[Qgis-developer] Vincenty's Formulae

[Jorge Tornero - Listas]

Hi, Martin, thank you for your answer.

Well, the problem is that QgsDistanceArea class provides a function to 
(that's what I think due to my limitations in C++) calculate the 
distance an bearing between two points (start-end points). This is what 
INVERSE Vicenty Formula does, and I think thatthat's the formula 
implemented in QgsDistanceArea with its method computeDistanceBearing. 
This metod, as stated in the API documentation,calculates distance from 
two points on ellipsoid based on inverse Vincenty's formulae: given a 
departure point P, and destination point P2, it yields the distance 
between the two points and the bearing from P to P2 as well as from P2 to P.

But I want to perform another calculation: Calculate the destination 
point P2 given an departure point P, a bearing B and a distance D. 
That's what direct Vincenty Formulae performs and it's what I'm looking 
for :(

Thank you very much,

Jorge Tornero





El 12/12/13 13:24, Martin Dobias escribió:
> On Thu, Dec 12, 2013 at 2:36 PM, Jorge Tornero - Listas
> <jtorlistas at gmail.com> wrote:
>> Dear all.
>>
>> I'm currently working on a python plugin for QGIS which deploys points along
>> lines on a given distance basis. The lines, say transects, are created
>> placing an initial point and then providing a bearing for the line. Then, n
>> stations/smapling points are deployed in its place.
>>
>> I'm using Vincenty's Formula to get the coordinates for the points. So far,
>> I've found an python implementation for this, but I haven't been able to
>> know under which license is released the code, as far as I have found the
>> code in a forum
>> (https://isis.astrogeology.usgs.gov/IsisSupport/index.php?topic=408.0) but
>> the link provided in the message for the original code can't be followed.
>>
>> As far as I know, in QGIS API there is no direct Vincenty's formula to
>> compute in this way (point, azimuth/bearing + distance to destiny), and I
>> want to make the plugin dependence-free as possible, so my questions are:
>>
>> 1) Do you know if, in QGIS API, is there and usable implementation of
>> Vincenty's direct formula?
> Hi Jorge
>
> What about QgsDistanceArea class? It does the calculation of distance
> / bearing on ellipsoid.
>
> Regards
> Martin