Research/Terra/ 618282
Task evidence / population-distance-share

How many people live within 1 km from a railway in Bangladesh

PassComputational taskUnpublished draft
Download evidence JSON ↓

The question

618282
How many people live within 1 km from a railway in Bangladesh
Exact submitted task and declared adaptations
How many people live within 1 km from a railway in Bangladesh

Task conventions: Use the frozen Bangladesh WorldPop 2018 bgd_pd_2018_1km_UNadj raster. Its verified units are people/km², NOT people per cell; preserve its original band, grid and missing mask. Convert density to population per cell using each original full WGS84 ellipsoidal meridian/parallel cell area in km², not a constant nominal 1 km². Use all original features in the supplied Bangladesh railway line inventory; no live railway substitutions, attribute exclusions or duplicated population from overlapping corridors. Define proximity by shortest planar distance from each original raster cell centre to the original railway geometries transformed into EPSG:32646 (UTM zone 46N), with original straight segments. A cell qualifies at distance <= 1000 metres. This is an explicit local projected cell-centre approximation, not travel distance or exact ellipsoidal distance. Projection distortion and unresolved within-cell population location remain limitations. The corridor includes the full cell when its centre qualifies, counting each cell once. Zero density is valid; missing/nonfinite cells remain unknown. Total and selected population are sums of density times physical cell area over valid cells; percentage is 100 times selected/total. Publish a selected-population raster (derived people per cell when qualifying, zero in other valid cells, original mask) and a distance raster in metres on that same original grid. The historical population and later railway snapshot do not prove contemporaneous access or census accuracy.



Compute the percentage and publish both inspectable rasters. A map is optional. End with a fenced JSON object: {count: qualifying cell count, unknown_count: original masked/nonfinite cell count, coverage_note, selection:{collectionId,itemId,assetKey}, distance:{collectionId,itemId,assetKey}, metrics:{selected_people:number,total_people:number,percentage:number}}. Label selected population as people per cell and distance as metres. Report the historical year and coverage limitations. Do not round machine-readable metrics to integers.

Delivery format: provide the answer object with all fields specified above as final_response on assess_result, alongside the inspected final artifact_refs. This replaces the JSON-code-block formatting requirement above. Blue attaches your explicit selection to the accepted final answer. Finish with a concise ordinary-language answer agreeing with that selected result; do not duplicate the JSON in chat.

Supplied immutable inputs:
[
  {
    "name": "Bangladesh population density, WorldPop 2018",
    "edition": "2018 UN-adjusted 1 km density; exact bytes verified against WorldPop product 45189, DOI WP00675",
    "units": {
      "band1": "people/km\u00b2"
    },
    "collectionId": "blue-generated--[resource id withheld]",
    "itemId": "[resource id withheld]",
    "assetKey": "data"
  },
  {
    "name": "Bangladesh railway lines, frozen OpenStreetMap extract",
    "edition": "GeoBenchX Geofabrik Bangladesh extract, 2025-02-01; ODbL attribution required",
    "units": {},
    "collectionId": "blue-generated--[resource id withheld]",
    "itemId": "[resource id withheld]",
    "assetKey": "data"
  }
]

Outcome & verification

Independent artifact and delivery checks passed.

Duration
20m 6s
Recorded Blue tool calls
49
Total tokens
2,530,972
Model cost
Not recorded
Application revision
d50497ea9084f29c91b05406688f87035df98d8a
Release
terra-geobenchx-v1

