Research/Terra/ 673274
Task evidence / population-distance-share

What percentage of Bangladesh's population lives within 5 km of a railway line?

PassComputational taskUnpublished draft
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The question

673274
What percentage of Bangladesh's population lives within 5 km of a railway line?
Exact submitted task and declared adaptations
What percentage of Bangladesh's population lives within 5 km of a railway line?

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 <= 5000 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
18m 8s
Recorded Blue tool calls
51
Total tokens
2,467,725
Model cost
Not recorded
Application revision
d50497ea9084f29c91b05406688f87035df98d8a
Release
terra-geobenchx-v1

Recorded final answer

Verified result: 39.9541358101781% of the valid population in the supplied Bangladesh WorldPop 2018 raster lies within 5 km of the supplied railway lines. That is 64,839,903.22934914 people out of 162,285,835.78281653, across 38,356 qualifying cells; 226,139 masked or nonfinite cells remained unknown and were excluded. I published both inspected rasters: selected population in people per cell, and distance in metres. Sources: WorldPop/CIESIN Bangladesh 2018 density raster (DOI 10.5258/SOTON/WP00675; retrieved from the supplied collection on 2026-10-07 UTC) and the frozen OpenStreetMap/Geofabrik Bangladesh railway extract dated 2025-02-01 (retrieved 2026-10-07 UTC). Limits: the population surface is historical 2018 data, the railways are a later snapshot, and the 5 km test is the requested planar EPSG:32646 cell-centre approximation to the original straight railway geometry. ### Limitations - Population is based on WorldPop 2018 density, not current population or contemporaneous access. - Railway geometry comes from a later frozen OpenStreetMap extract dated 2025-02-01 and does not prove 2018 rail service or access. - The 5 km measure is the requested planar EPSG:32646 cell-centre approximation to original straight railway segments; projection distortion and within-cell population location remain limitations. - Masked or nonfinite population cells remain unknown and are excluded from both the selected and total population sums. - Population comes from the supplied WorldPop/CIESIN Bangladesh 2018 density raster, so it does not prove current population or census accuracy. - Railway geometry comes from the frozen OpenStreetMap/Geofabrik Bangladesh extract dated 2025-02-01, so it does not prove 2018 rail service or access. - The 5 km test is the requested planar EPSG:32646 cell-centre distance to transformed original straight railway segments; projection distortion remains. - Within-cell population location is unresolved, and 226,139 original masked or nonfinite raster cells remained unknown and were excluded from both sums. - Historical 2018 population density does not prove current population or census accuracy. - The frozen railway snapshot is from 2025-02-01 and does not prove 2018 rail access or service. - Population still represents within-cell density applied uniformly across each valid cell. - Distance is the requested planar approximation in EPSG:32646 from raster cell centres to transformed original straight railway segments; projection distortion and within-cell location remain limitations. - Masked or nonfinite population cells remain unknown and are excluded from both 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
38356
Reported count
38356
Computation verified
Yes
Answer fulfilled
Yes
Full grading and rubric record
{
  "expectedCount": 38356,
  "actualCount": 38356,
  "expectedMetrics": {
    "selected_people": 64839903.12294957,
    "total_people": 162285835.55419007,
    "percentage": 39.95413580090198
  },
  "actualMetrics": {
    "percentage": 39.9541358101781,
    "total_people": 162285835.78281653,
    "selected_people": 64839903.22934914
  },
  "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 exact cell-area plus projected-features distance method preserve the original population grid/mask and produce the requested qualifying people-per-cell raster on a representative Bangladesh slice?

assess_trial · completed · assessment: sufficient

The tested processor chain produced the intended same-grid outputs on the full supplied Bangladesh WorldPop raster extent. The derived people-per-cell raster preserved the original CRS, transform, 559x728 grid, and 226,139-cell missing mask while converting valid density cells with exact ellipsoidal cell area. The projected-features distance raster also preserved that grid and mask, used EPSG:32646, and measured planar cell-centre distance to all 2,506 supplied railway features. The qualifying mask preserved missing cells and counted 38,356 qualifying valid cells. The selected-population raster preserved the mask and wrote zero in other valid cells. The statistics were internally consistent: selected people 64,839,903.22934914 did not exceed total people 162,285,835.78281653, and the mask sum matched the qualifying-cell count.

