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Andy · Guest

I have an assignment to read in a text file containing longitude and
latitude and convert to X,Y coordinates using the following formulas:
y = (latitude ' - 25 ) * 20 / 3 + latitude " * 11/100
x = 100 - ( (longitude '- 70 ) * 20 / 3 + longitude " * 11/100 )

25' 00" 70' 00"
25' 00" 85' 00"
40' 00" 85' 00"
40' 00" 70' 00"
30' 00" 80' 00"
32' 30" 77' 30"

How do I read in the latitude degree/minutes and the longitude
degree/minutes and assign them so they can be used in the conversion
formula?

What's the best way to parse the file and assign the degree/minutes
appropriately?

Any point in the right direction would be greatly appreciated.

Thanks,
Andy...

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Aniket Kulkarni · Guest

Hi Andy,
Using the istream extraction operator>> for long datatype this can be
achieved.
e.g:

/*
* Lets use this structure 'LL' to represent either of longitude and
* latitude. The degrees and minutes (Hopefully ' is deg and " is min,
* but I am not sure) are represented by deg and min respectively
*/
typedef struct longitude_latitude {
longitude_latitude( int d=0, int m=0 ) : deg(d), min(m) {}
long deg, min;
}LL;

/*
* The data is a pair of 2 LL structures, one for longitude, one for
* latitude and the storage would be a vector of such pairs
*/
typedef std::pair<LL, LL> DATA;
typedef std::vector<DATA> VEC;

/*
* The extraction operator, that will parse one line of the file
* It assumes the format shown above, and reads the long, and ingnores
* the following single/double qoutes and goes on to the next
*/
std::istream& operator>> (std::istream& in, DATA& l )
{
char quotes[3];
in >> l.first.deg; in >> quotes;
in >> l.first.min; in >> quotes;
in >> l.second.deg; in >> quotes;
in >> l.second.min; in >> quotes;
return in;
}

/*
* Thus for parsing the entire file, the following code would do
*/
ifstream in( "parse.txt" );
DATA l; VEC v;
while (in >> l) v.push_back( l ) ;

Now that the vector "v" has the data nicely parsed, we can transform
the data using the std::transform

/*
* Transform one DATA from the vector
*/
inline DATA formula( const DATA& l )
{
return DATA(
100 - ((l.first.deg - 70 ) * 20 / 3+l.first.min * 11/100), // x
(l.second.deg - 25) * 20 / 3 + l.second.min * 11/100 ); // y
}

/*
* Apply transformation.
* This overwrites vector v, and it now contains the X,Y coordinates.
* The X coordinate is v[0].first.deg and Y coordinate is
* v[0].second.deg
*/
std::transform( v.begin(), v.end(), v.begin(), formula );

for (VEC::iterator i = v.begin(); i != v.end() ; i++ )
std::cout << "X: " << (*i).first.deg
<< " Y: " << (*i).second.deg << "n";

In the example you have mentioned, this prints
X: 400 Y: 300
X: 400 Y: 400
X: 300 Y: 400
X: 300 Y: 300
X: 366 Y: 366
X: 350 Y: 349

HTH
~ aniket

Werner Salomon · Guest

[email]anaylor (AT) nc (DOT) rr.com[/email] (Andy) wrote in message news:<cc436276.0310252153.411320d1 (AT) posting (DOT) google.com>...