ArcGIS Pro 2.5: What does the “angular unit” represent in the geographic coordinate system?

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06-12-2020 11:37 AM
JamalNUMAN
Legendary Contributor

ArcGIS Pro 2.5: What does the “angular unit” represent in the geographic coordinate system?

 

I couldn’t figure out what does the “angular unit” represent in the Geographic coordinate system

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Jamal Numan
Geomolg Geoportal for Spatial Information
Ramallah, West Bank, Palestine
5 Replies
DanPatterson
MVP Esteemed Contributor

in general, angular units can be in degrees (or its variants like DMS), radians, grads or gons .

It is a property of a GCS and important in raster projection amongst other things.

Unit options—ArcGIS Pro | Documentation 

Direction units for editing—ArcGIS Pro | Documentation 

How the Cell Size Projection Method environment setting works—Geoprocessing | Documentation 


... sort of retired...
JamalNUMAN
Legendary Contributor

Right, but it’s not clear what does it represent.

 

For example, for the “Clarke 1880 Benoit” spheroid and “D Palestine 1923” Datum, the angular unit is 0.0174532925199433.

 

What does this value represent? What does it indicate for in terms of geometry?

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Jamal Numan
Geomolg Geoportal for Spatial Information
Ramallah, West Bank, Palestine
JoshuaBixby
MVP Esteemed Contributor

Geographic coordinate systems require an angular unit, but the value of the angular unit is really about geometry and not geography.  Since radians are the international unit for measuring angles, a geographic coordinate system that wants to use degrees or some other angular unit of measure must provide a conversion factor.  Since there are 2*pi radians in 360 degrees, 1 degree equals 0.0174532925199432.... radians.

JamalNUMAN
Legendary Contributor

Many thanks guys for the help.

 

It could be less confusing if the word radian follows the number

 

Angular Unit = Degree (0.0174532925199433 Radians)

 

I could see that the linear unit conforms with same logic

 

Linear unit: meter (1.0)

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Jamal Numan
Geomolg Geoportal for Spatial Information
Ramallah, West Bank, Palestine
DamilolaOlufemi
New Contributor

I think it also shows the ground/real measurement of the location. Hence the angular unit indicates the geometry of the area