DSC Analysis

This site documents the Distance Sample Count (DSC) Analysis Ecoscope workflow, which ingests wildlife survey patrol data from EarthRanger, calculates distance sampling geometry, labels transects with satellite-derived environmental covariates, and exports analysis-ready datasets for population density modelling.

Overview

The workflow supports multiple surveys per run. Each survey is automatically split into its detected activity periods — if a survey site was visited in, say, both February and June, the workflow produces two independent, period-tagged output sets instead of one combined one. For each survey period it produces:

Prerequisites

Before running the workflow, ensure you have:

• Access to an EarthRanger instance with DSC patrol data logged using:
  • distancecountpatrol_rep — survey metadata (transect ID, team, observer count)
  • distancecountwildlife_rep — wildlife observations (species, count, distance, radial angle)
• A Google Earth Engine service account configured in Ecoscope (for NDVI and slope imagery)
• The EarthRanger spatial group ID for each survey's transect lines
• The patrol type ID (numeric or UUID) for the DSC patrol type in EarthRanger
• Team members recorded on each patrol should correspond to named subjects/trackers in EarthRanger, so their GPS tracks can be used to compute field effort

Step-by-Step Configuration

https://github.com/wildlife-dynamics/dsc_analysis.git

Running the Workflow

Once all parameters are configured, click Submit. For each survey the workflow will:

1. Fetch patrol events matching the configured patrol type ID and the workflow's Time Range from EarthRanger.
2. Split the survey's patrol events into their detected activity periods — each period is processed as an independent branch, tagged with a {survey}_{yyyy}_{mm} label.
3. Fetch transect lines from the configured EarthRanger spatial group, once per survey period.
4. Retrieve individual wildlife observation events from the patrol event IDs.
5. Process and normalise survey metadata events — extract transect ID, team members, and observer count.
6. Propagate metadata fields to wildlife observation rows using backward/forward fill within each patrol.
7. Compute field effort per team member — daily distance travelled, duration, and man-hours, from EarthRanger subject GPS tracks.
8. Reproject events and transects to a UTM coordinate system for metric distance calculations.
9. Calculate the perpendicular distance from each observer position to the transect centreline (off_transect_dist).
10. Estimate the true animal position from each observation's radial angle and distance to centre (dist_to_centre).
11. Calculate the orthogonal distance from the estimated animal position to the transect centreline (ortho_dist).
12. Filter events to those that intersect a 500 m transect buffer corridor; discard unvisited transects.
13. Label visited transects with mean HLS NDVI (max 30 % cloud cover) and terrain slope from Google Earth Engine (30 m resolution).
14. Merge transect covariates into the wildlife observation dataset.
15. Export all outputs per survey period to $ECOSCOPE_WORKFLOWS_RESULTS.

Output Files

All outputs are written to $ECOSCOPE_WORKFLOWS_RESULTS/. Six files are produced for each survey period — {survey}_{period} is replaced by the name of the EarthRanger site (subdomain) that survey's connection points to, followed by the detected activity period (e.g. olaremotorogi_2026_02).

Further Reading

For an implementation-level breakdown of every task in the compiled workflow spec — dependency versions, skip conditions, filename construction, and the full processing pipeline — see the Technical Guide (PDF).