An alternate method for obtaining lat/lon was recently posted to the MapPoint newsgroup by Gilles Kohl that works with pushpins and also works in the European version.

Read the full article: http://www.mp2kmag.com/articles.asp?ArticleID=13

This was submitted by Peter Brooke (www.findware.com) today and is a translation of Gilles Kohl's original code (VB) to C#.

Code:

using System;
using MapPoint;

namespace MapHelper
{
	/// <summary>
	/// Summary description for MapPointUtilities.
	/// </summary>
	public class MapPointUtilities
	&#123;
		private static MapPoint.Location locNorthPole;
		private static MapPoint.Location locSantaCruz;  // Center of western hemisphere
		private static double dblHalfEarth; // Half circumference of the earth &#40;as a sphere&#41;
		private static double dblQuarterEarth;  // Quarter circumference of the earth &#40;as a sphere&#41;
		
		static MapPointUtilities&#40;&#41;
		&#123;
			//
			// TODO&#58; Add constructor logic here
			//
		&#125;
		
		// Compute latitude and longitude given a location object
		// Author&#58; Gilles Kohl
		// &#40;gilles@compuserve.com&#41;
		// 
		// This code is copyrighted freeware - use freely, but please leave this
		// header intact. Suggestions and comments welcome.
		//
		// Converted to C# by Peter Brooke &#40;peter@findware.com&#41;. The
		// same rules as above apply.
		//
		
		static public void CalcPos&#40; MapPoint.Map objMap, MapPoint.Location locX, out double dblLat, out double dblLon &#41;
		  &#123;
		  double l;
		  double d;
			
								// Check if initialization already done
		  if &#40; locNorthPole == null &#41; 
				&#123;
				locNorthPole = objMap.GetLocation&#40; 90, 0, 1 &#41;;
				locSantaCruz = objMap.GetLocation&#40; 0, -90, 1 &#41;;

						// Compute distance between north and south poles == half earth circumference
				dblHalfEarth = objMap.Distance&#40; locNorthPole, objMap.GetLocation&#40;-90, 0, 1&#41; &#41;;

					//  Quarter of that is the max distance a point may be away from locSantaCruz and still be in western hemisphere
				dblQuarterEarth = dblHalfEarth / 2;
				&#125;

				// Compute latitude from distance to north pole
			dblLat = 90 - 180 * objMap.Distance&#40;locNorthPole, locX&#41; / dblHalfEarth;

			d = objMap.Distance&#40;objMap.GetLocation&#40;dblLat, 0, 1&#41;, locX&#41;;

				// convert latitude to radian
			l = &#40;dblLat / 180&#41; * Math.PI;

				// Compute Longitude from great circle distance
			dblLon = 180 * Math.Acos&#40;&#40;Math.Cos&#40;&#40;d * 2 * Math.PI&#41; / &#40;2 * dblHalfEarth&#41;&#41; - Math.Sin&#40;l&#41; * Math.Sin&#40;l&#41;&#41; / &#40;Math.Cos&#40;l&#41; * Math.Cos&#40;l&#41;&#41;&#41; / Math.PI;
						
						//Correct longitude sign if located in western hemisphere
			if &#40; objMap.Distance&#40;locSantaCruz, locX&#41; < dblQuarterEarth &#41;
				dblLon = -dblLon;
		&#125;
	&#125;
&#125;

Hi -

I was wondering if you had any other C# mappoint COM examples. I have been having some trouble locating and making pins for only certain types of nearby features (such as all hospitals in a 2 mile radius of boston's city center.) Is anyone familiar with the PlaceCategory property?

Thanks!
Chris

Not thoroughly tested, and no error handling (ex: NULL pointers and bad hr's):

Code:

//
// Compute latitude and longitude given a location object
// Author: Gilles Kohl
// (gilles@compuserve.com)
//
// http://www.mp2kmag.com/a13--extract.lat.lon.mappoint.html
//
// This code is copyrighted freeware - use freely, but please leave this
// header intact. Suggestions and comments welcome.
//
HRESULT CalcPos(MapPoint::_Map* oMap, MapPoint::Location* oLocation, double* dLatitude, double* dLongitude)
{
	HRESULT hr = S_OK;

	static CComPtr<MapPoint&#58;&#58;Location>	locNorthPole	= NULL;
	static CComPtr<MapPoint&#58;&#58;Location>	locSouthPole	= NULL;
	static CComPtr<MapPoint&#58;&#58;Location>	locSantaCruz	= NULL;		// Center of western hemisphere
	static double						dHalfEarth;					// Half circumference of the earth &#40;as a sphere&#41;
	static double						dQuarterEarth;				// Quarter circumference of the earth &#40;as a sphere&#41;
	static double						dPi				= 3.14159265358979323846;	// TODO&#58; Where is M_PI?

