[OpenLayers-Users] Get point on line?

[shane_china]

Bill Thoen wrote:
> 
> shane_china wrote:
>> In openlayers,
>> I have a straight line with two endpoints. How could I get a point on the
>> line with given distance to one endpoint? Thank you. 
>>   
> 
> You can find a point anywhere on a line by using a ratio calculation.  
> Start with the distance to your point divided by the total distance of 
> your line, then your new X coordinate = the difference between the X 
> coordinates of the endpoints times the ratio (plus the X coordinate of 
> the starting line endpoint. For example, if your endpoints are at 
> coordinates (X0, Y0) and (X1,Y1) then the Cartesian distance is
> 
> D = sqrt((X1-X0)*(X1-X0) + (Y1-Y0)*(Y1-Y0))
> 
> Then if the ratio between this and the distance to your point is d, your 
> new point's coordinates will be:
> 
> X= X0+(X1-X0)*d/D
> Y=Y0+(Y1-Y0)*d/D
> 
> HTH,
> - Bill Thoen
> 
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> 





So thank you for your answer. Your advise is in X-Y coodinates. Does this
method also apply to lon lat coodinates? Our earth is a ball, so is it
different?
I haven't demonstrate it yet.
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