Types of source data supported in terrain datasets

Photogrammetrically derived mass points

Photogrammetrically derived breaklines

GPS points

Lidar points

Learn more about lidar data

Sonar

Points, lines, polygons (mass, break, clip, erase, replace)

The thematic data types used to derive a surface are stored in the geodatabase as features with different geometry types. These types are points, multipoints, polylines, and polygons. These geometry types can be incorporated into the terrain surface in different ways. You control how a feature is used by setting its surface feature type (SFType). The following table shows the relationships of different SFTypes, types of feature classes that can be used for each SFType, height source options, and thematic data examples.

Surface feature types in terrain datasets

Surface feature type

Feature class

Z-value source in the feature class

Thematic data type examples

Mass points (x,y,z locations)

Point feature class

  • Shape geometry; x,y,z per vertex

or

  • Attribute column holding one z-value per shape
  • Spot heights
  • Survey points
  • GPS points

Multipoint feature class

  • Shape geometry; x,y,z per vertex

or

  • Attribute column holding one z-value per shape
  • Lidar points
  • Sonar points

Line feature class

  • Shape geometry; x,y,z per vertex

or

  • Attribute column holding one z-value per shape
  • Contours

Polygon feature class

  • Shape geometry; x,y,z per vertex

or

  • Attribute column holding one z-value per shape
  • Shoreline delineation

Breaklines (hard or soft)

Line feature class

  • Shape geometry; x,y,z per vertex
  • Attribute column holding one z-value per shape
  • No height source; z-values interpolated for each feature from the surface before being added
  • Contours
  • Edge of pavement
  • Waterlines (streams, rivers, canals, shorelines)

Polygon feature class

  • Shape geometry; x,y,z per vertex
  • Attribute column holding one z-value per shape (such as a shoreline)
  • No height source; z-values interpolated for each feature from the surface before being added
  • Lake shoreline

Clipping polygons (hard or soft)

Polygon feature class

  • Shape geometry; x,y,z per vertex
  • Attribute column holding one z-value per shape (such as a shoreline)
  • No height source; z-values interpolated for each feature from the surface before being added
  • Study area boundary

Erase polygons (hard or soft)

Polygon feature class

  • Shape geometry; x,y,z per vertex
  • Attribute column holding one z-value per shape
  • No height source; z-values interpolated for each feature from the surface before being added
  • Lake shoreline
  • Obscured areas (dense forest canopy)

Replace polygons (hard or soft)

Polygon feature class

  • Shape geometry; x,y,z per vertex
  • Attribute column holding one z-value for all vertices in each shape
  • Water bodies

NoteNote:

It is best for the sake of terrain performance to place all hardlines together in one feature class. It is understood this might not be possible, for example, if you need to keep road and water features separate. Keep in mind, the fewer feature classes used to define a terrain, the better.

Replace SFType is used to set everything inside a polygon at a constant height. It is used mostly for lakes when there's inadvertently other data inside them, such as lidar points, whose heights are not exactly the same as the shoreline and therefore prevent the water bodies from being flat. Replace SFType does incur more processing cost than normal hard- or softlines, so it is best to avoid using it in a terrain dataset. Ideally, there should not be lidar samples in water bodies (consider adding this as a stipulation in the contract with your data provider), but if there are, you can use the Delete Terrain Points geoprocessing tool to handle them after the terrain dataset is built. Otherwise, you can eliminate any offending points before building your terrain using the Erase Point geoprocessing tool.

Related Topics

9/3/2014