Cross Section at Endpoints

Construct a cross-sectional elevation transect between two user-provided points.

Overview

The cross section at endpoints process (nldi-xsatendpts) constructs a cross-sectional elevation transect between two user-provided points. Unlike the single-point cross section , this process gives full control over both ends of the transect. It samples 3DEP elevation data at a configurable resolution along the connecting line.

How It Works

  1. The user supplies two coordinates as paired lat and lon arrays, defining the endpoints of the transect.
  2. The user specifies numpts (the number of elevation sample points along the transect) and optionally 3dep_res (the 3DEP elevation data resolution in meters: 1, 3, 5, 10, or 30; default is 10).
  3. The process samples elevation data at evenly spaced points along the straight line between the two endpoints.
  4. The process returns a JSON response containing the elevation profile.

Because the algorithm operates on user-specified endpoints, it can represent features such as:

  • Wide channel sections
  • Floodplain cross sections
  • Custom transects for modeling or design

Example Request

Construct a cross section with 101 points between two endpoints in Colorado, using 1-meter 3DEP elevation data:

POST https://api.water.usgs.gov/nldi/pygeoapi/processes/nldi-xsatendpts/execution?f=json
Content-Type: application/json

{
  "inputs": {
    "lat": [40.26772, 40.270568],
    "lon": [-103.801086, -103.80097],
    "numpts": 101,
    "3dep_res": 1
  }
}

3dep_res controls the resolution of the 3DEP elevation data used for sampling. Available resolutions are 1, 3, 5, 10, and 30 meters. Higher resolution (lower number) provides finer detail but may increase processing time. The default is 10 meters.

Explore the Full Parameter Schema

The pygeoapi process description provides the complete parameter schema: /processes/nldi-xsatendpts?f=json