How to find the Local Government Area name using lat/long?

Question

I'd like my iPhone app to respond to the device owner with his/her Australian LGA (local government area) name using their lat/long.

I've found this page below with a Shapefile:

http://www.abs.gov.au/AUSSTATS/[email protected]/DetailsPage/1259.0.30.001July%202010?OpenDocument

However, on my Windows server I only have MS-SQL and my programmer's preferred language is c#.

Can anyone possibly help with this?

My programmer is having some issues with this task and I am pasting his email below as someone may spot what the issue could be:

Bad News - SharpMap does not implements features we need (Within, Contains e.t.c.) for polygons our map contains. So, I could not write app logic we planned.

Good News - SharpMap loads SHP file more correct then my previous custom application and therefore there is no errors as I see after loading.

To keep moving forward I have found the next way: I fill each separate region using different color. In our case we have more than 500 regions. So, I shift B part in RGB color from 1 to 255, then G part, and then R part after all. So, I will have map like this one (in server memory, not displayed to user):

http://screencast.com/t/xxMtI181z

but more bigger size to avoid errors. Then I will re-calculate user coordinates to map pixel values and determine which pixel color is in that place. Using color value I will get region name from the list of regions (gotten from DBF file).

So, looks like we still can solve this task. I will continue today. My next steps are: bigger image, re-calc coordinates, determine color.

Answer 1

Can't you simply use point in polygon search?

Something like SELECT dbo.Point_In_Polygon etc, etc.

I'd simply load the coordinates of the polygon to one table and then perform a PiP on that table, using your coordinates.

Unless I have missed a point?

Here's http://www.vb-helper.com/howto_net_point_in_polygon.html a page which shows VB.NET code to do the search, but you do need to know the parts of the polygon

Answer 2

This might be a helpful start

https://stackoverflow.com/questions/2537723/iphone-sdk-get-gps-coordinates-from-google-maps

you can use the users location and have google maps locate the overlay (your shapefile in ms-sql) and do an intersect with the location point and polygon (shapefile). Extract the attributes and display the LGA.