Hi,
I think you're right again.
For a better result with non puntal geometries, one should use
getCentroid instead of getCoordinate in getCenterOfMass method
One could also compute something closer to a center of mass by using the
area or the length of the feature as the "mass" of each feature
Of course, computing getCentroid + getArea + getLength can take much
more time than a single getCoordinate()
Michaël
> While we are on the topic, could you guys look at the getCenterOfMass
> method in the same class. Its supposed to act like the
> Geometry.getCentroid method, but for a group of Feature objects.
> However, I didn't see any use of the getCentroid method on the member
> feature geometries from within the method. There is some math going on
> in the method using coordinates obtained via the getCoordinate()
> method, but I don't think it does what it is supposed to.
>
> I think we should clarify the purpose of the method in the javadoc
> comment, or perhaps discuss alternate implementations of the
> getCenterOfMass method. This might be a good discussion for the JTS
> mailing list.
>
> I know you guys are busy. Only peek if you have time. I'll have a
> revamped FeatureCollectionTools class ready by the end of the week I
> hope. There should be some stuff in there I can port back to OJ after
> you guys take a look. The revamped class will include a method to
> compare the equality of FeatureCollections, which should be handy for
> unit testing.
>
> SS
>
> On Wed, Jun 24, 2009 at 10:44 AM, Larry Becker<becker.la...@gmail.com> wrote:
>
>> Yes, you are right. The getCoordinate() only works when looping through a
>> single feature's points.
>>
>> Larry
>>
>> On Wed, Jun 24, 2009 at 12:12 PM, Sunburned Surveyor
>> <sunburned.surve...@gmail.com> wrote:
>>
>>> Thanks for the responses Larry and Michael. I have attached a text
>>> file with my modified method. (Note: There are other changes to my
>>> method that I would not include in the patch.) I believe that the use
>>> of getCoordinate method should be replaced with the
>>> getEnvelopeInternal method.
>>>
>>> But I could be wrong.
>>>
>>> SS
>>>
>>> On Wed, Jun 24, 2009 at 6:22 AM, Larry Becker<becker.la...@gmail.com>
>>> wrote:
>>>
>>>> Hi SS,
>>>>
>>>> If you are talking about this code, it looks like it works to me:
>>>>
>>>> public static Envelope getEnvelopeForFeatures(Feature[] features){
>>>> Envelope env = null;
>>>> Feature feat;
>>>>
>>>> for (int i=0; i<features.length; i++){
>>>> feat = features[i];
>>>> if (env==null){
>>>> env = new Envelope(feat.getGeometry().getCoordinate());
>>>> } else {
>>>> env.expandToInclude(feat.getGeometry().getCoordinate());
>>>> }
>>>> }
>>>>
>>>> return env;
>>>> }
>>>>
>>>> regards,
>>>> Larry
>>>>
>>>> 2009/6/24 Michaël Michaud <michael.mich...@free.fr>
>>>>
>>>>> Hi,
>>>>>
>>>>>> I believe there may be a bug in the getEnvelopeForFeatures method of
>>>>>> the FeatureCollectionTools class. It uses the Geometry.getCoordinate
>>>>>> method when it should use the Geometry.getEnvelopeInternal method.
>>>>>> This may result in the calculation of an envolope that does not
>>>>>> include the envelope of all features.
>>>>>>
>>>>>>
>>>>> I think you're right. Using getCoordinate to compute an envelope is not
>>>>> correct.
>>>>> Feel free to fix it. You've got a correct implementation in
>>>>> com.vividsolutions.jump.feature.FeatureDataset.getEnvelope().
>>>>>
>>>>> Michaël
>>>>>
>>>>>> When I get my modified version of the getEnvelopeForFeature method
>>>>>> tested I will submit a patch.
>>>>>>
>>>>>> SS
>>>>>>
>>>>>>
>>>>>>
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>>>>>> https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
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>>>>>
>>>>
>>>> --
>>>> Larry Becker
>>>> Integrated Systems Analysts, Inc.
>>>>
>>>>
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>>>>
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>>>>
>>>>
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>>>
>>
>> --
>> Larry Becker
>> Integrated Systems Analysts, Inc.
>>
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>>
>>
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