Research/Terra/ 208110
Task evidence / population-distance-share

Compare the population density along railways in Bangladesh with the national average

PassComputational taskUnpublished draft
Download evidence JSON ↓

The question

208110
Compare the population density along railways in Bangladesh with the national average
Exact submitted task and declared adaptations
Compare the population density along railways in Bangladesh with the national average

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.Along railways means the declared 5 km corridor. Compare area-weighted density: selected people divided by total area of qualifying valid cells versus total people divided by area of all valid cells. Do not average cell densities without area weighting or treat NoData as zero.



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. Also include metrics corridor_density and national_density in people/km², plus selected_area_km2 and total_area_km2. Explain which density is greater.

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
38m 10s
Recorded Blue tool calls
63
Total tokens
3,893,502
Model cost
Not recorded
Application revision
d50497ea9084f29c91b05406688f87035df98d8a
Release
terra-geobenchx-v1

Recorded final answer

About 39.95% of the valid-cell 2018 Bangladesh population falls within 5 km of the supplied railway lines. The rail corridor is denser: about 2,163.5 people/km² versus about 1,145.4 people/km² nationally across valid raster cells. I published the selected-population raster in people per cell and the rail-distance raster in metres on the original WorldPop grid and mask. Sources: WorldPop/CIESIN Bangladesh 2018 UN-adjusted 1 km population density (DOI 10.5258/SOTON/WP00675); frozen Bangladesh railway lines from the GeoBenchX Geofabrik extract dated 2025-02-01, © OpenStreetMap contributors. Limits: this compares a 2018 population surface with a later railway snapshot, uses the requested EPSG:32646 planar cell-centre distance approximation, and leaves masked/nonfinite raster cells unknown. ### Limitations - The population surface is historical WorldPop 2018 while the supplied railway inventory is a later 2025-02-01 snapshot, so the result is not contemporaneous access evidence. - Railway proximity is the requested local planar cell-centre approximation in EPSG:32646, not exact ellipsoidal distance, travel distance, or proof of service access. - Population within each raster cell is unresolved; counting a qualifying cell includes the whole cell once when its centre is within 5 km. - National comparison coverage uses all valid cells in the supplied Bangladesh raster extent and preserves its original mask; masked or nonfinite cells remain unknown. - Population uses the historical WorldPop 2018 Bangladesh surface, while railway geometry comes from a later frozen 2025-02-01 OpenStreetMap/Geofabrik snapshot, so the comparison is not contemporaneous access evidence. - Railway proximity is the requested local projected cell-centre approximation in EPSG:32646, not exact ellipsoidal distance, travel distance, or service access. - Population location within each raster cell is unresolved; when a cell centre qualifies within 5 km, the whole valid cell population is counted once. - Coverage uses all valid cells in the supplied Bangladesh WorldPop raster extent and original mask; 226,139 masked or nonfinite cells remain unknown and are excluded from totals and density denominators. - The population surface is historical 2018 data. - Masked or nonfinite cells remain unknown. - The railway snapshot is later than the population surface. - This is the requested local projected approximation in EPSG:32646, not exact ellipsoidal or travel distance. - Population within a qualifying cell is counted in full once its centre qualifies.

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,
    "corridor_density": 2163.5449148580387,
    "national_density": 1145.4277043032519,
    "selected_area_km2": 29969.289141013305,
    "total_area_km2": 141681.43039014962
  },
  "actualMetrics": {
    "percentage": 39.95413581017811,
    "total_people": 162285835.78281653,
    "total_area_km2": 141681.43039014962,
    "selected_people": 64839903.22934914,
    "corridor_density": 2163.5449144591976,
    "national_density": 1145.4277059169176,
    "selected_area_km2": 29969.28919571638
  },
  "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 planned processor chain preserve the original population grid and mask while converting density to people per cell and selecting cells within 5 km of the supplied railway lines using projected planar distance in EPSG:32646?

