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Consistent units of reference

By NGP Standards and Specifications

Units of reference need to be consistent for all three axes. 

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Status of this revision: Published in Lidar Base Specification 2022 rev. A

Background

Projects delivered in mixed units--for example, meters for X- and Y-dimensions and International Feet for Z--can lead to confusion, especially when bordering projects with different Z-units. This revision requires delivery in the same units for all three dimensions.

Current requirement: 

  • All references to the units of measure “Feet” and “Foot” shall specify “International,” “Intl,” “U.S. Survey,” or “US.” 

Change to: 

  • Horizontal and vertical units of measure will be in the same units (meters preferred). Mixed units (such as horizontal units of meters and vertical units of feet) are not recommended. Projects delivered with mixed units shall be considered as varying from the specification and will be noted as such in the spatial metadata.  

  • All references to the units of measure “Feet” and “Foot” shall specify “International,” “Intl,” “U.S. Survey,” or “US.”