Existing ground surface from UAS lidar, SR 599, Hickory Falls, Tennessee

Existing ground TIN, breaklines, and 1-ft contours developed from an unclassified UAS lidar point cloud and delivered as DXF and PDF plan sheets, marked preliminary until field verified. The surface has no ground returns over about 9,800 SF at the cross culvert outlet, two stockpiles were reclassified out of ground, and the north ditch flowline east of the culvert needs field shots.

UAS lidar flown Oct 21, 2026, 16.2 million pointsSR 599, Sta. 10+00 to 22+00, 18.2 acresNAD83(2011) Tennessee State Plane (FIPS 4100), US survey feet, NAVD 88 (GEOID18)Prepared Nov 5, 2026

Summary

Interpolated surface

No ground returns under the cedar thicket at the culvert outlet: about 9,800 SF interpolated

South of the road from Sta. 16+66 to 18+40, no pulses reach the ground. TIN triangles there span up to 85 ft, the toe of slope has a gap, and the culvert outlet cannot be picked from the cloud.

Action: take six ground shots and the outlet invert (CS-01 to CS-07).

Classification

Two stockpiles were classified as ground and added mounds of 5.5 and 3.2 ft

The gravel stockpile in the warehouse yard and a topsoil windrow along the hayfield passed the automatic ground filter. In the preliminary surface they are moved to Class 1, which changed 3,780 SF of the TIN.

Action: shoot the yard grade around the stockpile and the field next to the windrow (CS-14 to CS-16).

Breakline

North ditch flowline from Sta. 17+71 to 20+66 cannot be picked from the cloud

East of the culvert the ditch holds standing water, and cattails grow at the inlet end. The lowest returns sit on the water surface and in the cattails, so the flowline is flat and then rises 0.3 ft toward the inlet. The bottom under the water is not in the data.

Action: take flowline shots every 50 ft and the inlet invert (CS-08 to CS-13).

From point cloud to contours

Step from the unclassified cloud to contours and switch between automatic and corrected classification. Click an area in the view or the list for point density, ground share, and interpolated area.

Step
Classification
View
Show
points in the cloud, 1 in 200 shown
ground share (Class 2)
interpolated surface

Sources and method

Sources

  • SR599_HickoryFalls_UAS_Lidar_2026-10-21.lazUnclassified UAS lidar point cloud, LAS 1.4, all points Class 016.2M points
  • SR599_Orthomosaic_2026-10-21.tifOrthomosaic from the same flight, used to identify stockpiles, water, and vegetation0.8-in GSD
  • SR599_GNSS_Checkpoints.csvRTK GNSS checkpoints on asphalt and concrete, Oct 21, 20268 points
  • Hickory_Falls_Parcels_Buildings.dxfParcel and building linework, compared with the roofline1 file
  • SR599_Topo_Survey_Scope.pdfDatum, units, contour interval, CADD layers, and preliminary delivery requirements4 pages

Method

  1. The cloud was checked for point density and noise. Horizontal and vertical datums per the scope: NAD83(2011) Tennessee State Plane, FIPS 4100, US survey feet; NAVD 88 with GEOID18.
  2. Automatic classification to the ASPRS LAS standard classes: low noise (7), ground (2) by progressive TIN densification, vegetation (3–5) by height above ground, building (6) from planar roofs, and water (9) in the creek.
  3. The classification was reviewed against the orthomosaic. The gravel stockpile and the topsoil windrow were moved from ground to Class 1.
  4. The TIN was built from the lowest ground point in each 6.5 × 6.5 ft cell plus breakline vertices. The building footprint was clipped out.
  5. Breaklines were extracted from grade breaks. Ditch and creek flowlines were taken from the lowest point every 16 ft. Sections where the orthomosaic shows water or vegetation in the ditch bottom were flagged as uncertain.
  6. 1-ft contours were generated from the TIN with an index contour every 5 ft.
  7. The TIN was compared with 8 GNSS checkpoints on paved surfaces.
  8. DXF and PDF deliverables were exported with the preliminary stamp, and check shots were proposed for the open items.

Assumptions and limitations

  • This is a preliminary surface. Field verification and a formal accuracy report under the ASPRS Positional Accuracy Standards for Digital Geospatial Data have not been done; 8 checkpoints are too few for a formal accuracy statement, since Edition 2 of the standard calls for at least 30.
  • Interpolated area means 3.3 × 3.3 ft cells more than 6.5 ft from the nearest ground point. Long TIN edges are flagged from 26 ft.
  • The views show an even sample of 1 in 200 points. Statistics are computed on the same sample and scaled to the full cloud.
  • Checkpoints are on paved surfaces only. Vertical accuracy in vegetation and in ditches has not been tested.
  • The warehouse outline is the roofline from the cloud, not the wall line. The culvert location is approximate, and its size and material are unknown.
  • Coordinates are on NAD83(2011) Tennessee State Plane in US survey feet as the scope requires, not on the 2022 State Plane Coordinate System in international feet.
  • The creek flowline shows the water surface, not the channel bottom.