Spatial References

At all phases of planning, field acquisition, ground control collection, and data processing, particular emphasis is placed on the required spatial reference required in the final deliverable. Any offsets or error sources accumulated in each process are documented for inclusion in metadata. This becomes particularly apparent when collecting hi-accuracy airborne lidar or engineering-grade terrestrial mobile lidar data to survey accuracy. Depending on the collection location and the client's geodetic control monuments, significant offsets in both the vertical and horizontal can occur unless the appropriate datum adjustments are made to base station and reference station positions.

For projects where data delivery is destined for the U.S. NED, Point3Data employs NAD 83 (horiz) and NAVD 88 (vert) datums by default. However, we can deliver data formatted in a multitude of:

  • Horizontal ellipsoidal and Cartesian datums
  • Vertical ellipsoidal, orthometric and tidal datums
  • Geoid models
  • Units (US Survey Ft, International Ft, m)
  • Coordinate systems & map projections.
  • Although this can sometimes lead to unconventional combinations (including mixed-unit datasets) Point3Data can meet virtually any spatial reference requirements for legacy mapping compatibility.

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    The NGS has undertaken a project to redefine the gravity-based vertical datum.

    Gravity for the Redefinition of the American Vertical Datum (GRAV-D) is a 10-year project due to be completed by 2021. It is expected to provide an orthometric vertical datum accurate to 2 cm over the United States and its territories.

    To learn more or for a status update, click here.

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