Recorded final answer

About 20.74 million people, or 12.777704565401805% of the valid 2018 WorldPop population in this Bangladesh raster, live within 1 km of the supplied railway lines across 8,123 qualifying cells. I published the selected-population raster in people per cell and the distance raster in metres. This uses historical 2018 population with a later 2025 railway snapshot, and 226,139 masked cells remain unknown. ### Limitations - The population raster is historical 2018 density and the railway inventory is a later 2025 frozen snapshot, so the result does not prove contemporaneous access or census accuracy. - Distances use the requested planar EPSG:32646 cell-centre approximation with original straight segments; projection distortion remains and this is not travel distance. - Masked or nonfinite raster cells remain unknown and are excluded from the valid-population sums. - The population raster is historical 2018 density and the railway inventory is a later 2025 frozen snapshot, so this does not prove contemporaneous access or census accuracy. - Selection uses the requested planar EPSG:32646 cell-centre approximation with original straight segments; projection distortion and within-cell population location remain limitations. - Original masked or nonfinite raster cells remain unknown and are excluded from the valid-population totals. - The railway source is a frozen 2025-02-01 OpenStreetMap extract and does not prove current service or access. - Distances use the requested planar EPSG:32646 approximation with transformed straight segments; projection distortion remains and this is not travel distance or exact ellipsoidal distance. - Original masked or nonfinite raster cells remain unknown. - The population raster is a historical 2018 density surface and does not prove exact census accuracy or within-cell population location. - The railway source is a frozen OpenStreetMap extract dated 2025-02-01. - Distances use the requested planar EPSG:32646 cell-centre approximation with projection distortion and original straight segments, not travel distance or exact ellipsoidal distance. - Masked or nonfinite raster cells remain unknown and are excluded from valid-population totals.

Independent checks

These checks are separate from the agent's own assessment. A successful job or an assertion of success is not enough to pass.

Expected count
8123
Reported count
8123
Computation verified
Yes
Answer fulfilled
Yes
Full grading and rubric record
{
  "expectedCount": 8123,
  "actualCount": 8123,
  "expectedMetrics": {
    "selected_people": 20736404.66055608,
    "total_people": 162285835.55419007,
    "percentage": 12.777704591249947
  },
  "actualMetrics": {
    "percentage": 12.777704565401805,
    "total_people": 162285835.78281653,
    "selected_people": 20736404.647821426
  },
  "computationCorrect": true,
  "answerFulfilled": true,
  "adjudication": null,
  "qualification": null,
  "reasons": []
}

Recorded investigation findings

The agent's reported hypotheses and assessments, retained as evidence of its process—not independent proof that the answer is correct. Failed calls retain their requested verdict, not an accepted assessment.

run_trial · completed

Does the full requested processor chain preserve the supplied WorldPop grid and mask while correctly converting density to people per cell, selecting valid cells within 1000 metres of the supplied railways, and producing the requested Bangladesh-wide totals?

assess_trial · completed · assessment: sufficient

The full Bangladesh trial preserved the supplied WorldPop grid exactly at 559×728 cells in EPSG:4326 with the same bounds, transform, and 226139 missing cells across the people-per-cell, distance, and selected-population rasters. The distance surface used projected-features with EPSG:32646 over all 2506 supplied railway features and produced metres on the original valid-cell mask. Map algebra kept zero as a valid outside value and did not create finite output where an input was missing. The derived people-per-cell raster summed to 162285835.78281653 people over 180813 valid cells, the selected-population raster summed to 20736404.647821426 people, and the qualifying 0/1 mask summed to 8123 qualifying valid cells with the same 226139 unknown cells.

assess_result · completed · assessment: sufficient

The published selected-population raster is on the original Bangladesh WorldPop 2018 grid, is labelled in people per cell, keeps the original masked cells as unknown, and matches the fully assessed full-area computation for the 1 km railway selection. Current inspection shows zero as the valid outside value and the supporting qualifying-mask table shows 8123 selected valid cells counted once each.

assess_result · completed · assessment: sufficient

The published distance raster is on the original Bangladesh WorldPop grid, is labelled in metres, preserves the original missing mask, and records planar projected-feature distance to the supplied railway geometries in EPSG:32646.

assess_result · completed · assessment: sufficient

The published summary tables support the final Bangladesh result: 162285835.78281653 total people over valid cells, 20736404.647821426 selected people within 1 km of the supplied railways, 8123 qualifying valid cells, and 226139 unknown cells from the original mask. The published rasters that these tables summarize were also inspected on the original WorldPop grid, with selected population labelled people per cell and distance labelled metres.

