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- Comment procéder pour calculer des distances entre un champs A et un champs B ?

Vous posez un peu les mauvaises questions. Une distance n'a pas vraiment de signification entre deux champs. C'est entre deux points que vous pouvez calculez une distance.

Quand vous dites automatisez, c'est par un peu de prog MapBasic, ou juste une série de manipulation MapInfo. Les deux sont possibles. Si vous avez MapBasic et quelques bases, ça ne sera pas trop difficile. Avec MapInfo seul, c'est un peu plus fastidueux, il faudra effectivement dupliquer les tables, mais c'est faisable aussi. Méthode à déterminer avant de poursuivre...

Distance = Racine((X1-X2)²+Y1-Y2)²)

Distance( ) function

Purpose : Returns the distance between two locations.

Syntax : Distance ( x1 , y1 , x2 , y2 , unit_name )

x1 and x2 are x-coordinates (e.g., longitude)
y1 and y2 are y-coordinates (e.g., latitude)

unit_name is a string representing the name of a distance unit (e.g., “km”)

Return Value : Float

Description

The Distance( ) function calculates the distance between two locations. The function returns the distance measurement in the units specified by the unit_name parameter; for example, to obtain a distance in miles, specify “mi” as the unit_name parameter.

See the Set Distance Units statement for the list of available unit names.

The x- and y-coordinate parameters must use MapBasic’s current coordinate system. By default, MapInfo Professional expects coordinates to use a longitude, latitude coordinate system. You can reset MapBasic’s coordinate system through the Set CoordSys statement. If the current coordinate system is an earth coordinate system, Distance( ) returns the greatcircle
distance between the two points. A great-circle distance is the shortest distance between two points on a sphere. (A great circle is a circle that goes around the earth, with the circle’s center at the center of the earth; a great-circle distance between two points is the distance along the great circle which connects the two points.)

For the most part, MI Pro performs a Cartesian or Spherical operation. Generally, a spherical operation is performed unless the coordinate system is nonEarth, in which case, a Cartesian operation is performed.

Example

Code:

Dim dist, start_x, start_y, end_x, end_y As Float
Open Table ”cities”
Fetch First From cities
start_x = CentroidX(cities.obj)
start_y = CentroidY(cities.obj)
Fetch Next From cities
end_x = CentroidX(cities.obj)
end_y = CentroidY(cities.obj)
dist = Distance(start_x,start_y,end_x,end_y,”mi”)

See Also
Area( ), ObjectLen( ), Set CoordSys, Set Distance Units