assess_trial · completed · assessment: insufficient

The trial established that the requested full-Bangladesh computation path is viable: `distance-surface` with `projected-features` in EPSG:32646 produced a metres raster on the original WorldPop grid and preserved the original valid-data mask (180,813 valid cells; 226,139 missing cells). `raster-cell-area` plus map algebra converted density to people per cell without creating output where inputs were missing, and the selected-population raster likewise preserved the original mask while writing zero in non-qualifying valid cells. The trial also showed that my attempted qualifying-cell mask `where(dist_m <= 5000, 1, 0)` was not suitable for the final count because comparisons/where turned missing cells into finite zeros, yielding a mask with 406,952 valid cells instead of preserving the original 226,139 missing cells. The source-step area subset I supplied did not reduce the managed inputs, so the trial actually exercised the full Bangladesh raster extent rather than the intended local slice.

run_trial · completed

Can I derive an exact qualifying valid-cell count for the 5 km railway corridor while preserving the original WorldPop missing mask, using the already successful full-Bangladesh distance surface and a mask-preserving 0/1 expression?

assess_trial · completed · assessment: sufficient

The correction worked. Using the retained full-Bangladesh distance raster and a mask-preserving expression `(area_km2 / area_km2) * where(dist_m <= 5000, 1, 0)`, the qualifying-cell raster kept the original WorldPop mask exactly: 180,813 valid cells and 226,139 missing cells. The output contains only 0 and 1 among valid cells, and the qualifying valid-cell count is the raster sum 38,356. This resolves the remaining counting defect without changing the successful distance or selected-population methods.

assess_result · completed · assessment: sufficient

Using the supplied WorldPop 2018 Bangladesh density raster and the supplied frozen Bangladesh railway inventory, 64,839,903.22934914 people out of 162,285,835.78281653 valid-cell people fall within the declared 5 km railway corridor, or 39.95413581017811%. The qualifying valid-cell corridor covers 29,969.28919571638 km² out of 141,681.43039014962 km² of valid raster area. Its area-weighted density is 2,163.5449144591974 people/km² versus 1,145.4277059169175 people/km² for the national valid-cell average, so the railway corridor is denser. The published selected-population raster and distance raster are on the original grid and preserve the original missing mask.

Recorded workflow

  1. 01

    National area statistics

    Recorded raster-statistics · succeeded

  2. 02

    Cell area km2

    Recorded raster-cell-area · succeeded

  3. 03

    Qualifying cell count statistics

    Recorded raster-statistics · succeeded

  4. 04

    Selected population raster (people per cell)

    Recorded output · succeeded

  5. 05

    Rail distance raster (metres)