Recorded workflow

  1. 01

    Ellipsoidal cell area

    Recorded raster-cell-area · succeeded

  2. 02

    Qualifying cell count statistics

    Recorded raster-statistics · succeeded

  3. 03

    Bangladesh population within 1 km of railway lines

    Recorded output · succeeded

  4. 04

    Bangladesh distance to nearest supplied railway

    Recorded output · succeeded

  5. 05

    Bangladesh total population statistics

    Recorded output · succeeded

  6. 06

    Bangladesh selected population statistics

    Recorded output · succeeded

  7. 07

    Bangladesh qualifying cell count statistics

    Recorded output · succeeded

  8. 08

    Distance to railway

    Recorded distance-surface · succeeded

  9. 09

    Population per cell

    Recorded raster-map-algebra · succeeded

  10. 10

    Supplied Bangladesh population density raster

    Recorded source · succeeded

  11. 11

    Qualifying cell mask

    Recorded raster-map-algebra · succeeded

  12. 12

    Supplied Bangladesh railway lines

    Recorded source · succeeded

  13. 13

    Selected population within 1 km

    Recorded raster-map-algebra · succeeded

  14. 14

    Selected population statistics

    Recorded raster-statistics · succeeded

  15. 15

    Total population statistics

    Recorded raster-statistics · succeeded

  16. 16

    Ellipsoidal cell area

    Recorded raster-cell-area · succeeded

  17. 17

    Qualifying cell count statistics

    Recorded raster-statistics · succeeded

  18. 18

    Distance to railway

    Recorded distance-surface · succeeded

  19. 19

    Population per cell

    Recorded raster-map-algebra · succeeded

  20. 20

    Supplied Bangladesh population density raster

    Recorded source · succeeded

  21. 21

    Qualifying cell mask

    Recorded raster-map-algebra · succeeded

  22. 22

    Supplied Bangladesh railway lines

    Recorded source · succeeded

  23. 23

    Selected population within 1 km

    Recorded raster-map-algebra · succeeded

  24. 24

    Selected population statistics

    Recorded raster-statistics · succeeded

  25. 25

    Total population statistics

    Recorded raster-statistics · succeeded

  26. 26

    Population per cell

    Recorded output · succeeded

  27. 27

    Distance to railway

    Recorded output · succeeded

  28. 28

    Selected population within 1 km

    Recorded output · succeeded

  29. 29

    Total population statistics

    Recorded output · succeeded

  30. 30

    Selected population statistics

    Recorded output · succeeded

  31. 31

    Qualifying cell count statistics

    Recorded output · succeeded

Activity

Recorded actions

Recorded observable actions only, not private reasoning. Raw payloads, geometry, private links and credentials are omitted; full evidence is retained privately. Activity/workflow lists bounded at 500 entries.

  1. Progress update

    I’m checking the supplied Bangladesh raster and railway inputs, then I’ll test the smallest method that can produce the requested population-within-1 km result and the two output rasters.

  2. get_analysis

    Recorded tool call · completed

  3. Progress update

    I’ve started the analysis record. Next I’m confirming the exact grid, mask, and authorized file selections for the frozen population raster and railway lines, then I’ll inspect the processor options for the distance and cell-area method.

  4. get_collection

    Recorded tool call · completed

  5. get_collection

    Recorded tool call · completed

  6. inspect_artifact

    Recorded tool call · failed

  7. inspect_artifact

    Recorded tool call · failed

  8. Progress update

    I confirmed both immutable sources exist. Direct artifact inspection needs a workflow or trial output, so I’m switching to the source metadata path and then a small source-backed trial for the first real method check.

  9. get_item

    Recorded tool call · completed

  10. get_item

    Recorded tool call · completed

  11. list_processors

    Recorded tool call · completed

  12. describe_processors

    Recorded tool call · completed

  13. get_tool_help

    Recorded tool call · completed

  14. get_tool_help

    Recorded tool call · completed

  15. get_tool_help

    Recorded tool call · completed

  16. update_analysis_brief

    Recorded tool call · completed

  17. describe_processors

    Recorded tool call · completed

  18. describe_processors

    Recorded tool call · completed

  19. get_tool_help

    Recorded tool call · completed

  20. Progress update

    I’ve picked the likely processor chain: exact cell-area raster, exact projected-feature distance surface on the original grid, then map algebra and full-grid raster statistics. I’m checking the trial schema now so I can run one source-backed full-area proof and inspect both rasters plus the supporting totals.

  21. Progress update

    The consequential uncertainty is whether the exact-feature distance surface and the map-algebra masking keep the original WorldPop grid and missing mask while producing correct per-cell totals. I expect the full Bangladesh trial to keep one raster grid, one unknown-cell count, a distance raster in metres, and population sums that come only from density × ellipsoidal cell area over valid cells.

