If you do not have a database, its still possible, but a little bit more tricky, and you will need a knowledge of programming in a langauage such as Java or C/C++ or C# .

How many records are there in the source data ?
Can you post an example of one of the polygons ?

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[gmmastros]

There are many algorithms on the internet to do this.

http://en.wikipedia.org/wiki/Point_in_polygon

http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html

I have some VB code that I can post if you are interested. Let me know.

I was also working on a SQL Server solution to this problem. I haven't quite gotten it worked out, but you can take a look here: thread183-1184078 to see where I was headed.

-George

Strong and bitter words indicate a weak cause. - Fortune cookie wisdom

 

[Welshbird]

I think part of my problem is that we have (sort of) created the shape files in Arcview, but what we have done is allocate specific buildings into geographically chunks. But, that means we don't actually have real shape files, as these are not really shape files.


*sigh*

Just call us 'Arf a job Ltd..... Very limited....

Now I need (I guess) to try and work out where the boundaries really would be. Time for at least a glass of wine I suspect! (Well, it is Friday night)

Fee

The question should be [red]Is it worth trying to do?[/red] not [blue] Can it be done?[/blue]

 

[sedj]

So ... do you have the polygon ordinates ?

Do you want help in writing a programme/solution ?

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[Welshbird]

We sadly don't have the boundaries of an area. We have several points within it, but that's as far as it goes.

In actual fact we have the boundaries of the postcode areas which it is contained in; and this might be either full postcode, half-sector or sector. So, we kinda have this information, except where we have donut-type gaps.

I know this is going to come back and haunt me soon, but until then I'm still trying to ponder how I calculate the postcode area donuts. If these are bordered by one area then thats quite easy - its where they are bordered by two or more areas that I get confused.

(I'm just trying not to be cross about the original comment of "We don't need to write a spec - it'll only waste time - we'll just get on and do it"... Grrrrrr)

Fee

The question should be [red]Is it worth trying to do?[/red] not [blue] Can it be done?[/blue]

 

[detrix79]

What software are you useing? if you are using ESRI then you have the capability built in.

In arcview click on tools and then click add xy data. after you have added the data then you can do a select by location.

if you need further instruction plese let me know i would love to help.

peace

 

[Welshbird]

Thanks detrix - I might well come back to you on that!

Fee

The question should be [red]Is it worth trying to do?[/red] not [blue] Can it be done?[/blue]