# A Simple Geo Fencing Using Polygon Method

, 7 Mar 2010 CPOL
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A Simple Geo fencing using polygon method

## Introduction

One of the important feature of GPS Tracking software using GPS Tracking devices is geo-fencing and its ability to help keep track of assets. Geo-fencing allows users of a GPS Tracking Solution to draw zones (i.e., a Geo Fence) around places of work, customer’s sites and secure areas. These geo fences when crossed by a GPS equipped vehicle or person can trigger a warning to the user or operator via SMS or Email.

## Geo Fence

A Geo fence is a virtual perimeter on a geographic area using a location-based service, so that when the geo fencing device enters or exits the area, a notification is generated. The notification can contain information about the location of the device and might be sent to a mobile telephone or an email account. Reference: http://en.wikipedia.org/wiki/Geofence.

## Background

For geo-fencing, I used Polygonal geo-fencing method where a polygon is drawn around the route or area. Using this method, GPS Tracking devices can be tracked either inside or outside of the polygon.

## Determining a Point

The function will return `true `if the point X,Y is inside the polygon, or `false `if it is not. If the point is exactly on the edge of the polygon, then the function may return `true `or `false`. Thanks for the article “Determining Whether A Point Is Inside A Complex Polygon”.

```public bool FindPoint(double X, double Y)
{
int sides = this.Count() - 1;
int j = sides - 1;
bool pointStatus = false;
for (int i = 0; i < sides; i++)
{
if (myPts[i].Y < Y && myPts[j].Y >= Y ||
myPts[j].Y < Y && myPts[i].Y >= Y)
{
if (myPts[i].X + (Y - myPts[i].Y) /
(myPts[j].Y - myPts[i].Y) * (myPts[j].X - myPts[i].X) < X)
{
pointStatus = !pointStatus ;
}
}
j = i;
}
return pointStatus;
}```

## Creating a Polygon

On the map, draw a polygon to the area which is to be geo-fenced and capture the corner points of the polygon and store into XML file (see: PolygonPoints.XML). `loadData() `function will create a polygon using defined corner points in the XML file.

```private void loadData()
{
DataSet ds = new DataSet();

foreach (DataRow dr in ds.Tables[0].Rows)
{
Point p = new Point();

//Convert Latitude into degrees
String Lat = dr[0].ToString();
double LatSec = Double.Parse(Lat.Substring(4, 4)) / 6000;
double LatMin = (Double.Parse(Lat.Substring(2, 2)) + LatSec) / 60;
p.X = Double.Parse(Lat.Substring(0, 2)) + LatMin;

//Convert Longitude into degrees
String Long = dr[1].ToString();
double LongSec = Double.Parse(Long.Substring(5, 4)) / 6000;
double LongMin = (Double.Parse(Long.Substring(3, 2)) + LongSec) / 60;
p.Y = Double.Parse(Long.Substring(0, 3)) + LongMin;
}
} ```

## Sample Code

When you run and enter latitude and longitude outside the polygon, then a message shows point not found in the route and otherwise it shows point found in the route.

```PolyGon myRoute = new PolyGon(points);
bool stat = myRoute.FindPoint(Double.Parse(txtLat.Text.ToString()),
Double.Parse(txtLang.Text.ToString()));
if(stat)
{
lblResult.Text = "Point found in the route";
}
else

## Share

Architect Vajra Infratech Pvt. Ltd.,
India
No Biography provided

 First Prev Next
 Check Latlong is inside rectangle geofence or not Chintan Desai1988 23-Dec-14 23:11
 Return always => False Member 9835537 14-Feb-13 8:22
 how mark road and get coordinates HarshaAluthge 22-May-12 20:26
 Accessing coordinates of polygon Member 8267456 7-May-12 5:46
 My vote of 3 kiran kumar 412 21-Dec-11 22:33
 Quick question Member 8033562 18-Nov-11 7:09
 need help! Reinhard Navarro 5-Oct-11 19:26
 Formula Error borno 5-Aug-11 9:49
 Geofencing? Polygon? bulleh 4-Jul-11 1:40
 Re: Geofencing? Polygon? RajuBhupathi 5-Jul-11 0:41
 Re: Geofencing? Polygon? bulleh 7-Jul-11 2:22
 Re: Geofencing? Polygon? bulleh 20-Jul-11 1:22
 Re: Geofencing? Polygon? borno 5-Aug-11 9:40
 Re: Geofencing? Polygon? bulleh 6-Aug-11 0:38
 Re: Geofencing? Polygon? zinobu 24-Aug-11 8:30
 Getting decimal data to work. domanet 16-Jun-11 1:23
 Re: Getting decimal data to work. RajuBhupathi 19-Jun-11 23:44
 Re: Getting decimal data to work. domanet 20-Jun-11 8:04
 How to convert coordinates to XML file? Tadysas 26-Mar-11 7:12
 Re: How to convert coordinates to XML file? Tadysas 26-Mar-11 7:35
 formula error Noman Aftab 29-Dec-10 2:48
 i am using your geofence code in my gps application. i cannot call loadData(); before i am able to get the GPS coordinates. this is what my application does, when it launches, it get the GPS coordinates of the device, then using your geofence code, it searches through several of the xml files until it finds one where the result is "INSIDE", then it uses this data to show the location name. any other way to do this?
 How do you capture the points of the polygon? Qwertie 8-Mar-10 19:15
 Re: How do you capture the points of the polygon? RajuBhupathi 9-Mar-10 20:52
 ZIP corrupt Member 3279273 7-Mar-10 4:17
 Re: ZIP corrupt RajuBhupathi 7-Mar-10 5:34
 Re: ZIP corrupt Member 3279273 7-Mar-10 8:41
 Re: My vote of 2 RajuBhupathi 7-Mar-10 5:33
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