    Recorded output · succeeded

  6. 06

    National people statistics

    Recorded output · succeeded

  7. 07

    Corridor people statistics

    Recorded output · succeeded

  8. 08

    National area statistics

    Recorded output · succeeded

  9. 09

    Corridor area statistics

    Recorded output · succeeded

  10. 10

    Qualifying cell count statistics

    Recorded output · succeeded

  11. 11

    Rail distance metres

    Recorded distance-surface · succeeded

  12. 12

    People per cell

    Recorded raster-map-algebra · succeeded

  13. 13

    National people statistics

    Recorded raster-statistics · succeeded

  14. 14

    Bangladesh population density, WorldPop 2018

    Recorded source · succeeded

  15. 15

    Qualifying valid-cell mask

    Recorded raster-map-algebra · succeeded

  16. 16

    Bangladesh railway lines, frozen OpenStreetMap extract

    Recorded source · succeeded

  17. 17

    Selected area km2

    Recorded raster-map-algebra · succeeded

  18. 18

    Corridor area statistics

    Recorded raster-statistics · succeeded

  19. 19

    Selected population per cell

    Recorded raster-map-algebra · succeeded

  20. 20

    Corridor people statistics

    Recorded raster-statistics · succeeded

  21. 21

    Cell area km2

    Recorded raster-cell-area · succeeded

  22. 22

    Corrected qualifying-cell statistics

    Recorded raster-statistics · succeeded

  23. 23

    Retained full-Bangladesh distance raster

    Recorded source · succeeded

  24. 24

    Population raster

    Recorded source · succeeded

  25. 25

    Mask-preserving qualifying valid-cell raster

    Recorded raster-map-algebra · succeeded

  26. 26

    Mask-preserving qualifying valid-cell raster

    Recorded output · succeeded

  27. 27

    Corrected qualifying-cell statistics

    Recorded output · succeeded

  28. 28

    Area statistics

    Recorded raster-statistics · succeeded

  29. 29

    Cell area km2

    Recorded raster-cell-area · succeeded

  30. 30

    Qualifying-cell statistics

    Recorded raster-statistics · succeeded

  31. 31

    Rail distance metres

    Recorded distance-surface · succeeded

  32. 32

    People per cell

    Recorded raster-map-algebra · succeeded

  33. 33

    People-per-cell statistics

    Recorded raster-statistics · succeeded

  34. 34

    Population trial subset

    Recorded source · succeeded

  35. 35

    Population subset statistics

    Recorded raster-statistics · succeeded

  36. 36

    Qualifying valid-cell mask

    Recorded raster-map-algebra · succeeded

  37. 37

    Railway trial subset

    Recorded source · succeeded

  38. 38

    Selected area km2

    Recorded raster-map-algebra · succeeded

  39. 39

    Selected-area statistics

    Recorded raster-statistics · succeeded

  40. 40

    Selected people per cell

    Recorded raster-map-algebra · succeeded

  41. 41

    Selected-people statistics

    Recorded raster-statistics · succeeded

  42. 42

    Rail distance metres

    Recorded output · succeeded

  43. 43

    People per cell

    Recorded output · succeeded

  44. 44

    Selected people per cell

    Recorded output · succeeded

  45. 45

    Population subset statistics

    Recorded output · succeeded

  46. 46

    People-per-cell statistics

    Recorded output · succeeded

  47. 47

    Selected-people statistics

    Recorded output · succeeded

  48. 48

    Area statistics

    Recorded output · succeeded

  49. 49

    Selected-area statistics

    Recorded output · succeeded

  50. 50

    Qualifying-cell 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’ll verify the frozen inputs and test the key calculation path first: cell-area conversion on the original grid, centre-to-rail distance in UTM 46N, and outputs on the same raster grid. Then I’ll save the working method and finish the full run with inspectable rasters and checked metrics.

  2. Progress update

    I found the Blue analysis tools. Next I’m checking whether there is already a saved brief or proposal for this Bangladesh comparison, then I’ll inspect the frozen raster and railway inputs and pick the exact processors for the tested method.

  3. get_analysis

    Recorded tool call · completed

  4. get_analysis

    Recorded tool call · completed

  5. get_analysis

    Recorded tool call · completed

  6. get_analysis

    Recorded tool call · completed

  7. get_collection

    Recorded tool call · completed

  8. get_collection

    Recorded tool call · completed

  9. list_processors

    Recorded tool call · completed

  10. list_processors

    Recorded tool call · completed

  11. list_processors

    Recorded tool call · completed

  12. Progress update

    The core source pieces are promising: there is a native cell-area processor for geographic rasters and an exact `distance-surface` mode that measures planar distance from raster cell centres to line features in a chosen metre CRS while keeping the original grid and mask. I’m now fetching a Bangladesh boundary for an explicit study scope and then I’ll test the full vertical slice on a small area.

  13. describe_processors

    Recorded tool call · completed

  14. search_catalog

    Recorded tool call · completed

  15. search_catalog

    Recorded tool call · completed

  16. list_items

    Recorded tool call · completed

  17. list_items

    Recorded tool call · completed

  18. get_tool_help

    Recorded tool call · completed

  19. update_analysis_brief

    Recorded tool call · completed

  20. describe_processors

    Recorded tool call · completed

  21. get_tool_help

    Recorded tool call · completed

  22. get_tool_help

    Recorded tool call · completed

  23. Progress update

    I’ve set the method. The trial will answer one consequential question: does the exact-feature distance surface in UTM 46N, combined with ellipsoidal cell area and map algebra, keep the original mask and produce the right additive quantities on the original grid? If that works on a representative central slice, I can scale the same chain to all of Bangladesh.

  24. run_trial

    Recorded tool call · completed

  25. get_trial_report

    Recorded tool call · completed

  26. Progress update

    The trial finished. It already ran across the full Bangladesh raster, which is useful for the final extent, but it also exposed one real method problem: my qualifying-cell mask turned missing cells into zero. I’m reading the native trial report now, then I’ll record that finding and test a corrected count branch while reusing the successful full-Bangladesh outputs.

  27. Progress update

    The main outputs passed: distance, people-per-cell, and selected-population stayed on the original Bangladesh grid and kept the original missing mask. The remaining problem is narrower but important: a plain `where(dist<=5000,1,0)` mask filled missing cells with zero, so I need one correction trial for the qualifying-cell count before I save the production workflow.

