What is the PARAMETER["Height"] in CRS?

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11-17-2016 03:07 PM
LorenDawe
New Contributor II

A client has provided a PRJ file (attached) that contains a "Height" parameter:

Well-known text PROJCS["PTL1_Buenaventura",GEOGCS["GCS_MAGNA",DATUM["D_MAGNA",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["IGAC_Plano_Cartesiano"],PARAMETER["False_Easting",100000.0],PARAMETER["False_Northing",100000.0],PARAMETER["Longitude_Of_Center",-76.85094890833329],PARAMETER["Latitude_Of_Center",3.85779813888889],PARAMETER["Height",315.0],UNIT["Meter",1.0]]

I have three questions regarding this:

1 - What does this refer to?

2 - Does this parameter affect the horizontal coordinates in a transformation/re-projection?

3 - Can this be applied using PROJ4? If so, how?

Thanks in Advance,

Loren.

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2 Replies
DanPatterson_Retired
MVP Esteemed Contributor
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MelitaKennedy
Esri Notable Contributor

It's a parameter peculiar to this map projection algorithm--IGAC_Plano_Cartesiano. It's used for large scale data, generally a city. In a sense it's a scale factor, adjusting the horizontal coordinates based on the height of the city. It reduces the overall distortion, because the projection plane is located close to the GCS/ellipsoid surface. Adding in the height above that surface moves the plane to the local average elevation, so distances, etc. are closer to true.

EPSG has the same definitions, but calls the projection "Colombia urban". Neither EPSG nor Esri have a predefined definition for Buenaventura.

Unless it was added very recently, PROJ.4 doesn't support this projection.

Melita