assess_result · completed · assessment: sufficient

I verified the final published selected-population raster and distance raster on the original Bangladesh WorldPop 2018 grid, plus the three one-row summary tables used for the metrics. 38,356 valid raster cells qualify within 5 km of the supplied railway lines. 226,139 original masked or nonfinite population cells remain unknown. The selected population is 64,839,903.22934914 people out of 162,285,835.78281653 total valid people, which is 39.9541358101781%.

Recorded workflow

  1. 01

    Ellipsoidal cell area

    Recorded raster-cell-area · succeeded

  2. 02

    Bangladesh population within 5 km of railways (people per cell)

    Recorded output · succeeded

  3. 03

    Bangladesh cell-centre distance to railway lines (metres)

    Recorded output · succeeded

  4. 04

    Bangladesh total people-per-cell summary

    Recorded output · succeeded

  5. 05

    Bangladesh selected people-per-cell summary

    Recorded output · succeeded

  6. 06

    Bangladesh qualifying-cell summary

    Recorded output · succeeded

  7. 07

    Rail distance

    Recorded distance-surface · succeeded

  8. 08

    People per cell

    Recorded raster-map-algebra · succeeded

  9. 09

    Population raster

    Recorded source · succeeded

  10. 10

    Qualifying mask

    Recorded raster-map-algebra · succeeded

  11. 11

    Railway lines

    Recorded source · succeeded

  12. 12

    Selected population

    Recorded raster-map-algebra · succeeded

  13. 13

    Qualifying cell stats

    Recorded raster-statistics · succeeded

  14. 14

    Selected people stats

    Recorded raster-statistics · succeeded

  15. 15

    Total people stats

    Recorded raster-statistics · succeeded

  16. 16

    Ellipsoidal cell area

    Recorded raster-cell-area · succeeded

  17. 17

    Rail distance

    Recorded distance-surface · succeeded

  18. 18

    People per cell

    Recorded raster-map-algebra · succeeded

  19. 19

    Population slice

    Recorded source · succeeded

  20. 20

    Qualifying mask

    Recorded raster-map-algebra · succeeded

  21. 21

    Railway slice with margin

    Recorded source · succeeded

  22. 22

    Selected population

    Recorded raster-map-algebra · succeeded

  23. 23

    Qualifying cell stats

    Recorded raster-statistics · succeeded

  24. 24

    Selected people stats

    Recorded raster-statistics · succeeded

  25. 25

    Total people stats

    Recorded raster-statistics · succeeded

  26. 26

    People per cell

    Recorded output · succeeded

  27. 27

    Rail distance

    Recorded output · succeeded

  28. 28

    Qualifying mask

    Recorded output · succeeded

  29. 29

    Selected population

    Recorded output · succeeded

  30. 30

    Total people stats

    Recorded output · succeeded

  31. 31

    Selected people stats

    Recorded output · succeeded

  32. 32

    Qualifying cell stats

    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’ll verify the two supplied datasets, test the exact cell-area and 5 km method on a small private slice, then save and run the full Bangladesh workflow and inspect the published rasters.

  2. get_analysis

    Recorded tool call · completed

  3. Progress update

    I’ve confirmed there’s no saved Bangladesh analysis yet. Next I’m fixing the study boundary and inspecting the two frozen inputs before I build the trial.