  28. assess_trial

    Recorded tool call · completed

  29. Progress update

    I’ve isolated the remaining uncertainty. The next test is small in logic, not in area: keep the successful full-Bangladesh distance raster, rebuild only the qualifying-cell mask with a mask-preserving expression, and verify that its valid and missing counts match the original population raster.

  30. run_trial

    Recorded tool call · completed

  31. get_trial_report

    Recorded tool call · completed

  32. Progress update

    The correction worked. I now have the exact qualifying valid-cell count with the original mask preserved: 38,356 qualifying valid cells, 180,813 valid cells overall, and 226,139 original missing cells. Next I’m saving the checked production workflow around this tested Bangladesh-wide method, then I’ll inspect the final artifacts and record the answer object.

  33. get_tool_help

    Recorded tool call · completed

  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. assess_trial

    Recorded tool call · completed

  41. get_analysis

    Recorded tool call · completed

  42. get_analysis

    Recorded tool call · completed

  43. Progress update

    I have enough evidence to save the working plan now: same Bangladesh-wide method, same preserved raster grid and mask, plus the corrected mask-preserving count branch. After that I’ll resolve the earlier counting finding against the correction trial and inspect the workflow outputs as the final deliverables.

  44. update_analysis_brief

    Recorded tool call · completed

  45. propose_workflow

    Recorded tool call · completed

  46. Progress update

    I saved the draft plan. It’s scientifically ready, but Blue still needs the earlier counting defect explicitly resolved against this exact saved draft. I’m recording that now with the two trial runs: the first one for the Bangladesh-wide main branches, and the second one for the corrected qualifying-cell count.

  47. assess_plan

    Recorded tool call · failed

  48. get_tool_help

    Recorded tool call · completed

  49. assess_plan

    Recorded tool call · completed

  50. execute_workflow

    Recorded tool call · completed

  51. inspect_workflow_results

    Recorded tool call · completed

  52. Progress update

    The approved run completed in the background. I’m now reading its exact output identities and summaries, then I’ll check the final rasters against the requested conditions and attach the machine-readable answer object to the accepted result.

  53. Progress update

    I’m at the last verification step: reading the final workflow’s published rasters and summary tables so the answer object uses the current output items, not earlier trial artifacts. After that I’ll record the checked result and give you the short comparison in plain language.

  54. inspect_artifact

    Recorded tool call · completed

  55. inspect_artifact

    Recorded tool call · completed

  56. get_tool_help

    Recorded tool call · completed

  57. inspect_artifact

    Recorded tool call · completed

  58. inspect_artifact

    Recorded tool call · completed

  59. inspect_artifact

    Recorded tool call · completed

  60. inspect_artifact

    Recorded tool call · completed

  61. inspect_artifact

    Recorded tool call · completed

  62. Progress update

    The workflow is done; I’m just waiting on the last bounded inspections to return their exact rows and previews. Once those current output receipts are in hand, I can lock the answer object to the final published rasters instead of the earlier trial copies.

  63. inspect_artifact

    Recorded tool call · completed

  64. inspect_workflow_results

    Recorded tool call · completed

  65. inspect_artifact

    Recorded tool call · completed

  66. inspect_artifact

    Recorded tool call · completed

  67. inspect_artifact

    Recorded tool call · completed

  68. inspect_artifact

    Recorded tool call · completed

  69. inspect_artifact

    Recorded tool call · completed

  70. inspect_artifact

    Recorded tool call · completed

  71. Progress update

    The published rasters are already checked and match the requested grid and mask. I still need the final summary rows for total people and the qualifying-cell count from the current workflow outputs, then I can attach the machine-readable result to those final artifact identities.

  72. get_tool_help

    Recorded tool call · failed

  73. inspect_artifact

    Recorded tool call · completed

  74. inspect_artifact

    Recorded tool call · completed

  75. Progress update

    I have the final numbers now from the published workflow outputs. I’m doing one last formatting step: tying the answer object to the exact final artifact references that Blue expects for result acceptance, so the response points to the published rasters rather than the earlier trial copies.

  76. get_tool_help

    Recorded tool call · completed

  77. get_tool_help

    Recorded tool call · completed

  78. assess_result

    Recorded tool call · completed

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