WGS 84 with which datum to use ?

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04-30-2020 10:38 AM
PROBERT68
Frequent Contributor

Hi

What is good to use to measure the height/altitude/elevation for an projection for the world ?

I have looked at the WGS 84 for the world but doesn't say which vertical datum to use ?

Does anyone have an suggest for me to use it ?

I am looking at the longitude, latitude and altitude  information to work with.

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BojanŠavrič
Esri Contributor

There are a couple vertical coordinate systems (VCS-es) you can use with the generic WGS84.

For the ellipsoidal heights, you can use VCS WGS 1984 (WKID::115700). This is native output of GPS if your receiver does not convert your heights automatically. These heights are not very practical for measurements and an analysis might go wrong if you use those heights. For example, river stream might end up going upstream and not downstream. However, a lot of global height data is defined in this VCS. 

To measure the height/altitude/elevation you should be using gravity-related VCS-es, which are based on global geoid models (like EGMs) or they are based on some (mean) sea level. EGM2008 Geoid (WKID::3855) is most recent one and ArcGIS Pro has two vertical transformations that allows you to convert between ellipsoidal WGS 1984 and gravity-related EGM2008 Geoid heights. Keep in mind, you need to install ArcGIS Coordinate System Data to be able to transform your heights. 

Check also:

List of supported vertical coordinate systems

List of supported vertical transformations

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3 Replies
BojanŠavrič
Esri Contributor

There are a couple vertical coordinate systems (VCS-es) you can use with the generic WGS84.

For the ellipsoidal heights, you can use VCS WGS 1984 (WKID::115700). This is native output of GPS if your receiver does not convert your heights automatically. These heights are not very practical for measurements and an analysis might go wrong if you use those heights. For example, river stream might end up going upstream and not downstream. However, a lot of global height data is defined in this VCS. 

To measure the height/altitude/elevation you should be using gravity-related VCS-es, which are based on global geoid models (like EGMs) or they are based on some (mean) sea level. EGM2008 Geoid (WKID::3855) is most recent one and ArcGIS Pro has two vertical transformations that allows you to convert between ellipsoidal WGS 1984 and gravity-related EGM2008 Geoid heights. Keep in mind, you need to install ArcGIS Coordinate System Data to be able to transform your heights. 

Check also:

List of supported vertical coordinate systems

List of supported vertical transformations

PROBERT68
Frequent Contributor

Thank you very much.  Now I do  know why I am having issues with it....

Seems like when I am working on between GIS software (ArcGIS Pro) and Agisoft Metashape they do not match...

been wondering about this things is really annoying to me..

The points are all over that don't seem to make sense to me..

Now I can see why what you have just explained !!!

PROBERT68
Frequent Contributor

Not sure if I was able to add this from what you wrote on your blog here 

Vertical Coordinate Systems: Local Use Cases 

But I was able also add the EGM2008 Geoid (WKID 3865) to my Agisoft Metashape .

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