I'm thinking about some suitable model for storing meridians and parallles. Meridians and parallels should be kept as lines.
Possible models:
A) "Topologic" model Each point stores pointer to north, south, east and west points.
class Point
{
private:
double lat;
double lon;
Point *north;
Point *south;
Point *east;
Point *west;
...
};
class Meridian
{
private:
double longitude;
Point *start;
Point *end;
unsigned int points_total;
};
class Parallel
{
private:
double latitude;
Point *start;
Point *end;
unsigned int points_total;
};
Pros:
- We can traverse each meridian in north-south direction and vice versa. We can traverse each parallel in east-west direction and vice versa.
- We determine whether each point is inside meridian or parallel (using pointers).
- Small storage requirements...
Cons:
- Only sequential access to every meridian/parallel point
- Problems with copy constructors and operator =. A copy of a set of points should be done in several phases: Create a new instance of points, adding topological relations between points using std::map, change the endpoints of the meridian/parallel... It is rather slow...
The second disadvantage has led me to abandon the model.
B) List of points. Meridian/parallel stores list of points, there are no topological relationship.
class Point
{
private:
double lat;
double lon;
};
class Meridian
{
private:
double longitude;
std::vector <Point> points;
};
class Parallel
{
private:
double latitude;
std::vector <Point> points;
};
Pros:
- We can traverse each meridian in north-south direction and vice versa. We can traverse each parallel in east-west direction and vice versa.
- No problems with copy constructors and operator =
- Sequential and direct access to every point.
Cons:
- We can not determine whether each point belongs to any meridian/parallel (using pointers) or not.
- Larger storage requirements.
- At any point we are not able to find previous / next point of the meridian / parallel, we do not have pointers...
The last disadvantage could lead to the abandonment of a model and leads me to think about a modified variant of topological model....
I am performing some spatial simulations and representing results in several cartografic projections, so efficient data storage is very important for me.
Maybe someone could propose a better model :-). Thanks for your answers...
