Under the default parameters of the AreaCalculator transformer, their is a value of 3 given to the Multiplier? is their a specific value that will give Square Meters as the output?
AreaCalculator output units
Does anybody know how to get a different unit of measurement for the AreaCalculator? The default output is in Ground Map Units. I would like the output in Square Meters.
Userlevel 4
- 8177 replies
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30 December 2013
Hi,
according to the documentation, the AreaCalculator will only give results in square map units.
The multiplier will not change this, but will enable you to convert the result from, let's say square meters to hectares (= 10 000 sqm) without needing an additional transformer.
The FME Store does, however, have an AreaUnitConverter transformer that might be worth a look.
David
If you reproject your data to a meters projection (ie UTM) your ground units will be in meters. Then you can reproject your data back to whatever you use but keep the sq meters attribute.
Userlevel 4
- 8177 replies
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31 December 2013
Hi,
While the idea of reprojecting the data to meters is a good one, I'd be careful about reprojecting it back again as it may introduce slight shifts to your data (depending on the reprojection algorithm used). This might be a problem e.g. if you're depending on preserving topologial correctness, etc.
Have a look at the custom transformer GeographicAreaCalculator in the FME Store, I think it might be what you need.
David
David, the GeographicAreaCalculator appears to be exactly what i'm looking for. Unfortunatley when I run the workspace with it, it outputs 0 for all my areas?
I have the input Readers Coordinate System set (3TM114-83)....
?
David... was just thinking.
Project the data to meters, and do the calculation. But then instead of reprojecting back, do a feature merger and merge the new calculated field back onto the original data. Then you will still retain the original features/geometry with the appended calc field.
Again, just a thought.
Userlevel 2
+17
- Contributor
- 7538 replies
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2 January 2014
Hi,
Solution would depend on the actual coordinate system of the source dataset. If it was a projected coordinate system and also its ground units are meter, you could use the AreaCalculator simply. If it was a projected coordinate system but the ground units were not meter, you could use the AreaCalculator with appropriate Multiplier. For example, when the ground units of the source dataset were ft., the multiplier should be 0.3048x0.3048 (1 foot = 0.3048 meter). If it was a geographic coordinate system (latitude, longitude), it would be necessary to project geometries to an appropriate coordinate system before calculating area, as Matthew and David mentioned. Anyway, you will have to know the actual coordinate system of the source dataset exactly.
Takashi
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