  22. run_trial

    Recorded tool call · completed

  23. Progress update

    The full Bangladesh proof run finished successfully. I’m reading its previews now; if they match the numerical checks, I can promote this exact tested method into the production workflow instead of rebuilding it.

  24. get_trial_report

    Recorded tool call · completed

  25. assess_trial

    Recorded tool call · completed

  26. Progress update

    The method is now tested at full Bangladesh scale, so I’m saving a publishable workflow that reuses this exact computation. I’m also cleaning up the remaining notes so the final handoff keeps only real scientific limits, not stale “not checked yet” messages.

  27. get_tool_help

    Recorded tool call · completed

  28. get_tool_help

    Recorded tool call · completed

  29. get_tool_help

    Recorded tool call · completed

  30. get_tool_help

    Recorded tool call · completed

  31. get_tool_help

    Recorded tool call · completed

  32. get_tool_help

    Recorded tool call · completed

  33. get_tool_help

    Recorded tool call · completed

  34. get_tool_help

    Recorded tool call · completed

  35. propose_workflow

    Recorded tool call · completed

  36. Progress update

    The production workflow is validated and matches the tested Bangladesh computation. I’m running it now and then I’ll inspect the published rasters and supporting totals before I record the final answer object.

  37. execute_workflow

    Recorded tool call · completed

  38. Progress update

    The production run finished, so I’m inspecting the published outputs directly now. If their identities and values match the tested run, I can record the final selected result object without rerunning anything.

  39. inspect_workflow_results

    Recorded tool call · completed

  40. inspect_workflow_results

    Recorded tool call · completed

  41. Progress update

    I already have a completed production run, so I’m resuming from that exact run instead of rebuilding anything. Next I’m pulling the final output receipts and inspecting the published rasters and summary tables that will back the final answer object.

  42. inspect_workflow_results

    Recorded tool call · completed

  43. get_tool_help

    Recorded tool call · completed

  44. Progress update

    I’ve got the published artifact identities from the production run. I’m pulling the remaining deliverables and their previews/rows now so the final assessment can point to the actual published rasters and summary tables, not just the earlier private trial.

  45. Progress update

    I have the workflow receipts, but I still need one bounded inspection per final deliverable so the final assessment can cite current values and exact published outputs. After that I can record the final answer object.

  46. inspect_artifact

    Recorded tool call · completed

  47. inspect_artifact

    Recorded tool call · completed

  48. inspect_artifact

    Recorded tool call · completed

  49. inspect_artifact

    Recorded tool call · completed

  50. inspect_artifact

    Recorded tool call · completed

  51. inspect_artifact

    Recorded tool call · completed

  52. inspect_artifact

    Recorded tool call · completed

  53. inspect_workflow_results

    Recorded tool call · completed

  54. inspect_artifact

    Recorded tool call · completed

  55. inspect_artifact

    Recorded tool call · completed

  56. inspect_artifact

    Recorded tool call · completed

  57. Progress update

    I’m resuming the existing inspections instead of starting anything new. I need the current preview/row receipts for the two published rasters and the three supporting summary tables, then I can lock the final result to those exact artifacts.

  58. Progress update

    I’ve now inspected the published rasters and all three summary tables from the final run. I’m refreshing the brief to remove stale “not checked yet” notes, then I’ll record the final assessments and the machine-readable answer object against these exact published artifacts.

  59. update_analysis_brief

    Recorded tool call · completed

  60. Progress update

    I refreshed the brief, which makes the saved proposal formally stale even though the finished workflow result is unchanged. I’m revalidating that exact proposal now so the recorded method and the delivered result stay consistent.

  61. revise_workflow

    Recorded tool call · completed

  62. Progress update

    I’ve finished the current output inspections. Now I’m recording three final assessments: the selected-population raster, the distance raster, and the machine-readable totals that tie them together.

  63. assess_result

    Recorded tool call · completed

  64. assess_result

    Recorded tool call · completed

  65. Progress update

    The two rasters are now fully assessed. I’m recording the final machine-readable totals next, using the published selected raster, distance raster, and the three summary tables from the completed workflow.

  66. assess_result

    Recorded tool call · completed

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