	if &#40;locNorthPole == NULL&#41;
	&#123;
		hr = oMap->GetLocation&#40;90,		0,		0,	&locNorthPole&#41;;
		hr = oMap->GetLocation&#40;-90,		0,		0,	&locSouthPole&#41;;
		hr = oMap->GetLocation&#40;0,		-90,	0,	&locSantaCruz&#41;;

		// Compute distance between north and south poles == half earth circumference
		hr = oMap->Distance&#40;locNorthPole, locSouthPole, &dHalfEarth&#41;;

		// Quarter of that is the max distance a point may be away from locSantaCruz and still be in western hemisphere
		dQuarterEarth = dHalfEarth / 2.0;
	&#125;

	double dDistanceToNorthPole;
	hr = oMap->Distance&#40;locNorthPole, oLocation, &dDistanceToNorthPole&#41;;

	// Compute latitude from distance to north pole
	*dLatitude = 90.0 - &#40;180.0 * dDistanceToNorthPole / dHalfEarth&#41;;

	// Compute great circle distance to locX from point on Greenwich meridian and computed Latitude
	CComPtr<MapPoint&#58;&#58;Location>	locGreenwichAndLatitude;
	hr = oMap->GetLocation&#40;*dLatitude, 0, 0, &locGreenwichAndLatitude&#41;;

	double d;
	hr = oMap->Distance&#40;locGreenwichAndLatitude, oLocation, &d&#41;;

	// convert latitude to radian
	double l = &#40;*dLatitude / 180.0&#41; * dPi;

	// Compute Longitude from great circle distance
	*dLongitude = 180 * acos&#40;&#40;cos&#40;&#40;d * 2 * dPi&#41; / &#40;2 * dHalfEarth&#41;&#41; - sin&#40;l&#41; * sin&#40;l&#41;&#41; / &#40;cos&#40;l&#41; * cos&#40;l&#41;&#41;&#41; / dPi;

	// Correct longitude sign if located in western hemisphere
	hr = oMap->Distance&#40;locSantaCruz, oLocation, &d&#41;;
	if &#40;d < dQuarterEarth&#41;
		*dLongitude = -&#40;*dLongitude&#41;;

	return hr;
&#125;

Pv@swooby.com

I simply created a subclass of pushpin and keep track of the lat long in two members. It is a PITA but far less expesive and bug prone.

Plus the spherical model of the earth is only good if you don't require lots of precision (don't take that as a flame on your work you did a fine job.)

Here's a correction for the Arccos routine -- recently the trig functions were moved and renamed -- be sure to import System.Math

Private Function Arccos(ByVal x As Double) As Double
If x = 1 Then
Arccos = 0
Exit Function
End If
Arccos = Atan(-x / Sqrt(-x * x + 1)) + 2 * Atan(1)
End Function

Hi,

I made it with a singleton class. No need to create, it create itself and there is only one instance of it in the project:

Code:

    public sealed class MPTools
    {
        static readonly MPTools instance = new MPTools();
        static Map map;
        static Location locNorthPole;
        static Location locSantaCruz;
        static double halfEarth;
        static double quarterEarth;

        // Explicit static constructor to tell C# compiler
        // not to mark type as beforefieldinit
        static MPTools()
        {
        }

        MPTools()
        {
        }

        public static MPTools Instance
        {
            get
            {
                return instance;
            }
        }

        public static void CalcPos(Map activeMap, Location loc, out double lat, out double lon)
        {
            if (map != activeMap) { // user may have load another active map since last time
                map = activeMap;
                locNorthPole = map.GetLocation(90, 0, 0);
                locSantaCruz = map.GetLocation(0, -90, 0);
                halfEarth = map.Distance(locNorthPole, map.GetLocation(-90, 0, 0));
                quarterEarth = halfEarth / 2;
            }
            lat = 90 - 180 * map.Distance(locNorthPole, loc) / halfEarth;
            double D = map.Distance(map.GetLocation(lat, 0, 0), loc);
            double L = Deg2Rad(lat);
            lon = 180 * Math.Acos((Math.Cos(D * Math.PI / halfEarth) - Math.Pow(Math.Sin(L), 2)) / Math.Pow(Math.Cos(L), 2)) / Math.PI;
            if &#40;map.Distance&#40;locSantaCruz, loc&#41; < quarterEarth&#41;
                lon = -lon;
        &#125;

        private static double Rad2Deg&#40;double rad&#41;
        &#123;
            return rad * 180 / Math.PI;
        &#125;

        private static double Deg2Rad&#40;double degree&#41;
        &#123;
            return degree * Math.PI / 180;
        &#125;
    &#125;

Hi ,
I want lat long information for center of city how i could get it..?
please suggest me some ways to go ahead.
Thanks in advance
--Sidh