dhis2-devs team mailing list archive

[Calle Hedberg <calle.hedberg@xxxxxxxxx>]

Knut,

That makes no sense - nobody does area calculations on lat/long (i.e. the
geographical graticule), you must first project the lat/long data into a
suitable projection and then calculate areas.

For smaller areas (e.g. small and medium-sized countries) you would
typically use UTM (Transverse Mercator), but that is completely
inappropriate for larger areas. Just think about it: on a standard global
Mercator projection, Greenland looks twice as big as India - whereas the
reality is that India has a 50% larger area than Greenland.

Besides, if you do calculate areas using lat/long and decimal degrees, the
"result" will be squared decimal degrees - which means nothing to anybody.

Regards
Calle


On 25 April 2016 at 15:16, Knut Staring <knutst@xxxxxxxxx> wrote:

> AFAIK all coordinates are lat/lon, so I suppose that also goes for the
> area calculation.
>
> Knut
>
> On Mon, Apr 25, 2016 at 3:05 PM, Calle Hedberg <calle.hedberg@xxxxxxxxx>
> wrote:
>
>> Lars,
>>
>> Thanks - it is downloading
>>
>> One initial question re GIS area calculations: what projection is used
>> for the calculation?
>>
>> regards
>> calle
>>
>> On 25 April 2016 at 14:53, Lars Helge Øverland <lars@xxxxxxxxx> wrote:
>>
>>>
>>>
>>> On Mon, Apr 25, 2016 at 2:39 PM, Calle Hedberg <calle.hedberg@xxxxxxxxx>
>>> wrote:
>>>
>>>> Hi,
>>>>
>>>> Good stuff - will go through it in more detail, but please note that
>>>> trying to download the 2.23 demo database gives an error (file not found).
>>>>
>>>> regards
>>>> Calle
>>>>
>>>
>>>
>>> Right - fixed now.
>>>
>>>
>>> --
>>> Lars Helge Øverland
>>> Lead developer, DHIS 2
>>> University of Oslo
>>> Skype: larshelgeoverland
>>> http://www.dhis2.org <https://www.dhis2.org/>
>>>
>>>
>>
>>
>> --
>>
>> *******************************************
>>
>> Calle Hedberg
>>
>> 46D Alma Road, 7700 Rosebank, SOUTH AFRICA
>>
>> Tel/fax (home): +27-21-685-6472
>>
>> Cell: +27-82-853-5352
>>
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>>
>> Email: calle.hedberg@xxxxxxxxx
>>
>> Skype: calle_hedberg
>>
>> *******************************************
>>
>>
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>>
>
>
> --
> Knut Staring
> Dept. of Informatics, University of Oslo
> Norway: +4791880522
> Skype: knutstar
> http://dhis2.org
>



-- 

*******************************************

Calle Hedberg

46D Alma Road, 7700 Rosebank, SOUTH AFRICA

Tel/fax (home): +27-21-685-6472

Cell: +27-82-853-5352

Iridium SatPhone: +8816-315-19119

Email: calle.hedberg@xxxxxxxxx

Skype: calle_hedberg

*******************************************