  4. search_locations

    Recorded tool call · completed

  5. search_catalog

    Recorded tool call · completed

  6. search_catalog

    Recorded tool call · completed

  7. get_collection

    Recorded tool call · completed

  8. get_collection

    Recorded tool call · completed

  9. get_item

    Recorded tool call · completed

  10. get_item

    Recorded tool call · completed

  11. list_processors

    Recorded tool call · completed

  12. list_processors

    Recorded tool call · completed

  13. list_processors

    Recorded tool call · completed

  14. list_processors

    Recorded tool call · completed

  15. list_processors

    Recorded tool call · completed

  16. list_processors

    Recorded tool call · completed

  17. Progress update

    I found the core processors for this method: exact cell area on the original geographic grid, exact planar distance-to-line on the same valid raster grid, raster map algebra for the qualifying people-per-cell raster, and full raster statistics for totals. Now I’m checking the exact input schemas before I run the first slice test.

  18. describe_processors

    Recorded tool call · completed

  19. get_tool_help

    Recorded tool call · completed

  20. get_tool_help

    Recorded tool call · completed

  21. update_analysis_brief

    Recorded tool call · completed

  22. inspect_artifact

    Recorded tool call · failed

  23. inspect_artifact

    Recorded tool call · failed

  24. search_locations

    Recorded tool call · completed

  25. search_locations

    Recorded tool call · completed

  26. get_tool_help

    Recorded tool call · completed

  27. describe_processors

    Recorded tool call · completed

  28. Progress update

    I’m testing one coastal slice first. I expect the distance raster to keep the clipped WorldPop grid and mask, the people-per-cell conversion to use exact cell area, and the qualifying raster to preserve unknown cells while zeroing only valid cells beyond 5 km.

  29. run_trial

    Recorded tool call · completed

  30. Progress update

    The private test finished. It actually ran on the full Bangladesh raster extent, not the small slice I intended, which is useful for the final result but means I need to record that scope observation carefully before I save the production workflow.

  31. get_trial_report

    Recorded tool call · completed

  32. assess_trial

    Recorded tool call · completed

  33. Progress update

    The method is now tested. The practical result is that I can carry this exact full-country computation into a saved workflow without changing the science. Next I’m saving the publishable version with the two rasters and the summary tables I need for the final answer.

  34. get_tool_help

    Recorded tool call · completed

  35. get_tool_help

    Recorded tool call · completed

  36. get_tool_help

    Recorded tool call · completed

  37. get_tool_help

    Recorded tool call · completed

  38. get_tool_help

    Recorded tool call · completed

  39. get_tool_help

    Recorded tool call · completed

  40. get_tool_help

    Recorded tool call · completed

  41. get_tool_help

    Recorded tool call · completed

  42. propose_workflow

    Recorded tool call · completed

  43. Progress update

    The first saved draft is close, but it still carried the trial’s small declared scope. I’m correcting that now by saving the workflow with the full Bangladesh scope and clean source selections so it matches the requested production run.

  44. propose_workflow

    Recorded tool call · completed

  45. Progress update

    The production draft is now valid and ready. I’m running it next, then I’ll inspect the published rasters and attach the final answer object from those exact outputs.

  46. execute_workflow

    Recorded tool call · completed

  47. inspect_workflow_results

    Recorded tool call · completed

  48. inspect_workflow_results

    Recorded tool call · completed

  49. inspect_artifact

    Recorded tool call · completed

  50. inspect_artifact

    Recorded tool call · completed

  51. Progress update

    I have the final workflow receipts. I’m pulling the exact raster previews and the summary rows now so the final answer uses the finished published outputs and their verified counts.

  52. inspect_artifact

    Recorded tool call · completed

  53. inspect_artifact

    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. inspect_artifact

    Recorded tool call · completed

  58. inspect_artifact

    Recorded tool call · completed

  59. Progress update

    I’m reading the finished raster previews and the one-row summary tables from the final run. That gives me the exact artifact references Blue needs for the accepted answer.

  60. inspect_artifact

    Recorded tool call · completed

  61. Progress update

    I’ve verified the two final rasters and the total and selected population tables. I just need the qualifying-cell summary row now, then I can record the accepted result with the exact published raster IDs.

  62. assess_result

    Recorded tool call · completed

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